Hepatopancreas in the starving amphipod Ampelisca eschrichtii and the feeding amphipod Monoporeia affinis during vitellogenesis

Hepatopancreas in the starving amphipod Ampelisca eschrichtii and the feeding amphipod Monoporeia affinis during vitellogenesis | 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 Hepatopancreas in the starving amphipod Ampelisca eschrichtii and the feeding amphipod Monoporeia affinis during vitellogenesis Valentina B. Durkina, Natalia L. Demchenko This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5370478/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 30 Jul, 2025 Read the published version in Polar Biology → Version 1 posted 9 You are reading this latest preprint version Abstract A comparative analysis of the hepatopancreas of amphipod species Ampelisca eschrichtii and Monoporeia affinis collected on the northeastern shelf of Sakhalin Island (Okhotsk Sea) was carried out between 2013 and 2021 in summer and fall during the period of vitellogenic oocyte growth. As a result of different habitat conditions A. eschrichtii has seasonal starvation in summer and fall, while M. affinis has access to food. During the period of starvation, the hepatopancreas of A. eschrichtii exhibits the following characteristics: 1) the functional passivity of F-cells of the epithelium, which confirms the absence of food in the stomach of amphipods, 2) the R-cells destruction due to lipid utilization, 3) the activation of B-cells, which apparently digest membrane structures of destroyed R-cells. The morphology of R-, F- and B-cells of the epithelium of the hepatopancreas in M. affinis is consistent with the description of analogous cells of the epithelium of the hepatopancreas of decapods and provide evidence for the presence of a food in the habitat of this species. In M. affinis , in contrast to A. eschrichtii , R-cells appear to synthesize vitellogenin. The primary function of R-cells of A. eschrichtii during starvation is to provide previously stored nutrients (lipids) for oocyte vitellogenic growth and energy for vital function of the organism. Synthesis of vitellogenin in these cells is unlikely. hepatopancreas starvation amphipods Monoporeia affinis Ampelisca eschrichtii Figures Figure 1 Figure 2 Figure 3 Introduction Representatives of marine invertebrates (amphipods, sea urchins, bivalves) are able to store nutrients obtained from food in somatic tissues of the body and use them for gametogenesis, including periods of starvation (Pazos et al. 1997 ; Darriba et al. 2005 ; Unuma and Walker 2009 ; Noyon et al. 2011 ). The separation of vitellogenesis processes from the period of food availability was found in the benthic amphipod Ampelisca eschrichtii Krøyer, 1842 ( Ampeliscidae ) from the northeastern shelf of Sakhalin Island (Okhotsk Sea) (Durkina et al. 2018 ). Ampelisca eschrichtii forms large and dense aggregations at depths greater than 50, where water temperatures near the bottom are negative or close to 0ºC for most of the year (Demchenko et al. 2016 ). This amphipod species has a two-year life cycle. Reproduction and embryo brooding in A. eschrichtii occurs in winter and spring at the age of 2 years (when females reach a body length of 22 mm or more) (Demchenko et al. 2016 ), when intensive phytoplankton development occurs in the shelf waters of Sakhalin Island (Leonov et al. 2007 ). Microalgae settle on the bottom due to the prevailing vertical mixing of the Sakhalin shelf waters at this– time of year (Leonov et al. 2007 ), providing food supply for amphipods. The fatty acid composition of A. eschrichtii has shown that diatom microalgae are the main component of their food (Rodkina et al. 2020 ). During the warm season (summer, autumn), phytoplankton biomass is concentrated at the upper boundary of the thermocline to depths of 10–15 m (Sorokin and Sorokin 1999 ; Prants et al. 2017 ), which prevents microalgae availability for amphipods living at greater depths. Despite the lack of food, vitellogenic growth of oocytes was observed in sexually mature females of A. eschrichtii (body length 22–24 mm), indicating the presence of nutrient reserves in the amphipod body. However, about 75% of A. eschrichtii individuals complete oocyte growth, whereas in the remaining females all oocytes undergo lysis and resorption (Durkina et al. 2018 ). Previously, destruction and resorption of immature vitellogenic oocytes was observed in the barnacle Amphibalanus amphitrite (Darwin, 1854) and the predatory copepod Paraeuchaeta norvegica (Boeck, 1872) under starvation (Sastry 1983 ). It is possible that the formation of complete eggs during seasonal starvation in A. eschrichtii depends on the amount of nutrients stored in winter and spring in the body tissues of amphipods. The hepatopancreas (digestive gland) and muscle tissue of crustaceans are the main organs for the accumulation of food-derived nutrients that can be directed to reproductive processes during starvation (Vogt et al. 1989 ). Hepatopancreas cells are responsible for nutrient uptake, intracellular digestion, and accumulation of lipid and glycogen stores required when energy requirements increase or when food resources decrease (Sánchez-Paz et al. 2006 ). Close interaction between the hepatopancreas and ovaries of crustaceans is noted during vitellogenesis (Vogt et al. 1989 ). This relation is explained by the fact that the hepatopancreas is one of the sites of synthesis of the precursor of the oocyte yolk protein, vitellogenin (Han et al. 1994 ; Vogt 2019 ). The histological structure of the hepatopancreas has been investigated mainly in decapods and summarized in a number of reviews (Barker and Gibson 1979 ; Cervellione et al. 2017 ; Vogt 2019 ). The decapod hepatopancreas is represented by right and left lobes consisting of numerous (up to hundreds) blind outgrowths (diverticula) formed by the midgut. Each diverticulum is surrounded by a muscular network consisting of longitudinal and annular fibers and hemolymphatic sinuses. Inside the diverticula are covered by a single-layer epithelium, which is located on the basal lamina and forms rows of longitudinal ridges and depressions. There are three zones in diverticula: distal, medial, and proximal. The distal zone contains small “embryonic” E-cells with a high nuclear-cytoplasmic ratio. The medial zone contains “fibrillar” F-cells, “resorptive or absorptive” R-cells, and “secretory” B-cells. The proximal zone contains F- and R-cells. Stem E-cells, proliferating, produce R-, B-, and F-cells. R-cells form the apexes of diverticular ridges and contain numerous vacuoles in the cytoplasm. B-cells are also found at the apexes of the ridges and contain one very large vacuole that pushes the cytoplasm and nucleus toward the plasma membrane. F-cells are located in the depressions between the ridges of the epithelium and have a dark homogeneous cytoplasm, and mature F-cells contain one small vacuole (autophagosome) near the nucleus. In addition to the four cell types mentioned above, small M-cells of non-hepatopancreatic origin with a presumed endocrine function are found on the basal lamina of diverticula. Experimental starvation causes a number of morphological changes in the decapod hepatopancreas epithelium. Among these, the most frequently observed are a decrease, or disappearance, of lipid droplets in R-cells and a decrease in the number of R-cells, indicating that the body requires energy during starvation (Sacristán et al. 2016 ; Chen et al. 2017 ; Huang et al. 2020 ). Contrary to experimental data, we did not find information on how the digestive gland functions in crustaceans for which prolonged starvation is the normal and, more interestingly, when starvation coincides with vitellogenesis. The majority of articles devoted to the digestive tract of Malacostraca Latreille, 1802 refer to commercially important species and few widespread and easily accessible species (Štrus et al. 2019 ). Štrus et al. ( 2019 ) note that future studies should include species with an exclusive ecology, lifestyle, and feeding strategy. We suggest that the amphipod of A. eschrichtii can satisfy these requirements. In the present study, we intended to investigate 1) how the hepatopancreas of A. eschrichtii functions during vitellogenesis coinciding with seasonal starvation, and 2) whether starvation can be the cause of total destruction of vitellogenic oocytes, which we previously found (Durkina et al. 2018 ) in 25% of sexually mature females of A. eschrichtii . To assess adequately the condition of the hepatopancreas of A. eschrichtii , we compared it with that of the hepatopancreas of the amphipod Monoporeia affinis (Lindström, 1855) ( Pontoporeiidae ). M. affinis , like A. eschrichtii , occurs on the northeastern shelf of Sakhalin Island, but at shallower depths, predominantly up to 20 m (Demchenko 2010 ), where it does not appear to have food availability problems. Materials and methods The amphipods A. eschrichtii and M. affinis were collected from the northeastern shelf of the Sakhalin Island (Okhotsk Sea) during the summer-autumn season between the years 2013 and 2021 (Table 1 ) using a Van Veen grab with a surface area of 0.2 m 2 during the expeditions with participation of the A.V. Zhirmunsky Institute of Marine Biology (since 2016 A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences (NSCMB FEB RAS) in long-term studies of macrobenthos as part of the western gray whale monitoring program off the north-eastern coast of Sakhalin Island. This program was supported by Exxon Neftegas Limited and by Sakhalin Energy Investment Company Ltd. (Sakhalin Energy) between 2001 and 2021. Table 1 Dates, coordinates of sampling sites and environmental parameters in the habitats of amphipods A. eschrichtii and M. affinis Species Date (m/y) n Lat (N) Long (E) D, m T, C° S, psu Sedi-ment Vessel A. eschrichtii X/2013 6 52.02 143.75 53.9 3.9 31.6 n/d R/V "Pavel Gordienko" A. eschrichtii X/2015 8 51.93 143.75 58.3 4.1 32.0 SFS R/V "Igor Maksimov" A. eschrichtii VII/2015 8 51.92 143.73 59.7 n/d n/d SFS R/V "Igor Maksimov" A. eschrichtii VIII/2019 6 52.25 143.82 55.5 -0.8 33.2 SFS AHTS "Katun" A. eschrichtii VIII/2021 6 51.91 143.68 59.5 -0.3 32.8 MS AHTS "Beya" M. affinis X/2013 8 52.80 143.35 8.8 8.9 28.4 n/d R/V "Pavel Gordienko" M. affinis X/2014 3 52.85 143.36 14.8 9.7 28.4 SFS R/V "Pavel Gordienko" M. affinis VII/2021 5 52.55 143.33 10.2 4.8 29.4 SFS AHTS "Beya" M. affinis VIII/2021 10 52.88 143.33 8.8 8.0 29.2 SFS AHTS "Beya" Note. m/y – month/year, n - number of specimens used for histological analysis of hepatopancreas, lat – latitude, long -longitude, D – depth, T – bottom temperature, S – bottom salinity, n/d – no data, SFS - silty fine sand, MS - medium sand, R/V – Research/Survey Vessel, AHTS – Anchor-handling Tug/Supply To prepare histological slides, amphipods fixed in 4% formalin were washed in water for 24 h, dehydrated, clarified in xylene, and then soaked in paraffin and poured into paraffin blocks. Slices of 10 µm thickness were prepared for microscopic analysis. Slides containing hepatopancreas tissues were stained with hematoxylin-eosin, dehydrated, clarified in xylene, and permanent slides were prepared. We analyzed the state of F-, R- and B-cells of the hepatopancreas epithelium that participate in digestion processes. F-cells were identified by their location between the ridges of the epithelium, basophilia of the cytoplasm, and a single vacuole near the nucleus. R-cells were identified by their location at the apex of the ridges of the epithelium and numerous vacuoles in the cytoplasm. B-cells were identified by their location at the apex of the ridges of the epithelium and a large central vacuole pushing the nucleus and cytoplasm to the periphery of the cell. To illustrate the tissues and cells of the hepatopancreas of A. eschrichtii and M. affinis , preparations (the mounted slides) were photographed using VideoTesT ( http://www.zenit-npk.ru/fcatalog/info/74 ). Results Monoporeia affinis Amphipod species has four long ventral diverticula, two of which are adjacent to the ovaries. Three diverticula were found in one of the examined individuals, and five diverticula in another. The diverticula of the hepatopancreas of amphipods collected in October 2014 and July-August 2021 are characterized by sites with normal epithelium and sites with epithelial atrophy. The normal epithelium of diverticula forms longitudinal ridges, the central part of which is occupied by R-cells (in the proximal zone) or R- and B-cells (in the medial zone), and the depressions located between the ridges contain F-cells (Fig. 1 a). The nuclei of R-, B-, and F-cells have no pathological changes (Fig. 1 a). R-cells contain vacuoles, the number of which is less in the cells of the proximal zone than in the cells of the medial zone (Fig. 1 a). B-cells are located in the apical part of the epithelium and contain a large central vacuole (Fig. 1 a, b). F-cells contain a small single vacuole near the nucleus (Fig. 1 a, b). When the epithelium atrophies, the lumen of diverticula is filled with destroyed cells, among which there are sloughed B-cells (Fig. 1 c). Extended haemolymphatic sinuses with homogeneous contents are closely adjacent to the diverticula of the hepatopancreas and to the ovaries (Fig. 1 d). In 8 of the 18 examined specimens, normal epithelium occupies the proximal zone and the medial zone up to 1/4 − 2/3 of its length in different individuals, and the extent of normal epithelium may vary in different diverticula of the same individual. Distal to the normal epithelium, epithelial atrophy is observed. In 3 of 18 specimens, normal epithelium is located in the last third of the medial zone, and proximally the epithelium undergoes atrophy. In 2 of 18 specimens, normal epithelium is found in almost all diverticula, and it is absent in the diverticula of the other 2 specimens. Asynchrony of diverticular functioning is observed in 3 of 18 specimens. For example, two diverticula located on one side of the intestine have epithelium, while two diverticula on the opposite side have no epithelium (Fig. 1 e). It should be noted that the location of diverticula without epithelium relative to the intestine could vary. Atrophy of the epithelium is followed by an increase in the diameter of the diverticula. Hepatopancreas diverticula of specimens collected in October 2013 contain remnants of epithelium in the form of a small number of damaged cells. Individual epithelial cells and sparse amorphous material are found in the lumen of the diverticula (Fig. 1 f). Ampelisca eschrichtii Amphipod species has four long ventral diverticula, two of which are adjacent to the ovaries. Most of the epithelium of the diverticula in amphipods collected in July 2015 and August 2019 and 2021 is characterized by depletion. Normal epithelium is found in the proximal zone, but not in all specimens. Normal epithelium is also found in the last third of the medial zone of the diverticula in many specimens. The normal epithelium of the proximal zone of diverticula has ridges and depressions. R-cells with numerous vacuoles form the apexes of the ridges, and F-cells with basophilic cytoplasm fill the depressions between the ridges (Fig. 2 a). A small vacuole, which is usually present in the cytoplasm of F-cells of M. affinis , is rare in F-cells of A. eschrichtii . At the beginning of the medial zone, B-cells with a large vacuole appear among the R-cells (Fig. 2 b). The normal epithelium in the last third of the medial zone also retains high ridges (Fig. 2 c). There, the epithelium is represented mainly by R-cells and few F-cells, whereas B-cells appear to remain inactive and are thus invisible. In the initial stages of epithelial atrophy, the nuclei of R-cells are swollen and chromatin is concentrated in a clump in the center of the nuclei (Fig. 2 d). Then, the apical part of the cells is degraded and the nucleus is destructed, as a result of which lumps of condensed chromatin enter the lumen of the diverticula (Fig. 2 e). The basal part of degrading R-cells contains a relatively large optically empty vacuole, which is in close contact with the plasmatic membrane of the cell, where the latter is in contact with the basal lamina. This vacuole persists until complete cell destruction (Fig. 2 f). The destruction of R-cells leads to a decrease of the height of the epithelium of the hepatopancreas. There are young and mature B-cells in the epithelium of diverticula (Fig. 3 a). The young B-cells are less rare, have contact with the basal lamina, and, like R-cells, contain vacuoles, but larger than in R-cells. The nuclear area of young B-cells exceeds that of R cells (97.37 ± 10.32 and 61.64 ± 6.96 µm 2 , respectively; n = 15; P < 0.95). Mature B-cells have a large central vacuole and a pyknotic nucleus in the basal part of the cell. B-cells extending into the lumen of the diverticula are rare. Mature B-cells are commonly found in areas of diverticula with the most evident R-cell atrophy. They usually do not leave the epithelium, and their vacuole contents enter into the lumen of the diverticulum (Fig. 3 b). As a result of holocrine secretion, a cavity bounded by deformed F-cells remains on the place of B-cells (Fig. 3 c). In females with a normal vitellogenesis, no enlargement of haemolymphatic sinuses is observed. On the contrary, in females with lysis of all vitellogenic oocytes, the haemolymphatic sinuses are enlarged and their contents are represented by a homogeneous substance. The lumen of diverticula is filled by large clots of homogeneous substance, but total atrophy of hepatopancreas epithelium is not observed in these females (Fig. 3 d). In October 2013 and 2015, a small number of deformed F-cells remain in the proximal zone of A. eschrichtii diverticula and are sloughed off the basal lamina. The medial zone is usually without epithelium and the lumen of the diverticula is filled with sparse material (Fig. 3 e). In some individuals, the low epithelium persists at the end of the medial zone in 1–2 diverticula. The distal part of the diverticula of the hepatopancreas of M. affinis and A. eschrichtii contains E-cells. Discussion In amphipods, unlike decapods, the number of hepatopancreas diverticula involved in digestion is limited. Thus, in amphipod Hyalella azteca , this function is performed by four ventral diverticula (Schmitz and Scherrey 1983 ), while in Corophium volutator there is one ventral massive pair (Icely and Nott 1984 ). In A. eschrichtii and M. affinis , the process of digestion is carried out by two pairs of long ventral diverticula. As an exception, we found two specimens of M. affinis with three and five diverticula. Diverticula of the hepatopancreas of different specimens of M. affinis in July-August 2021 and in October 2014 have different localization of sites with normal and atrophied epithelium along the length of the diverticula, which seems to reflect different stages of the digestive cycle. The process of digestion in crustaceans is accompanied by ageing and degeneration of cells of the hepatopancreas epithelium (Al-Mohanna et al. 1985 ). At the end of the digestive cycle, there is a massive loss of B-cells that coincides with the phase of mitotic activity of embryonic E-cells (Al-Mohanna and Nott 1987 ). E-cells produce young R-, F- and B-cells and move them by pushing motions forward along the diverticulum (Vogt 2019 ). Thus, the localization of normal epithelium in the second half of the medial zone of diverticula in M. affinis could indicate its recovery after the last digestive cycle. In turn, the localization of normal epithelium in the proximal zone and in the beginning of the medial zone of diverticula can be a sign of a near completion of the digestive cycle. In general, the state of the epithelium of the hepatopancreas of M. affinis allows to state that in the natural environment, in the presence of food, different diverticula of one individual could be functioning more or less asynchronously. The discovery of specimens in which two of the diverticula contain normal epithelium and the other two are lacking it confirms this conclusion and might also indicate the constant feeding activity of amphipods. The duration of the digestive cycle in M. affinis is not known, but in the shore crab Carcinus maenas (Hopkin and Nott 1980 ) and the shrimp Penaeus semisulcatus (Al-Mohanna et al. 1985 ; Al-Mohanna and Nott 1987 ) it takes at least 24 hours. Almost complete atrophy of the hepatopancreas epithelium in all M. affinis individuals in October 2013 appears to reflect a lack of food resources for amphipods. In 2013, the coastal waters of the northwestern part of the Okhotsk Sea were affected for a long time by an extreme flood, which was observed in the region in autumn 2012 and in winter, spring and summer 2013. Thus, under the influence of the flood in 2013 in Academy Bay (northwest of the Okhotsk Sea), the salinity in the upper 5-meter layer was less than 20 PSU, and the maximum salinity values at the bottom slightly exceeded 27 PSU (Rogachev and Shlyk 2015 ; Rogachev et al. 2022 ). The shelf zone of the northeastern coast of Sakhalin Island is influenced by the flow of the Amur River, the flood of which in 2013 was the strongest in the entire period of observations in the Far East (Rogachev and Shlyk 2015 ). Extreme rainfall events supply significant amounts of nutrients and terrestrial material to nearshore marine waters (Fong et al. 2020 ). The oversupply of terrestrial particulate material in the water leads to reduced lighting of the water column and, consequently, to a decrease of phytoplankton primary production (Mihaljević et al. 2010 ; Paczkowska et al. 2020 ). In A. eschrichtii , unlike M. affinis , the location of sites with normal and atrophying epithelium along the length of the diverticula is not diverse. Thus, in most specimens in the summer months of 2015, 2019, and 2021, normal epithelium is frequently found in the proximal zone and in the last third of the medial zone of the diverticula, but most of the diverticula are occupied by atrophying epithelium. In autumn 2013 and 2015, a complete atrophy of the diverticulum epithelium is generally observed. The exception is some individuals with atrophying epithelium in the last third of the medial zone. There are no signs of epithelial regeneration in A. eschrichtii during summer and autumn. We suggest that proliferation of hepatopancreas E-cells in A. eschrichtii could be blocked to reduce energy consumption by the organism, as observed in the crab Eriocheir sinensis in a long-term (42 days) starvation experiment (Huang et al. 2020 ). The morphology of F-, R- and B-cells of the normal epithelium of the hepatopancreas of M. affinis corresponds to the morphology of analogous cells of the epithelium of the hepatopancreas of decapod (Barker and Gibson 1979 ; Cervellione et al. 2017 ; Vogt 2019 ), whereas F-, R- and B-cells of the epithelium of the hepatopancreas of A. eschrichtii have a number of peculiarities. Decapod F-cells are known to synthesize digestive enzymes that are intended for the primary treatment of food in the cardial compartment of the stomach. In the starving shrimp Penaeus semisulcatus , a supranuclear vacuole appears in F-cells 2 hours after feeding (Al-Mohanna et al. 1985 ), which represents an autophagosome that is characteristic of mature F-cells (Vogt 2019 ). In M. affinis F-cells usually contain a single small vacuole near the nucleus, whereas the same vacuole in F-cells of A. eschrichtii is rarely found, which indicate the absence of food in the stomach of these amphipods. Decapod R-cells absorb low-molecular weight digestion products and store large amounts of energy in the form of lipids and glycogen (Vogt 2019 ). Lipids and glycogen are directly transported from R-cells to other tissues via the haemolymph (Vogt 2019 , 2021 ) and can be used during starvation (Vogt et al. 1985 ) and vitellogenesis (Vogt et al. 1989 ). Lipids accumulate in the vacuoles of R-cells (Hemambika and Raj 1999 ). In A. eschrichtii , vacuoles fill almost the entire cytoplasm of R-cells, and this makes the accumulation of any significant glycogen stores in these cells doubtful. In summer and autumn (under conditions of seasonal starvation), the contents of vacuoles are gradually consumed for maintenance of life activity and formation of mature gametes. The appearance of a relatively large vacuole in the basal part of atrophying R-cells of A. eschrichtii could be a morphological sign of lipids transfer from the cells to the haemolymph. The accumulation of lipids for long-term storage in the hepatopancreas of A. eschrichtii should occur in winter and spring, when the same temperature throughout the water column is maintained and phytoplankton sinking to the bottom becomes available to amphipods. However, the absence of winter samples prevents to understand how the hepatopancreas of A. eschrichtii functions during this period. On the one hand, the entry of food into the stomach, its treatment and digestion should be accompanied by periodic renewal of the epithelium during digestive cycles. At another point, epithelial renewal does not seem to facilitate the accumulation in the R-cells of lipids intended for long-term storage. In species M. affinis , constant renewal of the epithelium of the hepatopancreas does not allow lipids and glycogen to accumulate in R-cells for long-term storage. The products of digestion from the cells immediately enter the haemolymph and are using for the needs of the organism, and the expanded haemolymphatic sinuses may serve as indirect evidence of this process. R-cells of the crustacean epithelium of the hepatopancreas may also be the location of vitellogenin synthesis. Its synthesis appears to occur in the basal part of the cells, where an extensive tubular system, a rough endoplasmic reticulum and the mitochondria are located (Vogt et al. 1989 ; Vogt 2019 ). It is confirmed by ultrastructural changes occurring in the basal part of the R-cells of the hepatopancreas of the black tiger shrimp Penaeus monodon in the late vitellogenesis (Vogt et al. 1989 ). Morphological differences between R-cells of M. affinis and A. eschrichtii and, in particular, atrophy of R-cells of A. eschrichtii , suggest that vitellogenin in the first species is synthesized in R-cells, while in the second species it is synthesized outside R-cells. So, in M. affinis , unlike A. eschrichtii , the basal part of R-cells (especially in the proximal zone of diverticula) is free from vacuoles, which provides a location for the protein synthesis apparatus. Moreover, in M. affinis during vitellogenesis there is a clear relation between the hepatopancreas and ovaries by the sinuses of the haemolymphatic system, through which not only the digestive products but also vitellogenin is transported (Tsukimura 2001 ). Guan et al. ( 2016 ) provide a list of crustacean species in which vitellogenin is either synthesized in the hepatopancreas, in the ovaries or in both organs simultaneously. Particularly, ovarian follicular cells could be a source of vitellogenin in the Kuruma prawn Penaeus japonicus (Yano and Chinzei 1987 ). Vitellogenin synthesis has also been found in adipocytes (fatty cells) of the amphipod Orchestia gammarellus (Meusy et al. 1983 ), the isopod Idotea balthica (= Idotea balthica basteri Audouin, 1826) (Souty and Picaud 1981 ), and the freshwater prawn Macrobrachium nipponense (Han et al. 1994 ). The examples mentioned above may indicate on the ovarian follicular cells or adipocytes of A. eschrichtii as possible centers of vitellogenin synthesis. B-cells of decapods according to Vogt ( 2019 ) are the most enigmatic cell type of the hepatopancreas. B-cells are involved in the digestion of all material (except for low molecular weight components) that remains in the lumen of the diverticula and possibly in lipid digestion. Food components enter into B-cells by pinocytosis. Much of the absorbed material is digested and remained in the central vacuole and later eliminates by holocrine secretion back into the diverticular lumen for further assimilation by R-cells (Arnaud et al. 1978 ). The formation of a large vacuole in the cytoplasm of the B-cell indicates the end of the digestive process (Franceschini-Vicentini et al. 2009 ). In M. affinis , mature B-cells contain a large central vacuole in the cytoplasm. In this form these cells enter the lumen of the diverticula and from there into the intestine. In A. eschrichtii , the functional activity of B-cells and the appearance of a large central vacuole in them appears to be stimulated by atrophy of R-cells. B-cells probably clean the diverticula of the hepatopancreas of A. eschrichtii from the degraded plasmatic membranes of R-cells, the main component of them are lipids. B-cells excrete the content of the vacuole into the lumen of the diverticula and die, leaving behind a lumen in the epithelium. Previously, we found (Durkina et al. 2018 ) that about 25% of sexually mature females of A. eschrichtii ( F0 females, body length 22–24 mm) resorb all vitellogenic oocytes during seasonal starvation. The present study suggests that oocyte utilization in these individuals is not associated with a complete atrophy of R-cells of the epithelium of the hepatopancreas. On the contrary, R-cells of the epithelium still retain some nutrient reserve in summer. It is possible that total degradation of vitellogenic oocytes in these females is explained by high density in the settlements (ampeliscid mats). It should be noted that A. eschrichtii forms aggregations with the highest biomass on the northeastern shelf of Sakhalin Island (Okhotsk Sea) among all studied amphipod populations in the world (Demchenko et al. 2016 ). The literature data indicate a negative effect of the high density of settlement of animals on their reproductive function. For instance, at high population densities, cultured Daphnia pulex reduce the release of offspring (Nishikawa and Ban 1998 ), and females of the New Zealand freshwater snail Potamopyrgus antipodarum produce fewer embryos (Zachar and Neiman 2013 ). High abundance of rats reduces the fecundity and increases embryonic mortality (Sadykov and Benenson 1992 ), and in mice cause an increase in the number of atretic follicles in the ovaries (Kim and You 2022 ). Conclusion The ability to store large amounts of lipids during productive seasons and use them for reproduction or for survival during periods of food shortage is well known in Arctic marine invertebrates (Noyon et al. 2011 ). The habitat conditions of A. eschrichtii (negative water temperature for most of the year and seasonal food availability) appear to be comparable to those of benthic invertebrates in Arctic seas. In winter in the waters of the Okhotsk Sea there is intensive development of phytoplankton (Leonov et al. 2007 ), which when sinking to the bottom becomes available for amphipods. The fatty acid composition of A. eschrichtii reveals that diatom microalgae are the main component of their food (Rodkina et al. 2020 ). Sampling of A. eschrichtii in winter on the northeastern shelf of the Sakhalin Island is impossible due to the presence of ice cover, but there is no doubt that amphipods at this time store large amounts of lipids in R-cells of the hepatopancreas. In summer and autumn, microalgae concentrate at the upper boundary of the thermocline within 10–15 m depth (Sorokin and Sorokin 1999 ; Prants et al. 2017 ), which leads to seasonal starvation of amphipods. During starvation in the hepatopancreas of A. eschrichtii , there is observed: 1) functional passivity of the F-cell epithelium, confirming the absence of food in the cardiac stomach; 2) gradual disappearance of vacuoles in R-cells due to lipid utilization and destruction of R-cells themselves; 3) activation of B-cells, which apparently digest membrane structures of destroyed R-cells, and death of B-cells after holocrine secretion. The main function of R-cells of A. eschrichtii during starvation is to supply energy and previously stored nutrients (lipids) for the needs of the organism and vitellogenic growth of oocytes. Atrophy of the epithelium of the proximal and medial zones of the hepatopancreas of A. eschrichtii is completed in October and, thus, the lipid reserve is depleted in the hepatopancreas, but oocytes have not yet reached definitive sizes by this time (Durkina et al. 2018 ). This suggests that adipocytes may be an additional source of nutrients in amphipod tissues. Information on the storage function of adipocytes of crustaceans is scarce. It is known, that adipocytes of the amphipod Orchestia gammarellus contain lipids and glycogen (Meusy et al. 1983 ), while adipocytes of the isopod Bathynomus giganteus contain predominantly lipids and proteins (Biesiot et al. 1999 ). Adipocytes (fat body) play an important role in insect life (Arrese and Soulages 2010 ). They store large stores of lipids necessary for growth and reproduction and supply energy needed during periods of prolonged starvation. The morphology of R-, F- and B-cells of the epithelium of the hepatopancreas of M. affinis consistent with the description of analogous cells of the epithelium of the hepatopancreas of decapods and confirms the presence of a food supply in the habitat of this species during vitellogenesis. Declarations Acknowledgements The authors are sincerely grateful to I.A. Shcherbakov (Laboratory of Marine Ecosystem Dynamics, NSCMB FEB RAS) as the leader of the benthos team during the expeditions to the north-eastern coast of the Sakhalin Island (Okhotsk Sea) for collaboration and field collecting of the valuable amphipod material. We are very grateful to Dr. John W. Chapman (Department of Fisheries, Wildlife and Conservation, Oregon State University, Newport, Oregon, United States of America) for reading and valuable comments on the manuscript. Funding This study was financed from the budget of the Zhirmunsky National Scientific Center for Marine Biology within framework of state assignment no. 1021062912499-0, “Dynamics of Marine Ecosystems, Adaptation of Marine Organisms and Communities to Changes in the Environment”. Competing interest The authors declare that they have no competing interest. Author contribution NLD determined the species, sex and size of amphipods and reproductive condition of females of A. eschrichtii and M. affinis in samples off the north-eastern shelf of the Sakhalin Island (Okhotsk Sea). The VBD prepared histological slides, analyzed the condition of the amphipod hepatopancreas and wrote the paper. VBD and NLD jointly discussed and prepared the final text of the paper. References Al-Mohanna SY, Nott JA (1987) R-cells and the digestive cycle in Penaeus semisulcatus (Crustacea: Decapoda). Mar Biol 95:129–137 Al-Mohanna SY, Nott JA, Lane DJW (1985) Mitotic E- and Secretory F-Cells in the Hepatopancreas of the Shrimp Penaeus semisulcatus (Crustacea: Decapoda). J Mar Biol Assoc U K 65:901–910 Arnaud J, Brunet M, Mazza J (1978) Studies on the midgut of Centropages typicus (copepod, calanoid). I. Structural and Ultrastructural Data. Cell Tissue Res 187:. https://doi.org/10.1007/BF00224375 Arrese EL, Soulages JL (2010) Insect fat body: energy, metabolism, and regulation. Annu Rev Entomol 55:207–225. https://doi.org/10.1146/annurev-ento-112408-085356 Barker P, Gibson R (1979) The decapod hepatopancreas. Oceanogr Mar Biol Annu Rev 17:285–346 Biesiot PM, Wang SY, Perry HM, Trigg C (1999) Organic reserves in the midgut gland and fat body of the giant deep-sea isopod Bathynomus giganteus . J Crustac Biol 19:450–458. https://doi.org/10.2307/1549253 Cervellione F, McGurk C, Van den Broeck W (2017) “Perigastric organ”: a replacement name for the “hepatopancreas” of Decapoda. J Crustac Biol 37:353–355. https://doi.org/10.1093/jcbiol/rux020 Chen Ch, Tan Q, Liu M, et al (2017) Effect of starvation on growth, histology and ultrastructure of digestive system of juvenile red swamp crayfish ( Procambarus clarkii Girard). Iran J Fish Sci 16:1214–1233 Darriba S, San Juan F, Guerra A (2005) Energy storage and utilization in relation to the reproductive cycle in the razor clam Ensis arcuatus (Jeffreys, 1865). ICES J Mar Sci 62:886–896. https://doi.org/10.1016/j.icesjms.2005.02.010 Demchenko NL (2010) Ecological aspects of the dominant amphipod Monoporeia affinis (Amphipoda: Pontoporeiidae) in the infralittoral zone on the northeastern coast of the Sakhalin Island (Sea of Okhotsk). Zool Baetica 21:143–149 Demchenko NL, Chapman JW, Durkina VB, Fadeev VI (2016) Life history and production of the western gray whale’s prey, Ampelisca eschrichtii Krøyer, 1842 (Amphipoda, Ampeliscidae). PLoS ONE 11:1–18. https://doi.org/10.1371/journal.pone.0147304 Durkina VB, Chapman JW, Demchenko NL (2018) Ampelisca eschrichtii Krøyer, 1842 (Ampeliscidae) of the Sakhalin Shelf in the Okhotsk Sea starve in summer and feast in winter. PeerJ 6:1–21. https://doi.org/10.7717/peerj.4841 Fong CR, Gaynus CJ, Carpenter RC (2020) Extreme rainfall events pulse substantial nutrients and sediments from terrestrial to nearshore coastal communities: a case study from French Polynesia. Sci Rep 10:2955. https://doi.org/10.1038/s41598-020-59807-5 Franceschini-Vicentini IB, Ribeiro K, Papa LP, et al (2009) Histoarchitectural features of the hepatopancreas of the Amazon River prawn Macrobrachium amazonicum . Int J Morphol 27:121–128. https://doi.org/10.4067/S0717-95022009000100022 Guan Z-B, Yin J, Chen K, et al (2016) The hepatopancreas and ovary are the sites of vitellogenin synthesis in female red swamp crayfish ( Procambarus clarkii (Girard, 1852)) (Decapoda: Astacoidea: Cambaridae). J Crustac Biol 36:637–641. https://doi.org/10.1163/1937240X-00002459 Han C-H, Okumura T, Suzuki Y, et al (1994) Immunocytochemical identification of the site of vitellogenin synthesis in the freshwater prawn Macrobrachium nipponense . Fish Sci 60:149–154. https://doi.org/10.2331/fishsci.60.149 Hemambika M, Raj RP (1999) An ultrastructural study of the hepatopancreas of Indian white prawn Penaeus indicus H. Milne Edwards. In: Fourth Indian Fiheries Forum Proceedings 24-28 November, 1996. Kochi, pp 291–294 Hopkin SP, Nott JA (1980) Studies on the digestive cycle of the shore crab Carcinus maenas (L.) with special reference to the b cells in the hepatopancreas. J Mar Biol Assoc U K 60:891–907. https://doi.org/10.1017/S0025315400041977 Huang X, Feng Y, Duan J, et al (2020) Antistarvation strategies of E. sinensis : regulatory networks under hepatopancreas consumption. Oxid Med Cell Longev 2020:6085343. https://doi.org/10.1155/2020/6085343 Icely JD, Nott JA (1984) On the morphology and fine structure of the alimentary canal of Corophium volutator (Pallas) (Crustacea: Amphipoda). Philos Trans R Soc Lond B Biol Sci 306:49–78 Kim J, You S (2022) High housing density-induced chronic stress diminishes ovarian reserve via granulosa cell apoptosis by angiotensin II overexpression in mice. Int J Mol Sci 23:8614. https://doi.org/10.3390/ijms23158614 Leonov AV, Mogil’nikova TA, Pishchal’nik VM, Zenkin OV (2007) Characteristic of microalgae development in the Sea of Okhotsk in winter and modeling of their annual dynamics in Aniva Bay. Water Resour 34:184–194. https://doi.org/10.1134/S0097807807020091 Meusy JJ, Zerbib C, Dacheux F, Dubois MP (1983) Subcellular localization of vitellogenin in crustacean adipocytes by the unlabelled antibody enzyme method. Tissue Cell 15:301–310. https://doi.org/10.1016/0040-8166(83)90024-1 Mihaljević M, Špoljarić D, Stević F, et al (2010) The influence of extreme floods from the River Danube in 2006 on phytoplankton communities in a floodplain lake: Shift to a clear state. Limnol - Ecol Manag Inland Waters 40:260–268. https://doi.org/10.1016/j.limno.2009.09.001 Nishikawa J, Ban S (1998) Effect of high population density on growth and reproduction of Daphnia pulex DeGeer. Plankton Biol Ecol 45:55–60 Noyon M, Narcy F, Gasparini S, Mayzaud P (2011) Growth and lipid class composition of the Arctic pelagic amphipod Themisto libellula . Mar Biol 158:883–892. https://doi.org/10.1007/s00227-010-1615-1 Paczkowska J, Brugel S, Rowe O, et al (2020) Response of coastal phytoplankton to high inflows of terrestrial matter. Front Mar Sci 7: 2020. https://doi.org/10.3389/fmars.2020.00080 Pazos AJ, Román G, Acosta CP, et al (1997) Seasonal changes in condition and biochemical composition of the scallop Pecten maximus L. from suspended culture in the Ria de Arousa (Galicia, N.W. Spain) in relation to environmental conditions. J Exp Mar Biol Ecol 211:169–193. https://doi.org/10.1016/S0022-0981(96)02724-4 Prants SV, Andreev AG, Uleysky MY, Budyansky MV (2017) Mesoscale circulation along the Sakhalin Island eastern coast. Ocean Dyn 67:345–356. https://doi.org/10.1007/s10236-017-1031-x Rodkina SA, Kiyashko SI, Demchenko NL (2020) Trophic basis of dominant amphipods in the gray whale feeding grounds near northeastern Sakhalin Island (the Sea of Okhotsk) inferred from fatty acid and stable isotope analyses. Mar Environ Res 158:104999. https://doi.org/10.1016/j.marenvres.2020.104999 Rogachev KA, Pomerleau C, Shlyk NV, Carmack EC (2022) Joint effects of sea ice melt, freshwater discharge and tidal currents on zooplankton abundance in the Sea of Okhotsk: 2004 and 2013. Polar Sci 31:100781. https://doi.org/10.1016/j.polar.2021.100781 Rogachev KA, Shlyk NV (2015) Prominent freshening of coastal waters in the north-western Sea of Okhotsk in 2013. Vestn Far East Branch Russ Acad Sci 118–125 Sacristán HJ, Ansaldo M, Franco-Tadic LM, et al (2016) Long-term starvation and posterior feeding effects on biochemical and physiological responses of midgut gland of Cherax quadricarinatus juveniles (Parastacidae). PLOS ONE 11:e0150854. https://doi.org/10.1371/journal.pone.0150854 Sadykov OF, Benenson IE (1992) Population dynamics of small mammals: concepts, hypotheses, models. Nauka, Moscow Sánchez-Paz A, García-Carreño F, Muhlia-Almazán A, et al (2006) Usage of energy reserves in crustaceans during starvation: status and future directions. Insect Biochem Mol Biol 36:241–249. https://doi.org/10.1016/j.ibmb.2006.01.002 Sastry AN (1983) Ecological aspects of reproduction. In: Vernberg W.B., eds. The biology of Crustacea: Environmental adaptations. Academic Press, New York, pp 179–270 Schmitz EH, Scherrey PM (1983) Digestive anatomy of Hyalella azteca (Crustacea, Amphipoda). J Morphol 175:91–100. https://doi.org/10.1002/jmor.1051750109 Sorokin YuI, Sorokin PY (1999) Production in the Sea of Okhotsk. J Plankton Res 21:201–230. https://doi.org/10.1093/plankt/21.2.201 Souty C, Picaud JL (1981) Vitellogenin synthesis in the fat body of the marine crustacean Isopoda, Idotea balthica basteri , during vitellogenesis. Reprod Nutr Dev 21:95–101. https://doi.org/10.1051/rnd:19810108 Štrus J, Žnidaršič N, Mrak P, et al (2019) Structure, function and development of the digestive system in malacostracan crustaceans and adaptation to different lifestyles. Cell Tissue Res 377:415–443. https://doi.org/10.1007/s00441-019-03056-0 Tsukimura B (2001) Crustacean Vitellogenesis: Its Role in Oocyte Development. Am Zool 41:465–476 Unuma T, Walker CW (2009) Relationship between gametogenesis and food quality in sea urchin gonads. Stickney R., Iwamoto R.; Rust M. (editors). Aquaculture technologies for invertebrates: proceedings of the thirty-sixth U.S.-Japan aquaculture panel symposium, Durham, New Hampshire, October 29–30, and Milford, Connecticut, November 2, 2007. U.S. Dept. Commerce, NOAA Tech. Memo. NMFS-F/SPO-99, p 73 Vogt G (2021) Synthesis of digestive enzymes, food processing, and nutrient absorption in decapod crustaceans: a comparison to the mammalian model of digestion. Zool Jena Ger 147:125945. https://doi.org/10.1016/j.zool.2021.125945 Vogt G (2019) Functional cytology of the hepatopancreas of decapod crustaceans. J Morphol 280:1405–1444. https://doi.org/10.1002/jmor.21040 Vogt G, Quinitio ET, Pascual FP (1989) Interaction of the midgut gland and the ovary in vitellogenesis and consequences for the breeding success: a comparison of unablated and ablated spawners of Penaeus monodon . In: De Pauw N, Jaspers E, Ackefors H, Wilkins N (eds) Aquaculture - A Biotechnology in Progress. Proceedings of the International Conference Aquaculture Europe ’87, Amsterdam, The Netherlands, June 2-5, 1987. European Aquaculture Society, Bredene, Belgium, pp 581–592 Vogt G, Storch V, Quinitio ET, Pascual FP (1985) Midgut gland as monitor organ for the nutritional value of diets in Penaeus monodon (Decapoda). Aquaculture 48:1–12. https://doi.org/10.1016/0044-8486(85)90047-X Yano I, Chinzei Y (1987) Ovary is the site of vitellogenin synthesis in kuruma prawn, Penaeus japonicus . Comp Biochem Physiol Part B Comp Biochem 86:213–218. https://doi.org/10.1016/0305-0491(87)90280-X Zachar N, Neiman M (2013) Profound effects of population density on fitness-related traits in an invasive freshwater snail. PLoS ONE 8:e80067. https://doi.org/10.1371/journal.pone.0080067 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 30 Jul, 2025 Read the published version in Polar Biology → Version 1 posted Editorial decision: Revision requested 27 Dec, 2024 Reviews received at journal 25 Dec, 2024 Reviewers agreed at journal 09 Dec, 2024 Reviews received at journal 07 Dec, 2024 Reviewers agreed at journal 01 Dec, 2024 Reviewers invited by journal 22 Nov, 2024 Editor assigned by journal 19 Nov, 2024 Submission checks completed at journal 02 Nov, 2024 First submitted to journal 01 Nov, 2024 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-5370478","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":373217117,"identity":"ad305d8b-0579-4f08-b43f-f7152a986dcb","order_by":0,"name":"Valentina B. Durkina","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAtElEQVRIiWNgGAWjYFCCBAbGBgMGBn4g88ADkrRINgC1JBCvBUgZHACziQAGx3PMPs4ouCNvfO3wQ6At9xIbCGo588Z45gaDZ4bbbqcZALUUE9YiOSPHmPGBwWHGbbcTQFoSiNdiv3l2+gfitPBLALVsMDicuEE6h0hb+HmeFTPOMDicPON2TsGBBIMEY4Ja2NiTNzP2/Dls2z87ffOHDxUJsgS1oAEDEtWPglEwCkbBKMAOAIGgQ0iK8gaQAAAAAElFTkSuQmCC","orcid":"","institution":"Russian Academy of Sciences","correspondingAuthor":true,"prefix":"","firstName":"Valentina","middleName":"B.","lastName":"Durkina","suffix":""},{"id":373217118,"identity":"bed991f1-f604-4796-9913-a8dea5851334","order_by":1,"name":"Natalia L. Demchenko","email":"","orcid":"","institution":"Russian Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Natalia","middleName":"L.","lastName":"Demchenko","suffix":""}],"badges":[],"createdAt":"2024-11-01 04:23:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5370478/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5370478/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00300-025-03411-8","type":"published","date":"2025-07-30T16:13:19+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":68991822,"identity":"dfdb8b06-1659-4862-9887-a7bddb9c952e","added_by":"auto","created_at":"2024-11-14 09:41:28","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":56686860,"visible":true,"origin":"","legend":"\u003cp\u003eStatus of the hepatopancreas of M. affinis during vitellogenesis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e Transverse section of the diverticula at the level of the proximal zone (lower and central diverticula) and the medial zone (upper diverticulum), showing F-cells (F), R-cells (R) and B-cells (B) of the epithelium. The lumen (L) of the lower diverticulum contains disrupted cells that are evacuated into the intestine. Scale bar 100 µm. \u003cstrong\u003eb\u003c/strong\u003e B-cells (B) of the medial zone of the diverticulum lose their link with the basal lamina and extend into the apical part of the epithelium. Longitudinal section. Scale bar 50 µm. \u003cstrong\u003ec\u003c/strong\u003e Transverse section through the proximal zone of the diverticula. The appearance of sloughed B-cells (B) among the cellular remnants in the lumen (L) of the lower diverticulum indicates the completion of the digestive cycle in this diverticulum. Scale bar 100 µm. \u003cstrong\u003ed\u003c/strong\u003e The extended haemal sinus (GS) is closely adjacent to the diverticulum (D) and ovary (OV). Transverse section. Scale bar 100 µm. \u003cstrong\u003ee\u003c/strong\u003eTransverse section of diverticula with different functional condition in relation to the intestine (G): with normal epithelium (NE), with atrophying epithelium (AE) and without epithelium (LE). Scale bar 100 µm. \u003cstrong\u003ef\u003c/strong\u003e Atrophy of the diverticular epithelium (D) in October 2013. Longitudinal section. Scale bar 100 µm\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5370478/v1/b7ed000800cdc6c45c288bdc.png"},{"id":68991936,"identity":"24bd5235-3395-4dd7-bd20-49052dbe3dff","added_by":"auto","created_at":"2024-11-14 09:49:28","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":70716970,"visible":true,"origin":"","legend":"\u003cp\u003eCondition of the hepatopancreas of \u003cem\u003eA. eschrichtii \u003c/em\u003eduring vitellogenesis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e Transverse section of the proximal zone of the diverticulum showing R-cells (R) and F-cells (F) of the epithelium. Scale bar 100 µm.\u003cstrong\u003e b\u003c/strong\u003e Transverse section of a region of the first third of the medial zone of the diverticulum with B-cells (B) at the apex of the ridges. Scale bar 100 µm.\u003cstrong\u003e с\u003c/strong\u003e Transverse section of the last third of the medial zone of the diverticulum with high ridges of R-cell epithelium (R) and a small lumen (L). Scale bar 100 µm.\u003cstrong\u003e d\u003c/strong\u003e The initial stage of atrophy of R-cells of diverticular epithelium is characterised by inflated nuclei (N) of cells and chromatin condensation. Longitudinal section. Scale bar 50 µm.\u003cstrong\u003e e\u003c/strong\u003eDestruction of the apical part of R-cells is accompanied by destruction of the nuclear membrane and release of condensed chromatin clumps (arrows with black heads) into the lumen (L) of the diverticulum. Relatively large vacuoles are formed in the basal part of R-cells (arrows with light-coloured heads). Longitudinal section. Scale bar 50 µm.\u003cstrong\u003e f \u003c/strong\u003eVacuoles in the basal part of R-cells (arrows with light-coloured heads) persist until the complete destruction of these cells. The lumen (L) of the diverticulum does not contain destroyed or sloughed epithelial cells. Scale bar 50 µm\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5370478/v1/bec7f6a5e24fe9d1f90c5ce1.png"},{"id":68991821,"identity":"ea5ecd58-ffa7-4c43-99c6-76bf047a31f8","added_by":"auto","created_at":"2024-11-14 09:41:27","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2997929,"visible":true,"origin":"","legend":"\u003cp\u003eCondition of the hepatopancreas of \u003cem\u003eA. eschrichtii\u003c/em\u003eduring vitellogenesis (continuation). \u003cstrong\u003ea\u003c/strong\u003eYoung (YB) and mature B-cells (B) in the epithelium of the medial zone of the hepatopancreas. Longitudinal section. Scale bar 50 µm.\u003cstrong\u003e b\u003c/strong\u003e The content of mature B-cells (B) is secreting into the lumen (L) of the diverticulum. Longitudinal section. Scale bar 50 µm.\u003cstrong\u003e c\u003c/strong\u003e Appearance of cavities (C) between F-cells (F) in the epithelium of diverticula as a result of holocrine secretion of B-cells. Longitudinal section. Scale bar 50 µm.\u003cstrong\u003e d\u003c/strong\u003e Epithelial atrophy (E) in the diverticula (D) of the hepatopancreas in a female with lysis of all vitellogenic oocytes (VO). The hemolymphatic sinuses (GS) are enlarged and filled with homogeneous contents. The lumen (L) of diverticula contains clots of homogeneous substance. Longitudinal section. Scale bar 200 µm.\u003cstrong\u003e e\u003c/strong\u003e In October the diverticula (D) are without epithelium and the lumen (L) of the diverticula contains sparse material. Longitudinal section. Scale bar 100 µm\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5370478/v1/a09c1f9d77c855d5bbbdfaf6.png"},{"id":88268474,"identity":"fd70a6bd-2b67-47be-b870-9f09e9215777","added_by":"auto","created_at":"2025-08-04 16:52:01","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":119669995,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5370478/v1/99b03c7e-10ee-45d0-a658-3577d7816152.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Hepatopancreas in the starving amphipod Ampelisca eschrichtii and the feeding amphipod Monoporeia affinis during vitellogenesis","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRepresentatives of marine invertebrates (amphipods, sea urchins, bivalves) are able to store nutrients obtained from food in somatic tissues of the body and use them for gametogenesis, including periods of starvation (Pazos et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Darriba et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Unuma and Walker \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Noyon et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). The separation of vitellogenesis processes from the period of food availability was found in the benthic amphipod \u003cem\u003eAmpelisca eschrichtii\u003c/em\u003e Kr\u0026oslash;yer, 1842 (\u003cem\u003eAmpeliscidae\u003c/em\u003e) from the northeastern shelf of Sakhalin Island (Okhotsk Sea) (Durkina et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). \u003cem\u003eAmpelisca eschrichtii\u003c/em\u003e forms large and dense aggregations at depths greater than 50, where water temperatures near the bottom are negative or close to 0\u0026ordm;C for most of the year (Demchenko et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). This amphipod species has a two-year life cycle. Reproduction and embryo brooding in \u003cem\u003eA. eschrichtii\u003c/em\u003e occurs in winter and spring at the age of 2 years (when females reach a body length of 22 mm or more) (Demchenko et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), when intensive phytoplankton development occurs in the shelf waters of Sakhalin Island (Leonov et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Microalgae settle on the bottom due to the prevailing vertical mixing of the Sakhalin shelf waters at this\u0026ndash; time of year (Leonov et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), providing food supply for amphipods. The fatty acid composition of \u003cem\u003eA. eschrichtii\u003c/em\u003e has shown that diatom microalgae are the main component of their food (Rodkina et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). During the warm season (summer, autumn), phytoplankton biomass is concentrated at the upper boundary of the thermocline to depths of 10\u0026ndash;15 m (Sorokin and Sorokin \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Prants et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), which prevents microalgae availability for amphipods living at greater depths. Despite the lack of food, vitellogenic growth of oocytes was observed in sexually mature females of \u003cem\u003eA. eschrichtii\u003c/em\u003e (body length 22\u0026ndash;24 mm), indicating the presence of nutrient reserves in the amphipod body. However, about 75% of \u003cem\u003eA. eschrichtii\u003c/em\u003e individuals complete oocyte growth, whereas in the remaining females all oocytes undergo lysis and resorption (Durkina et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Previously, destruction and resorption of immature vitellogenic oocytes was observed in the barnacle \u003cem\u003eAmphibalanus amphitrite\u003c/em\u003e (Darwin, 1854) and the predatory copepod \u003cem\u003eParaeuchaeta norvegica\u003c/em\u003e (Boeck, 1872) under starvation (Sastry \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1983\u003c/span\u003e). It is possible that the formation of complete eggs during seasonal starvation in \u003cem\u003eA. eschrichtii\u003c/em\u003e depends on the amount of nutrients stored in winter and spring in the body tissues of amphipods.\u003c/p\u003e \u003cp\u003eThe hepatopancreas (digestive gland) and muscle tissue of crustaceans are the main organs for the accumulation of food-derived nutrients that can be directed to reproductive processes during starvation (Vogt et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). Hepatopancreas cells are responsible for nutrient uptake, intracellular digestion, and accumulation of lipid and glycogen stores required when energy requirements increase or when food resources decrease (S\u0026aacute;nchez-Paz et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Close interaction between the hepatopancreas and ovaries of crustaceans is noted during vitellogenesis (Vogt et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). This relation is explained by the fact that the hepatopancreas is one of the sites of synthesis of the precursor of the oocyte yolk protein, vitellogenin (Han et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Vogt \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The histological structure of the hepatopancreas has been investigated mainly in decapods and summarized in a number of reviews (Barker and Gibson \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1979\u003c/span\u003e; Cervellione et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Vogt \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The decapod hepatopancreas is represented by right and left lobes consisting of numerous (up to hundreds) blind outgrowths (diverticula) formed by the midgut. Each diverticulum is surrounded by a muscular network consisting of longitudinal and annular fibers and hemolymphatic sinuses. Inside the diverticula are covered by a single-layer epithelium, which is located on the basal lamina and forms rows of longitudinal ridges and depressions.\u003c/p\u003e \u003cp\u003eThere are three zones in diverticula: distal, medial, and proximal. The distal zone contains small \u0026ldquo;embryonic\u0026rdquo; E-cells with a high nuclear-cytoplasmic ratio. The medial zone contains \u0026ldquo;fibrillar\u0026rdquo; F-cells, \u0026ldquo;resorptive or absorptive\u0026rdquo; R-cells, and \u0026ldquo;secretory\u0026rdquo; B-cells. The proximal zone contains F- and R-cells. Stem E-cells, proliferating, produce R-, B-, and F-cells. R-cells form the apexes of diverticular ridges and contain numerous vacuoles in the cytoplasm. B-cells are also found at the apexes of the ridges and contain one very large vacuole that pushes the cytoplasm and nucleus toward the plasma membrane. F-cells are located in the depressions between the ridges of the epithelium and have a dark homogeneous cytoplasm, and mature F-cells contain one small vacuole (autophagosome) near the nucleus. In addition to the four cell types mentioned above, small M-cells of non-hepatopancreatic origin with a presumed endocrine function are found on the basal lamina of diverticula.\u003c/p\u003e \u003cp\u003eExperimental starvation causes a number of morphological changes in the decapod hepatopancreas epithelium. Among these, the most frequently observed are a decrease, or disappearance, of lipid droplets in R-cells and a decrease in the number of R-cells, indicating that the body requires energy during starvation (Sacrist\u0026aacute;n et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Chen et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Huang et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Contrary to experimental data, we did not find information on how the digestive gland functions in crustaceans for which prolonged starvation is the normal and, more interestingly, when starvation coincides with vitellogenesis.\u003c/p\u003e \u003cp\u003eThe majority of articles devoted to the digestive tract of Malacostraca Latreille, 1802 refer to commercially important species and few widespread and easily accessible species (Štrus et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Štrus et al. (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) note that future studies should include species with an exclusive ecology, lifestyle, and feeding strategy. We suggest that the amphipod of \u003cem\u003eA. eschrichtii\u003c/em\u003e can satisfy these requirements. In the present study, we intended to investigate 1) how the hepatopancreas of \u003cem\u003eA. eschrichtii\u003c/em\u003e functions during vitellogenesis coinciding with seasonal starvation, and 2) whether starvation can be the cause of total destruction of vitellogenic oocytes, which we previously found (Durkina et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) in 25% of sexually mature females of \u003cem\u003eA. eschrichtii\u003c/em\u003e. To assess adequately the condition of the hepatopancreas of \u003cem\u003eA. eschrichtii\u003c/em\u003e, we compared it with that of the hepatopancreas of the amphipod \u003cem\u003eMonoporeia affinis\u003c/em\u003e (Lindstr\u0026ouml;m, 1855) (\u003cem\u003ePontoporeiidae\u003c/em\u003e). \u003cem\u003eM. affinis\u003c/em\u003e, like \u003cem\u003eA. eschrichtii\u003c/em\u003e, occurs on the northeastern shelf of Sakhalin Island, but at shallower depths, predominantly up to 20 m (Demchenko \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), where it does not appear to have food availability problems.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003eThe amphipods \u003cem\u003eA. eschrichtii\u003c/em\u003e and \u003cem\u003eM. affinis\u003c/em\u003e were collected from the northeastern shelf of the Sakhalin Island (Okhotsk Sea) during the summer-autumn season between the years 2013 and 2021 (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) using a Van Veen grab with a surface area of 0.2 m\u003csup\u003e2\u003c/sup\u003e during the expeditions with participation of the A.V. Zhirmunsky Institute of Marine Biology (since 2016 A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences (NSCMB FEB RAS) in long-term studies of macrobenthos as part of the western gray whale monitoring program off the north-eastern coast of Sakhalin Island. This program was supported by Exxon Neftegas Limited and by Sakhalin Energy Investment Company Ltd. (Sakhalin Energy) between 2001 and 2021.\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\u003eDates, coordinates of sampling sites and environmental parameters in the habitats of amphipods \u003cem\u003eA. eschrichtii\u003c/em\u003e and \u003cem\u003eM. affinis\u003c/em\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\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=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecies\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDate (m/y)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003en\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLat (N)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLong (E)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eD, m\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eT, C\u0026deg;\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eS, psu\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSedi-ment\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eVessel\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eA. eschrichtii\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eX/2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e52.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e143.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e53.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e31.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003en/d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eR/V \"Pavel Gordienko\"\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eA. eschrichtii\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eX/2015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e51.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e143.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e58.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e32.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSFS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eR/V \"Igor Maksimov\"\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eA. eschrichtii\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVII/2015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e51.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e143.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e59.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003en/d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003en/d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSFS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eR/V \"Igor Maksimov\"\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eA. eschrichtii\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVIII/2019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e52.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e143.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e55.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-0.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e33.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSFS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eAHTS \"Katun\"\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eA. eschrichtii\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVIII/2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e51.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e143.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e59.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e32.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eMS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eAHTS \"Beya\"\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eM. affinis\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eX/2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e52.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e143.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e8.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e28.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003en/d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eR/V \"Pavel Gordienko\"\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eM. affinis\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eX/2014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e52.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e143.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e14.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e9.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e28.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSFS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eR/V \"Pavel Gordienko\"\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eM. affinis\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVII/2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e52.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e143.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e10.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e29.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSFS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eAHTS \"Beya\"\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eM. affinis\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVIII/2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e52.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e143.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e8.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e29.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSFS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eAHTS \"Beya\"\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"10\"\u003eNote. m/y \u0026ndash; month/year, n - number of specimens used for histological analysis of hepatopancreas, lat \u0026ndash; latitude, long -longitude, D \u0026ndash; depth, T \u0026ndash; bottom temperature, S \u0026ndash; bottom salinity, n/d \u0026ndash; no data, SFS - silty fine sand, MS - medium sand, R/V \u0026ndash; Research/Survey Vessel, AHTS \u0026ndash; Anchor-handling Tug/Supply\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTo prepare histological slides, amphipods fixed in 4% formalin were washed in water for 24 h, dehydrated, clarified in xylene, and then soaked in paraffin and poured into paraffin blocks. Slices of 10 \u0026micro;m thickness were prepared for microscopic analysis. Slides containing hepatopancreas tissues were stained with hematoxylin-eosin, dehydrated, clarified in xylene, and permanent slides were prepared. We analyzed the state of F-, R- and B-cells of the hepatopancreas epithelium that participate in digestion processes. F-cells were identified by their location between the ridges of the epithelium, basophilia of the cytoplasm, and a single vacuole near the nucleus. R-cells were identified by their location at the apex of the ridges of the epithelium and numerous vacuoles in the cytoplasm. B-cells were identified by their location at the apex of the ridges of the epithelium and a large central vacuole pushing the nucleus and cytoplasm to the periphery of the cell. To illustrate the tissues and cells of the hepatopancreas of \u003cem\u003eA. eschrichtii\u003c/em\u003e and \u003cem\u003eM. affinis\u003c/em\u003e, preparations (the mounted slides) were photographed using VideoTesT (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.zenit-npk.ru/fcatalog/info/74\u003c/span\u003e\u003cspan address=\"http://www.zenit-npk.ru/fcatalog/info/74\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e).\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003eMonoporeia affinis\u003c/h2\u003e\n \u003cp\u003eAmphipod species has four long ventral diverticula, two of which are adjacent to the ovaries. Three diverticula were found in one of the examined individuals, and five diverticula in another. The diverticula of the hepatopancreas of amphipods collected in October 2014 and July-August 2021 are characterized by sites with normal epithelium and sites with epithelial atrophy. The normal epithelium of diverticula forms longitudinal ridges, the central part of which is occupied by R-cells (in the proximal zone) or R- and B-cells (in the medial zone), and the depressions located between the ridges contain F-cells (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea). The nuclei of R-, B-, and F-cells have no pathological changes (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea). R-cells contain vacuoles, the number of which is less in the cells of the proximal zone than in the cells of the medial zone (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea). B-cells are located in the apical part of the epithelium and contain a large central vacuole (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea, b). F-cells contain a small single vacuole near the nucleus (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea, b). When the epithelium atrophies, the lumen of diverticula is filled with destroyed cells, among which there are sloughed B-cells (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ec). Extended haemolymphatic sinuses with homogeneous contents are closely adjacent to the diverticula of the hepatopancreas and to the ovaries (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ed). In 8 of the 18 examined specimens, normal epithelium occupies the proximal zone and the medial zone up to 1/4\u0026thinsp;\u0026minus;\u0026thinsp;2/3 of its length in different individuals, and the extent of normal epithelium may vary in different diverticula of the same individual. Distal to the normal epithelium, epithelial atrophy is observed. In 3 of 18 specimens, normal epithelium is located in the last third of the medial zone, and proximally the epithelium undergoes atrophy. In 2 of 18 specimens, normal epithelium is found in almost all diverticula, and it is absent in the diverticula of the other 2 specimens. Asynchrony of diverticular functioning is observed in 3 of 18 specimens. For example, two diverticula located on one side of the intestine have epithelium, while two diverticula on the opposite side have no epithelium (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ee). It should be noted that the location of diverticula without epithelium relative to the intestine could vary. Atrophy of the epithelium is followed by an increase in the diameter of the diverticula. Hepatopancreas diverticula of specimens collected in October 2013 contain remnants of epithelium in the form of a small number of damaged cells. Individual epithelial cells and sparse amorphous material are found in the lumen of the diverticula (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ef).\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003eAmpelisca eschrichtii\u003c/h3\u003e\n\u003cp\u003eAmphipod species has four long ventral diverticula, two of which are adjacent to the ovaries. Most of the epithelium of the diverticula in amphipods collected in July 2015 and August 2019 and 2021 is characterized by depletion. Normal epithelium is found in the proximal zone, but not in all specimens. Normal epithelium is also found in the last third of the medial zone of the diverticula in many specimens.\u003c/p\u003e\n\u003cp\u003eThe normal epithelium of the proximal zone of diverticula has ridges and depressions. R-cells with numerous vacuoles form the apexes of the ridges, and F-cells with basophilic cytoplasm fill the depressions between the ridges (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ea). A small vacuole, which is usually present in the cytoplasm of F-cells of \u003cem\u003eM. affinis\u003c/em\u003e, is rare in F-cells of \u003cem\u003eA. eschrichtii\u003c/em\u003e. At the beginning of the medial zone, B-cells with a large vacuole appear among the R-cells (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eb). The normal epithelium in the last third of the medial zone also retains high ridges (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ec). There, the epithelium is represented mainly by R-cells and few F-cells, whereas B-cells appear to remain inactive and are thus invisible. In the initial stages of epithelial atrophy, the nuclei of R-cells are swollen and chromatin is concentrated in a clump in the center of the nuclei (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ed). Then, the apical part of the cells is degraded and the nucleus is destructed, as a result of which lumps of condensed chromatin enter the lumen of the diverticula (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ee). The basal part of degrading R-cells contains a relatively large optically empty vacuole, which is in close contact with the plasmatic membrane of the cell, where the latter is in contact with the basal lamina. This vacuole persists until complete cell destruction (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ef). The destruction of R-cells leads to a decrease of the height of the epithelium of the hepatopancreas.\u003c/p\u003e\n\u003cp\u003eThere are young and mature B-cells in the epithelium of diverticula (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ea). The young B-cells are less rare, have contact with the basal lamina, and, like R-cells, contain vacuoles, but larger than in R-cells. The nuclear area of young B-cells exceeds that of R cells (97.37\u0026thinsp;\u0026plusmn;\u0026thinsp;10.32 and 61.64\u0026thinsp;\u0026plusmn;\u0026thinsp;6.96 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e, respectively; n\u0026thinsp;=\u0026thinsp;15; P\u0026thinsp;\u0026lt;\u0026thinsp;0.95). Mature B-cells have a large central vacuole and a pyknotic nucleus in the basal part of the cell. B-cells extending into the lumen of the diverticula are rare. Mature B-cells are commonly found in areas of diverticula with the most evident R-cell atrophy. They usually do not leave the epithelium, and their vacuole contents enter into the lumen of the diverticulum (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eb). As a result of holocrine secretion, a cavity bounded by deformed F-cells remains on the place of B-cells (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ec).\u003c/p\u003e\n\u003cp\u003eIn females with a normal vitellogenesis, no enlargement of haemolymphatic sinuses is observed. On the contrary, in females with lysis of all vitellogenic oocytes, the haemolymphatic sinuses are enlarged and their contents are represented by a homogeneous substance. The lumen of diverticula is filled by large clots of homogeneous substance, but total atrophy of hepatopancreas epithelium is not observed in these females (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ed).\u003c/p\u003e\n\u003cp\u003eIn October 2013 and 2015, a small number of deformed F-cells remain in the proximal zone of \u003cem\u003eA. eschrichtii\u003c/em\u003e diverticula and are sloughed off the basal lamina. The medial zone is usually without epithelium and the lumen of the diverticula is filled with sparse material (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ee). In some individuals, the low epithelium persists at the end of the medial zone in 1\u0026ndash;2 diverticula.\u003c/p\u003e\n\u003cp\u003eThe distal part of the diverticula of the hepatopancreas of \u003cem\u003eM. affinis\u003c/em\u003e and \u003cem\u003eA. eschrichtii\u003c/em\u003e contains E-cells.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn amphipods, unlike decapods, the number of hepatopancreas diverticula involved in digestion is limited. Thus, in amphipod \u003cem\u003eHyalella azteca\u003c/em\u003e, this function is performed by four ventral diverticula (Schmitz and Scherrey \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e1983\u003c/span\u003e), while in \u003cem\u003eCorophium volutator\u003c/em\u003e there is one ventral massive pair (Icely and Nott \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e1984\u003c/span\u003e). In \u003cem\u003eA. eschrichtii\u003c/em\u003e and \u003cem\u003eM. affinis\u003c/em\u003e, the process of digestion is carried out by two pairs of long ventral diverticula. As an exception, we found two specimens of \u003cem\u003eM. affinis\u003c/em\u003e with three and five diverticula.\u003c/p\u003e \u003cp\u003eDiverticula of the hepatopancreas of different specimens of \u003cem\u003eM. affinis\u003c/em\u003e in July-August 2021 and in October 2014 have different localization of sites with normal and atrophied epithelium along the length of the diverticula, which seems to reflect different stages of the digestive cycle. The process of digestion in crustaceans is accompanied by ageing and degeneration of cells of the hepatopancreas epithelium (Al-Mohanna et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1985\u003c/span\u003e). At the end of the digestive cycle, there is a massive loss of B-cells that coincides with the phase of mitotic activity of embryonic E-cells (Al-Mohanna and Nott \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1987\u003c/span\u003e). E-cells produce young R-, F- and B-cells and move them by pushing motions forward along the diverticulum (Vogt \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Thus, the localization of normal epithelium in the second half of the medial zone of diverticula in \u003cem\u003eM. affinis\u003c/em\u003e could indicate its recovery after the last digestive cycle. In turn, the localization of normal epithelium in the proximal zone and in the beginning of the medial zone of diverticula can be a sign of a near completion of the digestive cycle. In general, the state of the epithelium of the hepatopancreas of \u003cem\u003eM. affinis\u003c/em\u003e allows to state that in the natural environment, in the presence of food, different diverticula of one individual could be functioning more or less asynchronously. The discovery of specimens in which two of the diverticula contain normal epithelium and the other two are lacking it confirms this conclusion and might also indicate the constant feeding activity of amphipods. The duration of the digestive cycle in \u003cem\u003eM. affinis\u003c/em\u003e is not known, but in the shore crab \u003cem\u003eCarcinus maenas\u003c/em\u003e (Hopkin and Nott \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1980\u003c/span\u003e) and the shrimp \u003cem\u003ePenaeus semisulcatus\u003c/em\u003e (Al-Mohanna et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1985\u003c/span\u003e; Al-Mohanna and Nott \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1987\u003c/span\u003e) it takes at least 24 hours.\u003c/p\u003e \u003cp\u003eAlmost complete atrophy of the hepatopancreas epithelium in all \u003cem\u003eM. affinis\u003c/em\u003e individuals in October 2013 appears to reflect a lack of food resources for amphipods. In 2013, the coastal waters of the northwestern part of the Okhotsk Sea were affected for a long time by an extreme flood, which was observed in the region in autumn 2012 and in winter, spring and summer 2013. Thus, under the influence of the flood in 2013 in Academy Bay (northwest of the Okhotsk Sea), the salinity in the upper 5-meter layer was less than 20 PSU, and the maximum salinity values at the bottom slightly exceeded 27 PSU (Rogachev and Shlyk \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Rogachev et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The shelf zone of the northeastern coast of Sakhalin Island is influenced by the flow of the Amur River, the flood of which in 2013 was the strongest in the entire period of observations in the Far East (Rogachev and Shlyk \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Extreme rainfall events supply significant amounts of nutrients and terrestrial material to nearshore marine waters (Fong et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The oversupply of terrestrial particulate material in the water leads to reduced lighting of the water column and, consequently, to a decrease of phytoplankton primary production (Mihaljević et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Paczkowska et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn \u003cem\u003eA. eschrichtii\u003c/em\u003e, unlike \u003cem\u003eM. affinis\u003c/em\u003e, the location of sites with normal and atrophying epithelium along the length of the diverticula is not diverse. Thus, in most specimens in the summer months of 2015, 2019, and 2021, normal epithelium is frequently found in the proximal zone and in the last third of the medial zone of the diverticula, but most of the diverticula are occupied by atrophying epithelium. In autumn 2013 and 2015, a complete atrophy of the diverticulum epithelium is generally observed. The exception is some individuals with atrophying epithelium in the last third of the medial zone. There are no signs of epithelial regeneration in \u003cem\u003eA. eschrichtii\u003c/em\u003e during summer and autumn. We suggest that proliferation of hepatopancreas E-cells in \u003cem\u003eA. eschrichtii\u003c/em\u003e could be blocked to reduce energy consumption by the organism, as observed in the crab \u003cem\u003eEriocheir sinensis\u003c/em\u003e in a long-term (42 days) starvation experiment (Huang et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe morphology of F-, R- and B-cells of the normal epithelium of the hepatopancreas of \u003cem\u003eM. affinis\u003c/em\u003e corresponds to the morphology of analogous cells of the epithelium of the hepatopancreas of decapod (Barker and Gibson \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1979\u003c/span\u003e; Cervellione et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Vogt \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), whereas F-, R- and B-cells of the epithelium of the hepatopancreas of \u003cem\u003eA. eschrichtii\u003c/em\u003e have a number of peculiarities. Decapod F-cells are known to synthesize digestive enzymes that are intended for the primary treatment of food in the cardial compartment of the stomach. In the starving shrimp \u003cem\u003ePenaeus semisulcatus\u003c/em\u003e, a supranuclear vacuole appears in F-cells 2 hours after feeding (Al-Mohanna et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1985\u003c/span\u003e), which represents an autophagosome that is characteristic of mature F-cells (Vogt \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). In \u003cem\u003eM. affinis\u003c/em\u003e F-cells usually contain a single small vacuole near the nucleus, whereas the same vacuole in F-cells of \u003cem\u003eA. eschrichtii\u003c/em\u003e is rarely found, which indicate the absence of food in the stomach of these amphipods.\u003c/p\u003e \u003cp\u003eDecapod R-cells absorb low-molecular weight digestion products and store large amounts of energy in the form of lipids and glycogen (Vogt \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Lipids and glycogen are directly transported from R-cells to other tissues via the haemolymph (Vogt \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2019\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) and can be used during starvation (Vogt et al. \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e1985\u003c/span\u003e) and vitellogenesis (Vogt et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). Lipids accumulate in the vacuoles of R-cells (Hemambika and Raj \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1999\u003c/span\u003e). In \u003cem\u003eA. eschrichtii\u003c/em\u003e, vacuoles fill almost the entire cytoplasm of R-cells, and this makes the accumulation of any significant glycogen stores in these cells doubtful. In summer and autumn (under conditions of seasonal starvation), the contents of vacuoles are gradually consumed for maintenance of life activity and formation of mature gametes. The appearance of a relatively large vacuole in the basal part of atrophying R-cells of \u003cem\u003eA. eschrichtii\u003c/em\u003e could be a morphological sign of lipids transfer from the cells to the haemolymph. The accumulation of lipids for long-term storage in the hepatopancreas of \u003cem\u003eA. eschrichtii\u003c/em\u003e should occur in winter and spring, when the same temperature throughout the water column is maintained and phytoplankton sinking to the bottom becomes available to amphipods. However, the absence of winter samples prevents to understand how the hepatopancreas of \u003cem\u003eA. eschrichtii\u003c/em\u003e functions during this period. On the one hand, the entry of food into the stomach, its treatment and digestion should be accompanied by periodic renewal of the epithelium during digestive cycles. At another point, epithelial renewal does not seem to facilitate the accumulation in the R-cells of lipids intended for long-term storage.\u003c/p\u003e \u003cp\u003eIn species \u003cem\u003eM. affinis\u003c/em\u003e, constant renewal of the epithelium of the hepatopancreas does not allow lipids and glycogen to accumulate in R-cells for long-term storage. The products of digestion from the cells immediately enter the haemolymph and are using for the needs of the organism, and the expanded haemolymphatic sinuses may serve as indirect evidence of this process. R-cells of the crustacean epithelium of the hepatopancreas may also be the location of vitellogenin synthesis. Its synthesis appears to occur in the basal part of the cells, where an extensive tubular system, a rough endoplasmic reticulum and the mitochondria are located (Vogt et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Vogt \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). It is confirmed by ultrastructural changes occurring in the basal part of the R-cells of the hepatopancreas of the black tiger shrimp \u003cem\u003ePenaeus monodon\u003c/em\u003e in the late vitellogenesis (Vogt et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). Morphological differences between R-cells of \u003cem\u003eM. affinis\u003c/em\u003e and \u003cem\u003eA. eschrichtii\u003c/em\u003e and, in particular, atrophy of R-cells of \u003cem\u003eA. eschrichtii\u003c/em\u003e, suggest that vitellogenin in the first species is synthesized in R-cells, while in the second species it is synthesized outside R-cells. So, in \u003cem\u003eM. affinis\u003c/em\u003e, unlike \u003cem\u003eA. eschrichtii\u003c/em\u003e, the basal part of R-cells (especially in the proximal zone of diverticula) is free from vacuoles, which provides a location for the protein synthesis apparatus. Moreover, in \u003cem\u003eM. affinis\u003c/em\u003e during vitellogenesis there is a clear relation between the hepatopancreas and ovaries by the sinuses of the haemolymphatic system, through which not only the digestive products but also vitellogenin is transported (Tsukimura \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). Guan et al. (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) provide a list of crustacean species in which vitellogenin is either synthesized in the hepatopancreas, in the ovaries or in both organs simultaneously. Particularly, ovarian follicular cells could be a source of vitellogenin in the Kuruma prawn \u003cem\u003ePenaeus japonicus\u003c/em\u003e (Yano and Chinzei \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e1987\u003c/span\u003e). Vitellogenin synthesis has also been found in adipocytes (fatty cells) of the amphipod \u003cem\u003eOrchestia gammarellus\u003c/em\u003e (Meusy et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e1983\u003c/span\u003e), the isopod \u003cem\u003eIdotea balthica\u003c/em\u003e (=\u0026thinsp;\u003cem\u003eIdotea balthica basteri\u003c/em\u003e Audouin, 1826) (Souty and Picaud \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e1981\u003c/span\u003e), and the freshwater prawn \u003cem\u003eMacrobrachium nipponense\u003c/em\u003e (Han et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1994\u003c/span\u003e). The examples mentioned above may indicate on the ovarian follicular cells or adipocytes of \u003cem\u003eA. eschrichtii\u003c/em\u003e as possible centers of vitellogenin synthesis.\u003c/p\u003e \u003cp\u003eB-cells of decapods according to Vogt (\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) are the most enigmatic cell type of the hepatopancreas. B-cells are involved in the digestion of all material (except for low molecular weight components) that remains in the lumen of the diverticula and possibly in lipid digestion. Food components enter into B-cells by pinocytosis. Much of the absorbed material is digested and remained in the central vacuole and later eliminates by holocrine secretion back into the diverticular lumen for further assimilation by R-cells (Arnaud et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1978\u003c/span\u003e). The formation of a large vacuole in the cytoplasm of the B-cell indicates the end of the digestive process (Franceschini-Vicentini et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). In \u003cem\u003eM. affinis\u003c/em\u003e, mature B-cells contain a large central vacuole in the cytoplasm. In this form these cells enter the lumen of the diverticula and from there into the intestine. In \u003cem\u003eA. eschrichtii\u003c/em\u003e, the functional activity of B-cells and the appearance of a large central vacuole in them appears to be stimulated by atrophy of R-cells. B-cells probably clean the diverticula of the hepatopancreas of \u003cem\u003eA. eschrichtii\u003c/em\u003e from the degraded plasmatic membranes of R-cells, the main component of them are lipids. B-cells excrete the content of the vacuole into the lumen of the diverticula and die, leaving behind a lumen in the epithelium.\u003c/p\u003e \u003cp\u003ePreviously, we found (Durkina et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) that about 25% of sexually mature females of \u003cem\u003eA. eschrichtii\u003c/em\u003e (\u003cem\u003eF0\u003c/em\u003e females, body length 22\u0026ndash;24 mm) resorb all vitellogenic oocytes during seasonal starvation. The present study suggests that oocyte utilization in these individuals is not associated with a complete atrophy of R-cells of the epithelium of the hepatopancreas. On the contrary, R-cells of the epithelium still retain some nutrient reserve in summer. It is possible that total degradation of vitellogenic oocytes in these females is explained by high density in the settlements (ampeliscid mats). It should be noted that \u003cem\u003eA. eschrichtii\u003c/em\u003e forms aggregations with the highest biomass on the northeastern shelf of Sakhalin Island (Okhotsk Sea) among all studied amphipod populations in the world (Demchenko et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The literature data indicate a negative effect of the high density of settlement of animals on their reproductive function. For instance, at high population densities, cultured \u003cem\u003eDaphnia pulex\u003c/em\u003e reduce the release of offspring (Nishikawa and Ban \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1998\u003c/span\u003e), and females of the New Zealand freshwater snail \u003cem\u003ePotamopyrgus antipodarum\u003c/em\u003e produce fewer embryos (Zachar and Neiman \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). High abundance of rats reduces the fecundity and increases embryonic mortality (Sadykov and Benenson \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e1992\u003c/span\u003e), and in mice cause an increase in the number of atretic follicles in the ovaries (Kim and You \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe ability to store large amounts of lipids during productive seasons and use them for reproduction or for survival during periods of food shortage is well known in Arctic marine invertebrates (Noyon et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). The habitat conditions of \u003cem\u003eA. eschrichtii\u003c/em\u003e (negative water temperature for most of the year and seasonal food availability) appear to be comparable to those of benthic invertebrates in Arctic seas. In winter in the waters of the Okhotsk Sea there is intensive development of phytoplankton (Leonov et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2007\u003c/span\u003e), which when sinking to the bottom becomes available for amphipods. The fatty acid composition of \u003cem\u003eA. eschrichtii\u003c/em\u003e reveals that diatom microalgae are the main component of their food (Rodkina et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Sampling of \u003cem\u003eA. eschrichtii\u003c/em\u003e in winter on the northeastern shelf of the Sakhalin Island is impossible due to the presence of ice cover, but there is no doubt that amphipods at this time store large amounts of lipids in R-cells of the hepatopancreas. In summer and autumn, microalgae concentrate at the upper boundary of the thermocline within 10\u0026ndash;15 m depth (Sorokin and Sorokin \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Prants et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), which leads to seasonal starvation of amphipods. During starvation in the hepatopancreas of \u003cem\u003eA. eschrichtii\u003c/em\u003e, there is observed: 1) functional passivity of the F-cell epithelium, confirming the absence of food in the cardiac stomach; 2) gradual disappearance of vacuoles in R-cells due to lipid utilization and destruction of R-cells themselves; 3) activation of B-cells, which apparently digest membrane structures of destroyed R-cells, and death of B-cells after holocrine secretion. The main function of R-cells of \u003cem\u003eA. eschrichtii\u003c/em\u003e during starvation is to supply energy and previously stored nutrients (lipids) for the needs of the organism and vitellogenic growth of oocytes. Atrophy of the epithelium of the proximal and medial zones of the hepatopancreas of \u003cem\u003eA. eschrichtii\u003c/em\u003e is completed in October and, thus, the lipid reserve is depleted in the hepatopancreas, but oocytes have not yet reached definitive sizes by this time (Durkina et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). This suggests that adipocytes may be an additional source of nutrients in amphipod tissues. Information on the storage function of adipocytes of crustaceans is scarce.\u003c/p\u003e \u003cp\u003eIt is known, that adipocytes of the amphipod \u003cem\u003eOrchestia gammarellus\u003c/em\u003e contain lipids and glycogen (Meusy et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e1983\u003c/span\u003e), while adipocytes of the isopod \u003cem\u003eBathynomus giganteus\u003c/em\u003e contain predominantly lipids and proteins (Biesiot et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1999\u003c/span\u003e). Adipocytes (fat body) play an important role in insect life (Arrese and Soulages \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). They store large stores of lipids necessary for growth and reproduction and supply energy needed during periods of prolonged starvation.\u003c/p\u003e \u003cp\u003eThe morphology of R-, F- and B-cells of the epithelium of the hepatopancreas of \u003cem\u003eM. affinis\u003c/em\u003e consistent with the description of analogous cells of the epithelium of the hepatopancreas of decapods and confirms the presence of a food supply in the habitat of this species during vitellogenesis.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors are sincerely grateful to I.A. Shcherbakov (Laboratory of Marine Ecosystem Dynamics, NSCMB FEB RAS) as the leader of the benthos team during the expeditions to the north-eastern coast of the Sakhalin Island (Okhotsk Sea) for collaboration and field collecting of the valuable amphipod material. We are very grateful to Dr. John W. Chapman (Department of Fisheries, Wildlife and Conservation, Oregon State University, Newport, Oregon, United States of America) for reading and valuable comments on the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was financed from the budget of the Zhirmunsky National Scientific Center for Marine Biology within framework of state assignment no. 1021062912499-0, \u0026ldquo;Dynamics of Marine Ecosystems, Adaptation of Marine Organisms and Communities to Changes in the Environment\u0026rdquo;.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNLD determined the species, sex and size of amphipods and reproductive condition of females of \u003cem\u003eA. eschrichtii\u0026nbsp;\u003c/em\u003eand \u003cem\u003eM. affinis\u003c/em\u003e in samples off the north-eastern shelf of the Sakhalin Island (Okhotsk Sea). The VBD prepared histological slides, analyzed the condition of the amphipod hepatopancreas and wrote the paper. VBD and NLD jointly discussed and prepared the final text of the paper.\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAl-Mohanna SY, Nott JA (1987) R-cells and the digestive cycle in \u003cem\u003ePenaeus semisulcatus\u003c/em\u003e (Crustacea: Decapoda). Mar Biol 95:129\u0026ndash;137\u003c/li\u003e\n\u003cli\u003eAl-Mohanna SY, Nott JA, Lane DJW (1985) Mitotic E- and Secretory F-Cells in the Hepatopancreas of the Shrimp \u003cem\u003ePenaeus semisulcatus\u003c/em\u003e (Crustacea: Decapoda). J Mar Biol Assoc U K 65:901\u0026ndash;910\u003c/li\u003e\n\u003cli\u003eArnaud J, Brunet M, Mazza J (1978) Studies on the midgut of \u003cem\u003eCentropages typicus\u003c/em\u003e (copepod, calanoid). I. Structural and Ultrastructural Data. Cell Tissue Res 187:. https://doi.org/10.1007/BF00224375\u003c/li\u003e\n\u003cli\u003eArrese EL, Soulages JL (2010) Insect fat body: energy, metabolism, and regulation. Annu Rev Entomol 55:207\u0026ndash;225. https://doi.org/10.1146/annurev-ento-112408-085356\u003c/li\u003e\n\u003cli\u003eBarker P, Gibson R (1979) The decapod hepatopancreas. Oceanogr Mar Biol Annu Rev 17:285\u0026ndash;346\u003c/li\u003e\n\u003cli\u003eBiesiot PM, Wang SY, Perry HM, Trigg C (1999) Organic reserves in the midgut gland and fat body of the giant deep-sea isopod \u003cem\u003eBathynomus giganteus\u003c/em\u003e. J Crustac Biol 19:450\u0026ndash;458. https://doi.org/10.2307/1549253\u003c/li\u003e\n\u003cli\u003eCervellione F, McGurk C, Van den Broeck W (2017) \u0026ldquo;Perigastric organ\u0026rdquo;: a replacement name for the \u0026ldquo;hepatopancreas\u0026rdquo; of Decapoda. J Crustac Biol 37:353\u0026ndash;355. https://doi.org/10.1093/jcbiol/rux020\u003c/li\u003e\n\u003cli\u003eChen Ch, Tan Q, Liu M, et al (2017) Effect of starvation on growth, histology and ultrastructure of digestive system of juvenile red swamp crayfish (\u003cem\u003eProcambarus clarkii\u003c/em\u003e Girard). Iran J Fish Sci 16:1214\u0026ndash;1233\u003c/li\u003e\n\u003cli\u003eDarriba S, San Juan F, Guerra A (2005) Energy storage and utilization in relation to the reproductive cycle in the razor clam \u003cem\u003eEnsis arcuatus\u003c/em\u003e (Jeffreys, 1865). ICES J Mar Sci 62:886\u0026ndash;896. https://doi.org/10.1016/j.icesjms.2005.02.010\u003c/li\u003e\n\u003cli\u003eDemchenko NL (2010) Ecological aspects of the dominant amphipod \u003cem\u003eMonoporeia affinis\u003c/em\u003e (Amphipoda: Pontoporeiidae) in the infralittoral zone on the northeastern coast of the Sakhalin Island (Sea of Okhotsk). Zool Baetica 21:143\u0026ndash;149\u003c/li\u003e\n\u003cli\u003eDemchenko NL, Chapman JW, Durkina VB, Fadeev VI (2016) Life history and production of the western gray whale\u0026rsquo;s prey, \u003cem\u003eAmpelisca eschrichtii\u003c/em\u003e Kr\u0026oslash;yer, 1842 (Amphipoda, Ampeliscidae). PLoS ONE 11:1\u0026ndash;18. https://doi.org/10.1371/journal.pone.0147304\u003c/li\u003e\n\u003cli\u003eDurkina VB, Chapman JW, Demchenko NL (2018) \u003cem\u003eAmpelisca eschrichtii\u003c/em\u003e Kr\u0026oslash;yer, 1842 (Ampeliscidae) of the Sakhalin Shelf in the Okhotsk Sea starve in summer and feast in winter. PeerJ 6:1\u0026ndash;21. https://doi.org/10.7717/peerj.4841\u003c/li\u003e\n\u003cli\u003eFong CR, Gaynus CJ, Carpenter RC (2020) Extreme rainfall events pulse substantial nutrients and sediments from terrestrial to nearshore coastal communities: a case study from French Polynesia. Sci Rep 10:2955. https://doi.org/10.1038/s41598-020-59807-5\u003c/li\u003e\n\u003cli\u003eFranceschini-Vicentini IB, Ribeiro K, Papa LP, et al (2009) Histoarchitectural features of the hepatopancreas of the Amazon River prawn \u003cem\u003eMacrobrachium amazonicum\u003c/em\u003e. Int J Morphol 27:121\u0026ndash;128. https://doi.org/10.4067/S0717-95022009000100022\u003c/li\u003e\n\u003cli\u003eGuan Z-B, Yin J, Chen K, et al (2016) The hepatopancreas and ovary are the sites of vitellogenin synthesis in female red swamp crayfish (\u003cem\u003eProcambarus clarkii\u003c/em\u003e (Girard, 1852)) (Decapoda: Astacoidea: Cambaridae). J Crustac Biol 36:637\u0026ndash;641. https://doi.org/10.1163/1937240X-00002459\u003c/li\u003e\n\u003cli\u003eHan C-H, Okumura T, Suzuki Y, et al (1994) Immunocytochemical identification of the site of vitellogenin synthesis in the freshwater prawn \u003cem\u003eMacrobrachium nipponense\u003c/em\u003e. Fish Sci 60:149\u0026ndash;154. https://doi.org/10.2331/fishsci.60.149\u003c/li\u003e\n\u003cli\u003eHemambika M, Raj RP (1999) An ultrastructural study of the hepatopancreas of Indian white prawn \u003cem\u003ePenaeus indicus\u003c/em\u003e H. Milne Edwards. In: Fourth Indian Fiheries Forum Proceedings 24-28 November, 1996. Kochi, pp 291\u0026ndash;294\u003c/li\u003e\n\u003cli\u003eHopkin SP, Nott JA (1980) Studies on the digestive cycle of the shore crab \u003cem\u003eCarcinus maenas\u003c/em\u003e (L.) with special reference to the b cells in the hepatopancreas. J Mar Biol Assoc U K 60:891\u0026ndash;907. https://doi.org/10.1017/S0025315400041977\u003c/li\u003e\n\u003cli\u003eHuang X, Feng Y, Duan J, et al (2020) Antistarvation strategies of \u003cem\u003eE. sinensis\u003c/em\u003e: regulatory networks under hepatopancreas consumption. Oxid Med Cell Longev 2020:6085343. https://doi.org/10.1155/2020/6085343\u003c/li\u003e\n\u003cli\u003eIcely JD, Nott JA (1984) On the morphology and fine structure of the alimentary canal of \u003cem\u003eCorophium volutator\u003c/em\u003e (Pallas) (Crustacea: Amphipoda). Philos Trans R Soc Lond B Biol Sci 306:49\u0026ndash;78\u003c/li\u003e\n\u003cli\u003eKim J, You S (2022) High housing density-induced chronic stress diminishes ovarian reserve via granulosa cell apoptosis by angiotensin II overexpression in mice. Int J Mol Sci 23:8614. https://doi.org/10.3390/ijms23158614\u003c/li\u003e\n\u003cli\u003eLeonov AV, Mogil\u0026rsquo;nikova TA, Pishchal\u0026rsquo;nik VM, Zenkin OV (2007) Characteristic of microalgae development in the Sea of Okhotsk in winter and modeling of their annual dynamics in Aniva Bay. Water Resour 34:184\u0026ndash;194. https://doi.org/10.1134/S0097807807020091\u003c/li\u003e\n\u003cli\u003eMeusy JJ, Zerbib C, Dacheux F, Dubois MP (1983) Subcellular localization of vitellogenin in crustacean adipocytes by the unlabelled antibody enzyme method. Tissue Cell 15:301\u0026ndash;310. https://doi.org/10.1016/0040-8166(83)90024-1\u003c/li\u003e\n\u003cli\u003eMihaljević M, \u0026Scaron;poljarić D, Stević F, et al (2010) The influence of extreme floods from the River Danube in 2006 on phytoplankton communities in a floodplain lake: Shift to a clear state. Limnol - Ecol Manag Inland Waters 40:260\u0026ndash;268. https://doi.org/10.1016/j.limno.2009.09.001\u003c/li\u003e\n\u003cli\u003eNishikawa J, Ban S (1998) Effect of high population density on growth and reproduction of \u003cem\u003eDaphnia pulex\u003c/em\u003e DeGeer. Plankton Biol Ecol 45:55\u0026ndash;60\u003c/li\u003e\n\u003cli\u003eNoyon M, Narcy F, Gasparini S, Mayzaud P (2011) Growth and lipid class composition of the Arctic pelagic amphipod \u003cem\u003eThemisto libellula\u003c/em\u003e. Mar Biol 158:883\u0026ndash;892. https://doi.org/10.1007/s00227-010-1615-1\u003c/li\u003e\n\u003cli\u003ePaczkowska J, Brugel S, Rowe O, et al (2020) Response of coastal phytoplankton to high inflows of terrestrial matter. Front Mar Sci 7: 2020. https://doi.org/10.3389/fmars.2020.00080\u003c/li\u003e\n\u003cli\u003ePazos AJ, Rom\u0026aacute;n G, Acosta CP, et al (1997) Seasonal changes in condition and biochemical composition of the scallop \u003cem\u003ePecten maximus\u003c/em\u003e L. from suspended culture in the Ria de Arousa (Galicia, N.W. Spain) in relation to environmental conditions. J Exp Mar Biol Ecol 211:169\u0026ndash;193. https://doi.org/10.1016/S0022-0981(96)02724-4\u003c/li\u003e\n\u003cli\u003ePrants SV, Andreev AG, Uleysky MY, Budyansky MV (2017) Mesoscale circulation along the Sakhalin Island eastern coast. Ocean Dyn 67:345\u0026ndash;356. https://doi.org/10.1007/s10236-017-1031-x \u003c/li\u003e\n\u003cli\u003eRodkina SA, Kiyashko SI, Demchenko NL (2020) Trophic basis of dominant amphipods in the gray whale feeding grounds near northeastern Sakhalin Island (the Sea of Okhotsk) inferred from fatty acid and stable isotope analyses. Mar Environ Res 158:104999. https://doi.org/10.1016/j.marenvres.2020.104999\u003c/li\u003e\n\u003cli\u003eRogachev KA, Pomerleau C, Shlyk NV, Carmack EC (2022) Joint effects of sea ice melt, freshwater discharge and tidal currents on zooplankton abundance in the Sea of Okhotsk: 2004 and 2013. Polar Sci 31:100781. https://doi.org/10.1016/j.polar.2021.100781\u003c/li\u003e\n\u003cli\u003eRogachev KA, Shlyk NV (2015) Prominent freshening of coastal waters in the north-western Sea of Okhotsk in 2013. Vestn Far East Branch Russ Acad Sci 118\u0026ndash;125\u003c/li\u003e\n\u003cli\u003eSacrist\u0026aacute;n HJ, Ansaldo M, Franco-Tadic LM, et al (2016) Long-term starvation and posterior feeding effects on biochemical and physiological responses of midgut gland of \u003cem\u003eCherax quadricarinatus\u003c/em\u003e juveniles (Parastacidae). PLOS ONE 11:e0150854. https://doi.org/10.1371/journal.pone.0150854\u003c/li\u003e\n\u003cli\u003eSadykov OF, Benenson IE (1992) Population dynamics of small mammals: concepts, hypotheses, models. Nauka, Moscow \u003c/li\u003e\n\u003cli\u003eS\u0026aacute;nchez-Paz A, Garc\u0026iacute;a-Carre\u0026ntilde;o F, Muhlia-Almaz\u0026aacute;n A, et al (2006) Usage of energy reserves in crustaceans during starvation: status and future directions. Insect Biochem Mol Biol 36:241\u0026ndash;249. https://doi.org/10.1016/j.ibmb.2006.01.002\u003c/li\u003e\n\u003cli\u003eSastry AN (1983) Ecological aspects of reproduction. In: Vernberg W.B., eds. The biology of Crustacea: Environmental adaptations. Academic Press, New York, pp 179\u0026ndash;270\u003c/li\u003e\n\u003cli\u003eSchmitz EH, Scherrey PM (1983) Digestive anatomy of \u003cem\u003eHyalella azteca\u003c/em\u003e (Crustacea, Amphipoda). J Morphol 175:91\u0026ndash;100. https://doi.org/10.1002/jmor.1051750109\u003c/li\u003e\n\u003cli\u003eSorokin YuI, Sorokin PY (1999) Production in the Sea of Okhotsk. J Plankton Res 21:201\u0026ndash;230. https://doi.org/10.1093/plankt/21.2.201\u003c/li\u003e\n\u003cli\u003eSouty C, Picaud JL (1981) Vitellogenin synthesis in the fat body of the marine crustacean Isopoda, \u003cem\u003eIdotea balthica basteri\u003c/em\u003e, during vitellogenesis. Reprod Nutr Dev 21:95\u0026ndash;101. https://doi.org/10.1051/rnd:19810108\u003c/li\u003e\n\u003cli\u003e\u0026Scaron;trus J, Žnidar\u0026scaron;ič N, Mrak P, et al (2019) Structure, function and development of the digestive system in malacostracan crustaceans and adaptation to different lifestyles. Cell Tissue Res 377:415\u0026ndash;443. https://doi.org/10.1007/s00441-019-03056-0\u003c/li\u003e\n\u003cli\u003eTsukimura B (2001) Crustacean Vitellogenesis: Its Role in Oocyte Development. Am Zool 41:465\u0026ndash;476\u003c/li\u003e\n\u003cli\u003eUnuma T, Walker CW (2009) Relationship between gametogenesis and food quality in sea urchin gonads. Stickney R., Iwamoto R.; Rust M. (editors). Aquaculture technologies for invertebrates: proceedings of the thirty-sixth U.S.-Japan aquaculture panel symposium, Durham, New Hampshire, October 29\u0026ndash;30, and Milford, Connecticut, November 2, 2007. U.S. Dept. Commerce, NOAA Tech. Memo. NMFS-F/SPO-99, p 73\u003c/li\u003e\n\u003cli\u003eVogt G (2021) Synthesis of digestive enzymes, food processing, and nutrient absorption in decapod crustaceans: a comparison to the mammalian model of digestion. Zool Jena Ger 147:125945. https://doi.org/10.1016/j.zool.2021.125945\u003c/li\u003e\n\u003cli\u003eVogt G (2019) Functional cytology of the hepatopancreas of decapod crustaceans. J Morphol 280:1405\u0026ndash;1444. https://doi.org/10.1002/jmor.21040\u003c/li\u003e\n\u003cli\u003eVogt G, Quinitio ET, Pascual FP (1989) Interaction of the midgut gland and the ovary in vitellogenesis and consequences for the breeding success: a comparison of unablated and ablated spawners of \u003cem\u003ePenaeus monodon\u003c/em\u003e. In: De Pauw N, Jaspers E, Ackefors H, Wilkins N (eds) Aquaculture - A Biotechnology in Progress. Proceedings of the International Conference Aquaculture Europe \u0026rsquo;87, Amsterdam, The Netherlands, June 2-5, 1987. European Aquaculture Society, Bredene, Belgium, pp 581\u0026ndash;592\u003c/li\u003e\n\u003cli\u003eVogt G, Storch V, Quinitio ET, Pascual FP (1985) Midgut gland as monitor organ for the nutritional value of diets in \u003cem\u003ePenaeus monodon\u003c/em\u003e (Decapoda). Aquaculture 48:1\u0026ndash;12. https://doi.org/10.1016/0044-8486(85)90047-X\u003c/li\u003e\n\u003cli\u003eYano I, Chinzei Y (1987) Ovary is the site of vitellogenin synthesis in kuruma prawn, \u003cem\u003ePenaeus japonicus\u003c/em\u003e. Comp Biochem Physiol Part B Comp Biochem 86:213\u0026ndash;218. https://doi.org/10.1016/0305-0491(87)90280-X\u003c/li\u003e\n\u003cli\u003eZachar N, Neiman M (2013) Profound effects of population density on fitness-related traits in an invasive freshwater snail. PLoS ONE 8:e80067. https://doi.org/10.1371/journal.pone.0080067\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"polar-biology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pobi","sideBox":"Learn more about [Polar Biology](http://link.springer.com/journal/300)","snPcode":"300","submissionUrl":"https://submission.nature.com/new-submission/300/3","title":"Polar Biology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"hepatopancreas, starvation, amphipods, Monoporeia affinis, Ampelisca eschrichtii","lastPublishedDoi":"10.21203/rs.3.rs-5370478/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5370478/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eA comparative analysis of the hepatopancreas of amphipod species \u003cem\u003eAmpelisca eschrichtii\u003c/em\u003e and \u003cem\u003eMonoporeia affinis\u003c/em\u003e collected on the northeastern shelf of Sakhalin Island (Okhotsk Sea) was carried out between 2013 and 2021 in summer and fall during the period of vitellogenic oocyte growth. As a result of different habitat conditions \u003cem\u003eA. eschrichtii\u003c/em\u003e has seasonal starvation in summer and fall, while \u003cem\u003eM. affinis\u003c/em\u003e has access to food. During the period of starvation, the hepatopancreas of \u003cem\u003eA. eschrichtii\u003c/em\u003e exhibits the following characteristics: 1) the functional passivity of F-cells of the epithelium, which confirms the absence of food in the stomach of amphipods, 2) the R-cells destruction due to lipid utilization, 3) the activation of B-cells, which apparently digest membrane structures of destroyed R-cells. The morphology of R-, F- and B-cells of the epithelium of the hepatopancreas in \u003cem\u003eM. affinis\u003c/em\u003e is consistent with the description of analogous cells of the epithelium of the hepatopancreas of decapods and provide evidence for the presence of a food in the habitat of this species. In \u003cem\u003eM. affinis\u003c/em\u003e, in contrast to \u003cem\u003eA. eschrichtii\u003c/em\u003e, R-cells appear to synthesize vitellogenin. The primary function of R-cells of \u003cem\u003eA. eschrichtii\u003c/em\u003e during starvation is to provide previously stored nutrients (lipids) for oocyte vitellogenic growth and energy for vital function of the organism. Synthesis of vitellogenin in these cells is unlikely.\u003c/p\u003e","manuscriptTitle":"Hepatopancreas in the starving amphipod Ampelisca eschrichtii and the feeding amphipod Monoporeia affinis during vitellogenesis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-11-14 09:41:22","doi":"10.21203/rs.3.rs-5370478/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-12-27T09:57:35+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-12-25T13:12:31+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"83688777623643302146605111308686293168","date":"2024-12-09T07:58:50+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-12-07T16:41:10+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"338189199227156569977675924708759150429","date":"2024-12-01T12:22:04+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-11-22T07:54:51+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-11-19T12:24:51+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-11-02T08:16:14+00:00","index":"","fulltext":""},{"type":"submitted","content":"Polar Biology","date":"2024-11-01T04:14:42+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"polar-biology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pobi","sideBox":"Learn more about [Polar Biology](http://link.springer.com/journal/300)","snPcode":"300","submissionUrl":"https://submission.nature.com/new-submission/300/3","title":"Polar Biology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"ce2c52e4-181c-4012-94a7-3f3448b52254","owner":[],"postedDate":"November 14th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-08-04T16:43:08+00:00","versionOfRecord":{"articleIdentity":"rs-5370478","link":"https://doi.org/10.1007/s00300-025-03411-8","journal":{"identity":"polar-biology","isVorOnly":false,"title":"Polar Biology"},"publishedOn":"2025-07-30 16:13:19","publishedOnDateReadable":"July 30th, 2025"},"versionCreatedAt":"2024-11-14 09:41:22","video":"","vorDoi":"10.1007/s00300-025-03411-8","vorDoiUrl":"https://doi.org/10.1007/s00300-025-03411-8","workflowStages":[]},"version":"v1","identity":"rs-5370478","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5370478","identity":"rs-5370478","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}