Reproductive biology of soft coral Sarcophyton serenei Tixier-Durivault, 1958 in Nha Trang Bay, Khanh Hoa province, Viet Nam

Reproductive biology of soft coral Sarcophyton serenei Tixier-Durivault, 1958 in Nha Trang Bay, Khanh Hoa province, Viet Nam | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Reproductive biology of soft coral Sarcophyton serenei Tixier-Durivault, 1958 in Nha Trang Bay, Khanh Hoa province, Viet Nam Lam Son Ho, Dang-Tran Tu Tram, Nguyen-Thi Nguyet Hue, Nguyen Truong Tan Tai, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7190639/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The study was conducted from August 2023 to July 2024, with monthly sampling on the full moon from mature colonies of the soft coral Sarcophyton serenei , distributed at depths of 5–10 m. Samples were collected from Cut Chim Island (12°15'55.9"N, 109°13'29.3"E) to Hon Chong Island (12°16'58.3"N, 109°12'51.3"E) in Nha Trang Bay to investigate specific reproductive biological characteristics of the species. The parameters analyzed included sex determination, sex ratio, developmental stages of oocytes and spermatocysts, maturation rates, spawning seasonality, and fecundity. The results revealed that S. serenei is a gonochoric species, with a natural sex ratio of 1.3:1 (male to female). The oocytes of S. serenei were white in the immature stage and turned pink or occasionally deep red upon maturation. The mean diameter of mature oocytes was 684.99 ± 28.50 µm, ranging from 631.89 to 735.97 µm. Immature spermatocysts were translucent gray, turning white upon maturation, with an average size of 235.29 ± 8.76 µm, ranging from 182.42 to 295.00 µm. Fecundity showed significant variability, with each polyp containing 14 to 26 eggs. The spawning season of S. serenei in Nha Trang Bay occurred annually in March. Sarcophyton S. serenei reproductive biology soft coral Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction Soft corals (Order Malacalcyonacea) are a prominent group of benthic organisms in Indo-Pacific coral reefs, ranking second only to hard corals and constituting the largest proportion of the class Octocorallia (McFadden et al. 2022 ). These species are mainly distributed from tropical to temperate regions, playing an important role in the biodiversity and ecological functioning of coral reefs. Members of this order are characterized by having either a largely proteinaceous skeletal axis or no skeletal axis at all (McFadden et al. 2022 ). Soft corals play a vital ecological role in tropical reef ecosystems by enhancing biodiversity and providing essential habitat structures. Their broad distribution encompasses all marine environments globally (McFadden et al. 2022 ), with notable abundance in regions such as the Indian Ocean, the Red Sea, and the Western Pacific (Fabricius and Alderslade 2001 ). This widespread presence is largely attributed to their exceptional adaptability, which allows them to colonize environments where hard corals are often limited, particularly in turbid or marginal conditions (Wilkens and Birkholz 1992 ; Ellis and Sharron 1999 ). To date, over 3,500 nominal species of soft corals, classified into 79 families, have been identified (McFadden et al. 2022 ). Among these, the genus Sarcophyton is particularly diverse, comprising approximately 80 recognized species (McFadden et al. 2025 ). Sarcophyton serenei , for instance, has been documented in several locations, including Nha Trang Bay and Ly Son (Viet Nam), as well as the Gulf of Suez (Tixier-Durivault 1958 ; Verseveldt 1982 ; Dautova 2011 ; Dautova and Savinkin 2013b ). In addition to their ecological significance, soft corals possess high ornamental and economic value. Their vivid coloration and resilience make them desirable in the marine aquarium trade. However, increasing market demand has led to unsustainable harvesting from wild populations. It is estimated that around 390,000 soft coral specimens, representing about 61 species, are collected annually for the aquarium industry, with popular genera including Sarcophyton , Sclerophytum , Dendronephthya , and Nephthea (Wabnitz 2003 ). Despite their adaptability, soft corals are not immune to environmental stressors. Similar to hard corals, they are vulnerable to the impacts of climate change and anthropogenic disturbances such as pollution, overfishing, chemical runoff, oil spills, ship groundings, tourism, and coral extraction (Burke et al. 2002 ). These pressures have contributed to notable population declines, with cascading effects on reef biodiversity and ecosystem stability (Rocha et al. 2015 ). In response to these challenges, research efforts have increasingly focused on developing sustainable approaches for soft coral reproduction and aquaculture. Advancements in this area are essential for both reducing pressure on natural populations and supporting reef restoration initiatives (Tlusty 2002 ; Rhyne et al. 2009 ). Soft corals also hold substantial economic value in the aquarium trade; however, overexploitation has led to population decline, threatening biodiversity (Wabnitz 2003 ; Rocha et al. 2015 ). Soft coral aquaculture has emerged as a critical solution for reducing natural harvesting and supporting reef restoration efforts (Leal et al. 2014 ). Several compounds derived from Sarcophyton have demonstrated antiviral activity against SARS-CoV-2 (Ibrahim et al. 2021 ) and antibacterial effects against Vibrio harveyi (Yan et al. 2022 ). Among soft corals, Sarcophyton serenei exhibits resistance to predation (Hoang et al. 2022 ), highlighting its adaptability and potential for research and restoration initiatives. Studies on soft coral reproduction have identified three primary reproductive modes in octocorals: broadcast spawning, external brooding, internal brooding (Alino and Coll 1989 ; Kahng et al. 2011 ; Jamodiong and Reimer 2023 ) and semi-brooding ((Alino and Coll 1989 ; Kahng et al. 2011 ; Jamodiong and Reimer 2023 ). Octocoral sexuality can generally be classified into three categories: hermaphroditism, where both male and female gametes develop within the same polyp or colony; gonochorism, in which male and female colonies are distinct; and a mixed strategy incorporating aspects of both reproductive types (Kahng et al. 2011 ). Up to 2011, the majority of examined octocorals exhibited broadcast spawning (49%) and gonochorism (89%) as their predominant reproductive traits (Kahng et al. 2011 ). Furthermore, available research suggests that tropical soft coral species tend to reproduce asynchronously without a fixed seasonal pattern, whereas temperate species typically follow periodic reproductive cycles (Kahng et al. 2011 ; Barbosa et al. 2014 ; Baran and Baria-Rodriguez 2021 ; Jamodiong and Reimer 2023 ). Reproductive timing in soft corals is correlated with water temperature (Hwang and Song 2007 ; Jamodiong and Reimer 2023 ) and lunar cycles (Hwang and Song 2007 ). Research on the reproductive biology of soft corals remains limited worldwide. Most studies have focused on populations in the Red Sea and the Great Barrier Reef (Alino and Coll 1989 ; Kahng et al. 2011 ), while data from other regions, including the Western Pacific Islands (Baran and Baria-Rodriguez 2021 ), remain scarce. Comprehensive studies on the reproductive biology of soft corals across various species and regions are therefore necessary. In Viet Nam, coral reproduction research is still limited, focusing mainly on hard corals and preliminary studies within international collaborative projects (Tuan et al. 2022 ). There have been no published studies on the sexual reproduction of soft corals, particularly S. serenei . Addressing this gap, this research aims to determine the sex ratio, spawning season, gamete sizes, and fecundity of S. serenei in Viet Nam. The results of this study provide essential baseline data for future research on the artificial reproduction of this coral species. Such efforts may contribute to a sustainable source of raw materials for the extraction of biologically active compounds, the development of marine ornamental organisms, and the conservation of this species. 2. Materials and methods 2.1. Species Identification The identification of Sarcophyton serenei , a species of soft coral, follows the taxonomic guidelines established by Tixier-Durivault ( 1958 ), Verseveldt ( 1982 ), and Dautova and Savinkin ( 2013a ). This species exhibits a yellow-brown to gray-brown coloration (Fig. 1 A). In the central region of the capitulum, the spacing between autozooids ranges from 2 to 4 mm. The autozooids closest to each other are associated with 6 to 8 siphonozooids, while the farthest ones are accompanied by 8 to 10 siphonozooids. At the capitulum margin, the spacing corresponds to 1 to 2 siphonozooids. The polyps reach a height of 4 to 6 mm and do not fully retract. The stalk contains sclerites that are elongated, either straight or curved spindles, measuring up to 1.20 mm in length and 0.28 mm in width, with surfaces covered in small warts (Fig. 1 B). 2.2. Field Sampling Soft coral samples of Sarcophyton serenei were randomly collected at depths of 5–10 m, spanning the area from Cut Chim Island (12°15'55.9"N, 109°13'29.3"E) to Hon Chong Island (12°16'58.3"N, 109°12'51.3"E) in Nha Trang Bay (Fig. 2 ). Sampling locations were selected based on preliminary surveys conducted across Nha Trang Bay, spanning from northern Hon Chong to southern Hon Tre, using SCUBA diving to identify areas with high densities of Sarcophyton serenei . Fixation and Preservation of Samples: Fragments of soft coral, measuring 4 cm in length from the capitulum edge to the center and 8–10 mm in thickness, were excised from parent colonies in the field. These fragments were rinsed with seawater to remove surface debris and preserved in a 10% formalin solution diluted with seawater for a minimum of 24 hours. The samples were rinsed with distilled water and then transferred to 70% ethanol for long-term storage until further analysis (Fan et al. 2005 ). These colonies were monitored, and reproductive biological samples were collected monthly during full moons from August 2023 to July 2024. In total, 380 colonies were sampled. Samples measuring approximately 1–2 cm² were excised from the center of the capitulum of each colony. The collected samples were visually assessed in the field once a month (e.g., recording egg coloration). When more than 50% of the eggs in a polyp showed signs of sexual maturity (color transitioning from white to other hues such as pink, orange, or red), sampling frequency was increased every three days. This process continued until no mature eggs (colored eggs) were observed in the polyps. 2.3. Techniques for decalcification and histological sectioning Sample processing was conducted at the Experimental Station Laboratory of the Marine Organism Culture Engineering Department, Institute of Oceanography. After measuring egg/spermatocyst size, the two coral groups (with sexes classified) were decalcified and processed for histological analysis to verify the initial assessment. The samples were processed following the method described by Fan et al. ( 2005 ). Sarcophyton serenei samples preserved in 70% ethanol were rinsed with distilled water, decalcified using 8% formic acid, and dehydrated in ethanol baths with gradually increasing concentrations up to 95%. After decalcification, the samples were placed on glass slides and longitudinally sectioned using a scalpel to observe the gonads under a Kruss MSZ 5000-T-IL-TL stereomicroscope (Germany). The presence of oocytes or sperm sacs in the gonads was recorded to distinguish male and female specimens, serving as a reference for histological analysis to ensure accurate results. Samples containing oocytes were photographed using the camera attached to the Kruss MSZ 5000-T-IL-TL stereomicroscope, while sperm sac sizes were measured based on histological images captured using an Olympus CX35 microscope. Histological Preparation of Gonadal Samples: After decalcification and cleaning, coral samples were embedded in Paraplast and cast in paraffin blocks. The sections were then stained with Hematoxylin and Eosin to observe and differentiate the developmental stages of the gonads. 2.3.1 Determination of Sex and Sex Ratio Colonies of the soft coral Sarcophyton serenei were randomly sampled from the collection sites between August 2023 to July 2024. This period was selected because oocytes and sperm could be observed in small sections (approximately 1–2 cm²) cut from the polyparia of each colony to examine the presence of sperm and/or eggs. The number of male and female colonies containing sperm and/or oocytes was identified and recorded under a stereo microscope (Kruss MSZ 5000-T-IL-TL, Gernany). The sex ratio was calculated using the method described by Fowler et al. ( 2013 ) as follows: Percentage of male individuals (%) = (a/c) × 100 Percentage of female individuals (%) = (b/c) × 100 Male-to-female ratio = a/b Where: a: Number of male individuals b: Number of female individuals c: Total number of samples 2.3.2. Determination of Fecundity and Gonadal Development The field samples were evaluated for fecundity and gamete diameter under a stereo microscope (Kruss MSZ 5000-T-IL-TL, Gernany). The fecundity of S. serenei was determined by counting the number of mature oocytes per polyp, based on three mature polyps per sample across 30 samples. The diameter of oocytes and sperm sacs (mean ± SD) was calculated as the square root of the product of the longest and shortest perpendicular diameters of each oocyte, following Vicentuan ( 2009 ), and analyzed using ImageJ software. Absolute fecundity was defined as the total number of eggs present in a single polyp at the mature stage. To accurately identify intact polyps, the sample should be thinly sectioned multiple times if necessary. A scalpel and needle are used to carefully separate tissue samples while minimizing damage to the eggs and preventing displacement between polyps. Only polyps containing intact eggs are counted, whereas eggs from adjacent polyps are removed during separation to ensure accurate fecundity estimation. The peak spawning period was identified based on the presence of mature gametes and their subsequent absence during successive sampling periods. Histological slides were observed under an Olympus CX35 (Japan) microscope. The developmental stages of eggs and spermatocysts were described based on their increasing size and the appearance of nuclei, using the four-stage classification system of Glynn et al. ( 1991 ) and Schleyer et al. ( 2004 ). 2.4. Data Processing All collected data were processed using Microsoft Excel 2007. The distribution of sex was tested for independence from the theoretical distribution (1:1) using the Chi-square method. 3. Results 3.1. Sex and Male-Female Ratio A total of 380 specimens of the soft coral Sarcophyton serenei were randomly collected from the Nha Trang marine area over the course of 19 sampling trips. The aim was to investigate sex distribution and the male-to-female ratio within the population. Histological analysis revealed that the gonads of S. serenei are located in the posterior half of the mesentery and do not extend to the oral disc or the base of the tentacles. In contrast, siphonozooids were found in association with the gonads. Sexual identification was feasible for all colonies with diameters ranging from 15 to 20 cm. During the study period, 217 male and 163 female colonies were identified. No hermaphroditic or sexually indeterminate colonies were recorded. A Chi-square test was conducted to compare the observed and expected male-to-female ratios. The result yielded a χ² value of 7.67, which exceeds the critical value of 6.64 (df = 1, P < 0.01), indicating a statistically significant deviation from a 1:1 sex ratio. The observed male-to-female ratio in this population was approximately 1.3:1. 3.2. Developmental Stages of Oocyte Table 1 Oocyte size across developmental stages Month Mean ± S.D.(µm) Range (µm) Stage August 16 250.54 ± 16.17 214.98–275.57 I September 20 256.90 ± 16.73 223.36–278.12 I October 26 292.57 ± 15.56 263.89–325.12 II November 29 335.07 ± 22.93 280.49–372.75 II December 27 352.70 ± 27.21 303.76–390.02 II January 24 354.26 ± 30.07 290.51–399.39 III February 22 445.26 ± 33.23 391.79–501.53 III March 17 519.99 ± 29.90 460.14–571.96 IV March 20 581.75 ± 10.64 566.31–613.71 IV March 23 633.20 ± 35.58 556.99–683.61 IV March 27 684.99 ± 28.50 631.89–735.97 IV March 30 158.21 ± 4.85 150.07–168.20 I April 22 162.80 ± 5.34 147.91–172.84 I May 22 171.82 ± 5.31 163.55–184.88 I June 17 193.27 ± 8.65 178.46–214.40 I July 19 205.51 ± 12.01 181.20–230.53 I The oocyte development process in Sarcophyton serenei is categorized into four stages, as illustrated in Fig. 4 , Additionally, egg size is shown in Table 1 . Observations in April revealed the presence of small oocytes (ranging from 147.91 to 172.84 µm), suggesting that S. serenei had reproduced in March. Stage I From April to September, newly formed oocytes exhibit a translucent appearance and appear round. At this stage, oocytes primarily consist of the nucleus and cytoplasm, with gonads only observed in the autozooids and attached to the mesentery via pedicles. Although the nucleus and cytoplasm were indistinguishable, oocytes were visible as clusters within the mesentery or interspersed with oocytes at later developmental stages (Fig. 4 A). In April, eggs measure 162.80 ± 5.34 µm, increasing to 256.90 ± 16.73 µm in September. The study results indicated that stage I oocytes persisted from April to September, stage II from October to December, stage III from January to February, and stage IV from February to March. Stage II From October to December, oocytes begin to adopt a round or oval shape and remain attached to the mesentery by pedicles (Fig. 4 B). During this stage, the nucleus and cytoplasm dominate the cell structure, with the nucleus centrally positioned within the oocyte. In October, eggs measure 292.57 ± 15.56 µm, increasing to 352.70 ± 27.21 µm in December. Stage III Occurring from January to February, this stage is marked by a rapid increase in oocyte size and detachment from the mesentery as they migrate closer to the polyp cavity (Fig. 4 C). Oocytes at this stage range in color from pink to bright red, with the nucleus migrating towards the periphery, and the cytoplasm becoming more uniform in size and pigmentation. The nuclear membrane begins to form a reticular structure, and oocytes develop thick borders, which is a defining characteristic of this stage. In January, eggs reach 354.26 ± 30.07 µm, increasing to 445.26 ± 33.23 µm in February. Stage IV This stage signifies the maturation of oocytes, occurring in late February and March (oocyte size > 450 µm), with the nucleus and cytoplasm localized at the periphery of the cell (Fig. 4 D). Significant growth in oocyte size was observed during this stage. By March, egg size ranges from 460.14 µm to 735.97 µm. 3.3. Developmental Stages of Spermaries Table 2 Spermary size across developmental stages Month Mean ± S.D. (µm) Range (µm) Stage August 16 69.38 ± 12.56 50.56–87.10 I September 20 141.56 ± 15.65 94.91–174.67 I October 26 149.25 ± 5.24 142.22–159.25 II November 29 184.59 ± 29.17 120.43–221.20 II December 27 195.49 ± 11.98 169.29–214.22 II January 24 222.41 ± 29.69 157.68–274.01 III February 22 219.98 ± 31.81 122.21–266.03 III March 27 229.09 ± 18.77 186.93–263.62 IV April 22 21.48 ± 1.11 18.42–25.01 I May 22 17.13 ± 1.89 14.15–21.13 I June 17 18.84 ± 3.17 12.77–25.24 I July 19 50.38 ± 4.44 44.45–58.68 I From April to August, spermatozoa cannot be observed with the naked eye. In September, stereomicroscopic observations show that the newly formed spermatozoa of Sarcophyton serenityi are spherical, translucent, and creamy white. As they approach maturity, the spermaries take on an oval shape and are extremely small, making them unmeasurable under a stereomicroscope. Their sizes were determined by histological analysis, as presented in Table 2 . The development of spermaries is divided into four stages, as illustrated in Fig. 6 . The study results indicated that stage I spermary persisted from April to August, stage II from September to December, stage III from January to February, and stage IV from February to March. Stage I (April to August) The development of spermaries begins with clusters of developing spermatogonia. At this stage, spermaries are very small, averaging 17.13 ± 1.89 µm in May, with a slow increase in size to 18.84 ± 3.17 µm in June. However, spermary size begins to grow rapidly from July, reaching an average of 50.38 ± 4.44 µm in July, 69.38 ± 12.56 µm in August, and eventually 141.56 ± 15.65 µm in September (Fig. 5 A). Stage II (September to December) (Fig. 5 B), spermatogonia remain connected to the mesentery, and spermary size continues to increase, reaching 149.25 ± 5.24 µm in October, 184.59 ± 29.17 µm in November, and 195.49 ± 11.98 µm in December. Stage III (January to February) is characterized by the concentration of sperm at the periphery of the spermaries, giving them a hollow appearance at the center. The size of spermaries during this stage reaches 222.41 ± 29.69 µm in January and 219.98 ± 31.81 µm in February (Fig. 5 C). Stage IV Spermary size ranged from 182.42 to 295.00 µm, with an average of 229.09 ± 18.77 µm in February and 241.48 ± 21.11 µm in March (Fig. 5 D). In contrast, sperm in samples collected in April and May 2024 measured only 14.15 to 25.01 µm, suggesting that spawning activity in this species occurs in March. 3.4. Maturity Rate and Reproductive Seasonality The analysis results indicated that the proportion of eggs larger than 450 µm (Eggs larger than 450 µm in size range from pink to bright red, with the iron coloration clearly visible to the naked eye) gradually increased over the months. Specifically, in January 2024, 100% of the eggs measured less than 450 µm in diameter. By February 2024, only 4% of the eggs reached sizes exceeding 450 µm. However, a significant increase in egg size was observed in March 2024, with 100% of the eggs being large, peaking from March 20 to March 27, 2024. Subsequently, no large eggs were recorded in the following months through the end of the year, while smaller eggs continued to appear consistently throughout the study period (Figs. 6 , 7 ) Observations during the sampling period revealed the continuous presence of eggs of varying sizes. Analysis of changes in egg diameter in S. serenei from August 2023 to July 2024 showed that in January, all eggs measured less than 450 µm. By March 17, this proportion had decreased to approximately 21%. From March onwards, egg size increased significantly, with 79% of eggs exceeding 450 µm in diameter, and 100% of eggs measuring larger than 450 µm from March 23 to March 27, 2024 (3 days after full moon). Subsequently, the proportion of large eggs declined, indicating the initiation of a new egg development cycle. Observations from April onwards did not record the presence of large eggs within the oocytes, confirming that S. serenei exhibits synchronized reproduction with a single annual spawning event. 3.5. Fecundity of Sarcophyton serenei In Nha Trang Bay, the fecundity of S. serenei at maturity ranged from 14 to 26 eggs per polyp, with an average of 18.11 ± 3.38 eggs per polyp (Fig. 9 ). 4. Discussion The findings on the sexual reproduction of several species within the soft coral genus Sarcophyton are summarized in Table 3 . The results indicate that the reproductive biology of Sarcophyton serenei generally aligns with other species of the same genus. However, notable differences emerged when comparing specific characteristics across species. These variations are consistent with natural biological principles, reflecting the unique biological traits of each species and their adaptations to particular environmental conditions. Table 3 An overview of reproductive biology in Sarcophyton Species Sex Ratio Mature Egg Diameter (µm) Spawning Season References S. crassocaule 1.3:1 915 4–6 Chou ( 2002 ) S. ehrenbergi - 710 10–11 Alino and Coll ( 1989 ) S. glaucum - 600 10–11 Alino and Coll ( 1989 ) S. glaucum 1:1 500–650 7 Benayahu and Loya (1986) S. glaucum 1:1 800 2–3 Schleyer et al. ( 2004 ) S. glaucum 1:1 400–450 12 − 1 Mohammed et al. ( 2016 ) S. elegans 1.3:1 450–620 9–10 Hellström et al. ( 2010 ) S. auritium - 621–689 7 Mandelberg-Aharon and Benayahu ( 2015 ) S. trocheliphorum - 763 - Chou ( 2002 ) Sarcophyton sp. - 600 10–11 Babcock ( 1986 ) S. serenei 1.3:1 450–736 3 This study Our study revealed that the soft coral Sarcophyton serenei is a gonochoric species, reflecting the general reproductive trend observed within the genus Sarcophyton , such as S. auritum (Mandelberg-Aharon and Benayahu 2015 ) and S. glaucum (Benayahu and Loya 1986; Mohammed et al. 2016 ). However, findings by Schleyer et al. ( 2004 ) from KwaZulu-Natal, South Africa, from September 1991 to November 1994, demonstrated that among 276 colonies of S. glaucum at an average depth of 15 m, 134 colonies were female, 96 male, 25 hermaphroditic (containing both oocytes and spermatocytes within polyps), and 21 colonies of indeterminate sex. These differences may be attributed to geographical factors. The sex of S. serenei cannot be determined through colony coloration, external morphology, or size but must be identified through anatomical dissection, stereomicroscopic examination, or histological analysis. The natural sex ratio of S. serenei in the studied area deviates from the theoretical 1:1 ratio, being approximately 1.3:1. This result is consistent with findings for S. crassocaule (Chou 2002 ) and S. elegans (Hellström et al. 2010 ), where both species exhibited a male-to-female ratio of 1.3:1. However, some studies within the Sarcophyton genus have reported a balanced 1:1 sex ratio. For instance, Hellström et al. ( 2010 ) reported a 1:1 sex ratio for Sarcophyton elegans , based on the analysis of 334 colonies (121 female colonies, 162 male colonies, and 51 colonies of undetermined sex). For Sarcophyton glaucum , the study by Benayahu and Loya (1986) indicated that the sex ratio did not significantly deviate from the theoretical 1:1 ratio. Their analysis of 267 colonies at depths of 3–5 m revealed 141 female colonies and 126 male colonies, while at depths of 27–30 m, they observed 136 female colonies and 107 male colonies. Morphological and histological analyses of the ovaries in this study indicated that mature oocytes of Sarcophyton serenei were distinctly observed from February to March, particularly between March 23 and March 27 (corresponding to the 14th to 18th day of the lunar calendar). This period represents the maturation phase, during which the coral is capable of reproduction. These findings suggest that S. serenei exhibits synchronized reproduction with an annual reproductive cycle, which is consistent with previous studies on the reproductive patterns of several Sarcophyton species, such as S. crassocaule , S. ehrenbergi , S. glaucum , S. elegans , and S. auritum (Table 3 ). Research on S. glaucum has documented reproductive activity during the period between the full moon and new moon in March, marked by the release of mature sperm sacs and oocytes (Schleyer et al. 2004 ). However, the spawning season for this species extends from August to February of the following year (Hellström et al. 2010 ). For S. auritum , reproduction occurs during the full moon in July (Mandelberg-Aharon and Benayahu 2015 ). Although oocytes of varying sizes are present throughout the year, the development of large oocytes accelerates significantly from January (416.0 ± 23.0 µm) to June (621.0 ± 39.0 µm). By July and August, the number of large oocytes decreases and they are absent by October. Smaller oocytes continued to appear throughout the study period, indicating continuous oocyte development. The significant increased in sperm sac diameter from January to June also indicated that reproduction occurs prior to July. In October, small sperm sacs with an average diameter of 43.0 ± 5.0 µm began to appear, increasing to 338.0 ± 44.0 µm by June. Spawning was observed in July, and by August, sperm sacs were no longer present in the polyps. These findings indicate that the oocyte size of Sarcophyton serenei at maturity is comparable to that of mature oocytes in Sarcophyton sp. (600 µm) and S. glaucum (500–650 µm), as previously reported in other studies (Babcock 1986 ; Benayahu and Loya 1986; Alino and Coll 1989 ). However, the oocyte size was smaller than that of other species in the genus Sarcophyton , such as S. crassocaule (915 µm), S. ehrenbergi (710 µm), and S. trocheliphorum (763 µm) (Benayahu et al. 1990 ; Chou 2002 ). Additionally, some studies have documented that mature oocytes of S. elegans (Hellström et al. 2010 )d glaucum (Mohammed et al. 2016 ) are smaller than those of S. serenei . While larger oocyte size may require a longer developmental period, no clear correlation has been established between oocyte size and oogenesis duration in corals. Research suggests that the development of large oocytes is associated with synchronization in gamete maturation and high reproductive potential, rather than an extended oogenesis cycle (Benayahu and Loya 1983 ; Benayahu and Loya 1986). Larger oocytes may facilitate more efficient fertilization due to their higher lipid reserves, which provide energy for larvae until they acquire zooxanthellae (Jones and Berkelmans 2011 ). This significantly influences larval development, survival rates, and the resilience of coral populations in natural environments (Levitan 2000 ). The timing of oocyte development in Sarcophyton serenei observed in this study differs from that recorded for S. elegans at Lizard Island, Great Barrier Reef (Hellström et al. 2010 ). Specifically, stage I oocytes of S. elegans are present from February to July, stage II oocytes from April to November, and stage III oocytes are present throughout the year. Stage IV oocytes are observed in polyps at the colony periphery just before the full moon in August and September. They are subsequently found in polyps closer to the colony center in the following months, but disappear by February of the following year (Hellström et al. 2010 ). Research on S. elegans has also shows that stage I and II spermatocytes appear in February and March, respectively. Sperm size gradually increases until August, reaching stage III, and continues developing to stage IV in August and September (Hellström et al. 2010 ). Differences in the timing of oocyte development and the presence of specific stages across different coral species may be attributed to variations in habitat adaptation, climatic conditions, and hydrological factors specific to different locations. Polyp fecundity, defined as the number of eggs produced per polyp, serves as a key indicator of reproductive output in soft corals (Jamodiong and Reimer 2023 ). Studies have shown that the fecundity of Sarcophyton serenei is lower than that of Sarcophyton glaucum . Specifically, S. glaucum has been reported to produce between 25 and 35 oocytes per polyp (Benayahu and Loya 1986). In contrast, S. serenei exhibits significantly higher fecundity compared to Lobophytum schoedei , which has an average fecundity of only 6.7 ± 3.9 oocytes per polyp (Baran and Baria-Rodriguez 2021 ). Additionally, research on Sclerophytum cf. heterospiculatum in the Japanese Sea indicates substantial variation in polyp fecundity, ranging from 1 to 25 oocytes per polyp (Jamodiong and Reimer 2023 ). Brazeau and Lasker ( 1989 ) proposed that reduced egg production in certain octocoral species may result from spatial constraints within the polyps, potentially due to their rigid and less flexible body structures. Overall, polyp fecundity in soft corals tends to be higher than in scleractinian corals, possibly due to the absence of a rigid skeleton, which provides more space for gamete development (Kahng et al. 2011 ). In summary, the reproductive biological characteristics of the soft coral Sarcophyton serenei in the waters of Nha Trang are as follows: S. serenei is a gonochoric species, with its reproductive season occurring annually in March (3 days after full moon). The natural male-to-female sex ratio is 1.3:1. The ovaries and testes of the soft coral S. serenei undergo four distinct stages of development. The average size of mature oocytes is 684.99 ± 28.50 µm, ranging from 631.89 to 735.97 µm. The fecundity of this species varies significantly, with each polyp containing 14 to 26 oocytes, with an average of 18.11 ± 3.63 eggs per polyp. The average size of sperm sacs is 235.29 ± 8.76 µm, with a range from 182.42 to 295.00 µm. The results of this study provide a foundation for further research on sexual reproduction and the development of soft coral aquaculture techniques in Vietnam, contributing to conservation efforts, pharmaceutical resource supply, and the marine ornamental trade. In addition, these findings offer valuable scientific data to support management strategies aimed at regulating the exploitation of this coral species, particularly by avoiding harvesting during its natural breeding season, which occurs in March each year. Declarations Acknowledgements The article utilizes data from the 2023 to 2024 museum mission of the Marine Organism Cultivation Engineering Department. We sincerely thank the Institute of Oceanography, Vietnam Academy of Science and Technology, for providing funding and facilities to support the completion of this research. In addition, this study is a part of the doctoral thesis of PhD student Ho Son Lam. Conflict of Interest: The authors declare that they have no conflict of interest. Ethical approval: All applicable international, national, and/or institutional guidelines for animal testing, animal care and use of animals were followed by the authors. Sampling and field studies: All necessary permits for sampling and observational field studies have been obtained by the authors from the competent authorities and are mentioned in the acknowledgements, if applicable. The study is compliant with CBD and Nagoya protocols. Authors’ Contribution Conceptualization: Ho Son Lam, Hoang-Xuan Ben, Dao-Viet Ha, Do-Huu Hoang; Experimental prodeduce and husbandry: Nguyen-Thi Nguyet Hue, Dang-Tran Tu Tram, Nguyen Truong Tan Tai, Phan Kim Hoang; Data and sample collection: Nguyen-Thi Nguyet Hue, Nguyen Truong Tan Tai, Phan Kim Hoang, Dang-Tran Tu Tram, Ho Son Lam; Writing - original draft preparation: Ho Son Lam, Hoang-Xuan Ben, Dao-Viet Ha, Do-Huu Hoang. References Alino PM, Coll JC (1989) Observations of the synchronized mass spawning and post settlement activity of octocorals on the Great Barrier Reef, Australia: biological aspects. Bulletin of Marine Science 45: 697-707. Babcock RC (1986) A comparison of the population ecology of reef flat corals of the family Faviidae (Goniastrea, Platygyra), James Cook University. Baran CC, Baria‐Rodriguez MV (2021) Sexual reproduction in the soft coral Lobophytum schoedei in Bolinao‐Anda Reef Complex, Pangasinan, northwestern Philippines. Invertebrate Biology 140: e12316. Barbosa TM, Gomes PB, Bergeron A-S, Santos AM, Chagas C, Freitas EM, Perez CD (2014) Comparisons of sexual reproduction in Carijoa riisei (Cnidaria, Alcyonacea) in South Atlantic, Caribbean, and Pacific areas. Hydrobiologia 734: 201-212. Benayahu Y, Loya Y (1983) Surface brooding in the Red Sea soft coral Parerythropodium fulvum fulvum (Forskal, 1775). The Biological Bulletin 165: 353-369. Benayahu Y, Loya Y (1986) Sexual reproduction of a soft coral: synchronous and brief annual spawning of Sarcophyton glaucum (Quoy & Gaimard, 1833). The Biological Bulletin 170: 32-42. Benayahu Y, Weil D, Kleinman M (1990) Radiation of broadcasting and brooding patterns in coral reef alcyonaceans. Advances in invertebrate reproduction 5: 323-328. Brazeau DA, Lasker HR (1989) The reproductive cycle and spawning in a Caribbean gorgonian. The Biological Bulletin 176: 1-7. Burke L, Selig E, Spalding M (2002) Reefs at Risk in Southeast Asia (UK: World Resources Institute, United Nations Environment Program-World Conservation Monitoring Centre, World Fish Centre, dan International Coral Reef Action Network) p 40. Chou Y (2002) Sexual reproduction of three alcyonacean species in southern Taiwan, MSc thesis, National Taiwan University. Dautova T, Savinkin O (2013a) Octocorallia: Alcyoniidae. Benthic fauna of the Bay of Nha Trang, Southern Vietnam (Vol. 3). Moscow, KMK. Dautova TN (2011) Biodiversity of soft corals alcyoniidae (cnidaria: octocorallia) and their taxonomy problem. Coastal Marine Biodiversity and Bioresources of Vietnam and adjacent areas to the South China Sea: 28. Dautova TN, Savinkin OV (2013b) Benthic fauna of the bay of Nha Trang: Southern Vietnam - Volume 3: Octocorallia: Alcyoniidae. Moscow, KMK, 271 pp. Ellis S, Sharron L (1999) The Culture of Soft Corals (Order: Alcyonacea) for the Marine Aquarium Trade. Publication No. 137. Center for Tropical and Subtropical Aquaculture, Waimanalo, Hawaii. Fabricius K, Alderslade P (2001) Soft corals and sea fans: a comprehensive guide to the tropical shallow water genera of the central-west Pacific, the Indian Ocean and the Red Sea. Australian Institute of Marine Science: Townsville. ISBN 0-642-32210-4. VIII, 264 pp. Fan TY, Chou YH, Dai CF (2005) Sexual reproduction of the alcyonacean coral Lobophytum pauciflorum in southern Taiwan. Bulletin of Marine Science 76: 143-154. Fowler J, Cohen L, Jarvis P (2013) Practical statistics for field biology . John Wiley & Sons. Glynn P, Gassman N, Eakin C, Cortes J, Smith D, Guzman H (1991) Reef coral reproduction in the eastern Pacific: Costa Rica, Panama, and Galapagos Islands (Ecuador) I. Pocilloporidae. Marine Biology 109: 355-368. Hellström M, Kavanagh KD, Benzie JA (2010) Multiple spawning events and sexual reproduction in the octocoral Sarcophyton elegans (Cnidaria: Alcyonacea) on Lizard Island, Great Barrier Reef. Marine Biology 157: 383-392. Hoang XB, Thai MQ, Minh-Thu P, Pham XK, Tung NN, Dao HV (2022) Antipredator Defenses in Soft Corals of the Genus Sarcophyton (Octocorallia; Alcyoniidae) from Coastal Waters of Central Vietnam. Russian Journal of Marine Biology 48: 122-128. Hwang S-J, Song J-I (2007) Reproductive biology and larval development of the temperate soft coral Dendronephthya gigantea (Alcyonacea: Nephtheidae). Marine Biology 152: 273-284. Ibrahim MA, Abdelrahman AH, Atia MA, Mohamed TA, Moustafa MF, Hakami AR, Khalifa SA, Alhumaydhi FA, Alrumaihi F, Abidi SH (2021) Blue biotechnology: computational screening of sarcophyton cembranoid diterpenes for SARS-CoV-2 main protease inhibition. Marine Drugs 19: 391. Jamodiong EA, Reimer JD (2023) Reproductive characteristics and gamete development of the soft coral Sclerophytum cf. heterospiculatum in Okinawa Island, Japan. Invertebrate Biology 142: e12404. Jones AM, Berkelmans R (2011) Tradeoffs to thermal acclimation: Energetics and reproduction of a reef coral with heat tolerant Symbiodinium type‐D. Journal of Marine Sciences 2011: 12. Kahng SE, Benayahu Y, Lasker HR (2011) Sexual reproduction in octocorals. Marine Ecology Progress Series 443: 265-283. Leal MC, Sheridan C, Osinga R, Dionísio G, Rocha RJM, Silva B, Rosa R, Calado R (2014) Marine Microorganism-Invertebrate Assemblages: Perspectives to Solve the “Supply Problem” in the Initial Steps of Drug Discovery. Marine Drugs 12: 3929-3952. Levitan DR (2000) Optimal egg size in marine invertebrates: theory and phylogenetic analysis of the critical relationship between egg size and development time in echinoids. The American Naturalist 156: 175-192. Mandelberg-Aharon Y, Benayahu Y (2015) Reproductive features of the Red Sea octocoral Sarcophyton auritum Verseveldt & Benayahu, 1978 are uniform within generic boundaries across wide biogeographical regions. Hydrobiologia 759: 119-132. McFadden C, Cordeiro R, Samimi-Namin K, Williams G, van Ofwegen L (2025) World List of Octocorallia. Sarcophyton Lesson, 1834. World Register of Marine Species https://www.marinespecies.org/aphia.php?p=taxdetails&id=205483 on the day 2025-02-18. McFadden CS, Van Ofwegen LP, Quattrini AM (2022) Revisionary systematics of Octocorallia (Cnidaria: Anthozoa) guided by phylogenomics. Bulletin of the Society of Systematic Biologists 1. Mohammed TA, Ali A-HA, El-Komi MM, El-Arab MAE, Shoukr FA (2016) Growth Rate Assessment of Alcyonacean Sarcophyton glaucum from Northern Hurghada, Red Sea, Egypt. Natural Resources 7: 384-398. Rhyne A, Rotjan R, Bruckner A, Tlusty M (2009) Crawling to collapse: ecologically unsound ornamental invertebrate fisheries. PLoS One 4: e8413. Rocha RJM, Bontas B, Cartaxana P, Leal MC, Ferreira JM, Rosa R, Serôdio J, Calado R (2015) Development of a Standardized Modular System for Experimental Coral Culture. Journal of the World Aquaculture Society 46: 235-251. Schleyer MH, Kruger A, Benayahu Y (2004) Reproduction and the unusual condition of hermaphroditism in Sarcophyton glaucum (Octocorallia, Alcyoniidae) in KwaZulu-Natal, South Africa. Hydrobiologia 530: 399-409. Tixier-Durivault A (1958) Révision de la famille des Alcyoniidae: les genres Sarcophytum et Lobophytum . Zoologische Verhandelingen 36: 1-179. Tlusty M (2002) The benefits and risks of aquacultural production for the aquarium trade. Aquaculture 205: 203-219. Tuan VS, Ho SL, Phan KH, Dang TTT, Harrison PL (2022) Varied spawning patterns of reef corals in Nha Trang Bay, Vietnam, western South China Sea. Regional Studies in Marine Science 55: 102631. Verseveldt J (1982) A revision of the genus Sarcophyton Lesson (Octocorallia, Alcyonacea). Zoologische Verhandelingen 192: 1-91. Vicentuan K (2009) Effects of fragmentation and transplantation on reproduction in Acropora muricata and Hydnophora rigida , University of the Philippines. Wabnitz C (2003) From ocean to aquarium: the global trade in marine ornamental species. UNEP/Earthprint. Wilkens P, Birkholz J (1992) Marine Invertebrates: Organ-Pipe and Leather Corals. Gorgonians, Craft Druck und Verlag GmbH, Ettlingen, Germany. Yan X, Liu J, Huang J, Wang Y, Leng X, Li T, Ouyang H, Yan X, He S (2022) Bistrochelides H−L: Biscembranoids from the south China sea soft coral Sarcophyton serenei . Phytochemistry 204: 113438. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7190639","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":498578943,"identity":"df74b3d3-a98f-4ed9-a864-abad48d6b04b","order_by":0,"name":"Lam Son Ho","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAw0lEQVRIiWNgGAWjYBACAwbmBhAtByIOPCBOCyNIi4ExWEsCKVoSwXYRpcWc/2Djpxtlf9Lnhx1+CLTFTk63gYAWyxmJzdI55wxyN95OMwBqSTY2O0DIYTcYG6Rz24BaZieAtBxI3EZQy/mDzb+BWtINZ6d/IFLLgcQ2kC0J8tI5xNpyI7HNOuecseEG6ZyCAwkGxPjl/OHDt3PK5OTlZ6dv/vChwk6OoBYIYAO5EGwCUcqhWuQbiFY9CkbBKBgFIw0AAASCSKg1W+rwAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0009-0001-2618-8203","institution":"VAST: Vietnam Academy of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Lam","middleName":"Son","lastName":"Ho","suffix":""},{"id":498578944,"identity":"b4fad5d4-9dbd-4c3b-8d1f-2434f786f76c","order_by":1,"name":"Dang-Tran Tu Tram","email":"","orcid":"","institution":"VAST: Vietnam Academy of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Dang-Tran","middleName":"Tu","lastName":"Tram","suffix":""},{"id":498578945,"identity":"98c3b503-ea3f-4d8d-bd6a-644cc7ba8ea5","order_by":2,"name":"Nguyen-Thi Nguyet Hue","email":"","orcid":"","institution":"VAST: Vietnam Academy of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Nguyen-Thi","middleName":"Nguyet","lastName":"Hue","suffix":""},{"id":498578946,"identity":"e77051bf-d25d-4576-8ca0-7743565a3496","order_by":3,"name":"Nguyen Truong Tan Tai","email":"","orcid":"","institution":"VAST: Vietnam Academy of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Nguyen","middleName":"Truong Tan","lastName":"Tai","suffix":""},{"id":498578947,"identity":"8bb393a4-4e10-41e6-8767-62596f494348","order_by":4,"name":"Phan Kim Hoang","email":"","orcid":"","institution":"VAST: Vietnam Academy of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Phan","middleName":"Kim","lastName":"Hoang","suffix":""},{"id":498578948,"identity":"848ed80c-92c0-440f-85af-2f7437ec0590","order_by":5,"name":"Hoang-Xuan Ben","email":"","orcid":"","institution":"VAST: Vietnam Academy of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Hoang-Xuan","middleName":"","lastName":"Ben","suffix":""},{"id":498578949,"identity":"b0b20769-500d-4aee-b1af-16010f331db5","order_by":6,"name":"Dao-Viet Ha","email":"","orcid":"","institution":"VAST: Vietnam Academy of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Dao-Viet","middleName":"","lastName":"Ha","suffix":""},{"id":498578950,"identity":"5a47a3f9-a841-472b-aab9-3fdebef4980f","order_by":7,"name":"Do-Huu Hoang","email":"","orcid":"","institution":"VAST: Vietnam Academy of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Do-Huu","middleName":"","lastName":"Hoang","suffix":""}],"badges":[],"createdAt":"2025-07-22 22:44:43","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7190639/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7190639/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":89385998,"identity":"01bc8f5a-4e4f-47c1-9fbf-290328a9d810","added_by":"auto","created_at":"2025-08-19 12:33:18","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":720879,"visible":true,"origin":"","legend":"\u003cp\u003eThe soft coral \u003cem\u003eSarcophyton serenei\u003c/em\u003e (A) and the coenenchymal sclerites in its stalk, which exhibit distinct tubercles as observed under scanning electron microscopy (SEM) (B).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7190639/v1/77fa835c8c5d95f645e36ad9.png"},{"id":89389623,"identity":"3d605cc7-b5e0-4939-b1ff-1cb6337125d4","added_by":"auto","created_at":"2025-08-19 12:49:18","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":319958,"visible":true,"origin":"","legend":"\u003cp\u003eMap of Survey and Sampling Locations in Nha Trang Bay, Viet Nam\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7190639/v1/96e201e85886be06da6c1e8b.png"},{"id":89384377,"identity":"fd6c9909-7cfb-40aa-9438-3af75edf695c","added_by":"auto","created_at":"2025-08-19 12:25:18","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":963036,"visible":true,"origin":"","legend":"\u003cp\u003eEggs of \u003cem\u003eSarcophyton serenei\u003c/em\u003e observed under a stereomicroscope\u003c/p\u003e\n\u003cp\u003e(A. Stage I eggs; B. Stage II eggs; C. Stage III eggs; C. Stage IV eggs)\u003c/p\u003e\n\u003cp\u003e(A: Stage I - The nucleus and cytoplasm are indistinct within the mesentery; B: Stage II - The nucleus is centrally located within the oocyte; C: Stage III - The nucleus migrates to the periphery and detaches from the mesentery; D: Stage IV - The oocyte undergoes rapid growth. Scale bar: 200 µm. O1, Stage I; O2, Stage II; O3, Stage III; O4, Stage IV; f (follicle layer); m (mesentery); n (nucleus); nc (nucleolus); p (pedicle).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7190639/v1/e77b5144f28981887e64efc6.png"},{"id":89384383,"identity":"6e93be8f-1936-4862-ac9a-a0ab7a4bb658","added_by":"auto","created_at":"2025-08-19 12:25:18","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1435575,"visible":true,"origin":"","legend":"\u003cp\u003eFour developmental stages of oocytes in the soft coral \u003cem\u003eSarcophyton serenei\u003c/em\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7190639/v1/143fb81b9a148601e40bb87d.png"},{"id":89385999,"identity":"91b8d0e9-7a38-4e9c-812b-5e948e484b2a","added_by":"auto","created_at":"2025-08-19 12:33:18","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1770983,"visible":true,"origin":"","legend":"\u003cp\u003eDevelopmental stages of spermaries in the soft coral \u003cem\u003eSarcophyton serenei\u003c/em\u003e (×20 magnification).\u003c/p\u003e\n\u003cp\u003e(A: Stage I (S1), B: Stage II – Sperm completely filling the spermary (S2), C: Stage III – Sperm migrate to the periphery (S3), leaving a hollow space within the spermary, D: Stage IV – Sperm enlarge (S4)).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStage IV:\u003c/strong\u003e Spermary size ranged from 182.42 to 295.00 µm, with an average of 229.09 ± 18.77 µm in February and 241.48 ± 21.11 µm in March (Figure 5D). In contrast, sperm in samples collected in April and May 2024 measured only 14.15 to 25.01 µm, suggesting that spawning activity in this species occurs in March.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7190639/v1/f31f0783947f20b774237d71.png"},{"id":89384389,"identity":"91facded-4266-4bb8-a844-fc3f1deea5db","added_by":"auto","created_at":"2025-08-19 12:25:18","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":55465,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eProportion of egg sizes in \u003c/strong\u003e\u003cem\u003eSarcophyton serenei (\u003c/em\u003efrom August 2023 to July 2024\u003cem\u003e)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7190639/v1/6e3782d30829b8473ad49114.png"},{"id":89388304,"identity":"bf84780e-7c38-45f2-8259-98fc0521cbf0","added_by":"auto","created_at":"2025-08-19 12:41:18","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":48725,"visible":true,"origin":"","legend":"\u003cp\u003eVariation in egg size of \u003cem\u003eSarcophyton serenei\u003c/em\u003e from August 2023 to July 2024.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7190639/v1/d4f9375f2970409695adbfd3.png"},{"id":89384387,"identity":"5aa26c2c-bd4e-4431-925a-b94825805e62","added_by":"auto","created_at":"2025-08-19 12:25:18","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":772175,"visible":true,"origin":"","legend":"\u003cp\u003eNumber of eggs within the polyp.\u003c/p\u003e\n\u003cp\u003e(A: Eggs collected on March 17, 2023 B: Eggs collected on March 27, 2024.)\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-7190639/v1/7bf3a986e0df0e6a6f30d868.png"},{"id":98431917,"identity":"a0bc6e0a-4561-4f74-8f3b-ea4d28248571","added_by":"auto","created_at":"2025-12-17 16:48:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":8493492,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7190639/v1/283be032-4afa-47e8-ae1c-a5e4b1c58840.pdf"}],"financialInterests":"","formattedTitle":"Reproductive biology of soft coral Sarcophyton serenei Tixier-Durivault, 1958 in Nha Trang Bay, Khanh Hoa province, Viet Nam","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eSoft corals (Order Malacalcyonacea) are a prominent group of benthic organisms in Indo-Pacific coral reefs, ranking second only to hard corals and constituting the largest proportion of the class Octocorallia (McFadden et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). These species are mainly distributed from tropical to temperate regions, playing an important role in the biodiversity and ecological functioning of coral reefs. Members of this order are characterized by having either a largely proteinaceous skeletal axis or no skeletal axis at all (McFadden et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eSoft corals play a vital ecological role in tropical reef ecosystems by enhancing biodiversity and providing essential habitat structures. Their broad distribution encompasses all marine environments globally (McFadden et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), with notable abundance in regions such as the Indian Ocean, the Red Sea, and the Western Pacific (Fabricius and Alderslade \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). This widespread presence is largely attributed to their exceptional adaptability, which allows them to colonize environments where hard corals are often limited, particularly in turbid or marginal conditions (Wilkens and Birkholz \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Ellis and Sharron \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1999\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eTo date, over 3,500 nominal species of soft corals, classified into 79 families, have been identified (McFadden et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Among these, the genus \u003cem\u003eSarcophyton\u003c/em\u003e is particularly diverse, comprising approximately 80 recognized species (McFadden et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). \u003cem\u003eSarcophyton serenei\u003c/em\u003e, for instance, has been documented in several locations, including Nha Trang Bay and Ly Son (Viet Nam), as well as the Gulf of Suez (Tixier-Durivault \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1958\u003c/span\u003e; Verseveldt \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1982\u003c/span\u003e; Dautova \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Dautova and Savinkin \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2013b\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn addition to their ecological significance, soft corals possess high ornamental and economic value. Their vivid coloration and resilience make them desirable in the marine aquarium trade. However, increasing market demand has led to unsustainable harvesting from wild populations. It is estimated that around 390,000 soft coral specimens, representing about 61 species, are collected annually for the aquarium industry, with popular genera including \u003cem\u003eSarcophyton\u003c/em\u003e, \u003cem\u003eSclerophytum\u003c/em\u003e, \u003cem\u003eDendronephthya\u003c/em\u003e, and \u003cem\u003eNephthea\u003c/em\u003e (Wabnitz \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2003\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eDespite their adaptability, soft corals are not immune to environmental stressors. Similar to hard corals, they are vulnerable to the impacts of climate change and anthropogenic disturbances such as pollution, overfishing, chemical runoff, oil spills, ship groundings, tourism, and coral extraction (Burke et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). These pressures have contributed to notable population declines, with cascading effects on reef biodiversity and ecosystem stability (Rocha et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn response to these challenges, research efforts have increasingly focused on developing sustainable approaches for soft coral reproduction and aquaculture. Advancements in this area are essential for both reducing pressure on natural populations and supporting reef restoration initiatives (Tlusty \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Rhyne et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2009\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eSoft corals also hold substantial economic value in the aquarium trade; however, overexploitation has led to population decline, threatening biodiversity (Wabnitz \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Rocha et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Soft coral aquaculture has emerged as a critical solution for reducing natural harvesting and supporting reef restoration efforts (Leal et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Several compounds derived from \u003cem\u003eSarcophyton\u003c/em\u003e have demonstrated antiviral activity against SARS-CoV-2 (Ibrahim et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) and antibacterial effects against \u003cem\u003eVibrio harveyi\u003c/em\u003e (Yan et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Among soft corals, \u003cem\u003eSarcophyton serenei\u003c/em\u003e exhibits resistance to predation (Hoang et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), highlighting its adaptability and potential for research and restoration initiatives.\u003c/p\u003e\u003cp\u003eStudies on soft coral reproduction have identified three primary reproductive modes in octocorals: broadcast spawning, external brooding, internal brooding (Alino and Coll \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Kahng et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Jamodiong and Reimer \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) and semi-brooding ((Alino and Coll \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Kahng et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Jamodiong and Reimer \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Octocoral sexuality can generally be classified into three categories: hermaphroditism, where both male and female gametes develop within the same polyp or colony; gonochorism, in which male and female colonies are distinct; and a mixed strategy incorporating aspects of both reproductive types (Kahng et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Up to 2011, the majority of examined octocorals exhibited broadcast spawning (49%) and gonochorism (89%) as their predominant reproductive traits (Kahng et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Furthermore, available research suggests that tropical soft coral species tend to reproduce asynchronously without a fixed seasonal pattern, whereas temperate species typically follow periodic reproductive cycles (Kahng et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Barbosa et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Baran and Baria-Rodriguez \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Jamodiong and Reimer \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Reproductive timing in soft corals is correlated with water temperature (Hwang and Song \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Jamodiong and Reimer \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) and lunar cycles (Hwang and Song \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2007\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eResearch on the reproductive biology of soft corals remains limited worldwide. Most studies have focused on populations in the Red Sea and the Great Barrier Reef (Alino and Coll \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Kahng et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), while data from other regions, including the Western Pacific Islands (Baran and Baria-Rodriguez \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), remain scarce. Comprehensive studies on the reproductive biology of soft corals across various species and regions are therefore necessary.\u003c/p\u003e\u003cp\u003eIn Viet Nam, coral reproduction research is still limited, focusing mainly on hard corals and preliminary studies within international collaborative projects (Tuan et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). There have been no published studies on the sexual reproduction of soft corals, particularly \u003cem\u003eS. serenei\u003c/em\u003e. Addressing this gap, this research aims to determine the sex ratio, spawning season, gamete sizes, and fecundity of \u003cem\u003eS. serenei\u003c/em\u003e in Viet Nam. The results of this study provide essential baseline data for future research on the artificial reproduction of this coral species. Such efforts may contribute to a sustainable source of raw materials for the extraction of biologically active compounds, the development of marine ornamental organisms, and the conservation of this species.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Species Identification\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eThe identification of \u003cem\u003eSarcophyton serenei\u003c/em\u003e, a species of soft coral, follows the taxonomic guidelines established by Tixier-Durivault (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1958\u003c/span\u003e), Verseveldt (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1982\u003c/span\u003e), and Dautova and Savinkin (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2013a\u003c/span\u003e). This species exhibits a yellow-brown to gray-brown coloration (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA). In the central region of the capitulum, the spacing between autozooids ranges from 2 to 4 mm. The autozooids closest to each other are associated with 6 to 8 siphonozooids, while the farthest ones are accompanied by 8 to 10 siphonozooids. At the capitulum margin, the spacing corresponds to 1 to 2 siphonozooids. The polyps reach a height of 4 to 6 mm and do not fully retract. The stalk contains sclerites that are elongated, either straight or curved spindles, measuring up to 1.20 mm in length and 0.28 mm in width, with surfaces covered in small warts (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB).\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Field Sampling\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eSoft coral samples of \u003cem\u003eSarcophyton serenei\u003c/em\u003e were randomly collected at depths of 5\u0026ndash;10 m, spanning the area from Cut Chim Island (12\u0026deg;15'55.9\"N, 109\u0026deg;13'29.3\"E) to Hon Chong Island (12\u0026deg;16'58.3\"N, 109\u0026deg;12'51.3\"E) in Nha Trang Bay (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Sampling locations were selected based on preliminary surveys conducted across Nha Trang Bay, spanning from northern Hon Chong to southern Hon Tre, using SCUBA diving to identify areas with high densities of \u003cem\u003eSarcophyton serenei\u003c/em\u003e.\u003c/p\u003e\u003cp\u003eFixation and Preservation of Samples: Fragments of soft coral, measuring 4 cm in length from the capitulum edge to the center and 8\u0026ndash;10 mm in thickness, were excised from parent colonies in the field. These fragments were rinsed with seawater to remove surface debris and preserved in a 10% formalin solution diluted with seawater for a minimum of 24 hours. The samples were rinsed with distilled water and then transferred to 70% ethanol for long-term storage until further analysis (Fan et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2005\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThese colonies were monitored, and reproductive biological samples were collected monthly during full moons from August 2023 to July 2024. In total, 380 colonies were sampled. Samples measuring approximately 1\u0026ndash;2 cm\u0026sup2; were excised from the center of the capitulum of each colony.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe collected samples were visually assessed in the field once a month (e.g., recording egg coloration). When more than 50% of the eggs in a polyp showed signs of sexual maturity (color transitioning from white to other hues such as pink, orange, or red), sampling frequency was increased every three days. This process continued until no mature eggs (colored eggs) were observed in the polyps.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Techniques for decalcification and histological sectioning\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eSample processing was conducted at the Experimental Station Laboratory of the Marine Organism Culture Engineering Department, Institute of Oceanography. After measuring egg/spermatocyst size, the two coral groups (with sexes classified) were decalcified and processed for histological analysis to verify the initial assessment. The samples were processed following the method described by Fan et al. (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). \u003cem\u003eSarcophyton serenei\u003c/em\u003e samples preserved in 70% ethanol were rinsed with distilled water, decalcified using 8% formic acid, and dehydrated in ethanol baths with gradually increasing concentrations up to 95%.\u003c/p\u003e\u003cp\u003eAfter decalcification, the samples were placed on glass slides and longitudinally sectioned using a scalpel to observe the gonads under a Kruss MSZ 5000-T-IL-TL stereomicroscope (Germany). The presence of oocytes or sperm sacs in the gonads was recorded to distinguish male and female specimens, serving as a reference for histological analysis to ensure accurate results. Samples containing oocytes were photographed using the camera attached to the Kruss MSZ 5000-T-IL-TL stereomicroscope, while sperm sac sizes were measured based on histological images captured using an Olympus CX35 microscope. Histological Preparation of Gonadal Samples: After decalcification and cleaning, coral samples were embedded in Paraplast and cast in paraffin blocks. The sections were then stained with Hematoxylin and Eosin to observe and differentiate the developmental stages of the gonads.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\u003ch2\u003e2.3.1 Determination of Sex and Sex Ratio\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eColonies of the soft coral \u003cem\u003eSarcophyton serenei\u003c/em\u003e were randomly sampled from the collection sites between August 2023 to July 2024. This period was selected because oocytes and sperm could be observed in small sections (approximately 1\u0026ndash;2 cm\u0026sup2;) cut from the polyparia of each colony to examine the presence of sperm and/or eggs. The number of male and female colonies containing sperm and/or oocytes was identified and recorded under a stereo microscope (Kruss MSZ 5000-T-IL-TL, Gernany).\u003c/p\u003e\u003cp\u003eThe sex ratio was calculated using the method described by Fowler et al. (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) as follows:\u003c/p\u003e\u003cp\u003ePercentage of male individuals (%) = (a/c) \u0026times; 100\u003c/p\u003e\u003cp\u003ePercentage of female individuals (%) = (b/c) \u0026times; 100\u003c/p\u003e\u003cp\u003eMale-to-female ratio\u0026thinsp;=\u0026thinsp;a/b\u003c/p\u003e\u003cp\u003eWhere:\u003c/p\u003e\u003cp\u003ea: Number of male individuals\u003c/p\u003e\u003cp\u003eb: Number of female individuals\u003c/p\u003e\u003cp\u003ec: Total number of samples\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section3\"\u003e\u003ch2\u003e2.3.2. Determination of Fecundity and Gonadal Development\u003c/h2\u003e\u003cp\u003eThe field samples were evaluated for fecundity and gamete diameter under a stereo microscope (Kruss MSZ 5000-T-IL-TL, Gernany). The fecundity of \u003cem\u003eS. serenei\u003c/em\u003e was determined by counting the number of mature oocytes per polyp, based on three mature polyps per sample across 30 samples. The diameter of oocytes and sperm sacs (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD) was calculated as the square root of the product of the longest and shortest perpendicular diameters of each oocyte, following Vicentuan (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2009\u003c/span\u003e), and analyzed using ImageJ software. Absolute fecundity was defined as the total number of eggs present in a single polyp at the mature stage. To accurately identify intact polyps, the sample should be thinly sectioned multiple times if necessary. A scalpel and needle are used to carefully separate tissue samples while minimizing damage to the eggs and preventing displacement between polyps. Only polyps containing intact eggs are counted, whereas eggs from adjacent polyps are removed during separation to ensure accurate fecundity estimation.\u003c/p\u003e\u003cp\u003eThe peak spawning period was identified based on the presence of mature gametes and their subsequent absence during successive sampling periods.\u003c/p\u003e\u003cp\u003eHistological slides were observed under an Olympus CX35 (Japan) microscope. The developmental stages of eggs and spermatocysts were described based on their increasing size and the appearance of nuclei, using the four-stage classification system of Glynn et al. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1991\u003c/span\u003e) and Schleyer et al. (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2004\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Data Processing\u003c/h2\u003e\u003cp\u003eAll collected data were processed using Microsoft Excel 2007. The distribution of sex was tested for independence from the theoretical distribution (1:1) using the Chi-square method.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Sex and Male-Female Ratio\u003c/h2\u003e\u003cp\u003eA total of 380 specimens of the soft coral \u003cem\u003eSarcophyton serenei\u003c/em\u003e were randomly collected from the Nha Trang marine area over the course of 19 sampling trips. The aim was to investigate sex distribution and the male-to-female ratio within the population. Histological analysis revealed that the gonads of \u003cem\u003eS. serenei\u003c/em\u003e are located in the posterior half of the mesentery and do not extend to the oral disc or the base of the tentacles. In contrast, siphonozooids were found in association with the gonads.\u003c/p\u003e\u003cp\u003eSexual identification was feasible for all colonies with diameters ranging from 15 to 20 cm. During the study period, 217 male and 163 female colonies were identified. No hermaphroditic or sexually indeterminate colonies were recorded. A Chi-square test was conducted to compare the observed and expected male-to-female ratios. The result yielded a χ\u0026sup2; value of 7.67, which exceeds the critical value of 6.64 (df\u0026thinsp;=\u0026thinsp;1, P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), indicating a statistically significant deviation from a 1:1 sex ratio. The observed male-to-female ratio in this population was approximately 1.3:1.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Developmental Stages of Oocyte\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eOocyte size across developmental stages\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMonth\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;S.D.(\u0026micro;m)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRange (\u0026micro;m)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eStage\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAugust 16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e250.54\u0026thinsp;\u0026plusmn;\u0026thinsp;16.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e214.98\u0026ndash;275.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSeptember 20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e256.90\u0026thinsp;\u0026plusmn;\u0026thinsp;16.73\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e223.36\u0026ndash;278.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOctober 26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e292.57\u0026thinsp;\u0026plusmn;\u0026thinsp;15.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e263.89\u0026ndash;325.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eII\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNovember 29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e335.07\u0026thinsp;\u0026plusmn;\u0026thinsp;22.93\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e280.49\u0026ndash;372.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eII\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDecember 27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e352.70\u0026thinsp;\u0026plusmn;\u0026thinsp;27.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e303.76\u0026ndash;390.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eII\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eJanuary 24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e354.26\u0026thinsp;\u0026plusmn;\u0026thinsp;30.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e290.51\u0026ndash;399.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIII\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFebruary 22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e445.26\u0026thinsp;\u0026plusmn;\u0026thinsp;33.23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e391.79\u0026ndash;501.53\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIII\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMarch 17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e519.99\u0026thinsp;\u0026plusmn;\u0026thinsp;29.90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e460.14\u0026ndash;571.96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIV\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMarch 20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e581.75\u0026thinsp;\u0026plusmn;\u0026thinsp;10.64\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e566.31\u0026ndash;613.71\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIV\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMarch 23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e633.20\u0026thinsp;\u0026plusmn;\u0026thinsp;35.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e556.99\u0026ndash;683.61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIV\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMarch 27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e684.99\u0026thinsp;\u0026plusmn;\u0026thinsp;28.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e631.89\u0026ndash;735.97\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIV\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMarch 30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e158.21\u0026thinsp;\u0026plusmn;\u0026thinsp;4.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e150.07\u0026ndash;168.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eApril 22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e162.80\u0026thinsp;\u0026plusmn;\u0026thinsp;5.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e147.91\u0026ndash;172.84\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMay 22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e171.82\u0026thinsp;\u0026plusmn;\u0026thinsp;5.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e163.55\u0026ndash;184.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eJune 17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e193.27\u0026thinsp;\u0026plusmn;\u0026thinsp;8.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e178.46\u0026ndash;214.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eJuly 19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e205.51\u0026thinsp;\u0026plusmn;\u0026thinsp;12.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e181.20\u0026ndash;230.53\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe oocyte development process in \u003cem\u003eSarcophyton serenei\u003c/em\u003e is categorized into four stages, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, Additionally, egg size is shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Observations in April revealed the presence of small oocytes (ranging from 147.91 to 172.84 \u0026micro;m), suggesting that \u003cem\u003eS. serenei\u003c/em\u003e had reproduced in March.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eStage I\u003c/strong\u003e\u003cp\u003eFrom April to September, newly formed oocytes exhibit a translucent appearance and appear round. At this stage, oocytes primarily consist of the nucleus and cytoplasm, with gonads only observed in the autozooids and attached to the mesentery via pedicles. Although the nucleus and cytoplasm were indistinguishable, oocytes were visible as clusters within the mesentery or interspersed with oocytes at later developmental stages (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA). In April, eggs measure 162.80\u0026thinsp;\u0026plusmn;\u0026thinsp;5.34 \u0026micro;m, increasing to 256.90\u0026thinsp;\u0026plusmn;\u0026thinsp;16.73 \u0026micro;m in September. The study results indicated that stage I oocytes persisted from April to September, stage II from October to December, stage III from January to February, and stage IV from February to March.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eStage II\u003c/strong\u003e\u003cp\u003eFrom October to December, oocytes begin to adopt a round or oval shape and remain attached to the mesentery by pedicles (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB). During this stage, the nucleus and cytoplasm dominate the cell structure, with the nucleus centrally positioned within the oocyte. In October, eggs measure 292.57\u0026thinsp;\u0026plusmn;\u0026thinsp;15.56 \u0026micro;m, increasing to 352.70\u0026thinsp;\u0026plusmn;\u0026thinsp;27.21 \u0026micro;m in December.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eStage III\u003c/strong\u003e\u003cp\u003eOccurring from January to February, this stage is marked by a rapid increase in oocyte size and detachment from the mesentery as they migrate closer to the polyp cavity (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eC). Oocytes at this stage range in color from pink to bright red, with the nucleus migrating towards the periphery, and the cytoplasm becoming more uniform in size and pigmentation. The nuclear membrane begins to form a reticular structure, and oocytes develop thick borders, which is a defining characteristic of this stage. In January, eggs reach 354.26\u0026thinsp;\u0026plusmn;\u0026thinsp;30.07 \u0026micro;m, increasing to 445.26\u0026thinsp;\u0026plusmn;\u0026thinsp;33.23 \u0026micro;m in February.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eStage IV\u003c/strong\u003e\u003cp\u003eThis stage signifies the maturation of oocytes, occurring in late February and March (oocyte size\u0026thinsp;\u0026gt;\u0026thinsp;450 \u0026micro;m), with the nucleus and cytoplasm localized at the periphery of the cell (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eD). Significant growth in oocyte size was observed during this stage. By March, egg size ranges from 460.14 \u0026micro;m to 735.97 \u0026micro;m.\u003c/p\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Developmental Stages of Spermaries\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSpermary size across developmental stages\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMonth\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;S.D. (\u0026micro;m)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRange (\u0026micro;m)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eStage\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAugust 16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e69.38\u0026thinsp;\u0026plusmn;\u0026thinsp;12.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e50.56\u0026ndash;87.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSeptember 20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e141.56\u0026thinsp;\u0026plusmn;\u0026thinsp;15.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e94.91\u0026ndash;174.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOctober 26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e149.25\u0026thinsp;\u0026plusmn;\u0026thinsp;5.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e142.22\u0026ndash;159.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eII\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNovember 29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e184.59\u0026thinsp;\u0026plusmn;\u0026thinsp;29.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e120.43\u0026ndash;221.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eII\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDecember 27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e195.49\u0026thinsp;\u0026plusmn;\u0026thinsp;11.98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e169.29\u0026ndash;214.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eII\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eJanuary 24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e222.41\u0026thinsp;\u0026plusmn;\u0026thinsp;29.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e157.68\u0026ndash;274.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIII\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFebruary 22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e219.98\u0026thinsp;\u0026plusmn;\u0026thinsp;31.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e122.21\u0026ndash;266.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIII\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMarch 27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e229.09\u0026thinsp;\u0026plusmn;\u0026thinsp;18.77\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e186.93\u0026ndash;263.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIV\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eApril 22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e21.48\u0026thinsp;\u0026plusmn;\u0026thinsp;1.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e18.42\u0026ndash;25.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMay 22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e17.13\u0026thinsp;\u0026plusmn;\u0026thinsp;1.89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e14.15\u0026ndash;21.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eJune 17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e18.84\u0026thinsp;\u0026plusmn;\u0026thinsp;3.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e12.77\u0026ndash;25.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eJuly 19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e50.38\u0026thinsp;\u0026plusmn;\u0026thinsp;4.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e44.45\u0026ndash;58.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eFrom April to August, spermatozoa cannot be observed with the naked eye. In September, stereomicroscopic observations show that the newly formed spermatozoa of \u003cem\u003eSarcophyton serenityi\u003c/em\u003e are spherical, translucent, and creamy white. As they approach maturity, the spermaries take on an oval shape and are extremely small, making them unmeasurable under a stereomicroscope. Their sizes were determined by histological analysis, as presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The development of spermaries is divided into four stages, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The study results indicated that stage I spermary persisted from April to August, stage II from September to December, stage III from January to February, and stage IV from February to March.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eStage I\u003c/strong\u003e\u003cp\u003e(April to August) The development of spermaries begins with clusters of developing spermatogonia. At this stage, spermaries are very small, averaging 17.13\u0026thinsp;\u0026plusmn;\u0026thinsp;1.89 \u0026micro;m in May, with a slow increase in size to 18.84\u0026thinsp;\u0026plusmn;\u0026thinsp;3.17 \u0026micro;m in June. However, spermary size begins to grow rapidly from July, reaching an average of 50.38\u0026thinsp;\u0026plusmn;\u0026thinsp;4.44 \u0026micro;m in July, 69.38\u0026thinsp;\u0026plusmn;\u0026thinsp;12.56 \u0026micro;m in August, and eventually 141.56\u0026thinsp;\u0026plusmn;\u0026thinsp;15.65 \u0026micro;m in September (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eA).\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eStage II\u003c/strong\u003e\u003cp\u003e(September to December) (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB), spermatogonia remain connected to the mesentery, and spermary size continues to increase, reaching 149.25\u0026thinsp;\u0026plusmn;\u0026thinsp;5.24 \u0026micro;m in October, 184.59\u0026thinsp;\u0026plusmn;\u0026thinsp;29.17 \u0026micro;m in November, and 195.49\u0026thinsp;\u0026plusmn;\u0026thinsp;11.98 \u0026micro;m in December.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eStage III\u003c/strong\u003e\u003cp\u003e(January to February) is characterized by the concentration of sperm at the periphery of the spermaries, giving them a hollow appearance at the center. The size of spermaries during this stage reaches 222.41\u0026thinsp;\u0026plusmn;\u0026thinsp;29.69 \u0026micro;m in January and 219.98\u0026thinsp;\u0026plusmn;\u0026thinsp;31.81 \u0026micro;m in February (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eC).\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eStage IV\u003c/strong\u003e\u003cp\u003eSpermary size ranged from 182.42 to 295.00 \u0026micro;m, with an average of 229.09\u0026thinsp;\u0026plusmn;\u0026thinsp;18.77 \u0026micro;m in February and 241.48\u0026thinsp;\u0026plusmn;\u0026thinsp;21.11 \u0026micro;m in March (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eD). In contrast, sperm in samples collected in April and May 2024 measured only 14.15 to 25.01 \u0026micro;m, suggesting that spawning activity in this species occurs in March.\u003c/p\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.4. Maturity Rate and Reproductive Seasonality\u003c/h2\u003e\u003cp\u003eThe analysis results indicated that the proportion of eggs larger than 450 \u0026micro;m (Eggs larger than 450 \u0026micro;m in size range from pink to bright red, with the iron coloration clearly visible to the naked eye) gradually increased over the months. Specifically, in January 2024, 100% of the eggs measured less than 450 \u0026micro;m in diameter. By February 2024, only 4% of the eggs reached sizes exceeding 450 \u0026micro;m. However, a significant increase in egg size was observed in March 2024, with 100% of the eggs being large, peaking from March 20 to March 27, 2024. Subsequently, no large eggs were recorded in the following months through the end of the year, while smaller eggs continued to appear consistently throughout the study period (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e)\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eObservations during the sampling period revealed the continuous presence of eggs of varying sizes. Analysis of changes in egg diameter in \u003cem\u003eS. serenei\u003c/em\u003e from August 2023 to July 2024 showed that in January, all eggs measured less than 450 \u0026micro;m. By March 17, this proportion had decreased to approximately 21%. From March onwards, egg size increased significantly, with 79% of eggs exceeding 450 \u0026micro;m in diameter, and 100% of eggs measuring larger than 450 \u0026micro;m from March 23 to March 27, 2024 (3 days after full moon).\u003c/p\u003e\u003cp\u003eSubsequently, the proportion of large eggs declined, indicating the initiation of a new egg development cycle. Observations from April onwards did not record the presence of large eggs within the oocytes, confirming that \u003cem\u003eS. serenei\u003c/em\u003e exhibits synchronized reproduction with a single annual spawning event.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.5. Fecundity of Sarcophyton serenei\u003c/h2\u003e\u003cp\u003eIn Nha Trang Bay, the fecundity of \u003cem\u003eS. serenei\u003c/em\u003e at maturity ranged from 14 to 26 eggs per polyp, with an average of 18.11\u0026thinsp;\u0026plusmn;\u0026thinsp;3.38 eggs per polyp (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e9\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThe findings on the sexual reproduction of several species within the soft coral genus \u003cem\u003eSarcophyton\u003c/em\u003e are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The results indicate that the reproductive biology of \u003cem\u003eSarcophyton serenei\u003c/em\u003e generally aligns with other species of the same genus. However, notable differences emerged when comparing specific characteristics across species. These variations are consistent with natural biological principles, reflecting the unique biological traits of each species and their adaptations to particular environmental conditions.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eAn overview of reproductive biology in \u003cem\u003eSarcophyton\u003c/em\u003e\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSpecies\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSex Ratio\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMature Egg Diameter (\u0026micro;m)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eSpawning Season\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eReferences\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eS. crassocaule\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.3:1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e915\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4\u0026ndash;6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eChou (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2002\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eS. ehrenbergi\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e710\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10\u0026ndash;11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eAlino and Coll (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1989\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eS. glaucum\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e600\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10\u0026ndash;11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eAlino and Coll (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1989\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eS. glaucum\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1:1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e500\u0026ndash;650\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eBenayahu and Loya (1986)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eS. glaucum\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1:1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e800\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2\u0026ndash;3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eSchleyer et al. (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2004\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eS. glaucum\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1:1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e400\u0026ndash;450\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e12\u0026thinsp;\u0026minus;\u0026thinsp;1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMohammed et al. (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2016\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eS. elegans\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.3:1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e450\u0026ndash;620\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e9\u0026ndash;10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eHellstr\u0026ouml;m et al. (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2010\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eS. auritium\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e621\u0026ndash;689\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMandelberg-Aharon and Benayahu (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2015\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eS. trocheliphorum\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e763\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eChou (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2002\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eSarcophyton\u003c/em\u003e sp.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e600\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10\u0026ndash;11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eBabcock (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1986\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eS. serenei\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.3:1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e450\u0026ndash;736\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eThis study\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eOur study revealed that the soft coral \u003cem\u003eSarcophyton serenei\u003c/em\u003e is a gonochoric species, reflecting the general reproductive trend observed within the genus \u003cem\u003eSarcophyton\u003c/em\u003e, such as \u003cem\u003eS. auritum\u003c/em\u003e (Mandelberg-Aharon and Benayahu \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) and \u003cem\u003eS. glaucum\u003c/em\u003e (Benayahu and Loya 1986; Mohammed et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). However, findings by Schleyer et al. (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2004\u003c/span\u003e) from KwaZulu-Natal, South Africa, from September 1991 to November 1994, demonstrated that among 276 colonies of \u003cem\u003eS. glaucum\u003c/em\u003e at an average depth of 15 m, 134 colonies were female, 96 male, 25 hermaphroditic (containing both oocytes and spermatocytes within polyps), and 21 colonies of indeterminate sex. These differences may be attributed to geographical factors. The sex of \u003cem\u003eS. serenei\u003c/em\u003e cannot be determined through colony coloration, external morphology, or size but must be identified through anatomical dissection, stereomicroscopic examination, or histological analysis.\u003c/p\u003e\u003cp\u003eThe natural sex ratio of \u003cem\u003eS. serenei\u003c/em\u003e in the studied area deviates from the theoretical 1:1 ratio, being approximately 1.3:1. This result is consistent with findings for \u003cem\u003eS. crassocaule\u003c/em\u003e (Chou \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2002\u003c/span\u003e) and \u003cem\u003eS. elegans\u003c/em\u003e (Hellstr\u0026ouml;m et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), where both species exhibited a male-to-female ratio of 1.3:1. However, some studies within the \u003cem\u003eSarcophyton\u003c/em\u003e genus have reported a balanced 1:1 sex ratio. For instance, Hellstr\u0026ouml;m et al. (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) reported a 1:1 sex ratio for \u003cem\u003eSarcophyton elegans\u003c/em\u003e, based on the analysis of 334 colonies (121 female colonies, 162 male colonies, and 51 colonies of undetermined sex). For \u003cem\u003eSarcophyton glaucum\u003c/em\u003e, the study by Benayahu and Loya (1986) indicated that the sex ratio did not significantly deviate from the theoretical 1:1 ratio. Their analysis of 267 colonies at depths of 3\u0026ndash;5 m revealed 141 female colonies and 126 male colonies, while at depths of 27\u0026ndash;30 m, they observed 136 female colonies and 107 male colonies.\u003c/p\u003e\u003cp\u003eMorphological and histological analyses of the ovaries in this study indicated that mature oocytes of \u003cem\u003eSarcophyton serenei\u003c/em\u003e were distinctly observed from February to March, particularly between March 23 and March 27 (corresponding to the 14th to 18th day of the lunar calendar). This period represents the maturation phase, during which the coral is capable of reproduction. These findings suggest that \u003cem\u003eS. serenei\u003c/em\u003e exhibits synchronized reproduction with an annual reproductive cycle, which is consistent with previous studies on the reproductive patterns of several \u003cem\u003eSarcophyton\u003c/em\u003e species, such as \u003cem\u003eS. crassocaule\u003c/em\u003e, \u003cem\u003eS. ehrenbergi\u003c/em\u003e, \u003cem\u003eS. glaucum\u003c/em\u003e, \u003cem\u003eS. elegans\u003c/em\u003e, and \u003cem\u003eS. auritum\u003c/em\u003e (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Research on \u003cem\u003eS. glaucum\u003c/em\u003e has documented reproductive activity during the period between the full moon and new moon in March, marked by the release of mature sperm sacs and oocytes (Schleyer et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). However, the spawning season for this species extends from August to February of the following year (Hellstr\u0026ouml;m et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). For \u003cem\u003eS. auritum\u003c/em\u003e, reproduction occurs during the full moon in July (Mandelberg-Aharon and Benayahu \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Although oocytes of varying sizes are present throughout the year, the development of large oocytes accelerates significantly from January (416.0\u0026thinsp;\u0026plusmn;\u0026thinsp;23.0 \u0026micro;m) to June (621.0\u0026thinsp;\u0026plusmn;\u0026thinsp;39.0 \u0026micro;m). By July and August, the number of large oocytes decreases and they are absent by October. Smaller oocytes continued to appear throughout the study period, indicating continuous oocyte development. The significant increased in sperm sac diameter from January to June also indicated that reproduction occurs prior to July. In October, small sperm sacs with an average diameter of 43.0\u0026thinsp;\u0026plusmn;\u0026thinsp;5.0 \u0026micro;m began to appear, increasing to 338.0\u0026thinsp;\u0026plusmn;\u0026thinsp;44.0 \u0026micro;m by June. Spawning was observed in July, and by August, sperm sacs were no longer present in the polyps.\u003c/p\u003e\u003cp\u003eThese findings indicate that the oocyte size of \u003cem\u003eSarcophyton serenei\u003c/em\u003e at maturity is comparable to that of mature oocytes in \u003cem\u003eSarcophyton\u003c/em\u003e sp. (600 \u0026micro;m) and \u003cem\u003eS. glaucum\u003c/em\u003e (500\u0026ndash;650 \u0026micro;m), as previously reported in other studies (Babcock \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1986\u003c/span\u003e; Benayahu and Loya 1986; Alino and Coll \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). However, the oocyte size was smaller than that of other species in the genus \u003cem\u003eSarcophyton\u003c/em\u003e, such as \u003cem\u003eS. crassocaule\u003c/em\u003e (915 \u0026micro;m), \u003cem\u003eS. ehrenbergi\u003c/em\u003e (710 \u0026micro;m), and \u003cem\u003eS. trocheliphorum\u003c/em\u003e (763 \u0026micro;m) (Benayahu et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1990\u003c/span\u003e; Chou \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). Additionally, some studies have documented that mature oocytes of \u003cem\u003eS. elegans\u003c/em\u003e (Hellstr\u0026ouml;m et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2010\u003c/span\u003e)d \u003cem\u003eglaucum\u003c/em\u003e (Mohammed et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) are smaller than those of \u003cem\u003eS. serenei\u003c/em\u003e.\u003c/p\u003e\u003cp\u003eWhile larger oocyte size may require a longer developmental period, no clear correlation has been established between oocyte size and oogenesis duration in corals. Research suggests that the development of large oocytes is associated with synchronization in gamete maturation and high reproductive potential, rather than an extended oogenesis cycle (Benayahu and Loya \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1983\u003c/span\u003e; Benayahu and Loya 1986). Larger oocytes may facilitate more efficient fertilization due to their higher lipid reserves, which provide energy for larvae until they acquire zooxanthellae (Jones and Berkelmans \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). This significantly influences larval development, survival rates, and the resilience of coral populations in natural environments (Levitan \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). The timing of oocyte development in \u003cem\u003eSarcophyton serenei\u003c/em\u003e observed in this study differs from that recorded for \u003cem\u003eS. elegans\u003c/em\u003e at Lizard Island, Great Barrier Reef (Hellstr\u0026ouml;m et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Specifically, stage I oocytes of \u003cem\u003eS. elegans\u003c/em\u003e are present from February to July, stage II oocytes from April to November, and stage III oocytes are present throughout the year. Stage IV oocytes are observed in polyps at the colony periphery just before the full moon in August and September. They are subsequently found in polyps closer to the colony center in the following months, but disappear by February of the following year (Hellstr\u0026ouml;m et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Research on \u003cem\u003eS. elegans\u003c/em\u003e has also shows that stage I and II spermatocytes appear in February and March, respectively. Sperm size gradually increases until August, reaching stage III, and continues developing to stage IV in August and September (Hellstr\u0026ouml;m et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Differences in the timing of oocyte development and the presence of specific stages across different coral species may be attributed to variations in habitat adaptation, climatic conditions, and hydrological factors specific to different locations.\u003c/p\u003e\u003cp\u003ePolyp fecundity, defined as the number of eggs produced per polyp, serves as a key indicator of reproductive output in soft corals (Jamodiong and Reimer \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Studies have shown that the fecundity of \u003cem\u003eSarcophyton serenei\u003c/em\u003e is lower than that of \u003cem\u003eSarcophyton glaucum\u003c/em\u003e. Specifically, \u003cem\u003eS. glaucum\u003c/em\u003e has been reported to produce between 25 and 35 oocytes per polyp (Benayahu and Loya 1986). In contrast, \u003cem\u003eS. serenei\u003c/em\u003e exhibits significantly higher fecundity compared to \u003cem\u003eLobophytum schoedei\u003c/em\u003e, which has an average fecundity of only 6.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3.9 oocytes per polyp (Baran and Baria-Rodriguez \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Additionally, research on \u003cem\u003eSclerophytum cf. heterospiculatum\u003c/em\u003e in the Japanese Sea indicates substantial variation in polyp fecundity, ranging from 1 to 25 oocytes per polyp (Jamodiong and Reimer \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Brazeau and Lasker (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e1989\u003c/span\u003e) proposed that reduced egg production in certain octocoral species may result from spatial constraints within the polyps, potentially due to their rigid and less flexible body structures. Overall, polyp fecundity in soft corals tends to be higher than in scleractinian corals, possibly due to the absence of a rigid skeleton, which provides more space for gamete development (Kahng et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn summary, the reproductive biological characteristics of the soft coral \u003cem\u003eSarcophyton serenei\u003c/em\u003e in the waters of Nha Trang are as follows: \u003cem\u003eS. serenei\u003c/em\u003e is a gonochoric species, with its reproductive season occurring annually in March (3 days after full moon). The natural male-to-female sex ratio is 1.3:1. The ovaries and testes of the soft coral \u003cem\u003eS. serenei\u003c/em\u003e undergo four distinct stages of development. The average size of mature oocytes is 684.99\u0026thinsp;\u0026plusmn;\u0026thinsp;28.50 \u0026micro;m, ranging from 631.89 to 735.97 \u0026micro;m. The fecundity of this species varies significantly, with each polyp containing 14 to 26 oocytes, with an average of 18.11\u0026thinsp;\u0026plusmn;\u0026thinsp;3.63 eggs per polyp. The average size of sperm sacs is 235.29\u0026thinsp;\u0026plusmn;\u0026thinsp;8.76 \u0026micro;m, with a range from 182.42 to 295.00 \u0026micro;m. The results of this study provide a foundation for further research on sexual reproduction and the development of soft coral aquaculture techniques in Vietnam, contributing to conservation efforts, pharmaceutical resource supply, and the marine ornamental trade. In addition, these findings offer valuable scientific data to support management strategies aimed at regulating the exploitation of this coral species, particularly by avoiding harvesting during its natural breeding season, which occurs in March each year.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe article utilizes data from the 2023 to 2024 museum mission of the Marine Organism Cultivation Engineering Department. We sincerely thank the Institute of Oceanography, Vietnam Academy of Science and Technology, for providing funding and facilities to support the completion of this research.\u0026nbsp;In addition, this study is a part of the doctoral thesis of PhD student Ho Son Lam.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest:\u0026nbsp;\u003c/strong\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval:\u003c/strong\u003e All applicable international, national, and/or institutional guidelines for animal testing, animal care and use of animals were followed by the authors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSampling and field studies:\u003c/strong\u003e All necessary permits for sampling and observational field studies have been obtained by the authors from the competent authorities and are mentioned in the acknowledgements, if applicable. The study is compliant with CBD and Nagoya protocols.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; Contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConceptualization:\u003c/strong\u003e Ho Son Lam, Hoang-Xuan Ben, Dao-Viet Ha, Do-Huu Hoang; \u003cstrong\u003eExperimental prodeduce and husbandry:\u003c/strong\u003e Nguyen-Thi Nguyet Hue, Dang-Tran Tu Tram, Nguyen Truong Tan Tai, Phan Kim Hoang; \u003cstrong\u003eData and sample collection:\u003c/strong\u003e Nguyen-Thi Nguyet Hue, Nguyen Truong Tan Tai, Phan Kim Hoang, Dang-Tran Tu Tram, Ho Son Lam; \u003cstrong\u003eWriting - original draft preparation:\u003c/strong\u003e Ho Son Lam, Hoang-Xuan Ben, Dao-Viet Ha, Do-Huu Hoang.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAlino PM, Coll JC (1989) Observations of the synchronized mass spawning and post settlement activity of octocorals on the Great Barrier Reef, Australia: biological aspects. Bulletin of Marine Science 45: 697-707.\u003c/li\u003e\n\u003cli\u003eBabcock RC (1986) A comparison of the population ecology of reef flat corals of the family Faviidae (Goniastrea, Platygyra), James Cook University.\u003c/li\u003e\n\u003cli\u003eBaran CC, Baria‐Rodriguez MV (2021) Sexual reproduction in the soft coral Lobophytum schoedei in Bolinao‐Anda Reef Complex, Pangasinan, northwestern Philippines. Invertebrate Biology 140: e12316.\u003c/li\u003e\n\u003cli\u003eBarbosa TM, Gomes PB, Bergeron A-S, Santos AM, Chagas C, Freitas EM, Perez CD (2014) Comparisons of sexual reproduction in Carijoa riisei (Cnidaria, Alcyonacea) in South Atlantic, Caribbean, and Pacific areas. Hydrobiologia 734: 201-212.\u003c/li\u003e\n\u003cli\u003eBenayahu Y, Loya Y (1983) Surface brooding in the Red Sea soft coral \u003cem\u003eParerythropodium fulvum fulvum\u003c/em\u003e (Forskal, 1775). The Biological Bulletin 165: 353-369.\u003c/li\u003e\n\u003cli\u003eBenayahu Y, Loya Y (1986) Sexual reproduction of a soft coral: synchronous and brief annual spawning of \u003cem\u003eSarcophyton glaucum\u003c/em\u003e (Quoy \u0026amp; Gaimard, 1833). The Biological Bulletin 170: 32-42.\u003c/li\u003e\n\u003cli\u003eBenayahu Y, Weil D, Kleinman M (1990) Radiation of broadcasting and brooding patterns in coral reef alcyonaceans. Advances in invertebrate reproduction 5: 323-328.\u003c/li\u003e\n\u003cli\u003eBrazeau DA, Lasker HR (1989) The reproductive cycle and spawning in a Caribbean gorgonian. The Biological Bulletin 176: 1-7.\u003c/li\u003e\n\u003cli\u003eBurke L, Selig E, Spalding M (2002) \u003cem\u003eReefs at Risk in Southeast Asia \u003c/em\u003e(UK: World Resources Institute, United Nations Environment Program-World Conservation Monitoring Centre, World Fish Centre, dan International Coral Reef Action Network) p 40.\u003c/li\u003e\n\u003cli\u003eChou Y (2002) Sexual reproduction of three alcyonacean species in southern Taiwan, MSc thesis, National Taiwan University.\u003c/li\u003e\n\u003cli\u003eDautova T, Savinkin O (2013a) Octocorallia: Alcyoniidae. Benthic fauna of the Bay of Nha Trang, Southern Vietnam (Vol. 3). Moscow, KMK.\u003c/li\u003e\n\u003cli\u003eDautova TN (2011) Biodiversity of soft corals alcyoniidae (cnidaria: octocorallia) and their taxonomy problem. Coastal Marine Biodiversity and Bioresources of Vietnam and adjacent areas to the South China Sea: 28.\u003c/li\u003e\n\u003cli\u003eDautova TN, Savinkin OV (2013b) \u003cem\u003eBenthic fauna of the bay of Nha Trang: Southern Vietnam - Volume 3: Octocorallia: Alcyoniidae.\u003c/em\u003e Moscow, KMK, 271 pp.\u003c/li\u003e\n\u003cli\u003eEllis S, Sharron L (1999) The Culture of Soft Corals (Order: Alcyonacea) for the Marine Aquarium Trade. Publication No. 137. Center for Tropical and Subtropical Aquaculture, Waimanalo, Hawaii.\u003c/li\u003e\n\u003cli\u003eFabricius K, Alderslade P (2001) Soft corals and sea fans: a comprehensive guide to the tropical shallow water genera of the central-west Pacific, the Indian Ocean and the Red Sea. Australian Institute of Marine Science: Townsville. ISBN 0-642-32210-4. VIII, 264 pp.\u003c/li\u003e\n\u003cli\u003eFan TY, Chou YH, Dai CF (2005) Sexual reproduction of the alcyonacean coral \u003cem\u003eLobophytum pauciflorum\u003c/em\u003e in southern Taiwan. Bulletin of Marine Science 76: 143-154.\u003c/li\u003e\n\u003cli\u003eFowler J, Cohen L, Jarvis P (2013) \u003cem\u003ePractical statistics for field biology\u003c/em\u003e. John Wiley \u0026amp; Sons.\u003c/li\u003e\n\u003cli\u003eGlynn P, Gassman N, Eakin C, Cortes J, Smith D, Guzman H (1991) Reef coral reproduction in the eastern Pacific: Costa Rica, Panama, and Galapagos Islands (Ecuador) I. Pocilloporidae. Marine Biology 109: 355-368.\u003c/li\u003e\n\u003cli\u003eHellstr\u0026ouml;m M, Kavanagh KD, Benzie JA (2010) Multiple spawning events and sexual reproduction in the octocoral \u003cem\u003eSarcophyton elegans\u003c/em\u003e (Cnidaria: Alcyonacea) on Lizard Island, Great Barrier Reef. Marine Biology 157: 383-392.\u003c/li\u003e\n\u003cli\u003eHoang XB, Thai MQ, Minh-Thu P, Pham XK, Tung NN, Dao HV (2022) Antipredator Defenses in Soft Corals of the Genus Sarcophyton (Octocorallia; Alcyoniidae) from Coastal Waters of Central Vietnam. Russian Journal of Marine Biology 48: 122-128.\u003c/li\u003e\n\u003cli\u003eHwang S-J, Song J-I (2007) Reproductive biology and larval development of the temperate soft coral \u003cem\u003eDendronephthya gigantea\u003c/em\u003e (Alcyonacea: Nephtheidae). Marine Biology 152: 273-284.\u003c/li\u003e\n\u003cli\u003eIbrahim MA, Abdelrahman AH, Atia MA, Mohamed TA, Moustafa MF, Hakami AR, Khalifa SA, Alhumaydhi FA, Alrumaihi F, Abidi SH (2021) Blue biotechnology: computational screening of \u003cem\u003esarcophyton \u003c/em\u003ecembranoid diterpenes for SARS-CoV-2 main protease inhibition. Marine Drugs 19: 391.\u003c/li\u003e\n\u003cli\u003eJamodiong EA, Reimer JD (2023) Reproductive characteristics and gamete development of the soft coral \u003cem\u003eSclerophytum cf. heterospiculatum\u003c/em\u003e in Okinawa Island, Japan. Invertebrate Biology 142: e12404.\u003c/li\u003e\n\u003cli\u003eJones AM, Berkelmans R (2011) Tradeoffs to thermal acclimation: Energetics and reproduction of a reef coral with heat tolerant Symbiodinium type‐D. Journal of Marine Sciences 2011: 12.\u003c/li\u003e\n\u003cli\u003eKahng SE, Benayahu Y, Lasker HR (2011) Sexual reproduction in octocorals. Marine Ecology Progress Series 443: 265-283.\u003c/li\u003e\n\u003cli\u003eLeal MC, Sheridan C, Osinga R, Dion\u0026iacute;sio G, Rocha RJM, Silva B, Rosa R, Calado R (2014) Marine Microorganism-Invertebrate Assemblages: Perspectives to Solve the \u0026ldquo;Supply Problem\u0026rdquo; in the Initial Steps of Drug Discovery. Marine Drugs 12: 3929-3952.\u003c/li\u003e\n\u003cli\u003eLevitan DR (2000) Optimal egg size in marine invertebrates: theory and phylogenetic analysis of the critical relationship between egg size and development time in echinoids. The American Naturalist 156: 175-192.\u003c/li\u003e\n\u003cli\u003eMandelberg-Aharon Y, Benayahu Y (2015) Reproductive features of the Red Sea octocoral \u003cem\u003eSarcophyton auritum\u003c/em\u003e Verseveldt \u0026amp; Benayahu, 1978 are uniform within generic boundaries across wide biogeographical regions. Hydrobiologia 759: 119-132.\u003c/li\u003e\n\u003cli\u003eMcFadden C, Cordeiro R, Samimi-Namin K, Williams G, van Ofwegen L (2025) World List of Octocorallia. \u003cem\u003eSarcophyton \u003c/em\u003eLesson, 1834. World Register of Marine Species https://www.marinespecies.org/aphia.php?p=taxdetails\u0026amp;id=205483 on the day 2025-02-18.\u003c/li\u003e\n\u003cli\u003eMcFadden CS, Van Ofwegen LP, Quattrini AM (2022) Revisionary systematics of Octocorallia (Cnidaria: Anthozoa) guided by phylogenomics. Bulletin of the Society of Systematic Biologists 1.\u003c/li\u003e\n\u003cli\u003eMohammed TA, Ali A-HA, El-Komi MM, El-Arab MAE, Shoukr FA (2016) Growth Rate Assessment of Alcyonacean \u003cem\u003eSarcophyton glaucum\u003c/em\u003e from Northern Hurghada, Red Sea, Egypt. Natural Resources 7: 384-398.\u003c/li\u003e\n\u003cli\u003eRhyne A, Rotjan R, Bruckner A, Tlusty M (2009) Crawling to collapse: ecologically unsound ornamental invertebrate fisheries. PLoS One 4: e8413.\u003c/li\u003e\n\u003cli\u003eRocha RJM, Bontas B, Cartaxana P, Leal MC, Ferreira JM, Rosa R, Ser\u0026ocirc;dio J, Calado R (2015) Development of a Standardized Modular System for Experimental Coral Culture. Journal of the World Aquaculture Society 46: 235-251.\u003c/li\u003e\n\u003cli\u003eSchleyer MH, Kruger A, Benayahu Y (2004) Reproduction and the unusual condition of hermaphroditism in \u003cem\u003eSarcophyton glaucum\u003c/em\u003e (Octocorallia, Alcyoniidae) in KwaZulu-Natal, South Africa. Hydrobiologia 530: 399-409.\u003c/li\u003e\n\u003cli\u003eTixier-Durivault A (1958) R\u0026eacute;vision de la famille des Alcyoniidae: les genres \u003cem\u003eSarcophytum \u003c/em\u003eet \u003cem\u003eLobophytum\u003c/em\u003e. Zoologische Verhandelingen 36: 1-179.\u003c/li\u003e\n\u003cli\u003eTlusty M (2002) The benefits and risks of aquacultural production for the aquarium trade. Aquaculture 205: 203-219.\u003c/li\u003e\n\u003cli\u003eTuan VS, Ho SL, Phan KH, Dang TTT, Harrison PL (2022) Varied spawning patterns of reef corals in Nha Trang Bay, Vietnam, western South China Sea. Regional Studies in Marine Science 55: 102631.\u003c/li\u003e\n\u003cli\u003eVerseveldt J (1982) A revision of the genus \u003cem\u003eSarcophyton Lesson\u003c/em\u003e (Octocorallia, Alcyonacea). Zoologische Verhandelingen 192: 1-91.\u003c/li\u003e\n\u003cli\u003eVicentuan K (2009) Effects of fragmentation and transplantation on reproduction in \u003cem\u003eAcropora muricata \u003c/em\u003eand \u003cem\u003eHydnophora rigida\u003c/em\u003e, University of the Philippines.\u003c/li\u003e\n\u003cli\u003eWabnitz C (2003) From ocean to aquarium: the global trade in marine ornamental species. UNEP/Earthprint.\u003c/li\u003e\n\u003cli\u003eWilkens P, Birkholz J (1992) Marine Invertebrates: Organ-Pipe and Leather Corals. Gorgonians, Craft Druck und Verlag GmbH, Ettlingen, Germany.\u003c/li\u003e\n\u003cli\u003eYan X, Liu J, Huang J, Wang Y, Leng X, Li T, Ouyang H, Yan X, He S (2022) Bistrochelides H\u0026minus;L: Biscembranoids from the south China sea soft coral \u003cem\u003eSarcophyton serenei\u003c/em\u003e. Phytochemistry 204: 113438.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Sarcophyton, S. serenei, reproductive biology, soft coral","lastPublishedDoi":"10.21203/rs.3.rs-7190639/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7190639/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe study was conducted from August 2023 to July 2024, with monthly sampling on the full moon from mature colonies of the soft coral \u003cem\u003eSarcophyton serenei\u003c/em\u003e, distributed at depths of 5\u0026ndash;10 m. Samples were collected from Cut Chim Island (12\u0026deg;15'55.9\"N, 109\u0026deg;13'29.3\"E) to Hon Chong Island (12\u0026deg;16'58.3\"N, 109\u0026deg;12'51.3\"E) in Nha Trang Bay to investigate specific reproductive biological characteristics of the species. The parameters analyzed included sex determination, sex ratio, developmental stages of oocytes and spermatocysts, maturation rates, spawning seasonality, and fecundity. The results revealed that \u003cem\u003eS. serenei\u003c/em\u003e is a gonochoric species, with a natural sex ratio of 1.3:1 (male to female). The oocytes of \u003cem\u003eS. serenei\u003c/em\u003e were white in the immature stage and turned pink or occasionally deep red upon maturation. The mean diameter of mature oocytes was 684.99\u0026thinsp;\u0026plusmn;\u0026thinsp;28.50 \u0026micro;m, ranging from 631.89 to 735.97 \u0026micro;m. Immature spermatocysts were translucent gray, turning white upon maturation, with an average size of 235.29\u0026thinsp;\u0026plusmn;\u0026thinsp;8.76 \u0026micro;m, ranging from 182.42 to 295.00 \u0026micro;m. Fecundity showed significant variability, with each polyp containing 14 to 26 eggs. The spawning season of \u003cem\u003eS. serenei\u003c/em\u003e in Nha Trang Bay occurred annually in March.\u003c/p\u003e","manuscriptTitle":"Reproductive biology of soft coral Sarcophyton serenei Tixier-Durivault, 1958 in Nha Trang Bay, Khanh Hoa province, Viet Nam","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-19 12:25:13","doi":"10.21203/rs.3.rs-7190639/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"6c21b56d-ab7c-4dad-a104-88eb4598b1d5","owner":[],"postedDate":"August 19th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-12-15T09:15:29+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-19 12:25:13","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7190639","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7190639","identity":"rs-7190639","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}