Gonadal Growth Research Articles

The Effect of Sausage Tree Fruit (Kigelia africana) on Gonadal Development and Growth Performance of Oreochromis andersonii

In Zambia fish farms, Oreochromis andersonii is an important common indigenous fish species. Naturally, safe phytochemicals can effectively improve fish reproduction performance and their production potential. Therefore, this study was conducted to determine the effect of Kigelia africana on the gonadal development and the performance of Oreochromis andersonii. A total of 96 male fingerlings were randomly assigned to four dietary treatments (D1-D4), and each treatment group had three replicates. The D1, D2, D3, and D4 groups were formulated to receive 0, 50, 100, and 150 g of powdered Kigelia africana/kg, respectively. The fish were fed the diets for 9 weeks, followed by the study parameter measurements at the end of the experiment. The highest mean body weight and gonadal weight were (29.8 ± 0.63 and 0.09 ± 0.010 g, respectively) for fish in the D2 group. There was no significant difference between the mean body weight of fish in different groups, but their mean gonadal weights differed significantly. The gonadal somatic index of fish differed significantly among treatment groups, with those in D2 having the highest mean value (0.36 ± 0.060). The highest mean standard length (103.3 ± 0.63 mm) and total length (126.0 ± 0.11 mm) of fish were observed for D1 and D2 groups, respectively. Additionally, the mean values for those parameters decreased with increasing Kigelia africana in the diet. The physicochemical parameters of water, including temperature and dissolved oxygen, ranged 16.8-23.1℃ and 0.6-2.2 mg/L, respectively; these were generally at low levels considering the optimum requirements for this fish species. In conclusion, Kigelia africana improved gonadal growth and development but did not promote overall fish growth. The best gonadal growth/development results of Kigelia africana powder were observed at a level of 50 g/kg, which can be used as a performance booster in the aquaculture production of Oreochromis andersonii.

Temporal expression of thyroid hormone regulating genes (tsh-b, tsh-r, dio2 and dio3) and their correlation with annual reproductive cycle of the Indian freshwater catfish, Heteropneustes fossilis (Bloch).

Photoperiod and temperature are well-established environmental cues for gonadal growth in seasonally reproducing organisms. The photoperiod is known to regulate seasonal reproduction via induction of thyroid hormone regulating genes in the saccus vasculosus (SV) of fishes. However, SV is absent in many seasonally breeding fishes, including Heteropneustes fossilis. H. fossilis is a long-day breeding catfish in which gonadal recrudescence begins six months earlier than spawning. The present study attempted to analyse the expression of thyroid hormone-regulating genes (tsh-b, tsh-r, dio2 and dio3) in the brain, liver and ovary. In the brain, upregulated expression of thyrotropin-beta subunit (tsh-b), deiodinase2 (dio2) and deiodinase3 (dio3) genes is concomitant with the increasing photoperiod and temperature in nature, which may appear to regulate seasonal reproduction. Both deiodinases, dio2 and dio3, were also upregulated in the liver and ovarian tissue during the gonadal growth phase. The upregulation of deiodinases may enhance the metabolism and activity of tissues, thereby facilitating their respective roles. The expression of these genes was also assessed in the brain, liver, ovary, kidney, skin, spleen and gill tissues during the spawning period. The ubiquitous expression of deiodinases may point to enhanced activity in their organ-specific role. The present study speculates that expression of tsh-b, tsh-r, dio2 and dio3 genes during the reproductive phase of H. fossilis might be involved in the regulation of seasonal reproduction.

The influence of plant odours on sexual readiness in an insectivorous songbird.

Many organisms rely on environmental cues to predict and anticipate the annual optimal timing of reproduction. In insectivorous birds, preparation for breeding often coincides with the time vegetation starts to develop in spring. Whether there is a direct relationship between the two, and through which mechanisms this link could come about, has rarely been investigated. Plants release Herbivore-Induced Plant Volatiles (HIPVs) when they are attacked by insects, and recent studies have shown that birds can detect and orient to those odours when searching for food. If those volatiles also stimulate sexual reproductive development and timing of reproduction remains to be discovered. We tested this hypothesis by monitoring gonadal growth in pairs of blue tits (Cyanistes caerueus) exposed to air from caterpillar infested oak trees or from a control, in spring. We found that while males and females grew their gonads over time, gonads grew at the same rate in both odor treatments. More exploratory (i.e. a proxy of personality) females did however have larger ovarian follicle sizes when exposed to the HIPVs than to the control air, which is consistent with earlier results showing that fast explorers have larger gonads in spring and are more sensitive to HIPVs. If HIPVs constitute powerful attractants in foraging birds, their influence on gonadal development prior to breeding appears to be relatively subtle and only enhance reproductive readiness in some individuals. These results are nevertheless important as they set olfaction as a new player in seasonal timing of reproduction in birds.

Functional inhibition of deep brain non-visual opsins facilitates acute long day induction of reproductive recrudescence in male Japanese quail

For nearly a century, we have known that brain photoreceptors regulate avian seasonal biology. Two photopigments, vertebrate ancient opsin (VA) and neuropsin (OPN5), provide possible molecular substrates for these photoreceptor pathways. VA fulfills many criteria for providing light input to the reproductive response, but a functional link has yet to be demonstrated. This study examined the role of VA and OPN5 in the avian photoperiodic response of Japanese quail (Coturnix japonica). Non-breeding male quail were housed under short days (6L:18D) and received an intracerebroventricular infusion of adeno-associated viral vectors with shRNAi that selectively inhibited either VA or OPN5. An empty viral vector acted as a control. Quail were then photostimulated (16L:8D) to stimulate gonadal growth. Two long days significantly increased pituitary thyrotrophin-stimulating hormone β-subunit (TSHβ) and luteinizing hormone β-subunit (LHβ) mRNA of VA shRNAi treated quail compared to controls. Furthermore, at one week there was a significant increase, compared to controls, in both hypothalamic gonadotrophin releasing hormone-I (GnRH-I) mRNA and paired testicular mass in VA shRNAi birds. Opn5 shRNAi facilitated the photoinduced increase in TSHβ mRNA at 2 days, but no other differences were identified compared to controls. Contrary to our expectations, the silencing of deep brain photoreceptors enhanced the response of the reproductive axis to photostimulation rather than preventing it. In addition, we show that VA opsin plays a dominant role in the light-dependent neuroendocrine control of seasonal reproduction in birds. Together our findings suggest the photoperiodic response involves at least two photoreceptor types and populations working together with VA opsin playing a dominant role.

Lipid and fatty acid composition of muscle, liver, ovary, and peritoneal fat in wild flathead grey mullet (Mugil cephalus) according to ovarian development

Wild adult females of a low trophic omnivore teleost species, the flathead grey mullet (Mugil cephalus), caught in the western Mediterranean were sampled. The lipid and fatty acid composition of ovaries, liver, muscle, and peritoneal fat were analysed at previtellogenesis, early-vitellogenesis —first observed at mid-summer (early August)—, late-vitellogenesis, and the post-spawning period —from mid-September to mid-October—. During ovarian development, the lipid content of muscle was low and constant (3.85%–4.92%), indicating that the muscle was not used to store lipids for gonadal growth. Although constant, lipid content in the liver was higher (18.46%–22.62%) than in the muscle, and HSI% increased during gonad development, suggesting a dynamism in the mobilization of the hepatic lipids. Total lipids in the gonads significantly increased with maturation (from 4.90% to 34.59%) in parallel with the GSI (from 0.8% to 15.5%) to decrease after spawning. Peritoneal fat was probably transitional fat that could be rapidly metabolized or transferred to other tissues but no specific function could be assigned because its presence in previtellogenic and early-vitellogenic females varied greatly. One of the main sources of lipids accumulated in the ovary was most likely diet. The total percentage of ΣMUFA, mainly 17:1 —previously not identified in high quantities in teleost vitellogenic ovaries and likely of bacterial origin— and 16:1, strongly increased in the ovaries with maturation. The 16:1 might be an important source of lipids for embryo development. High percentages of DHA, EPA, and ARA were found in the ovary during previtellogenesis available to be used during gonadal maturation. Understanding lipid and fatty acid changes in broodstock tissues can increase our knowledge of the nutritional requirements of the fish used in aquaculture breeding programs.

Lipid and Protein Content in Rainbow Trout in Relation to Gonadal Growth

Abstract The purpose of this study was to examine various lipid classes as well as the protein content in rainbow trout ovaries. A total of 80 samples of Oncorhynchus mykiss (Walbaum 1792) were collected from Kokernag and Verinag hatcheries (Jammu and Kashmir, India) between 2017 and 2019. The mature stage in female fish had the highest gonadosomatic index (GSI) and minimal GSI in the spent stage. Higher lipid content of the ovary was reported during the mature stage (36%), as compared to other pre-breeding stages. Similarly, lipid classes also showed fluctuation during the development of the ovary. The lipid classes, i.e. glycolipids, free fatty acids, cholesterol and triglycerides, had a higher content in the mature stage, while the phospholipid content was higher in the mature stage. The protein content was also higher in the mature ovary than in the other developmental stages. The study provides reference values for various biochemical parameters in rainbow trout that could be useful for population monitoring programs and for the development of diets and management methods for fish production under controlled conditions.

Investigation of somatic and gonadal growth of female rainbow trout (Oncorhynchus mykiss) reared in cage in the Caspian Sea

Investigation of somatic and gonadal growth of female rainbow trout (Oncorhynchus mykiss) reared in cage in the Caspian Sea

Differential DNA methylation in Pacific oyster reproductive tissue in response to ocean acidification

BackgroundThere is a need to investigate mechanisms of phenotypic plasticity in marine invertebrates as negative effects of climate change, like ocean acidification, are experienced by coastal ecosystems. Environmentally-induced changes to the methylome may regulate gene expression, but methylome responses can be species- and tissue-specific. Tissue-specificity has implications for gonad tissue, as gonad-specific methylation patterns may be inherited by offspring. We used the Pacific oyster (Crassostrea gigas) — a model for understanding pH impacts on bivalve molecular physiology due to its genomic resources and importance in global aquaculture— to assess how low pH could impact the gonad methylome. Oysters were exposed to either low pH (7.31 ± 0.02) or ambient pH (7.82 ± 0.02) conditions for 7 weeks. Whole genome bisulfite sequencing was used to identify methylated regions in female oyster gonad samples. C- > T single nucleotide polymorphisms were identified and removed to ensure accurate methylation characterization.ResultsAnalysis of gonad methylomes revealed a total of 1284 differentially methylated loci (DML) found primarily in genes, with several genes containing multiple DML. Gene ontologies for genes containing DML were involved in development and stress response, suggesting methylation may promote gonad growth homeostasis in low pH conditions. Additionally, several of these genes were associated with cytoskeletal structure regulation, metabolism, and protein ubiquitination — commonly-observed responses to ocean acidification. Comparison of these DML with other Crassostrea spp. exposed to ocean acidification demonstrates that similar pathways, but not identical genes, are impacted by methylation.ConclusionsOur work suggests DNA methylation may have a regulatory role in gonad and larval development, which would shape adult and offspring responses to low pH stress. Combined with existing molluscan methylome research, our work further supports the need for tissue- and species-specific studies to understand the potential regulatory role of DNA methylation.

Impact of low-cost diets on maturation of the red claw crayfish Cherax quadricarinatus: An integrative approach during a long-term study

The onset of sexual maturity represents a complex step in animal life involving morphological, physiological, and behavioral changes. From this point onward, the energy income from food will be involved in three energetic-demanding-competing processes: metabolism-homeostasis, growth, and reproduction. Hence, in cultured species formulated feeds need to cover all nutritional requirements of the growing phase and the additional cost demanded by reproduction. Two low-cost diets, AD1: 0.56 and 2 CE: 0.64 U$S kg−1 manufactured with local supplies specifically formulated for Cherax quadricarinatus, were evaluated in a prolonged assay with females at the transition from juvenile to mature. Protein content was 440,2 and 380 g kg−1 and lipid content was 134,8 and 114,9 g kg−1 for AD1 and AD2, respectively. Females were obtained in the laboratory from our reproductive stock and were fed daily at 1.5% of their weight/day. The female mean initial total length was 6.5 ± 0.6 cm and mean body mass was 6.8 ± 0.7 g, which represents juveniles at the beginning of vitellogenesis. The experiment ended after three molting events when females achieved the full mature condition (⁓16–20 g). Somatic indices, growth, feed efficiency, biochemical composition of the ovary and hepatopancreas, ovarian growth, and histological alterations in hepatopancreas were analyzed. Both diets demonstrated that the high demands of both somatic and ovarian growth in maturating females were not covered, contrasting with previous results in early juveniles. This highlights the enormous energetic cost of vitellogenesis at the start of sexual maturity and the differential nutrients demand during crayfish growth. Biochemical analysis demonstrated a lower oocyte quality due to the experimental diets, as well as decreased reserves both of lipids and carbohydrates and a possible impact on carotenoids content. The hepatopancreas also showed partial histological damage and differences in its biochemical content. Although further analysis is required, lower embryo survival, hatching rate, and early performance of juveniles are expected in progeny from females fed with both diets. The low-cost diets tested are useful as a baseline from which modified formulations can be considered to achieve a more adequate composition enhancing somatic and gonad growth as well as feed efficiency in maturing females.

Effects of Spring Warming on Seasonal Neuroendocrinology and Activation of the Reproductive Axis in Hibernating Arctic Ground Squirrels.

Many animals adjust the timing of seasonal events, such as reproduction, molt, migration, and hibernation, in response to interannual variation and directional climate-driven changes in temperature. However, the mechanisms by which temperature influences seasonal timing are relatively under-explored. Seasonal timing involves retrograde signaling in which thyrotropin (TSH) in the pars tuberalis (PT) alters expression of thyroid hormone (TH) deiodinases (Dio2/Dio3) in tanycyte cells lining the third ventricle of the hypothalamus. This, in turn, affects the availability of triiodothyronine (T3) within the mediobasal hypothalamus-increased hypothalamic T3 restores a summer phenotype and activates the reproductive axis in long-day breeders. Recently, we showed that retrograde TH signaling is activated during late hibernation in arctic ground squirrels (Urocitellus parryii) held in constant darkness and constant ambient temperature. Sensitivity of seasonal pathways to nonphotic cues, such as temperature, is likely particularly important to hibernating species that are sequestered in hibernacula during spring. To address this issue, we exposed captive arctic ground squirrels of both sexes to an ecologically relevant increase in ambient temperature (from -6 to -1°C) late in hibernation and examined the effects of warming on the seasonal retrograde TSH/Dio/T3 signaling pathway, as well as downstream elements of the reproductive axis. We found that warmed males tended to have higher PT TSHβ expression and significantly heavier testis mass whereas the TSH/Dio/T3 signaling pathway was unaffected by warming in females, although warmed females exhibited a slight decrease in ovarian mass. Our findings suggest that temperature could have different effects on gonadal growth in male and female arctic ground squirrels, which could lead to mismatched timing in response to rapid climate change.

Trophic Requirements of the Sea Urchin Paracentrotus lividus Varies at Different Life Stages: Comprehension of Species Ecology and Implications for Effective Feeding Formulations

Investigations on trophic requirements of different life cycle stages of Paracentrotus lividus are crucial for the comprehension of species ecology and for its artificial rearing. The future success of echinoculture depends heavily on the development of suitable and cost-effective diets that are specifically designed to maximize somatic growth during the early life stages and gonadal production in the later stages. In this context, a considerable number of studies have recommended animal sources as supplements in sea urchin diets. However, with the exception of Fernandez and Boudouresque (2000), no studies have investigated the dietary requirements over the different life stages of the sea urchin. In the present study, the growth and nutrition of three life stages of P. lividus (juveniles: 15-25 mm; subadults: 25-35 mm; adults: 45-55 mm) were analyzed over a 4-month rearing experiment. Three experimental diets, with 0%, 20% and 40% of animal sourced enrichments, were tested in parallel in sea urchin three size classes. The food conversion ratio, somatic and gonadal growth were assessed in each condition in order to evaluate the optimal level of animal-sourced supplements for each life stage. A general growth model covering the full post-metamorphic P. lividus life cycle was defined for each condition. During the juvenile stage P. lividus requires higher animal supply (40%), while a feeding requirement shift takes place toward lower animal supply (20%) in sub-adult and adult stages. Our results evidenced that the progressive increase in size after the metamorphosis led to a consequent variation of trophic requirements and food energy allocation in the sea urchin P. lividus. Macronutrient requirements varied widely during the different life stages, in response to changes in the energy allocation from somatic growth to reproductive investment. This study sheds light on P. lividus trophic ecology, broadening our basic knowledge of the dietary requirements of juveniles, sub-adults and adults as a function of their behavior also in the natural environment.

Effects of the Herbicide Atrazine on Crustacean Reproduction. Mini-Review.

Atrazine, one of the most intensively applied herbicides worldwide, is commonly found in several water bodies, affecting the associated fauna. Autochthon crustacean species have been relatively less studied, compared to vertebrate species, particularly concerning reproductive success. In this mini-review, we summarize the relevant information about the effects of atrazine exposure on the main reproductive aspects of crustaceans. One of these effects is related to the inhibition of ovarian growth. In this respect, a diminished vitellogenin content was found in the ovary of crabs exposed to atrazine during the entire period of ovarian growth, in correlation with a reduced oocyte size and a delay of ovarian maturation. Similar results were observed in crayfish. Atrazine was also able to affect the reproductive process, acting as an endocrine disruptor. In this sense, this herbicide was suspected to affect the secretion of some neurohormones involved in the gonadal growth, as well as to alter the circulating levels of steroid hormones which promote the synthesis of vitellogenin for ovarian growth. Moreover, atrazine induced sexual differentiation in juvenile crayfish toward a higher proportion of females, while it produced an increment of males in daphnids. Another aspect affected by this herbicide was the reduction of offspring production, as well as several embryonic abnormalities; genotoxic effects have been also reported in crayfish. Finally, some metabolic imbalances, such as reduction in energy reserves, have been observed in some species, together with oxidative stress and histopathological effects.

Effects of laboratory salmon louse infection on mortality, growth, and sexual maturation in Atlantic salmon

Abstract Elevated salmon louse infection pressure generated by salmon farming represents a major threat for wild Atlantic salmon (Salmo salar). This study explored the effect of salmon lice on mortality, and body and gonad growth in F1 wild Atlantic salmon. Mature males (jacks) and immature fish were either infected with two different louse infection intensities (LIIs, 0.08 or 0.35 lice g−1) or kept as uninfected controls. Fish maturation was thereafter environmentally stimulated in seawater, followed by transfer to freshwater for 38 d to simulate river ascendance. No females matured, while 99% of the initially immature males started puberty. Jacks had high, and immature and maturing fish low, seawater mortality, independent of lice. The parasites had an LII-dependent negative effect on growth in length, weight, and condition factor in seawater. In freshwater, after the lice had detached, fish that were previously infected in seawater had reduced growth in length but not weight when compared to the uninfected control. The parasites did not affect relative gonad size in any fish phenotypes. The present results show that Atlantic salmon has a complex, and unexplored, regulation of growth when recovering from lice infection under laboratory settings. Further, the results suggest that possible negative effects of salmon louse on reproductive success in Atlantic salmon is most likely governed by the reduced body size and condition. However, further work on possible effects of salmon louse on semen quality is encouraged.

Prospective association of dietary soy and fibre intake with puberty timing: a cohort study among Chinese children

sBackgroundDietary phytoestrogens have been suggested to influence puberty timing, a critical stage for well-being in adulthood. We hypothesized that childhood soy intake might prospectively influence puberty timing and that dietary fibre and the key isoflavone metabolite equol might play roles.MethodsCox proportional hazard regression models were performed in 4781 children (2152 girls and 2629 boys) aged 6–8 years old from the Chinese Adolescent Cohort Study for whom a food frequency questionnaire at baseline and information about potential confounders were available. Anthropometry and pubertal status including age at Tanner stage 2 for breast development (B2) or age at the initiation of gonadal growth (G2), and age at menarche (M) or voice break (VB) were assessed annually. Equol excretion was determined by urine samples from 1311 participants.ResultsAmong girls and boys, higher soy intake was associated with later puberty timing (hazard ratio (HR)-B2: 0.88 (95% CI, 0.80–0.96), p=0.02; HR-M, 0.87 (0.77–0.94), p=0.01; HR-G2, 0.91 (0.82–0.98), p=0.013; HR-VB, 0.90 (0.82–0.9), p=0.02), independent of prepubertal body fatness and fibre intake. These associations were more pronounced among children with a high urinary equol level (pfor-interaction ≤ 0.04) or with a high cereal fibre intake (pfor-interaction ≤ 0.06). Intake of dietary fibre or its subtype was not prospectively associated with puberty onset after adjusting for dietary soy intake (p≥0.06).ConclusionHigher childhood soy intake is prospectively associated with later puberty timing in both Chinese girls and boys, independent of prepubertal body fatness, and the association is particularly pronounced among individuals with a higher urinary equol level.

Modelling the Caenorhabditis elegans gonad over developmental time using the Distal Tip Cell marker lag-2p::gfp.

Development is a process that occurs over time, but defects are often scored at the end point of the process being studied. We are interested in understanding the molecular basis of gonad development in Caenorhabditis elegans and have used the Distal Tip Cell marker lag-2p::gfp to develop a larval size model of gonad growth. We found that gonad length demonstrates two distinct phases relative to larval length, with a breakpoint in mid-L3 stage. We hope that this model will help determine at what point in gonad development our genes of interest act.

Food and temperature change photoperiodic responses in two vole species.

Seasonal timing of reproduction in voles is driven by photoperiod. We hypothesized that a negative energy balance can modify spring-programmed photoperiodic responses in the hypothalamus, controlling reproductive organ development. We manipulated energy balance by the 'work-for-food' protocol, in which voles were exposed to increasing levels of food scarcity at different ambient temperatures under long photoperiod. We found that in common voles (Microtus arvalis) and tundra voles (Microtus oeconomus), photoperiod-induced pars tuberalis thyroid-stimulating hormone β-subunit (Tshβ) expression is reduced to potentially inhibit gonadal development when food is scarce. Reduction in gonadal size is more pronounced in tundra voles, in which anterior hypothalamic Kiss1 is additionally downregulated, especially in males. Low temperature additionally leads to decreased hypothalamic Rfrp expression, which potentially may facilitate further suppression of gonadal growth. Shutting off the photoperiodic axis when food is scarce in spring may be an adaptive response to save energy, leading to delayed reproductive organ development until food resources are sufficient for reproduction, lactation and offspring survival. Defining the mechanisms through which metabolic cues modify photoperiodic responses will be important for a better understanding of how environmental cues impact reproduction.

Filling in data gaps on the phaeton dragonet [Synchiropus phaeton (Günther, 1861)]: a study on biological characteristics in the eastern Mediterranean (Aegean Sea, Greece)

ABSTRACT The main objective of this work is to provide information on the age and growth, gonadal maturity and the feeding habits of the phaeton dragonet [Synchiropus phaeton (Günther, 1861)] in the eastern Mediterranean (Aegean Sea), a species for which there exists limited information. The phaeton dragonet is a demersal fish species with a wide distribution in the eastern Atlantic and the Mediterranean Sea and is considered as a by-catch in bottom-trawl fisheries. The species demonstrated a negative allometric growth in both sexes, though it exhibited an increasing sex-related gonad growth associated with each reproductive stage. The age range of the Aegean population was 0–7 years. Finally, the main food items in the stomach contents of the species were Crustacea and Polychaeta, and the fractional trophic level was estimated as 3.01 ± 0.3, classifying the species as an omnivore with preference for animal material. Despite the fact that the data of this study derived from a single sampling, this work can be considered as an effort to fill in knowledge gaps in the biology of this species.

Advances in Reproductive Endocrinology and Neuroendocrine Research Using Catfish Models.

Catfishes, belonging to the order siluriformes, represent one of the largest groups of freshwater fishes with more than 4000 species and almost 12% of teleostean population. Due to their worldwide distribution and diversity, catfishes are interesting models for ecologists and evolutionary biologists. Incidentally, catfish emerged as an excellent animal model for aquaculture research because of economic importance, availability, disease resistance, adaptability to artificial spawning, handling, culture, high fecundity, hatchability, hypoxia tolerance and their ability to acclimate to laboratory conditions. Reproductive system in catfish is orchestrated by complex network of nervous, endocrine system and environmental factors during gonadal growth as well as recrudescence. Lot of new information on the molecular mechanism of gonadal development have been obtained over several decades which are evident from significant number of scientific publications pertaining to reproductive biology and neuroendocrine research in catfish. This review aims to synthesize key findings and compile highly relevant aspects on how catfish can offer insight into fundamental mechanisms of all the areas of reproduction and its neuroendocrine regulation, from gametogenesis to spawning including seasonal reproductive cycle. In addition, the state-of-knowledge surrounding gonadal development and neuroendocrine control of gonadal sex differentiation in catfish are comprehensively summarized in comparison with other fish models.

A Review on the Reproductive Dysfunction in Farmed Finfish

Globally, fish production in the wild is decreasing, and different aquaculture systems are presently being used for broodstock development in the captivity. Seasonally, broodstock raised in captivity exhibit different form of reproductive dysfunction at the level of the brain-pituitary-gonad (BPG) axis. Primarily, vitellogenic completion and final oocyte maturation are inhibited in females, and males fail to spermiate spontaneously in the captivity. Reproductive dysfunctions are also observed during sexual differentiation, pubertal onset and sex conversion periods in teleosts. To overcome these problems, different hormonal preparations, primarily gonadotropin-releasing hormones (GnRH) are used. In recent years, kisspeptins have been shown to be potent in inducing gonadal growth and maturation in teleost fish. Understanding the form of reproductive dysfunction is important in formulating suitable hormonal preparations for inducing gametogenesis. The paper reviews the problem of reproductive dysfunction and their possible reason for formulating different hormonal preparations.

Seasonal changes of biological condition and reproductive cycle of hampback shrimp <i>Pandalus hypsinotus</i> (Caridea, Pandalidae) in the Tatar Strait

Research and commercial trawl catches of humpback shrimp Pandalus hypsinotus from the Tatar Strait (Japan Sea) in 2004–2020 were investigated, with bioanalysis of about 45 thousand specimens. Average timing of group molting, spawning, and eggs laying are determined, terms of gonads and eggs development are estimated. Prespawning and molting of the females occur between January-April, with the peaks in early February and middle February, respectively. All oviparous females have 30–40 days to lay eggs, and molt during 50–55 days; the peak of the eggs laying occurs in late June. The males molt in July-August, afterwards the largest individuals change gender and new intersexes are formed. The males have the second molting in October-December, with the peak in late November. In January, after finish of the males molting, a new annual reproduction cycle starts from the prespawning molting of females. Both vitellogenesis and embryogenesis are observed through the year, though females with developing gonads prevail from August to January (because of a long time span between winter and summer moltings while the egg carrying continued 15 months) but oviparous females — from February to July. The individual reproductive cycle of Pandalus hypsinotus in the Tatar Strait lasts 24 months, with 9 months of vitellogenesis (quick growth of gonads) and 15 months of embryogenesis. During the 2-year reproductive cycle, most of females pass through the following stages: i) gonads development (just after eggs laying) when almost all oviparous females (up to 95 % in May) have green gonads under carapace that corresponds to the stage of development «eggs laid — gonads weakly developed»; ii) summer molting from August when females lose hairs on pleopods and the gonads growth accelerates; iii) respawning in January-March (together with the firstly spawning intersexes, with slight delay of the latter); iv) initial developing of eggs during summer; v) stage of «eyed eggs» from December to March; and vi) eggs laying and molting from late March to late May; then the 2-year reproductive cycle repeats.