First Record of Butis humeralis (Gobiiformes: Butidae) from the West Coast of India with special emphasis to its Early Developmental Stages

First Record of Butis humeralis (Gobiiformes: Butidae) from the West Coast of India with special emphasis to its Early Developmental Stages | 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 First Record of Butis humeralis (Gobiiformes: Butidae) from the West Coast of India with special emphasis to its Early Developmental Stages M. K. Shameena, Ratheesh Kumar, V. L. Sruthy, K. A. Sajeela, P. Kaladharan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3954230/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 Dark sleeper or olive flathead-gudgeon, Butis humeralis (Valenciennes 1837), was discovered for the first time from the west coast of India. Till date, there have only been reports of this species from India's east coast. A cluster of sparsely distributed eggs of B. humeralis were observed in the gritted glass panel submerged for biofouling studies in aquaculture cage sites near Kalamukku fishing harbour in the Cochin Estuary. The egg mass covered an area of 61.80 cm 2 with an average abundance of 124.51 ± 27.25 eggs/cm 2 . Molecular characterization of the eggs was done to affirm the species identification. The eggs of B. humeralis were, adhesive, pyriform-shaped and translucent with brownish yellow colour with a size measurement of 0.41 ± 0.01 mm and 0.36 ± 0.01 mm diameters along long and short axis, respectively. The eggs were reared up to 144 hph (hour post-hatch) subsequently. The newly hatched larvae of B. humeralis were slender and translucent with 1.01 ± 0.037 mm total length (TL) with a yolk sac of size 0.624 ± 0.05 mm and 0.415 ± 0.05 mm along longitudinal and horizontal axis, respectively. After 72 hph, fully pigmented eyes were observed whereas a well-developed mouth with distinct upper and lower jaw appeared on the fifth day of hatching. The TL of the preflexion larvae after 144 hph ranged between 2.08–2.12 mm. The first report of this lesser-known species from the west coast of India demonstrating the developmental stages signifies the need to evaluate their current ecological and conservation status in the ecosystem. Dark sleeper Butidae Butis Cochin Estuary Embryonic Larval development Figures Figure 1 Figure 2 Figure 3 Introduction Sleeper gobies or gudgeons belong to the family Butidae comprising of 47 species classified under 10 genera (Fricke et al. 2022 ). Butids are robust, heavy-bodied fishes characterised by cylindrical appearance with rayed dorsal fins and discrete pelvic fins not joined by any membrane (Hoese 1984 ; Hoese and Gill 1993 ). They often attain a size of 10–25 cm and exhibits heavier scalation (Eschmeyer 2008 ). Butids are primarily found in tropical and sub-tropical brackish and freshwater zones of Asia, Africa, Australia and Oceania (Thacker 2011 ). They are primarily benthic as most of the species lack swim bladders to maintain buoyancy in the water column (Zeyl et al. 2016 ). Their resilience and tolerance to low oxygen and salinity makes them an excellent candidate in experimental studies (Nilsson et al. 2004 ; Ip et al. 2005 ). The great diversity in morphology, behavioural adaptations and niche specializations exhibited by these fishes is an indication of the wide range of environmental circumstances they confront (Untersteggaber et al. 2014 ). 9 species belonging to 5 genera— Butis , Bostrychus , Odonteleotris , Ophiocara , and Incara of the family Butidae are reported from Indian waters among which Butis is the most diverse. The species of genus Butis is extensively dispersed, from brackish waters, mangroves, estuaries to the lower reaches of freshwater rivers. These ambush hunters occur in mud bottoms, bank flora, and dead branches, preying on small fish and crustaceans like prawns and shrimps (Keith et al. 2010 , 2021 ; Nguyen and Din 2021). According to Kottelat ( 2013 ) and Fricke et al. ( 2022 ), the genus Butis contains five to six valid species, including B. butis , B. humeralis , B. koilomatodon , B. gymnopomus , B. amboinensis , and B. prismaticus . Of these, B. humeralis and B. amboinensis were only reported from the east coast of India, while B. butis , B. koilomatodon , and B. gymnopomous were found in estuarine waters of Kerala (Geevargheese 1981; Gopi 2006 ; Raghunathan 2007 ; Zeena & Beevi 2011; Hariprakash et al. 2023 ). The present study is the first report of B. humeralis from the west-coast of India from Cochin Estuary (CE), Kerala. The study also gives a detailed description of the egg morphology, hatching and changes associated with growth and development of B. humeralis under laboratory conditions. Materials and methods Study area and Sampling method To study the biofouling impacts on aquaculture cages, gritted glass panels (150 mm × 150 mm × 2 mm) were suspended at a depth of 1-1.5 m near cage sites at Kalamukku Fishing Harbour (9⁰59'11.7 "N 76⁰14'43.7" E), in Cochin Estuary (CE), Kerala, one of the largest estuaries along the west coast of India. Upon retrieval of the glass panels in August 20, 2022, numerous eggs were found adhered to it. The glass panels with the eggs were carefully detached from the cages and transported to laboratory for further investigation. The physico-chemical characteristics of surface water samples collected from the sites were conducted as per standard procedures (APHA 1998 ). Microscopic examination of the egg samples A cluster of eggs were observed on the gritted glass panel, whose measurements were taken under the stereo microscope (Nikon SMZ25 – NIS Elements D 5.30.00). The area of attachment of eggs on gritted glass panel were recorded by counting the total number of grits containing eggs and multiply it with the area of a single grit and the average number of eggs found within that single grit. These eggs were carefully detached from the panel using a brush and kept in a 1000 ml glass jar containing estuarine water collected from the cage sites and observed every 24 h to study the early developmental stages. Molecular characterization of the eggs Eggs were collected and preserved in 95% ethanol. Total DNA was isolated using DNeasy Blood and Tissue kit (Qiagen, Germany) followed by the manufacturer's instructions. The quality and quantity of the extracted DNA were estimated using a NanoDrop One Microvolume UV-Vis Spectrophotometer (Thermo-Fisher Scientific). The molecular phylogenetic studies were carried out using mitochondrial Cytochrome Oxidase I (COI) universal primers - Fish F1 5’-TCAACCAACCACAAAGACATTGGCAC-3' and Fish R1 5’-TAGACTTCTGGGTGGCCAAAGAAT CA-3' (Ward et al. 2005 ). PCR Amplification was performed in 25 µl reactions containing 2X PCR Master mix (Takara Bio INC) using 20 pM of primers and 20 ng of template DNA. The reaction mixture was pre-heated at 94 0 C for 5 minutes followed by 25 cycles (94 0 C for 30 seconds, 50 0 C for 30 seconds, and 72 0 C for 35 seconds) and a final extension at 72 0 C for 5 minutes. PCR products were visualized in a 1.5% agarose gel and compared with a NEX-GEN 100 bp DNA ladder (Genetix Biotech Asia Pvt. Ltd., New Delhi, India). PCR products were sent for sequencing to the sequencing facility (Enfys Lifesciences Pvt. Ltd., Kerala, India). The forward and reverse DNA sequences were aligned and assembled using the Bio Edit sequence alignment editor, version 7.0.5.2 (Hall, 1999 ). The sequences were searched using BLAST in GenBank ( www.ncbi.nlm.nih.gov/nucloetide ) to verify the morphological identifications at the species level. Result Family: BUTIDAE Butis humeralis (Valenciennes, 1837). Olive flathead gudgeon or dark sleeper. Distribution B. humeralis is a fish indigenous to the waters of Indonesia and Indochina (Froese and Pauly 2015 ). Spawning habit A cluster of eggs was found on gritted glass panel submerged for biofouling studies in aquaculture cages near Kalamukku fishing harbour in CE. The egg mass covered an area of 61.80 cm 2 on the glass panel with an average of 124.51 ± 27.25 eggs/cm 2 (mean ± SD; n = 10). Egg masses were irregularly distributed on the surface of the glass panel (Fig. 1 a and b). The egg mass appeared to be a single clutch due to their homogenous growth and appearance. Owing due to the sparseness in distribution, minute size of the eggs, and variability of the density within an egg mass, it was difficult to determine the accurate number of eggs within the clutch. Nevertheless, a rough estimate of the number of eggs from subsamples showed that the clutch comprises of approximately 7,000 eggs. The atmospheric temperature, water temperature, salinity and pH of the study area during sample collection was 28⁰C, 26⁰C, 6 PSU, and 7.29, respectively. Other physiochemical parameters like turbidity, total suspended solids (TSS) and dissolved oxygen (DO) during the sampling period was 7.58 ± 0.88 NTU, 28.67 ± 0.002 mg L − 1 and 5.43 ± 0.14 mg L − 1 , respectively. The nutrients, including inorganic nitrate, nitrite, inorganic phosphate, silicate, and ammonia were 0.129 ± 0.002 mg L − 1 , 0.008 ± 0.002 mg L − 1 , 0.063 ± 0.017 mg L − 1 , 1.34 ± 0.22 mg L − 1, and 0.03 ± 0.018 mg L − 1 , respectively. Early development i. Egg morphology and Hatching Eggs of B. humeralis were pyriform in shape, with a protuberance at the micropylar (proximal) end comprising of a bundle of adhesive filaments that held the eggs together on to the surface (Fig. 2 a). Eggs were demersal and brownish yellow in colour. The mean vertical diameter of 10 eggs from the egg mass, ranged between 0.40 and 0.42 mm (0.41 ± 0.01), whereas the mean horizontal diameter ranged between 0.34 and 0.36 mm (0.36 ± 0.01). The eggs showed twitching and heart beating movements. Both tail and head-end were clearly visible. The embryonic head was located at the distal part of the egg while the tail of the embryo was coiled around within the egg membrane. Egg possessed primitive optic vesicle, notochord and yolk sac with numerous oil globules of diameter 0.076 ± 0.03 mm. Twitching and wriggling movements became more vigorous just before hatching and the embryo ruptured the egg capsule and yolk sac larva came out within 2 to 3 hours after brought to the laboratory (Fig. 2 b). Larval Development Day 1 (0 - hour post-hatching (hph)) According to Hubbs ( 1943 ), a recently hatched embryo which is completely reliant on the yolk for nourishment is regarded as a prolarva. Newly hatched prolarvae of B. humeralis (Fig. 3 a) were slender and translucent with 0.97–1.09 mm NL. Larvae had large, slightly oval, brownish yolk sac with diameter of 0.55–0.62 mm along longitudinal axis and 0.36–0.47 mm along horizontal axis. Numerous oil globules were found on the yolk sac with diameters ranging between 0.02 and 0.11 mm. The mouth of the newly hatched larvae was not developed, and primitive optic vesicles and otoliths formed laterally on the head, and the eyes were unpigmented. Melanophores appeared on the tip of the snout, above the eyes, on the anterior and posterior margins of the yolk sac, ventrally on the posterior half of the trunk, ventrally on the anterior two-thirds of the tail, and dorsally on the midtail. All the melanophores were associated with xanthophores. The caudal fin and digestive tract were not visible in the early pre-flexion larvae. Day 2 (24 hph) One day after hatching (Fig. 3 b), the larvae exhibited marked growth and increased in size to 1.15 − 1.2 mm NL with TL ranged between 1.19–1.25 mm. The yolk sac was partially decreased in diameter with 0.29–0.34 mm and 0.23–0.25 mm diameters along vertical and horizontal axes respectively. Oil droplets coalesced into two globules with 0.05–0.08 mm diameter. The embryonic fin fold formed. Myomeres were partially visible. Melanophores and xanthophores above the eyes vanished, and portions of the eye margin turned pigmented. Ventral melanophores and xanthophores reduced on the anterior margins of the yolk sac and irregular bands of pigments appeared on its trunk and caudal region. The larvae showed slight movements with "swim up, sink down" behaviour by using its tail. Day 3 (48 hph): Two days after hatching (Fig. 3 c), the larvae of B. humeralis increased in notochord length (NL) to 1.53–1.55 mm. The head and unopened mouth appeared as a prominence or bump. The yolk sac further reduced in diameter to 0.12–013 mm (vertical) and 0.15–0.16 mm (horizontal). Oil globules were completely absorbed. Lens and choroid fissures were formed on the eye located at the anterior-lateral position of the head. Notochord became distinct. Myomeres became well developed with fifteen pre-anal and forty-five post-anal myomeres. Anus and pectoral fin bud was slightly visible. Melanophores appeared above the eye, yolk sac and head. Vertical melanophore bands prominently appeared on the body and caudal region. Larvae started swimming with constant tail movements. Day 4 (72 hph): Three days after hatching (Fig. 3 d), the size of larvae remained similar to that of the previous day. Remnants of the yolk sac were apparent (0.08–0.1 mm diameter). Mouth cleft was prominent. The eyes became dark and fully pigmented with a diameter of 0.11–0.12 mm. Pectoral fins developed. Day 5 (96 hph): Four days after hatching (Fig. 3 e), well developed mouth formed with clearly distinct upper and lower jaws. The yolk sac was completely absorbed. Larvae displayed wandering movements with frequent opening of the upper and lower jaws. Melanophores were observed in series along the lower jaw, below the gut, and dorsal and ventral lines of the body. Dorsal, anal, and caudal fin folds were also present. Day 6 (120 hph): Six days after hatching (Fig. 3 f), the size of the larvae slightly increased with NL and TL ranging between 1.6–1.7 mm and 1.67–1.69 mm, respectively. Mouth opened with a gape of 0.04–0.05 mm. Body depth at anus was 0.25–0.26 mm. Pectoral fin length was 0.12–0.14 mm. Head length and head depth were 0.28–0.29 mm and 0.26–0.27 mm, respectively. Eye diameter was 0.12–0.13 mm. Day 7 (144 hph): Seven days after hatching (Fig. 3 g), the NL and TL of the larvae ranged between 1.96–2.0 mm and 2.08–2.12 mm, respectively. The growth of upper and lower jaw slowed compared to the previous days. Head length slightly increased and was characterized by a diameter of 0.28–0.36 mm. Table 1 Changes in the length and width of yolk sac from 0 to 96 hph After hatching hours Yolk sac length (mm) Yolk sac width (mm) 0 0.55–0.62 0.36–0.47 24 0.29–0.34 0.23–0.25 48 0.12–013 0.15–0.16 72 0.1 0.08 96 Yolk exhausted Molecular taxonomy of B. humeralis Sequences of 687 bp length were obtained after sequencing and alignment. Similarity search (BLAST) in the NCBI database showed 99.84% identity to Butis humeralis with 92% query coverage. The sequence was submitted to NCBI GenBank with accession no. OP872738 Discussion B. humeralis (Valenciennes 1837), also known as dark sleeper or olive flathead-gudgeon, was previously reported as B. melanostigma (Bleeker 1874) from Parangipettai (Porto Novo) coastal waters, Tamil Nadu (Ramaiyan et al. 1986 ). It was also known from Indian Sundarbans and Digha coast, West Bengal (Chatterjee et al. 2013 ; Mishra and Gopi 2017 ; Yennawar et al. 2015 ) and coastal and estuarine waters of Tamil Nadu (Jeyaseelen and Krishnamurthy 1980 ). Previous reports from Kerala have described three species of Butis ; but the probable existence of other congeners is scanty, possibly due to little commercial interest in these species. The current study revealed the occurrence of B. humeralis in Kerala waters, which is the first report of its existence along west-coast of India. Although the information related to the early developmental stages of B. humeralis ’ are lacking, the present study finds relevance as it details the egg morphology, hatching and development of preflexion larva utpo 144 HPH by monitoring the changes of eyes, pigmentation, fins, yolk sac size, oil globules and mouth. According to Koumans ( 1953 ) and Miller et al. ( 1989 ), the habitat of B. humeralis and B. koilomatodon varies from marine to freshwater. In the present study, the brackish water environment where B. humeralis eggs were found was influenced by tidal incursion with marked fluctuations in salinity ranging from 0 to 20 ppt. According to Hui et al. ( 2010 ), though B. humeralis may survive in freshwater, they may not breed successfully if access to the marine environment is restricted. B. humeralis shares similarity in egg morphology with that of the two sleeper gobies of Eleotridae, Eleotris fusca and E. acanthopoma , as well as with an indigenous Hawaiin goby, Lenticeps concolor . The eggs of these gobies appear pear-shaped and adhere to the substrate using a bundle of adhesive filaments at their proximal end, and even interconnect with the neighbouring eggs to form a monolayer. (Lindstorm 1998; Maeda et al. 2008 ). The average vertical and horizontal diameters of the eggs of B. humeralis are also comparable to those of E. fusca and E. acanthopoma . Majority of gobiids have an iteroparous pattern of reproduction, with females releasing eggs on vegetation or substrates, while males assist in their post-fertilization care. The lunar cycle is crucial for their spawning and larval recruitment in estuaries (Miller 1984 ; Thresher 1984 ; Berra 2001 ; Dinh et al. 2016 ). In this study, the matured eggs of B. humeralis was collected five days prior to the new moon from CE. Eggs attached to substrate spawns during morning hours and are less vulnerable to predation due to parental care and their placement in protected areas (Brinley 1939 ; Myrberg Jr et al. 1967 ; Goulet 1995 ; Anil et al. 2012 ; Rohini Krishna et al. 2016 ) than the pelagic eggs, which is more prone to high mortality (Hirst and Lopez-Urrutia 2006). Gobies lay pear-shaped eggs in demersal habitats, where they attach to surfaces in single layers (Russell, 1976 ). A clutch of pear-shaped eggs (7,680 eggs / 61.80 cm 2 ) connected to the glass substrate in the present study suggests that B. humeralis is benthic and iteroparous species exhibiting external fertilization and parental care, offering better protection to eggs. Despite the fact that most gobioid fish deposits eggs on submerged objects and were cared by male (Miller 1984 , Kinzie 1997 , Keith 2003 ), B. humeralis had an egg mass of sparsely distributed tiny eggs similar to E. oxycephala (Dotu and Fujita 1959 ), E. fusca and E. acanthopoma (Maeda et al. 2008 ). This helped to distinguish their egg masses with those of other species. The embryonic head of B. humeralis was located at the distal part of the egg before hatching which is observed to be common in many gobioid fishes while in O. mormoratus , the embryonic head was located at basal part of the egg and has been referred to as “agrippa egg” (Shinomiya et al. 1981 a, b; Suzuki et al. 1988 ; Suzuki et al. 1989 ). The embryonic head or tail of B. humeralis emerged out at the distal end of the egg capsule upon hatching. For many gobies, hatching usually happens after eye pigmentation (Shinomiya et al. 1981 a,b; Suzuki et al. 1988 ; Suzuki et al. 1989 ). Like E. fusca and E. acanthopoma , eye pigmentation in B. humeralis started at 24-hour post-hatch and at 72 HPH, the eyes became densely pigmented (Dotu and Fujita 1959 ; Maeda et al. 2008 ). However, O. mormoratus hatched before, during and after eye pigmentation with ideal hatching stage occurred just before and after the slight pigmentation of embryonic eyes (Tan and Lam 1973 ; Senoo et al. 1994 ). Eggs and newly hatched larvae of B. humeralis were very small with 0.41 mm diameter and 0.97–1.09 mm NL respectively, characterized by lack of pigmented eyes, mouth, and pectoral fins. However, the eggs and newly hatched larvae of all Eleotris species like E. oxycephala (Dotu and Fujita 1959 ; Dotsu et al. 2004 ); E. sandwicensis (Lindstrom 1999 ), described to date, were smaller in size and similar morphologies. Reports state that morphologically similar and smaller eggs and larvae were observed in a number of other eleotrid fish species, including Hypseleotris spp ., Ophieleotris aporos , and Dormitator latifrons , as well as sicydiine gobies and their relatives, including Sicyopterus spp ., Sicydium punctatum , Stiphodon percnopterygionus , Lentipes concolor , Awaous spp ., and Stenogobius hawaiiensis . (Dotsu et al. 1998 , 2000 ; Lindstrom 1999 ; Yamasaki and Tachihara 2006 , 2007 ). Hence the reproductive strategy of B. humeralis characterized by numerous smaller eggs and smaller newly hatched larvae are shared with several eleotrid fishes and sicydiine gobies, as described earlier. B. humeralis larvae were poorly developed at time of hatching and lacked a functional mouth, pigmented eye and differentiated fins due to the smaller size of eggs with narrow perivitelline space and yolk diameters less than 1 mm (Table 1 ). The presence and position of oil globules in yolk-sac larvae varies among fishes. Yolk sac stage starts at hatching and ends when the yolk is absorbed (Kendall 1984). In the present study, the absorption times of the yolk and oil globules were observed at 96 HPH as in Dormitator latrifrons of Eleotridae (Reyes-Mero et al. 2022 ). During the period of yolk and oil globule exhaustion, the larvae of B. humeralis developed pigmented eyes, functional mouth and differentiated fins enabling them to survive progressive starvation during the switch from endogenous to exogenous feeding. Conclusion CE, a part of the Vembanad-Kol Wetland, one of Kerala's three Ramsar sites, is the largest estuary along south west coast of India. The present study reports the occurrence of olive flathead gudgeon with special reference to its early developmental stages for the first time, from the west coast of India. To date, it has been exclusively reported from the east coast of India. More solid body, lack of two black spots at pectoral fin base and the termination of maxilla to the front or middle of eye distinguishes B. humeralis from its close relative, B. butis . B. humeralis belongs to the family Butidae and are widely distributed in the Indo-West Pacific region and has been given the IUCN status as Not Assessed (NA) and Rare (R) species. The presence of B. humeralis eggs in CE indicates that this estuary provides ideal conditions for the breeding and nursing of this species. The present study is the first report of B. humeralis in the west coast of India which illustrates its early larval developmental stages and requires further extensive research to ascertain the demographics of this gobiid fish species from the Indian coast. Declarations Acknowledgements The authors acknowledge the support given by The Director, Head and all the members of the MBEM division, CMFRI. Gratitude to CUSAT for providing institutional support. The authors also acknowledge Dr. Vineetha Gopinath for the critical review, valuable suggestions and thorough correction and editing of the manuscript. Special thanks to the CMFRI In-house project Marine eggs and larval studies along the Indian Coast (PEL/EL/40). Financial support from the CSIR as a research fellowship provided to the first author is gratefully acknowledged. Author Contributions Shameena M. K. designed and executed the study, analysed and interpreted the data and drafted the manuscript. Sruthy V. L. contributed in the conceptualization and execution of the study, molecular characterization and manuscript preparation. Dr. Ratheesh Kumar R. critically edited the article. Dr. Sajeela K. A. provided molecular characterization and analysis and manuscript writing. Dr. P. Kaladharan supervised the work and critically revised the manuscript. All authors have approved the final version of the manuscript. Funding This study was funded by Council of Scientific and Industrial Research (CSIR), Ministry of Human Resources Development, Government of India [01-07-2017-365410]. Competing Interests The authors declare no competing interests Ethical Approval Not applicable Availability of data and materials Sequence data that supports the finding of this study deposited and the Accession number generated in NCBI with primary accession number OP872738. References Anil MK, Santhosh B, Prasad BO, George RM (2012) Broodstock development and breeding of black-finned anemone fish Amphiprion nigripes Regan, 1908 under captive conditions. Indian J Fish pp 59(1):77–82 APHA (1998) Standard Methods for Examination of Water and Wastewater. American Public Health Association, New York, pp 22 Berra TM (2001) Freshwater fish distribution. Academic press, USA Brinley FJ (1939) Spawning habits and development of Beaugregory ( Pomacentrus leucostictus ). Copeia, 185–188. https://doi.org/10. 2307/1436876 Chatterjee TK, Barman RP, Mishra SS (2013) Mangrove associate gobies (Teleostei: Gobioidei) of Indian Sundarbans. Records of the Zool Surv India pp 113(3): 59-77. https://doi.org/10.26515/rzsi/v113/i3/2013/121799 Coates D (1992) Biology of Oxyeleotris heterodon and its major prey, Ophieleotris aporos , two floodplain sleepers (Pisces: Eleotrididae) of the Sepik River fishery, northern Papua New Guinea. Environ Biol Fishes pp 34: 51–64. https://doi.org/10.1007/BF00004784 Dinh QM, Qin J, Dittmann S, Tran, DD (2016). Reproductive biology of the burrow dwelling goby Parapocryptes serperaster . Ichthyol Res pp 63: 324-332. https://doi.org/10.1007/s10228-015-0502-7 Dotsu Y, Miyaki K, Matsuo T, Ono Y, Takahama H (2004) Induced spawning, larval rearing and development of the sleeper, Eleotris oxycephala Temmink et Schlegel, gobioid fish. Bull Fac Fish Nagasaki Univ pp 85: 1–8 Dotsu Y, Suzuki T, Yanagi M (1998) Spawning-induction, embryonic development and larvae of the carp-like sleeper Hypseleotris cyprinoides , gobiid fish. Trans. Nagasaki Biol Soc pp 49: 15–21 Dotsu Y, Yanagi M, Inui T (2000) Spawning-induction and larva-rearing of the Australian gobiid fish Hypseleotris compressus . Bull Fac Fish Nagasaki Univ pp 81:43–48 Dotu, Y, Fujita S (1959) The bionomics and life history of the eleotrid fish, Eleotris oxycephala Temmink et Schlegel. Bull Fac Fish Nagasaki Univ pp 8:191–195 Eschmeyer WN (Eds) (2008) Online Version of the Catalog of Fishes. www.calacademy.org/research/ichthyology/catalog/fishcatsearch.html. (Updated 18 September 2008, Accessed November 2008) Fricke R, Eschmeyer WN, Van der Laan R (Eds) (2022) Eschmeyer’s catalog of fishes: Genera, species, references. California Academy of Sciences, San Francisco, CA, USA. https://researcharchive.calacademy.org/research/ichthyology/catalog/SpeciesByFamily.asp. (Accessed 3 August 2022) Froese R, Pauly D (2015) Welcome to FishBase. In: Froese R, Pauly D (Eds) FishBase. World Wide Web electronic publication. www.fishbase.org, version (10/2015). http://www.fishbase.org/manual/English/PDF/Welcome_to_FishBase_RFroese_etal2015.pdf Geevarghese C (1981) Studies on gobioid fishes of the southwest coast of India. PhD Thesis, University of Kerala Gopi KC (2006) Fish fauna of Kozhikode District, Kerala, South India. Zool Surv India Goulet D (1995) Temporal patterns of reproduction in the Red Sea damselfish Amblyglyphidodon leucogaster . Bull Mar Sci 57:582–595 Hall TA (1999). BioEdit: a user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT. In Nucleic acids symposium series, London, pp 41: 95-98. https://doi.org/10.1098/rstb.2005.1716 Hariprakash KPK, Varada MS, Krishnasadanam ML, Hamsa AAP (2023) First report of the Olive flathead gudgeon, Butis gymnopomus (Bleeker 1853) from Kerala waters with taxonomic notes on B. butis (Hamilton 1822) and B. koilomatodon (Bleeker 1849). Research Square Platform LLC. https://doi.org/10.21203/rs.3.rs-3056597/v1 Hirst A, López-Urrutia A (2006) Effects of evolution on egg development time. Mar Ecol Prog Ser pp 326:29–35 Hoese DF (1984) Gobioidei: Relationships. In: Ontogeny and Systematics of Fishes. H.G. Moser (ed) Special Publication of the American Society of Ichthyologists and Herpetologists No.1. Allen Press, Lawrence, Kansas, pp 588-591. Hoese DF, Gill AC (1993) Phylogenetic relationships of eleotridid fishes (Perciformes: Gobioidei). Bull Mar Sci 52 (1): 415-440. Hubbs CL (1943) Terminology of early stages of fishes. Copeia pp 1943(4): 260-260. https://doi.org/10.2307/1438152 Hui TH, Low ME, Peng KLK (2010) Fishes of the Marina Basin, Singapore, before the erection of the Marina Barrage. The Raffles Bull Zool pp 58(1): 137-144 Ip YK, Leong MWF, Sim MY, Goh GS, Wong WP, Chew SF (2005) Chronic and acute ammonian toxicity in mudskippers, Periophthalmodon schlosseri and Boleophthalmus boddaerti : brain ammonia and glutamine contents and effects of methionine sulfoximine and MK801. J Exp Biol pp 208:1993–2004. https://doi.org/10.1242/jeb.01586 Jeyaseelen MJP, Krishnamurthy K (1980) Role of mangrove forests of Pichavaram as fish nurseries. Proceedings of the Indian National Science Academy pp 46(1): 48-53 Keith P (2003) Biology and ecology of amphidromous Gobiidae of the Indo-Pacific and the Caribbean regions. J Fish Biol pp 63: 831–847. https://doi.org/10.1046/j.1095-8649.2003.00197.x Keith P, Marquet G, Lord C, Kalfatak D, Vigneux E (2010) Vanuatu Freshwater Fish and Crustaceans. French Icthyological Society, Cybium, pp 254 Keith P, Boseto D & Lord C (2021) Freshwater Fish of Solomon Islands. French Icthyological Society, Cybium, pp 174 Kendall Jr AW, Ahlstrom EH, Moser HG (1984) Early life history stages of fishes and their characters. Ontogeny and systematics of fishes - Ahlstrom Symposium, 11-22 Kinzie RA (1997) Evolution and life history patterns in freshwater gobies. Micronesica pp 30: 27–40 Kottelat M (2013) The fishes of the inland waters of Southeast Asia: a catalogue and core bibliography of the fishes known to occur in freshwaters, mangroves and estuaries The Raffles Bulletin of Zoology Suppl. 27:1-663 Koumans FP (1953) Gobioidea. In: Weber M, Beaufort LF (eds) The fishes of the Indo-Australian Archipelago X. Brill, Leiden, pp (10):423 Lindstrom DP (1998) Reproduction, early development and larval transport dynamics of amphidromous Hawaiian gobioids. PhD Thesis, University of Hawai'i at Manoa Lindstrom DP (1999) Molecular species identification of newly hatched Hawaiian amphidromous gobioid larvae. Mar Biotechnol pp 1: 167–174. https://doi.org/10.1007/PL00011764 Lindstrom DP (1999) Molecular species identification of newly hatched Hawaiian amphidromous gobioid larvae. Mar Biotechnol pp 1: 167–174. https://doi.org/10.1007/PL00011764 Maeda K, Yamasaki N, Kondo M, Tachihara K (2008) Reproductive Biology and Early Development of Two Species of Sleeper, Eleotris acanthopoma and Eleotris fusca (Teleostei: Eleotridae) 1. Pacific Science pp 62(3): 327-340.https://doi.org/10.2984/1534-6188(2008)62[327:RBAEDO]2.0.CO;2 Miller PJ (1984) The tokology of gobioid fishes. In: GW, Wooten RJ (ed) Fish reproduction: Strategies and tactics. Academic Press, Orlando, FL USA, pp 119-152 Miller PJ, Wright J, Wongrat P (1989) An Indo-Pacific goby (Teleostei: Gobioidei) from West Africa, with systematic notes on Butis and related eleotridine genera. J Nat Hist 23:311–324. https://doi.org/10.1080/00222938900770201 Mishra SS, Gopi KC (2017) Fish diversity of Indian Sundarban and its resource and research prospects In: Kailash Chandra, JRB Alfred, Bulganin Mitra, Biswajit Roy Chowdhury (eds) Fauna of Sundarban Biosphere Reserve, Zool Surv India, Kolkata, pp107-127 Myrberg Jr AA, Brahy BD, Emery AR (1967) Field observations on reproduction of the damselfish, Chromis multilineata (Pomacentridae), with additional notes on general behavior. Copeia pp (4): 819-827. https://doi.org/10.2307/1441893 Nguyen HPT, Dinh QM (2021) Diet composition of Duckbill sleeper Butis butis (Hamilton, 1822) living in some coastal regions in the Mekong Delta, Vietnam. Aqua Aquarium Cons Legisl Bioflux pp 14(5): 2939-2946. http://www.bioflux.com.ro/aacl Nilsson GE, Hobbs JP, Munday PL, Ostlund-Nilsson S (2004) Coward or braveheart: extreme habitat fidelity through hypoxia tolerance in coral-dwelling goby. J Exp Biol pp 207:33–39. https://doi.org/10.1242/jeb.00713 Raghunathan MB (2007) Faunal Diversity of Ashtatmudi Wetlands, Kerala, India. Rec. Zool Surv India pp 276:1–38 Ramaiyan, V., Purushothaman, A., & Natarajan, R. (1986). Check-list of estuarine and marine fishes of Parangipettai (Porto Novo) coastal waters. Matsya pp 12-13: 1-19. https://api.semanticscholar.org/CorpusID:82239334 Reyes-Mero BM, Santana-Piñeros AM, Muñoz-Chumo LG, Cruz-Quintana Y, Gisbert E (2022) Yolk Absorption Rate and Mouth Development in Larvae of Dormitator latifrons (Perciformes: Eleotridae). Fishes pp 7(6): 375. https://doi.org/10.3390/fishes7060375 Rohini Krishna MV, Anil MK, Neethu Raj P, Santhosh B (2016) Seed production and growth of Neopomacentrus cyanomos (Bleeker, 1856) in captivity. Indian J Fish pp 63(3): 50-56. https://doi.org/10.21077/ijf.2016.63.3.55058-06 Russell FS (1976). The eggs and planktonic stages of British marine fishes. Academic Press, London, New York, 482-510 Senoo S, Kaneko M, Cheah SH, Ang KJ (1994) Egg development, hatching, and larval development of marble goby Oxyeleotris marmoratus under artificial rearing conditions. Fisheries Science pp 60(1): 1-8. https://doi.org/10.2331/fishsci.60.1 Shinomiya A, Maeyama K, Imai S (1981a) Reproductive behaviour of the goby Eviota storthynv (Rofen). Mere Fac Fish Kagoshima Univ pp 30: 237-246 Shinomiya A, Tsuchiya T, Imai S (1981b) Reproductive behaviour of the goby Parioglossus taeniatus (Regan). Mem Fac Fish Kagoshirna Univ 30: 247-255 Suzuki N, Sakurai N, Sugihara T (1988) Development of eggs, larvae and juveniles of the goby Glossogobius ohvaceus reared in the laboratory. Suisanzoshoku 35: 203-212. https://doi.org/10.11233/aquaculturesci1953.35.203 Suzuki N, Sakurai N, Sugihara T (1989) Development of eggs, larvae and juveniles of the Oriental goby Acanthogobius flavimanus reared in laboratory. Suisanzoshoku pp 36: 277-289. https://doi.org/10.11233/aquaculturesci1953.36.277 Tan OKK, Lam TJ (1973) Induced breeding and early development of the marble goby ( Oxyeleotris inarmorata , Blk.). Aquaculture pp 2(44): 411-423. https://doi.org/10.1016/0044-8486(73)90172-5 Thacker CE (2011) Systematics of Butidae and Eleotridae. In: Patzner R, Tassell JLV, Kovacic M, Kapoor BG (eds) The biology of gobies. CRC Press, Broca Raton, pp 79-85. https://doi.org/10.1201/b11397-7 Thresher RE (1984) Reproduction in reef fishes. T.F.H. Publications, Neptune City, pp 399 Untersteggaber L, Mitteroecker P, Herler J (2014) Coral architecture affects the habitat choice and form of associated gobiid fishes. Mar Biol pp 161(3):521–530. https://doi.org/10.1007/s00227-013-2354-x Ward RD, Zemlak TS, Innes BH, Last PR, Hebert PD (2005) DNA barcoding Australia's fish species. Philosophical Transactions of the Royal Society B: Biological Sciences pp 360(1462): 1847-1857. https://doi.org/10.1098/rstb.2005.1716 Yamasaki N, Tachihara K (2006) Reproductive biology and morphology of eggs and larvae of Stiphodon percnopterygionus (Gobiidae: Sicydiinae) collected from Okinawa Island. Ichthyol Res pp 53:12–18. https://doi.org/10.1007/s10228-005-0307-1 Yamasaki N, Tachihara K (2007) Eggs and larvae of Awaous melanocephalus (Teleostei: Gobiidae). Ichthyol Res pp 54: 89-91. https://doi.org/10.1007/s10228-006-0380-0 Yennawar, P., Mohapatra, A., Ray, D., & Tudu, P. (2015). Ichthyofauna of Digha Coast, India In: Marine Faunal Diversity in India. Taxonomy, Ecol and Conserv pp 235-248. https://doi.org/10.1016/B978-0-12-801948-1.00015-X Zeena KV, Jameela Beevi KS (2011) Fish diversity in Ithipuzha and Murinjapuzha, Kerala, India. Journal of Bombay Natural History Society pp 108(2): 98 Zeyl JN, Malavasi S, Holt DE, Noel P, Lugli M, Johnston CE (2016) Convergent aspects of acoustic communication in darters, sculpins, and gobies. Fish hearing and bioacoustics: an anthology in honour of Arthur N. Popper and Richard R. Fay, pp 93-120. https://doi.org/10.1007/978-3-319-21059-96 Additional Declarations No competing interests reported. Supplementary Files captured007.mp4 captured026.mp4 captured033.mp4 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-3954230","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":272993990,"identity":"0e7607e7-a360-4162-9512-6e1e1ea9a590","order_by":0,"name":"M. K. Shameena","email":"","orcid":"","institution":"ICAR - Central Marine Fisheries Research Institute (CMFRI)","correspondingAuthor":false,"prefix":"","firstName":"M.","middleName":"K.","lastName":"Shameena","suffix":""},{"id":272993991,"identity":"13dfefe9-d499-450b-8939-25daa9bf4de7","order_by":1,"name":"Ratheesh Kumar","email":"","orcid":"","institution":"ICAR - Central Marine Fisheries Research Institute (CMFRI)","correspondingAuthor":false,"prefix":"","firstName":"Ratheesh","middleName":"","lastName":"Kumar","suffix":""},{"id":272993992,"identity":"4dc955df-78d8-40ba-8a06-860744ae43ec","order_by":2,"name":"V. L. Sruthy","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzklEQVRIiWNgGAWjYJACZiCW4QexEgqI08HYDCR4JBtAWgxI0WJwAMQmRov87DPmjwvbDvMYn1+d+OGBAYM8v9gB/FoMzuUYNs8EajG78XazBNBhhjNnJxDQwsNj2MzblgbUcnYDSEuCwW0CWuR7oFqMZ5zd/IMoLQxnwFpseAz4e7cRZ4vBGbbC2TznbHgkbvBus0gwkCDsF/ke5g2fecok5Pj7z26++aPCRp5fmpDDQICRDUhIgFVKEKEcDP4AMf8BYlWPglEwCkbBSAMAs2M+r6aAYRMAAAAASUVORK5CYII=","orcid":"","institution":"ICAR - Central Marine Fisheries Research Institute (CMFRI)","correspondingAuthor":true,"prefix":"","firstName":"V.","middleName":"L.","lastName":"Sruthy","suffix":""},{"id":272993993,"identity":"a5416393-c440-4cb4-b317-05ef72c1f487","order_by":3,"name":"K. A. Sajeela","email":"","orcid":"","institution":"ICAR - Central Marine Fisheries Research Institute (CMFRI)","correspondingAuthor":false,"prefix":"","firstName":"K.","middleName":"A.","lastName":"Sajeela","suffix":""},{"id":272993994,"identity":"bbb921a6-496b-4ea3-adf5-076c17951073","order_by":4,"name":"P. Kaladharan","email":"","orcid":"","institution":"ICAR - Central Marine Fisheries Research Institute (CMFRI)","correspondingAuthor":false,"prefix":"","firstName":"P.","middleName":"","lastName":"Kaladharan","suffix":""}],"badges":[],"createdAt":"2024-02-13 19:14:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3954230/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3954230/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":51240387,"identity":"bb2ea18d-8d11-4ddb-b93a-887bc8cf4fe8","added_by":"auto","created_at":"2024-02-16 17:32:29","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":5692829,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea \u003c/strong\u003eSurface of the fouled gritted glass panel with egg mass of \u003cem\u003eB. humeralis \u003c/em\u003e(shown within red heart shape) after 20 days immersion in August 2022 near Kalamukku Fishing Harbour, Cochin Estuary, Kerala. \u003cstrong\u003eb \u003c/strong\u003eMagnified picture of the centre of \u003cem\u003eB. humeralis\u003c/em\u003e egg mass deposited on the surface of the gritted glass panel, showing the typical arrangement of \u003cem\u003eB. humeralis\u003c/em\u003eeggs\u003c/p\u003e","description":"","filename":"Fig1aandb.png","url":"https://assets-eu.researchsquare.com/files/rs-3954230/v1/151bd14ec1a681b94d841217.png"},{"id":51240386,"identity":"f7647009-609b-4d5f-9ada-0aa36f711913","added_by":"auto","created_at":"2024-02-16 17:32:29","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2261120,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea \u003c/strong\u003eEggs of \u003cem\u003eB. humeralis\u003c/em\u003e in twitching and heart beating stage showing the orientation of embryos within the chorionic cavity. Adhesive filaments at the micropylar (proximal) end adhered the eggs with each other and to the surface of the spawning site. \u003cstrong\u003eb\u003c/strong\u003e Prolarval hatching of \u003cem\u003eB. humeralis \u003c/em\u003eby penetrating through the egg membrane\u003c/p\u003e","description":"","filename":"Figure2ab.png","url":"https://assets-eu.researchsquare.com/files/rs-3954230/v1/9308d8087207cc40a5f6b39e.png"},{"id":51240388,"identity":"a7c5ffec-832a-404e-93b5-779ac88b9a4e","added_by":"auto","created_at":"2024-02-16 17:32:30","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":8125910,"visible":true,"origin":"","legend":"\u003cp\u003ea-g Larval development of \u003cem\u003eB. \u003c/em\u003ehumeralis. \u003cstrong\u003ea\u003c/strong\u003e 0- hour post-hatching (hph) \u003cstrong\u003eb\u003c/strong\u003e 24 hph \u003cstrong\u003ec\u003c/strong\u003e 48 HPH \u003cstrong\u003ed\u003c/strong\u003e 72 HPH \u003cstrong\u003ee\u003c/strong\u003e 96 HPH \u003cstrong\u003ef\u003c/strong\u003e 120 HPH \u003cstrong\u003eg\u003c/strong\u003e 144 HPH (dorsal view)\u003c/p\u003e","description":"","filename":"Figure3ag.png","url":"https://assets-eu.researchsquare.com/files/rs-3954230/v1/5646e2c1246a7c6f23a33604.png"},{"id":59409427,"identity":"38e48ddd-5df3-4ecf-bd39-91e6d45e8b6a","added_by":"auto","created_at":"2024-07-01 12:14:32","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":22262922,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3954230/v1/117a4514-7255-4026-b3b9-e4b945a3476e.pdf"},{"id":51240390,"identity":"d298f65e-07f8-4bb6-860e-5050c45867d4","added_by":"auto","created_at":"2024-02-16 17:32:30","extension":"mp4","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":16873824,"visible":true,"origin":"","legend":"","description":"","filename":"captured007.mp4","url":"https://assets-eu.researchsquare.com/files/rs-3954230/v1/a8d925eebc6c4b0c7693ebc7.mp4"},{"id":51240391,"identity":"68ef01b7-d31b-4dc8-9db6-c472929f18be","added_by":"auto","created_at":"2024-02-16 17:32:31","extension":"mp4","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":26142948,"visible":true,"origin":"","legend":"","description":"","filename":"captured026.mp4","url":"https://assets-eu.researchsquare.com/files/rs-3954230/v1/4cd230e56ced2c67c93ef53c.mp4"},{"id":51240392,"identity":"ea132478-5157-40c5-b95a-5015c367e7a6","added_by":"auto","created_at":"2024-02-16 17:32:32","extension":"mp4","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":43342112,"visible":true,"origin":"","legend":"","description":"","filename":"captured033.mp4","url":"https://assets-eu.researchsquare.com/files/rs-3954230/v1/5df8f533be6e29c4dfaf301e.mp4"}],"financialInterests":"No competing interests reported.","formattedTitle":"First Record of Butis humeralis (Gobiiformes: Butidae) from the West Coast of India with special emphasis to its Early Developmental Stages","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSleeper gobies or gudgeons belong to the family Butidae comprising of 47 species classified under 10 genera (Fricke et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Butids are robust, heavy-bodied fishes characterised by cylindrical appearance with rayed dorsal fins and discrete pelvic fins not joined by any membrane (Hoese \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e1984\u003c/span\u003e; Hoese and Gill \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1993\u003c/span\u003e). They often attain a size of 10\u0026ndash;25 cm and exhibits heavier scalation (Eschmeyer \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2008\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eButids are primarily found in tropical and sub-tropical brackish and freshwater zones of Asia, Africa, Australia and Oceania (Thacker \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). They are primarily benthic as most of the species lack swim bladders to maintain buoyancy in the water column (Zeyl et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Their resilience and tolerance to low oxygen and salinity makes them an excellent candidate in experimental studies (Nilsson et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Ip et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). The great diversity in morphology, behavioural adaptations and niche specializations exhibited by these fishes is an indication of the wide range of environmental circumstances they confront (Untersteggaber et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e9 species belonging to 5 genera\u0026mdash;\u003cem\u003eButis\u003c/em\u003e, \u003cem\u003eBostrychus\u003c/em\u003e, \u003cem\u003eOdonteleotris\u003c/em\u003e, \u003cem\u003eOphiocara\u003c/em\u003e, and \u003cem\u003eIncara\u003c/em\u003e of the family Butidae are reported from Indian waters among which \u003cem\u003eButis\u003c/em\u003e is the most diverse. The species of genus \u003cem\u003eButis\u003c/em\u003e is extensively dispersed, from brackish waters, mangroves, estuaries to the lower reaches of freshwater rivers. These ambush hunters occur in mud bottoms, bank flora, and dead branches, preying on small fish and crustaceans like prawns and shrimps (Keith et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2010\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Nguyen and Din 2021). According to Kottelat (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) and Fricke et al. (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), the genus \u003cem\u003eButis\u003c/em\u003e contains five to six valid species, including \u003cem\u003eB. butis\u003c/em\u003e, \u003cem\u003eB. humeralis\u003c/em\u003e, \u003cem\u003eB. koilomatodon\u003c/em\u003e, \u003cem\u003eB. gymnopomus\u003c/em\u003e, \u003cem\u003eB. amboinensis\u003c/em\u003e, and \u003cem\u003eB. prismaticus\u003c/em\u003e. Of these, \u003cem\u003eB. humeralis\u003c/em\u003e and \u003cem\u003eB. amboinensis\u003c/em\u003e were only reported from the east coast of India, while \u003cem\u003eB. butis\u003c/em\u003e, \u003cem\u003eB. koilomatodon\u003c/em\u003e, and \u003cem\u003eB. gymnopomous\u003c/em\u003e were found in estuarine waters of Kerala (Geevargheese 1981; Gopi \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Raghunathan \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Zeena \u0026amp; Beevi 2011; Hariprakash et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe present study is the first report of \u003cem\u003eB. humeralis\u003c/em\u003e from the west-coast of India from Cochin Estuary (CE), Kerala. The study also gives a detailed description of the egg morphology, hatching and changes associated with growth and development of \u003cem\u003eB. humeralis\u003c/em\u003e under laboratory conditions.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003eStudy area and Sampling method\u003c/h2\u003e\n \u003cp\u003eTo study the biofouling impacts on aquaculture cages, gritted glass panels (150 mm \u0026times; 150 mm \u0026times; 2 mm) were suspended at a depth of 1-1.5 m near cage sites at Kalamukku Fishing Harbour (9⁰59\u0026apos;11.7 \u0026quot;N 76⁰14\u0026apos;43.7\u0026quot; E), in Cochin Estuary (CE), Kerala, one of the largest estuaries along the west coast of India. Upon retrieval of the glass panels in August 20, 2022, numerous eggs were found adhered to it. The glass panels with the eggs were carefully detached from the cages and transported to laboratory for further investigation. The physico-chemical characteristics of surface water samples collected from the sites were conducted as per standard procedures (APHA \u003cspan class=\"CitationRef\"\u003e1998\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003eMicroscopic examination of the egg samples\u003c/h2\u003e\n \u003cp\u003eA cluster of eggs were observed on the gritted glass panel, whose measurements were taken under the stereo microscope (Nikon SMZ25 \u0026ndash; NIS Elements D 5.30.00). The area of attachment of eggs on gritted glass panel were recorded by counting the total number of grits containing eggs and multiply it with the area of a single grit and the average number of eggs found within that single grit. These eggs were carefully detached from the panel using a brush and kept in a 1000 ml glass jar containing estuarine water collected from the cage sites and observed every 24 h to study the early developmental stages.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003eMolecular characterization of the eggs\u003c/h2\u003e\n \u003cp\u003eEggs were collected and preserved in 95% ethanol. Total DNA was isolated using DNeasy Blood and Tissue kit (Qiagen, Germany) followed by the manufacturer\u0026apos;s instructions. The quality and quantity of the extracted DNA were estimated using a NanoDrop One Microvolume UV-Vis Spectrophotometer (Thermo-Fisher Scientific). The molecular phylogenetic studies were carried out using mitochondrial Cytochrome Oxidase I (COI) universal primers - Fish F1 5\u0026rsquo;-TCAACCAACCACAAAGACATTGGCAC-3\u0026apos; and Fish R1 5\u0026rsquo;-TAGACTTCTGGGTGGCCAAAGAAT CA-3\u0026apos; (Ward et al. \u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003ePCR Amplification was performed in 25 \u0026micro;l reactions containing 2X PCR Master mix (Takara Bio INC) using 20 pM of primers and 20 ng of template DNA. The reaction mixture was pre-heated at 94\u003csup\u003e0\u003c/sup\u003eC for 5 minutes followed by 25 cycles (94\u003csup\u003e0\u003c/sup\u003eC for 30 seconds, 50\u003csup\u003e0\u003c/sup\u003eC for 30 seconds, and 72\u003csup\u003e0\u003c/sup\u003eC for 35 seconds) and a final extension at 72\u003csup\u003e0\u003c/sup\u003eC for 5 minutes. PCR products were visualized in a 1.5% agarose gel and compared with a NEX-GEN 100 bp DNA ladder (Genetix Biotech Asia Pvt. Ltd., New Delhi, India). PCR products were sent for sequencing to the sequencing facility (Enfys Lifesciences Pvt. Ltd., Kerala, India). The forward and reverse DNA sequences were aligned and assembled using the Bio Edit sequence alignment editor, version 7.0.5.2 (Hall, \u003cspan class=\"CitationRef\"\u003e1999\u003c/span\u003e). The sequences were searched using BLAST in GenBank (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ewww.ncbi.nlm.nih.gov/nucloetide\u003c/span\u003e\u003c/span\u003e) to verify the morphological identifications at the species level.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Result","content":"\u003cp\u003eFamily: BUTIDAE\u003c/p\u003e \u003cp\u003e \u003cem\u003eButis humeralis\u003c/em\u003e (Valenciennes, 1837).\u003c/p\u003e \u003cp\u003eOlive flathead gudgeon or dark sleeper.\u003c/p\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eDistribution\u003c/h2\u003e \u003cp\u003e \u003cem\u003eB. humeralis\u003c/em\u003e is a fish indigenous to the waters of Indonesia and Indochina (Froese and Pauly \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eSpawning habit\u003c/h2\u003e \u003cp\u003eA cluster of eggs was found on gritted glass panel submerged for biofouling studies in aquaculture cages near Kalamukku fishing harbour in CE. The egg mass covered an area of 61.80 cm\u003csup\u003e2\u003c/sup\u003e on the glass panel with an average of 124.51\u0026thinsp;\u0026plusmn;\u0026thinsp;27.25 eggs/cm\u003csup\u003e2\u003c/sup\u003e (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD; n\u0026thinsp;=\u0026thinsp;10). Egg masses were irregularly distributed on the surface of the glass panel (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea and b).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe egg mass appeared to be a single clutch due to their homogenous growth and appearance. Owing due to the sparseness in distribution, minute size of the eggs, and variability of the density within an egg mass, it was difficult to determine the accurate number of eggs within the clutch. Nevertheless, a rough estimate of the number of eggs from subsamples showed that the clutch comprises of approximately 7,000 eggs.\u003c/p\u003e \u003cp\u003eThe atmospheric temperature, water temperature, salinity and pH of the study area during sample collection was 28⁰C, 26⁰C, 6 PSU, and 7.29, respectively. Other physiochemical parameters like turbidity, total suspended solids (TSS) and dissolved oxygen (DO) during the sampling period was 7.58\u0026thinsp;\u0026plusmn;\u0026thinsp;0.88 NTU, 28.67\u0026thinsp;\u0026plusmn;\u0026thinsp;0.002 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 5.43\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. The nutrients, including inorganic nitrate, nitrite, inorganic phosphate, silicate, and ammonia were 0.129\u0026thinsp;\u0026plusmn;\u0026thinsp;0.002 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 0.008\u0026thinsp;\u0026plusmn;\u0026thinsp;0.002 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 0.063\u0026thinsp;\u0026plusmn;\u0026thinsp;0.017 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1.34\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1,\u003c/sup\u003e and 0.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.018 mg L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively.\u003c/p\u003e \u003cp\u003e \u003cb\u003eEarly development\u003c/b\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003ei. Egg morphology and Hatching\u003c/h2\u003e \u003cp\u003eEggs of \u003cem\u003eB. humeralis\u003c/em\u003e were pyriform in shape, with a protuberance at the micropylar (proximal) end comprising of a bundle of adhesive filaments that held the eggs together on to the surface (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). Eggs were demersal and brownish yellow in colour. The mean vertical diameter of 10 eggs from the egg mass, ranged between 0.40 and 0.42 mm (0.41\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01), whereas the mean horizontal diameter ranged between 0.34 and 0.36 mm (0.36\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01). The eggs showed twitching and heart beating movements. Both tail and head-end were clearly visible. The embryonic head was located at the distal part of the egg while the tail of the embryo was coiled around within the egg membrane. Egg possessed primitive optic vesicle, notochord and yolk sac with numerous oil globules of diameter 0.076\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03 mm. Twitching and wriggling movements became more vigorous just before hatching and the embryo ruptured the egg capsule and yolk sac larva came out within 2 to 3 hours after brought to the laboratory (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eLarval Development\u003c/h2\u003e \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e \u003ch2\u003eDay 1 (0 - hour post-hatching (hph))\u003c/h2\u003e \u003cp\u003eAccording to Hubbs (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e1943\u003c/span\u003e), a recently hatched embryo which is completely reliant on the yolk for nourishment is regarded as a prolarva. Newly hatched prolarvae of \u003cem\u003eB. humeralis\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea) were slender and translucent with 0.97\u0026ndash;1.09 mm NL. Larvae had large, slightly oval, brownish yolk sac with diameter of 0.55\u0026ndash;0.62 mm along longitudinal axis and 0.36\u0026ndash;0.47 mm along horizontal axis. Numerous oil globules were found on the yolk sac with diameters ranging between 0.02 and 0.11 mm. The mouth of the newly hatched larvae was not developed, and primitive optic vesicles and otoliths formed laterally on the head, and the eyes were unpigmented. Melanophores appeared on the tip of the snout, above the eyes, on the anterior and posterior margins of the yolk sac, ventrally on the posterior half of the trunk, ventrally on the anterior two-thirds of the tail, and dorsally on the midtail. All the melanophores were associated with xanthophores. The caudal fin and digestive tract were not visible in the early pre-flexion larvae.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eDay 2 (24 hph)\u003c/h2\u003e \u003cp\u003eOne day after hatching (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb), the larvae exhibited marked growth and increased in size to 1.15 \u0026minus;\u0026thinsp;1.2 mm NL with TL ranged between 1.19\u0026ndash;1.25 mm. The yolk sac was partially decreased in diameter with 0.29\u0026ndash;0.34 mm and 0.23\u0026ndash;0.25 mm diameters along vertical and horizontal axes respectively. Oil droplets coalesced into two globules with 0.05\u0026ndash;0.08 mm diameter. The embryonic fin fold formed. Myomeres were partially visible. Melanophores and xanthophores above the eyes vanished, and portions of the eye margin turned pigmented. Ventral melanophores and xanthophores reduced on the anterior margins of the yolk sac and irregular bands of pigments appeared on its trunk and caudal region. The larvae showed slight movements with \"swim up, sink down\" behaviour by using its tail.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eDay 3 (48 hph):\u003c/h2\u003e \u003cp\u003eTwo days after hatching (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec), the larvae of \u003cem\u003eB. humeralis\u003c/em\u003e increased in notochord length (NL) to 1.53\u0026ndash;1.55 mm. The head and unopened mouth appeared as a prominence or bump. The yolk sac further reduced in diameter to 0.12\u0026ndash;013 mm (vertical) and 0.15\u0026ndash;0.16 mm (horizontal). Oil globules were completely absorbed. Lens and choroid fissures were formed on the eye located at the anterior-lateral position of the head. Notochord became distinct. Myomeres became well developed with fifteen pre-anal and forty-five post-anal myomeres. Anus and pectoral fin bud was slightly visible. Melanophores appeared above the eye, yolk sac and head. Vertical melanophore bands prominently appeared on the body and caudal region. Larvae started swimming with constant tail movements.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eDay 4 (72 hph):\u003c/h2\u003e \u003cp\u003eThree days after hatching (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed), the size of larvae remained similar to that of the previous day. Remnants of the yolk sac were apparent (0.08\u0026ndash;0.1 mm diameter). Mouth cleft was prominent. The eyes became dark and fully pigmented with a diameter of 0.11\u0026ndash;0.12 mm. Pectoral fins developed.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eDay 5 (96 hph):\u003c/h2\u003e \u003cp\u003eFour days after hatching (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee), well developed mouth formed with clearly distinct upper and lower jaws. The yolk sac was completely absorbed. Larvae displayed wandering movements with frequent opening of the upper and lower jaws. Melanophores were observed in series along the lower jaw, below the gut, and dorsal and ventral lines of the body. Dorsal, anal, and caudal fin folds were also present.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eDay 6 (120 hph):\u003c/h2\u003e \u003cp\u003eSix days after hatching (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef), the size of the larvae slightly increased with NL and TL ranging between 1.6\u0026ndash;1.7 mm and 1.67\u0026ndash;1.69 mm, respectively. Mouth opened with a gape of 0.04\u0026ndash;0.05 mm. Body depth at anus was 0.25\u0026ndash;0.26 mm. Pectoral fin length was 0.12\u0026ndash;0.14 mm. Head length and head depth were 0.28\u0026ndash;0.29 mm and 0.26\u0026ndash;0.27 mm, respectively. Eye diameter was 0.12\u0026ndash;0.13 mm.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eDay 7 (144 hph):\u003c/h2\u003e \u003cp\u003eSeven days after hatching (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eg), the NL and TL of the larvae ranged between 1.96\u0026ndash;2.0 mm and 2.08\u0026ndash;2.12 mm, respectively. The growth of upper and lower jaw slowed compared to the previous days. Head length slightly increased and was characterized by a diameter of 0.28\u0026ndash;0.36 mm.\u003c/p\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\u003eChanges in the length and width of yolk sac from 0 to 96 hph\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAfter hatching hours\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYolk sac length (mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eYolk sac width (mm)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.55\u0026ndash;0.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.36\u0026ndash;0.47\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.29\u0026ndash;0.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.23\u0026ndash;0.25\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.12\u0026ndash;013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.15\u0026ndash;0.16\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.08\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eYolk exhausted\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\u003e \u003cb\u003eMolecular taxonomy of\u003c/b\u003e \u003cb\u003eB. humeralis\u003c/b\u003e\u003c/p\u003e \u003cp\u003eSequences of 687 bp length were obtained after sequencing and alignment. Similarity search (BLAST) in the NCBI database showed 99.84% identity to \u003cem\u003eButis humeralis\u003c/em\u003e with 92% query coverage. The sequence was submitted to NCBI GenBank with accession no. OP872738\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003e \u003cem\u003eB. humeralis\u003c/em\u003e (Valenciennes 1837), also known as dark sleeper or olive flathead-gudgeon, was previously reported as \u003cem\u003eB. melanostigma\u003c/em\u003e (Bleeker 1874) from Parangipettai (Porto Novo) coastal waters, Tamil Nadu (Ramaiyan et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e1986\u003c/span\u003e). It was also known from Indian Sundarbans and Digha coast, West Bengal (Chatterjee et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Mishra and Gopi \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Yennawar et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) and coastal and estuarine waters of Tamil Nadu (Jeyaseelen and Krishnamurthy \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1980\u003c/span\u003e). Previous reports from Kerala have described three species of \u003cem\u003eButis\u003c/em\u003e; but the probable existence of other congeners is scanty, possibly due to little commercial interest in these species. The current study revealed the occurrence of \u003cem\u003eB. humeralis\u003c/em\u003e in Kerala waters, which is the first report of its existence along west-coast of India. Although the information related to the early developmental stages of \u003cem\u003eB. humeralis\u003c/em\u003e\u0026rsquo; are lacking, the present study finds relevance as it details the egg morphology, hatching and development of preflexion larva utpo 144 HPH by monitoring the changes of eyes, pigmentation, fins, yolk sac size, oil globules and mouth.\u003c/p\u003e \u003cp\u003eAccording to Koumans (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1953\u003c/span\u003e) and Miller et al. (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e1989\u003c/span\u003e), the habitat of \u003cem\u003eB. humeralis\u003c/em\u003e and \u003cem\u003eB. koilomatodon\u003c/em\u003e varies from marine to freshwater. In the present study, the brackish water environment where \u003cem\u003eB. humeralis\u003c/em\u003e eggs were found was influenced by tidal incursion with marked fluctuations in salinity ranging from 0 to 20 ppt. According to Hui et al. (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), though \u003cem\u003eB. humeralis\u003c/em\u003e may survive in freshwater, they may not breed successfully if access to the marine environment is restricted.\u003c/p\u003e \u003cp\u003e \u003cem\u003eB. humeralis\u003c/em\u003e shares similarity in egg morphology with that of the two sleeper gobies of Eleotridae, \u003cem\u003eEleotris fusca\u003c/em\u003e and \u003cem\u003eE. acanthopoma\u003c/em\u003e, as well as with an indigenous Hawaiin goby, \u003cem\u003eLenticeps concolor\u003c/em\u003e. The eggs of these gobies appear pear-shaped and adhere to the substrate using a bundle of adhesive filaments at their proximal end, and even interconnect with the neighbouring eggs to form a monolayer. (Lindstorm 1998; Maeda et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). The average vertical and horizontal diameters of the eggs of \u003cem\u003eB. humeralis\u003c/em\u003e are also comparable to those of \u003cem\u003eE. fusca\u003c/em\u003e and \u003cem\u003eE. acanthopoma\u003c/em\u003e.\u003c/p\u003e \u003cp\u003eMajority of gobiids have an iteroparous pattern of reproduction, with females releasing eggs on vegetation or substrates, while males assist in their post-fertilization care. The lunar cycle is crucial for their spawning and larval recruitment in estuaries (Miller \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1984\u003c/span\u003e; Thresher \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e1984\u003c/span\u003e; Berra \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Dinh et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). In this study, the matured eggs of \u003cem\u003eB. humeralis\u003c/em\u003e was collected five days prior to the new moon from CE. Eggs attached to substrate spawns during morning hours and are less vulnerable to predation due to parental care and their placement in protected areas (Brinley \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1939\u003c/span\u003e; Myrberg Jr et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e1967\u003c/span\u003e; Goulet \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Anil et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Rohini Krishna et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) than the pelagic eggs, which is more prone to high mortality (Hirst and Lopez-Urrutia 2006). Gobies lay pear-shaped eggs in demersal habitats, where they attach to surfaces in single layers (Russell, \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e1976\u003c/span\u003e). A clutch of pear-shaped eggs (7,680 eggs / 61.80 cm\u003csup\u003e2\u003c/sup\u003e) connected to the glass substrate in the present study suggests that \u003cem\u003eB. humeralis\u003c/em\u003e is benthic and iteroparous species exhibiting external fertilization and parental care, offering better protection to eggs.\u003c/p\u003e \u003cp\u003eDespite the fact that most gobioid fish deposits eggs on submerged objects and were cared by male (Miller \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1984\u003c/span\u003e, Kinzie \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e1997\u003c/span\u003e, Keith \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2003\u003c/span\u003e), \u003cem\u003eB. humeralis\u003c/em\u003e had an egg mass of sparsely distributed tiny eggs similar to \u003cem\u003eE. oxycephala\u003c/em\u003e (Dotu and Fujita \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1959\u003c/span\u003e), \u003cem\u003eE. fusca and E. acanthopoma\u003c/em\u003e (Maeda et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). This helped to distinguish their egg masses with those of other species.\u003c/p\u003e \u003cp\u003eThe embryonic head of \u003cem\u003eB. humeralis\u003c/em\u003e was located at the distal part of the egg before hatching which is observed to be common in many gobioid fishes while in \u003cem\u003eO. mormoratus\u003c/em\u003e, the embryonic head was located at basal part of the egg and has been referred to as \u0026ldquo;agrippa egg\u0026rdquo; (Shinomiya et al. 1981 a, b; Suzuki et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Suzuki et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). The embryonic head or tail of \u003cem\u003eB. humeralis\u003c/em\u003e emerged out at the distal end of the egg capsule upon hatching.\u003c/p\u003e \u003cp\u003eFor many gobies, hatching usually happens after eye pigmentation (Shinomiya et al. 1981 a,b; Suzuki et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Suzuki et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). Like \u003cem\u003eE. fusca\u003c/em\u003e and \u003cem\u003eE. acanthopoma\u003c/em\u003e, eye pigmentation in \u003cem\u003eB. humeralis\u003c/em\u003e started at 24-hour post-hatch and at 72 HPH, the eyes became densely pigmented (Dotu and Fujita \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1959\u003c/span\u003e; Maeda et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). However, \u003cem\u003eO. mormoratus\u003c/em\u003e hatched before, during and after eye pigmentation with ideal hatching stage occurred just before and after the slight pigmentation of embryonic eyes (Tan and Lam \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e1973\u003c/span\u003e; Senoo et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e1994\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eEggs and newly hatched larvae of \u003cem\u003eB. humeralis\u003c/em\u003e were very small with 0.41 mm diameter and 0.97\u0026ndash;1.09 mm NL respectively, characterized by lack of pigmented eyes, mouth, and pectoral fins. However, the eggs and newly hatched larvae of all \u003cem\u003eEleotris\u003c/em\u003e species like \u003cem\u003eE. oxycephala\u003c/em\u003e (Dotu and Fujita \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1959\u003c/span\u003e; Dotsu et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2004\u003c/span\u003e); E. \u003cem\u003esandwicensis\u003c/em\u003e (Lindstrom \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1999\u003c/span\u003e), described to date, were smaller in size and similar morphologies. Reports state that morphologically similar and smaller eggs and larvae were observed in a number of other eleotrid fish species, including \u003cem\u003eHypseleotris spp\u003c/em\u003e., \u003cem\u003eOphieleotris aporos\u003c/em\u003e, and \u003cem\u003eDormitator latifrons\u003c/em\u003e, as well as sicydiine gobies and their relatives, including \u003cem\u003eSicyopterus spp\u003c/em\u003e., \u003cem\u003eSicydium punctatum\u003c/em\u003e, \u003cem\u003eStiphodon percnopterygionus\u003c/em\u003e, \u003cem\u003eLentipes concolor\u003c/em\u003e, \u003cem\u003eAwaous spp\u003c/em\u003e., and \u003cem\u003eStenogobius hawaiiensis\u003c/em\u003e. (Dotsu et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1998\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Lindstrom \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Yamasaki and Tachihara \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2006\u003c/span\u003e, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Hence the reproductive strategy of \u003cem\u003eB. humeralis\u003c/em\u003e characterized by numerous smaller eggs and smaller newly hatched larvae are shared with several eleotrid fishes and sicydiine gobies, as described earlier.\u003c/p\u003e \u003cp\u003e \u003cem\u003eB. humeralis\u003c/em\u003e larvae were poorly developed at time of hatching and lacked a functional mouth, pigmented eye and differentiated fins due to the smaller size of eggs with narrow perivitelline space and yolk diameters less than 1 mm (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The presence and position of oil globules in yolk-sac larvae varies among fishes. Yolk sac stage starts at hatching and ends when the yolk is absorbed (Kendall 1984). In the present study, the absorption times of the yolk and oil globules were observed at 96 HPH as in \u003cem\u003eDormitator latrifrons\u003c/em\u003e of Eleotridae (Reyes-Mero et al. \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). During the period of yolk and oil globule exhaustion, the larvae of \u003cem\u003eB. humeralis\u003c/em\u003e developed pigmented eyes, functional mouth and differentiated fins enabling them to survive progressive starvation during the switch from endogenous to exogenous feeding.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eCE, a part of the Vembanad-Kol Wetland, one of Kerala's three Ramsar sites, is the largest estuary along south west coast of India. The present study reports the occurrence of olive flathead gudgeon with special reference to its early developmental stages for the first time, from the west coast of India. To date, it has been exclusively reported from the east coast of India. More solid body, lack of two black spots at pectoral fin base and the termination of maxilla to the front or middle of eye distinguishes \u003cem\u003eB. humeralis\u003c/em\u003e from its close relative, \u003cem\u003eB. butis\u003c/em\u003e. \u003cem\u003eB. humeralis\u003c/em\u003e belongs to the family Butidae and are widely distributed in the Indo-West Pacific region and has been given the IUCN status as Not Assessed (NA) and Rare (R) species. The presence of \u003cem\u003eB. humeralis\u003c/em\u003e eggs in CE indicates that this estuary provides ideal conditions for the breeding and nursing of this species. The present study is the first report of \u003cem\u003eB. humeralis\u003c/em\u003e in the west coast of India which illustrates its early larval developmental stages and requires further extensive research to ascertain the demographics of this gobiid fish species from the Indian coast.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e The authors acknowledge the support given by The Director, Head and all the members of the MBEM division, CMFRI. Gratitude to CUSAT for providing institutional support. The authors also acknowledge Dr. Vineetha Gopinath for the critical review, valuable suggestions and thorough correction and editing of the manuscript. Special thanks to the CMFRI In-house project Marine eggs and larval studies along the Indian Coast (PEL/EL/40). Financial support from the CSIR as a research fellowship provided to the first author is gratefully acknowledged.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u0026nbsp;\u003c/strong\u003eShameena M. K. designed and executed the study, analysed and interpreted the data and drafted the manuscript. Sruthy V. L. contributed in the conceptualization and execution of the study, molecular characterization and manuscript preparation. Dr. Ratheesh Kumar R. critically edited the article. Dr. Sajeela K. A. provided molecular characterization and analysis and manuscript writing. Dr. P. Kaladharan supervised the work and critically revised the manuscript. All authors have approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003eThis study was funded by Council of Scientific and Industrial Research (CSIR), Ministry of Human Resources Development, Government of India [01-07-2017-365410].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u0026nbsp;\u003c/strong\u003eThe authors declare no competing interests\u0026nbsp;\u003c/p\u003eEthical Approval \n\nNot applicable\n\nAvailability of data and materials \n\nSequence data that supports the finding of this study deposited and the Accession number generated in NCBI with primary accession number OP872738."},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAnil MK, Santhosh B, Prasad BO, George RM (2012) Broodstock development and breeding of black-finned anemone fish \u003cem\u003eAmphiprion nigripes\u003c/em\u003e Regan, 1908 under captive conditions. Indian J Fish pp 59(1):77\u0026ndash;82\u003c/li\u003e\n\u003cli\u003eAPHA (1998) Standard Methods for Examination of Water and Wastewater. American Public Health Association, New York, pp 22\u003c/li\u003e\n\u003cli\u003eBerra TM (2001) Freshwater fish distribution. Academic press, USA\u003c/li\u003e\n\u003cli\u003eBrinley FJ (1939) Spawning habits and development of Beaugregory (\u003cem\u003ePomacentrus leucostictus\u003c/em\u003e). Copeia, 185\u0026ndash;188. https://doi.org/10. 2307/1436876\u003c/li\u003e\n\u003cli\u003eChatterjee TK, Barman RP, Mishra SS (2013) Mangrove associate gobies (Teleostei: Gobioidei) of Indian Sundarbans. Records of the Zool Surv India pp 113(3): 59-77. https://doi.org/10.26515/rzsi/v113/i3/2013/121799\u003c/li\u003e\n\u003cli\u003eCoates D (1992) Biology of \u003cem\u003eOxyeleotris heterodon \u003c/em\u003eand its major prey, \u003cem\u003eOphieleotris aporos\u003c/em\u003e, two floodplain sleepers (Pisces: Eleotrididae) of the Sepik River fishery, northern Papua New Guinea. Environ Biol Fishes pp 34: 51\u0026ndash;64. https://doi.org/10.1007/BF00004784\u003c/li\u003e\n\u003cli\u003eDinh QM, Qin J, Dittmann S, Tran, DD (2016). Reproductive biology of the burrow dwelling goby \u003cem\u003eParapocryptes serperaster\u003c/em\u003e. Ichthyol Res pp 63: 324-332. https://doi.org/10.1007/s10228-015-0502-7\u003c/li\u003e\n\u003cli\u003eDotsu Y, Miyaki K, Matsuo T, Ono Y, Takahama H (2004) Induced spawning, larval rearing and development of the sleeper, \u003cem\u003eEleotris oxycephala\u003c/em\u003e Temmink et Schlegel, gobioid fish. Bull Fac Fish Nagasaki Univ pp 85: 1\u0026ndash;8 \u003c/li\u003e\n\u003cli\u003eDotsu Y, Suzuki T, Yanagi M (1998) Spawning-induction, embryonic development and larvae of the carp-like sleeper \u003cem\u003eHypseleotris cyprinoides\u003c/em\u003e, gobiid fish. Trans. Nagasaki Biol Soc pp 49: 15\u0026ndash;21\u003c/li\u003e\n\u003cli\u003eDotsu Y, Yanagi M, Inui T (2000) Spawning-induction and larva-rearing of the Australian gobiid fish \u003cem\u003eHypseleotris compressus\u003c/em\u003e. Bull Fac Fish Nagasaki Univ pp 81:43\u0026ndash;48\u003c/li\u003e\n\u003cli\u003eDotu, Y, Fujita S (1959) The bionomics and life history of the eleotrid fish, \u003cem\u003eEleotris oxycephala\u003c/em\u003e Temmink et Schlegel. Bull Fac Fish Nagasaki Univ pp 8:191\u0026ndash;195 \u003c/li\u003e\n\u003cli\u003eEschmeyer WN (Eds) (2008) Online Version of the Catalog of Fishes. www.calacademy.org/research/ichthyology/catalog/fishcatsearch.html. (Updated 18 September 2008, Accessed November 2008)\u003c/li\u003e\n\u003cli\u003eFricke R, Eschmeyer WN, Van der Laan R (Eds) (2022) Eschmeyer\u0026rsquo;s catalog of fishes: Genera, species, references. California Academy of Sciences, San Francisco, CA, USA. https://researcharchive.calacademy.org/research/ichthyology/catalog/SpeciesByFamily.asp. (Accessed 3 August 2022)\u003c/li\u003e\n\u003cli\u003eFroese R, Pauly D (2015) Welcome to FishBase. In: Froese R, Pauly D (Eds) FishBase. World Wide Web electronic publication. www.fishbase.org, version (10/2015). http://www.fishbase.org/manual/English/PDF/Welcome_to_FishBase_RFroese_etal2015.pdf \u003c/li\u003e\n\u003cli\u003eGeevarghese C (1981) Studies on gobioid fishes of the southwest coast of India. PhD Thesis, University of Kerala\u003c/li\u003e\n\u003cli\u003eGopi KC (2006) Fish fauna of Kozhikode District, Kerala, South India. Zool Surv India\u003c/li\u003e\n\u003cli\u003eGoulet D (1995) Temporal patterns of reproduction in the Red Sea damselfish \u003cem\u003eAmblyglyphidodon leucogaster\u003c/em\u003e. Bull Mar Sci 57:582\u0026ndash;595\u003c/li\u003e\n\u003cli\u003eHall TA (1999). BioEdit: a user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT. In Nucleic acids symposium series, London, pp 41:\u003cem\u003e \u003c/em\u003e95-98. https://doi.org/10.1098/rstb.2005.1716\u003c/li\u003e\n\u003cli\u003eHariprakash KPK, Varada MS, Krishnasadanam ML, Hamsa AAP (2023) First report of the Olive flathead gudgeon, \u003cem\u003eButis gymnopomus\u003c/em\u003e (Bleeker 1853) from Kerala waters with taxonomic notes on \u003cem\u003eB. butis\u003c/em\u003e (Hamilton 1822) and \u003cem\u003eB. koilomatodon\u003c/em\u003e (Bleeker 1849). Research Square Platform LLC. https://doi.org/10.21203/rs.3.rs-3056597/v1 \u003c/li\u003e\n\u003cli\u003eHirst A, L\u0026oacute;pez-Urrutia A (2006) Effects of evolution on egg development time. Mar Ecol Prog Ser pp 326:29\u0026ndash;35\u003c/li\u003e\n\u003cli\u003eHoese DF (1984) Gobioidei: Relationships. In: Ontogeny and Systematics of Fishes. H.G. Moser (ed) Special Publication of the American Society of Ichthyologists and Herpetologists No.1. Allen Press, Lawrence, Kansas, pp 588-591.\u003c/li\u003e\n\u003cli\u003eHoese DF, Gill AC (1993) Phylogenetic relationships of eleotridid fishes (Perciformes: Gobioidei). Bull Mar Sci 52 (1): 415-440.\u003c/li\u003e\n\u003cli\u003eHubbs CL (1943) Terminology of early stages of fishes. Copeia pp 1943(4): 260-260. https://doi.org/10.2307/1438152\u003c/li\u003e\n\u003cli\u003eHui TH, Low ME, Peng KLK (2010) Fishes of the Marina Basin, Singapore, before the erection of the Marina Barrage. The Raffles Bull Zool pp 58(1): 137-144\u003c/li\u003e\n\u003cli\u003eIp YK, Leong MWF, Sim MY, Goh GS, Wong WP, Chew SF (2005) Chronic and acute ammonian toxicity in mudskippers, \u003cem\u003ePeriophthalmodon schlosseri\u003c/em\u003e and \u003cem\u003eBoleophthalmus boddaerti\u003c/em\u003e: brain ammonia and glutamine contents and effects of methionine sulfoximine and MK801. J Exp Biol pp 208:1993\u0026ndash;2004. https://doi.org/10.1242/jeb.01586 \u003c/li\u003e\n\u003cli\u003eJeyaseelen MJP, Krishnamurthy K (1980) Role of mangrove forests of Pichavaram as fish nurseries. Proceedings of the Indian National Science Academy pp 46(1): 48-53\u003c/li\u003e\n\u003cli\u003eKeith P (2003) Biology and ecology of amphidromous Gobiidae of the Indo-Pacific and the Caribbean regions. J Fish Biol pp 63: 831\u0026ndash;847. https://doi.org/10.1046/j.1095-8649.2003.00197.x \u003c/li\u003e\n\u003cli\u003eKeith P, Marquet G, Lord C, Kalfatak D, Vigneux E (2010) Vanuatu Freshwater Fish and Crustaceans. French Icthyological Society, Cybium, pp 254\u003c/li\u003e\n\u003cli\u003eKeith P, Boseto D \u0026amp; Lord C (2021) Freshwater Fish of Solomon Islands. French Icthyological Society, Cybium, pp 174\u003c/li\u003e\n\u003cli\u003eKendall Jr AW, Ahlstrom EH, Moser HG (1984) Early life history stages of fishes and their characters. Ontogeny and systematics of fishes - Ahlstrom Symposium, 11-22\u003c/li\u003e\n\u003cli\u003eKinzie RA (1997) Evolution and life history patterns in freshwater gobies. \u003cem\u003eMicronesica\u003c/em\u003e pp 30: 27\u0026ndash;40\u003c/li\u003e\n\u003cli\u003eKottelat M (2013) The fishes of the inland waters of Southeast Asia: a catalogue and core bibliography of the fishes known to occur in freshwaters, mangroves and estuaries The Raffles Bulletin of Zoology Suppl. 27:1-663\u003c/li\u003e\n\u003cli\u003eKoumans FP (1953) Gobioidea. In: Weber M, Beaufort LF (eds) The fishes of the Indo-Australian Archipelago X. Brill, Leiden, pp (10):423\u003c/li\u003e\n\u003cli\u003eLindstrom DP (1998) Reproduction, early development and larval transport dynamics of amphidromous Hawaiian gobioids. PhD Thesis, University of Hawai\u0026apos;i at Manoa\u003c/li\u003e\n\u003cli\u003eLindstrom DP (1999) Molecular species identification of newly hatched Hawaiian amphidromous gobioid larvae. Mar Biotechnol pp 1: 167\u0026ndash;174. https://doi.org/10.1007/PL00011764\u003c/li\u003e\n\u003cli\u003eLindstrom DP (1999) Molecular species identification of newly hatched Hawaiian amphidromous gobioid larvae. Mar Biotechnol pp 1: 167\u0026ndash;174. https://doi.org/10.1007/PL00011764\u003c/li\u003e\n\u003cli\u003eMaeda K, Yamasaki N, Kondo M, Tachihara K (2008) Reproductive Biology and Early Development of Two Species of Sleeper, \u003cem\u003eEleotris acanthopoma\u003c/em\u003e and \u003cem\u003eEleotris fusca\u003c/em\u003e (Teleostei: Eleotridae) 1. Pacific Science pp 62(3): 327-340.https://doi.org/10.2984/1534-6188(2008)62[327:RBAEDO]2.0.CO;2\u003c/li\u003e\n\u003cli\u003eMiller PJ (1984) The tokology of gobioid fishes. In: GW, Wooten RJ (ed) Fish reproduction: Strategies and tactics. Academic Press, Orlando, FL USA, pp 119-152\u003c/li\u003e\n\u003cli\u003eMiller PJ, Wright J, Wongrat P (1989) An Indo-Pacific goby (Teleostei: Gobioidei) from West Africa, with systematic notes on Butis and related eleotridine genera. J Nat Hist 23:311\u0026ndash;324. https://doi.org/10.1080/00222938900770201\u003c/li\u003e\n\u003cli\u003eMishra SS, Gopi KC (2017) Fish diversity of Indian Sundarban and its resource and research prospects In: Kailash Chandra, JRB Alfred, Bulganin Mitra, Biswajit Roy Chowdhury (eds) Fauna of Sundarban Biosphere Reserve, Zool Surv India, Kolkata, pp107-127\u003c/li\u003e\n\u003cli\u003eMyrberg Jr AA, Brahy BD, Emery AR (1967) Field observations on reproduction of the damselfish, \u003cem\u003eChromis multilineata\u003c/em\u003e (Pomacentridae), with additional notes on general behavior. Copeia pp (4): 819-827. https://doi.org/10.2307/1441893\u003c/li\u003e\n\u003cli\u003eNguyen HPT, Dinh QM (2021) Diet composition of Duckbill sleeper \u003cem\u003eButis butis\u003c/em\u003e (Hamilton, 1822) living in some coastal regions in the Mekong Delta, Vietnam. Aqua Aquarium Cons Legisl Bioflux pp 14(5): 2939-2946. http://www.bioflux.com.ro/aacl\u003c/li\u003e\n\u003cli\u003eNilsson GE, Hobbs JP, Munday PL, Ostlund-Nilsson S (2004) Coward or braveheart: extreme habitat fidelity through hypoxia tolerance in coral-dwelling goby. J Exp Biol pp 207:33\u0026ndash;39. https://doi.org/10.1242/jeb.00713 \u003c/li\u003e\n\u003cli\u003eRaghunathan MB (2007) Faunal Diversity of Ashtatmudi Wetlands, Kerala, India. Rec. Zool Surv India pp 276:1\u0026ndash;38\u003c/li\u003e\n\u003cli\u003eRamaiyan, V., Purushothaman, A., \u0026amp; Natarajan, R. (1986). Check-list of estuarine and marine fishes of Parangipettai (Porto Novo) coastal waters. Matsya pp 12-13: 1-19. https://api.semanticscholar.org/CorpusID:82239334\u003c/li\u003e\n\u003cli\u003eReyes-Mero BM, Santana-Pi\u0026ntilde;eros AM, Mu\u0026ntilde;oz-Chumo LG, Cruz-Quintana Y, Gisbert E (2022) Yolk Absorption Rate and Mouth Development in Larvae of \u003cem\u003eDormitator latifrons\u003c/em\u003e (Perciformes: Eleotridae). Fishes pp 7(6): 375. https://doi.org/10.3390/fishes7060375\u003c/li\u003e\n\u003cli\u003eRohini Krishna MV, Anil MK, Neethu Raj P, Santhosh B (2016) Seed production and growth of \u003cem\u003eNeopomacentrus cyanomos\u003c/em\u003e (Bleeker, 1856) in captivity. Indian J Fish pp 63(3): 50-56. https://doi.org/10.21077/ijf.2016.63.3.55058-06\u003c/li\u003e\n\u003cli\u003eRussell FS (1976). The eggs and planktonic stages of British marine fishes. Academic Press, London, New York, 482-510\u003c/li\u003e\n\u003cli\u003eSenoo S, Kaneko M, Cheah SH, Ang KJ (1994) Egg development, hatching, and larval development of marble goby \u003cem\u003eOxyeleotris marmoratus\u003c/em\u003e under artificial rearing conditions. Fisheries Science pp 60(1): 1-8. https://doi.org/10.2331/fishsci.60.1\u003c/li\u003e\n\u003cli\u003eShinomiya A, Maeyama K, Imai S (1981a) Reproductive behaviour of the goby \u003cem\u003eEviota storthynv\u003c/em\u003e (Rofen). Mere Fac Fish Kagoshima Univ pp 30: 237-246 \u003c/li\u003e\n\u003cli\u003eShinomiya A, Tsuchiya T, Imai S (1981b) Reproductive behaviour of the goby \u003cem\u003eParioglossus taeniatus\u003c/em\u003e (Regan). Mem Fac Fish Kagoshirna Univ 30: 247-255 \u003c/li\u003e\n\u003cli\u003eSuzuki N, Sakurai N, Sugihara T (1988) Development of eggs, larvae and juveniles of the goby \u003cem\u003eGlossogobius ohvaceus\u003c/em\u003e reared in the laboratory. Suisanzoshoku 35: 203-212. https://doi.org/10.11233/aquaculturesci1953.35.203\u003c/li\u003e\n\u003cli\u003eSuzuki N, Sakurai N, Sugihara T (1989) Development of eggs, larvae and juveniles of the Oriental goby \u003cem\u003eAcanthogobius flavimanus\u003c/em\u003e reared in laboratory. Suisanzoshoku pp 36: 277-289. https://doi.org/10.11233/aquaculturesci1953.36.277\u003c/li\u003e\n\u003cli\u003eTan OKK, Lam TJ (1973) Induced breeding and early development of the marble goby (\u003cem\u003eOxyeleotris inarmorata\u003c/em\u003e, Blk.). Aquaculture pp 2(44): 411-423. https://doi.org/10.1016/0044-8486(73)90172-5\u003c/li\u003e\n\u003cli\u003eThacker CE (2011) Systematics of Butidae and Eleotridae. In: Patzner R, Tassell JLV, Kovacic M, Kapoor BG (eds) The biology of gobies. CRC Press, Broca Raton, pp 79-85. https://doi.org/10.1201/b11397-7 \u003c/li\u003e\n\u003cli\u003eThresher RE (1984) Reproduction in reef fishes. T.F.H. Publications, Neptune City, pp 399\u003c/li\u003e\n\u003cli\u003eUntersteggaber L, Mitteroecker P, Herler J (2014) Coral architecture affects the habitat choice and form of associated gobiid fishes. Mar Biol pp 161(3):521\u0026ndash;530. https://doi.org/10.1007/s00227-013-2354-x\u003c/li\u003e\n\u003cli\u003eWard RD, Zemlak TS, Innes BH, Last PR, Hebert PD (2005) DNA barcoding Australia\u0026apos;s fish species. Philosophical Transactions of the Royal Society B: Biological Sciences pp 360(1462): 1847-1857. https://doi.org/10.1098/rstb.2005.1716 \u003c/li\u003e\n\u003cli\u003eYamasaki N, Tachihara K (2006) Reproductive biology and morphology of eggs and larvae of \u003cem\u003eStiphodon percnopterygionus\u003c/em\u003e (Gobiidae: Sicydiinae) collected from Okinawa Island. Ichthyol Res pp 53:12\u0026ndash;18. https://doi.org/10.1007/s10228-005-0307-1\u003c/li\u003e\n\u003cli\u003eYamasaki N, Tachihara K (2007) Eggs and larvae of \u003cem\u003eAwaous melanocephalus\u003c/em\u003e (Teleostei: Gobiidae). Ichthyol Res pp 54: 89-91. https://doi.org/10.1007/s10228-006-0380-0\u003c/li\u003e\n\u003cli\u003eYennawar, P., Mohapatra, A., Ray, D., \u0026amp; Tudu, P. (2015). Ichthyofauna of Digha Coast, India In: Marine Faunal Diversity in India. Taxonomy, Ecol and Conserv pp 235-248. https://doi.org/10.1016/B978-0-12-801948-1.00015-X\u003c/li\u003e\n\u003cli\u003eZeena KV, Jameela Beevi KS (2011) Fish diversity in Ithipuzha and Murinjapuzha, Kerala, India. Journal of Bombay Natural History Society pp 108(2): 98\u003c/li\u003e\n\u003cli\u003eZeyl JN, Malavasi S, Holt DE, Noel P, Lugli M, Johnston CE (2016) Convergent aspects of acoustic communication in darters, sculpins, and gobies. Fish hearing and bioacoustics: an anthology in honour of Arthur N. Popper and Richard R. Fay, pp 93-120. https://doi.org/10.1007/978-3-319-21059-96\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":false,"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":"Dark sleeper, Butidae, Butis, Cochin Estuary, Embryonic, Larval development","lastPublishedDoi":"10.21203/rs.3.rs-3954230/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3954230/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eDark sleeper or olive flathead-gudgeon, \u003cem\u003eButis humeralis\u003c/em\u003e (Valenciennes 1837), was discovered for the first time from the west coast of India. Till date, there have only been reports of this species from India's east coast. A cluster of sparsely distributed eggs of \u003cem\u003eB. humeralis\u003c/em\u003e were observed in the gritted glass panel submerged for biofouling studies in aquaculture cage sites near Kalamukku fishing harbour in the Cochin Estuary. The egg mass covered an area of 61.80 cm\u003csup\u003e2\u003c/sup\u003e with an average abundance of 124.51\u0026thinsp;\u0026plusmn;\u0026thinsp;27.25 eggs/cm\u003csup\u003e2\u003c/sup\u003e. Molecular characterization of the eggs was done to affirm the species identification. The eggs of \u003cem\u003eB. humeralis\u003c/em\u003e were, adhesive, pyriform-shaped and translucent with brownish yellow colour with a size measurement of 0.41\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01 mm and 0.36\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01 mm diameters along long and short axis, respectively. The eggs were reared up to 144 hph (hour post-hatch) subsequently. The newly hatched larvae of \u003cem\u003eB. humeralis\u003c/em\u003e were slender and translucent with 1.01\u0026thinsp;\u0026plusmn;\u0026thinsp;0.037 mm total length (TL) with a yolk sac of size 0.624\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05 mm and 0.415\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05 mm along longitudinal and horizontal axis, respectively. After 72 hph, fully pigmented eyes were observed whereas a well-developed mouth with distinct upper and lower jaw appeared on the fifth day of hatching. The TL of the preflexion larvae after 144 hph ranged between 2.08\u0026ndash;2.12 mm. The first report of this lesser-known species from the west coast of India demonstrating the developmental stages signifies the need to evaluate their current ecological and conservation status in the ecosystem.\u003c/p\u003e","manuscriptTitle":"First Record of Butis humeralis (Gobiiformes: Butidae) from the West Coast of India with special emphasis to its Early Developmental Stages","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-02-16 17:32:24","doi":"10.21203/rs.3.rs-3954230/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":"970397b0-8b54-42bb-9a81-6bcad6b4e56d","owner":[],"postedDate":"February 16th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-07-01T12:06:12+00:00","versionOfRecord":[],"versionCreatedAt":"2024-02-16 17:32:24","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3954230","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3954230","identity":"rs-3954230","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}