Sex Inversion Research Articles

The effect of sex hormones on sex inversion in the mussel Mytilusgalloprovincialis

Global changes in the coastal ecosystems of oceans and seas, influenced by natural environmental factors and anthropogenic load, have led to a shift in the sexual structure of the mussel Mytilus galloprovincialis, a species cultivated in many countries. This paper is the first to study the effects of steroid hormones on sex inversion and mortality in the M. galloprovincialis. A unidirectional pattern of sex change from females to males was observed. A 100% sex change of females was achieved under the influence of the hormone testosterone during the period of post-spring restructuring of the gonads. No sex change occurred when males and females were exposed to 17β-estradiol. The mortality of mollusks did not exceed 5%.

Sex steroid hormones and steroid secretory cells in the gonads of cyclostomes and fish

. The purpose of this work is to generalize data on the content of sex steroid hormones in cyclostomes and fish in connection with the different state of the gonads, as well as on the localization and ultrastructural organization of steroid secretory cells (SCs). Method used: generalization of literature data. Novelty: for the first time, data on the development of SC in the gonads of juvenile fish are presented on the scale of a literature review; changes in their localization and functional activity are shown. Results: Most of the data on the steroidogenic function of the gonads in fish were obtained in connection with the study of sex differentiation (inversion) and sexual maturation (spawning). The issues of the synthesis of sex steroid hormones and their molecular structure, blood levels in various states of the gonads, as well as the localization and ultrastructural organization of SCs are considered. It has been noted that SCs appear in the gonads long before sex differentiation and can be present among stromal, granulosa, and theca cells. In cyclostomes and fish — juvenile protogynous hermaphrodites in the gonads of genetic males, SCs do not appear in the membranes around the oocytes of the previtellogenesis period, which determines their deficiency of estrogen hormones and, as a result, sex inversion. With induced sex reversal, the development of the steroidogenic function of the gonads proceeds in the opposite direction to its natural development: in males, oocytes appear and steroid activity shifts from the stroma of the gonads into granulosa and theca; in females, on the contrary, secretory activity in the follicular membranes decreases and increases in the stroma of the gonads. Practical significance: the results of the analysis will give insight into the nature of sex steroid hormones, their dynamics in the blood, and their role in the implementation of various processes of gonadogenesis and gametogenesis before their practical use in fish farms.

Animal welfare of embryos and newly hatched chicks: A review

The welfare of farm animals is a hotly debated issue today. There are few technical materials available focused on hatcheries that address and incorporate practices adopting the welfare level required by civil society. However, about 33% of the production period of a broiler chicken occurs on the hatchery. Recent studies have shown that day-old chick production has points that need to be improved. Technical standards indicate that the process of welfare should begin during egg storage such that the best conditions are provided for embryos prior to incubation. Storage until 28 days at temperatures above 12ºC can kill embryos, while exposure of eggs to 30 ºC until 14 days causes a negative impact under the hatchability. The available results regarding in ovo nutrition show that it should be considered for benefit neonate quality since inoculation of substances such vitamin E (60.4 IU) promote better incubation results. Feeding immediately after hatching is a management for welfare because animals feed-fed soon after hatch perform better up to 35 d. The most criticized point in hatcheries is the slaughter of neonates, for which some strategies are being investigated, including the use of dual-purpose aptitude strains, in ovo sexing by different methodologies, sex inversion and hormonal-based sexing. It is noted that procedures involving bird incubation require greater attention to welfare. Therefore, it is necessary to align theoretical knowledge with practical applications so that the demands of society, as well as those of industry, are met.

Age, Growth, Maturation and Mortality of Picarel Spicara flexuosa (Sparidae) from the Crimea Water Area (Black Sea)

The results of the study of the sex and size-age structure, growth, maturation, sexual inversion, dynamics of the gonadosomatic index and mortality of 1948 individuals of the picarel Spicara flexuosa caught in the Crimea water area in 2020–2021 are presented. The total sex ratio in catches is biased towards females (3.5 : 1.0); sex inversion was recorded in 50% of females with a total body length of 13.5 ± 0.05 cm at the age of 3+. The maximum length of females is 15.1 cm, males, 22.0 cm; the weight is 29.0 and 132.2 g, respectively. The maximum age of females and males is 4 and 7 years, respectively. The values of the parameters of the von Bertalanffy equation are calculated: for females, the asymptotic length is 15.69 cm, the asymptotic weight is 32.0 g, the growth coefficient is 0.49 year–1; for males, 18.32 cm, 59.7 g and 0.44 year–1, respectively. A value of the exponent in the length-weight relationship is 2.68 for females (negative allometry) and 3.0 for males (isometry). The sexual maturity of 50% of females occurs at a length of 10.34 ± 0.21 cm at the age of 1+. The peak of spawning occurs in June. The rates of total, natural and fishing mortality are 1.2, 1.9 and 0.3 year–1, respectively in both sexes; the exploitation rate is 0.25, which indicates a low fishing pressure. It is established that S. flexuosa from northern populations is characterized by larger maximum sizes, a higher growth rate and a longer life expectancy

Atrazine alters early sexual development of the South American silverside, Odontesthes bonariensis

Atrazine (ATZ) is a frequent contaminant in freshwater ecosystems within agricultural regions. The capacity of this herbicide to interfere with the vertebrate endocrine system is broadly recognized, but the mechanisms and responses usually differ among species. In this study, ATZ effects on hypothalamus-pituitary-gonadal (HPG) axis key genes expression and early gonadal development were evaluated in Odontesthes bonariensis larvae waterborne exposed during the gonadal differentiation period. Fish were treated to 0, 0.7, 7.0, and 70 µg ATZ/L at 25 °C from the 2nd to 6th week after hatching (wah), and a group was kept in clean water until the 12th wah. Parallelly, a group was submitted to 0.05 µg/L of ethinylestradiol (EE2) as a positive estrogenic control. From each treatment, eight larvae were sampled at 6 wah for gene expression analysis and twelve larvae at 12 wah for phenotypic sex histological determination. The expression of gnrh1, lhb, fshb, and cyp19a1b was assessed in the head, and the ones of amha, 11βhsd2, and cyp19a1a in the trunk. Fish growth was significantly higher in fish exposed to 7 and 70 µg ATZ/L in the 6 wah, but the effect vanished at the 12 wah. The expression of lhb was upregulated in both sex larvae exposed from 7 µg ATZ/L. However, a dimorphic effect was induced on cyp19a1a expression at 70 µg ATZ/L, up or downregulating mRNA transcription in males and females, respectively. Delayed ovarian development and increased number of testicular germ cells were histologically observed from 7 to 70 µg ATZ/L, respectively, and a sex inversion (genotypic male to phenotypic female) was found in one larva at 70 µg ATZ/L. The lhb expression was also upregulated by EE2, but the cyp19a1a expression was not affected, and a complete male-to-female reversal was induced. Further, EE2 upregulated gnrh1 in females and cyp19a1b in both sexes, but it did not alter any assessed gene in the trunk. In conclusion, ATZ disrupted HPG axis physiology and normal gonadal development in O. bonariensis larvae at environmentally relevant concentrations. The responses to ATZ only partially overlapped and were less active when compared to the model estrogenic compound EE2.

Dietary inclusion of pine pollen alters sex ratio and promotes growth of Nile tilapia (Oreochromis niloticus, L. 1758)

The potential of pine pollen (PP) to masculinize sexually undifferentiated Nile tilapia was evaluated by feeding graded levels of PP (0.08–3.20 g kg-1 basal diet) to triplicate groups of three-day-old Nile tilapia for 28 days. Masculinization and associated differences in growth were compared to fish individuals fed the same basal diet with no PP (CT; negative control) and with 0.06 g 17α-methyltestosterone (MT) kg-1 basal diet (positive control). Both PP and MT treatments significantly skewed the expected 50:50 (male: female) ratio towards more male individuals. Notably, MT and 1.28 g PP kg-1 of diet produced a significantly high proportion of males (89.2 ± 2.2% and 80.0 ± 2.9% respectively), compared to 50.8 ± 2.2% in the CT treatment (P < 0.001). Except for 0.08 g PP kg-1 of diet, the final body weight and specific growth rate of individuals fed PP and MT-supplemented feeds were significantly higher than fish from the CT group. Although 1.28 g PP kg-1 diet produced the highest masculinization, the fish fed 3.20 g PP kg-1 diet had the highest final weight (14.73 ± 0.54 g), suggesting the presence of growth enhancers in PP. Similarly, a superior feed conversion ratio was recorded in both PP and MT-treated groups compared to the CT treatment (P = 0.024). However, the condition factor and survival rate of fish in all groups did not differ significantly. Overall, 1.28 g PP kg-1 diet was potent in sex inversion and promoted the growth of Nile tilapia, making PP a promising alternative to MT in the production of all-male stock.

Effects of heavy metals on sex inversion of the mussel Mytilus galloprovincialis Lam., 1819 in coastal zone of the Black Sea

Sex inversion in the mussel Mytilus galloprovincialis under the influence of heavy metals as one of the reasons for the shift in the sex ratio in the mussel population on the Black Sea coastal zone of Crimea were considered in the work. The present study is the first to directly show that heavy metals can cause females of the mussel M. galloprovincialis to change into males during post-spawning development of gonads. The degree of impact of heavy metals on the sex change in mussel females was different and decreased in the following sequence: Cu2+ → Cd2+ → Hg2+ → Pb2+ → Zn2+. Copper ions had the greatest effect, which caused a sex inversion in 54 % of females. The heavy metals Hg2+ and Pb2+ were also quite toxic causing mortality in 13 % and 10 % of individuals, respectively. It is possible to use M. galloprovincialis as a model organism in the study of mechanism of environmental sex reversal in bivalves.

Hormonal Sex Inversion by 17α-Methyl testosterone in common carp (Cyprinus carpio) through egg Immersion Technique (IT)

ABSTRACT The trial was conducted to evaluating the effect of different hormone concentrations of 17α-methyltestosterone @ (HC): (200, 400, 600, and 800 μg/L−1), immersion times (IT): 48, 60 and 72 h and the interaction effect of (HC × IT) on the hatching percentage of Cyprinus carpio egg, percent survival and percent of males. Results indicated that survival of treated fry was affected by the increasing IT (p < 0.001). The main interaction effect of HC × IT showed that the highest percent of male individuals 96% was attained at 800 μg/L HC at 72 h IT and lowest was recorded 49% in control (p < 0.05). Increased percent male of C. carpio was obtained with increasing HC across all IT. It is concluded that the immersion treatment at 800 µg/L for 72 h is more effective to change sex ratios of C. carpio. Masculinization of C. carpio by egg immersion is an alternative technique of oral method, manual sorting of sexes, gene manipulation and hybridization.

Microencapsulated dietary supplementation coupled with sexual inversion improves the immune and antioxidant response of Nile tilapia larvae under stressful conditions

In tilapia aquaculture, the cultivation of single-sex animals is extremely widespread, as it allows for the standardization of lots, in addition to improving the general performance of the animals. However, it is possible that hormonal inversion interacts with other factors, such as environmental and nutritional management, and modulates the immune response and antioxidant system of animals in a distinct manner. In order to test this hypothesis, an experiment was carried out using Nile tilapia larvae six days after hatching, divided into four experimental groups: NI (non-inverted animals), I (sexual inverted animals), NI + M (non-inverted supplemented with microencapsulated products) and I + M (sexual inverted and supplemented with microencapsulated products; half of which were subjected to transportation-related stress after 28 days of the experiment. At the end, the survival rate was evaluated; the gene expression of heat shock protein (HSP70), interleukin 1 beta (IL-1β) and cyclooxygenase-2 (COX 2) via RT-PCR; also evaluated were the activity of catalase (CAT) and superoxide dismutase (SOD) enzymes, as well as the total antioxidant capacity by 2,2-diphenyl-1-picryl-hydrazyl (DPPH). Animals from the I and I + M groups had the highest survival rate (p < 0.001) regardless of transportation stress. The highest expressions of HSP70 were found in the NI group (p < 0.001, with and without transportation). For the IL-1β gene, there was an increase in expression for animals belonging to groups NI and NI + M (no transportation); and NI (p < 0.0001, with transportation). Increased COX 2 expression was observed for all groups after transportation (p < 0.0001). The highest SOD activities were observed in groups I and I + M (without transportation, p = 0.0004), and I (with transportation, p < 0.0001). The transportation decreased the total antioxidant capacity of DPPH in all treatments (p < 0.001). Finally, when evaluating all of the results together, we came to a conclusion that sex inversion improves the immune response and antioxidant profile of animals under stressful conditions when associated with microencapsulated dietary supplementation.

Mutagenic effect of the sex reversal hormone Diethylstilbestrol in the Nile tilapia (Oreochromis niloticus, L) through sister chromatid exchange analysis

The current study was conducted to explore the mutagenic effect of DES hormone on the treated Nile tilapia chromosomes using sister chromatid exchange (SCE) analysis. Two concentrations of DES hormone (100mg DES/kg and 200mg DES/kg diet) were addressed. The fry were fed for 60 days at 15% of the body weight daily. Two cell replication cycles, in the presence of 5-bromodeoxyuridine (BrdU) were achieved, and intestine tissues were used for chromosomes preparation. For slide staining, acridine orange (AO) was added, and the fluorescent microscope was used to the observation of AO fluorescence of stained slides. The obtained results indicated that the frequency of SCEs per cell and the percentage of cells exhibiting three SCEs per cell increased with the increasing hormone concentration. The present findings confirmed the mutagenic effect of DES hormone and clarified the possibility of using O. niloticus as an in vivo system for detecting mutagenic and carcinogenic chemicals. In addition, it is recommended not to use the hormone directly in the food served to humans. However, it can be used in the induction of fish sex inversion to XY females and followed by progeny testing, to generate super male YY.

Age, Growth, Mortality and Reproduction Biology of the Black Seabream, Spondyliosoma cantharus in North Aegean Sea, Turkey, Mediterranean Basin

In the present study, the population parameters (length-length and length-weight relationships, age, growth, mortality) and reproductive biology (sex ratio, GSI, condition, length at first maturity, spawning period, fecundity) of black seabream (Spondyliosoma cantharus Linnaeus, 1758) were investigated. The length-length relationship and length-weight relationship were calculated as FL=0.911TL-0.0433 and W=0.0123TL3.0614 (R2=0.97), respectively. Parameters of the von Bertalanffy growth equation were: L∞=33.21 cm, K=0.21 per year, t0= −1.84 year and age varied between 0 and 8 years. The instantaneous rates of total mortality (Z) and natural mortality (M) were 0.64 and 0.47 per year, respectively. Rates for fishing mortality (F) and exploitation (E) were 0.17 and 0.27 per year, respectively. The spawning season extended from February to May and peaked in March and April. The female/male ratio was found to be 3.49/1 and sex inversion from female to male occurred after the 24 cm TL length group. Total lengths at 50% maturity were 22.25 cm for males and 20.59 cm for females. The mean absolute fecundity (F) was 109,457±8,011 oocytes, ranging from 59,666 to 182,589.

Female sex inversion as a reason for an unbalanced sex ratio in the neotropical species Brycon orbignyanus

The objective of this study was to temporally identify sex differentiation to morphologically characterize the formation of female and male germinal epithelium and verify the occurrence of the sex disproportion reported for this species in aquaculture. Specimens of Brycon orbignyanus cultivated in water recirculation systems with a constant temperature of 27 ± 0.5°C were used. Monthly samplings of B. orbignyanus (n = 15) were performed from two months of age until 1 year of age, and posteriorly isolated sampling was performed on specimens of two and three years of age. The gonads of the specimens were removed and processed for light microscopy. In the beginning, the undifferentiated gonads develop into ovaries (females; at three months of age) and functional testicles (primary males; at five months of age); however, some of the females go through a sex inversion process creating intersex individuals and posteriorly secondary males (at five months of age). Due to the processes of sex inversion and gonadal remodelling, the population sex proportion fluctuates until it is finally established at 1♀:2♂. Females above 15 cm are differentiated, while in males (primary and secondary), differentiation will only occur after the animal reaches 20 cm. At the end of the first year of age, primary males and secondary males reach sexual maturity, while female sexual maturity is only observed at three years of age.

The use of plant extracts to control tilapia reproduction: Current status and future perspectives

AbstractControl of prolific reproduction is vital for a profitable tilapia aquaculture enterprise. All‐male tilapia culture is a popular method used to control prolific breeding, because the male individuals grow faster than female and mixed‐sex populations. Presently, most farmers use 17α‐methyl testosterone (MT) to produce all‐male tilapia individuals, although synthetic hormones are linked to human health and environmental risks. Recently, considerable attention has focused on plant‐based products as alternatives to MT, because they are affordable, safe, and eco‐friendly. Despite the growing interest in using plant extracts to prevent frequent spawning in tilapia production, the available information is not collated to standardize application guidelines. Accordingly, this review article consolidates existing knowledge on the use of plant extracts to control prolific breeding in tilapia culture systems. In addition, limitations to commercial application of the extracts are identified. To date, seed, root, and leaf extracts of 20 plant species, most notably, Tribulus terrestris, Mucuna pruriens, and Carica papaya, exhibit potential for controlling unwanted breeding in tilapia production systems. The extracts are mainly administered orally, incorporated in fish feeds. Saponins and flavanoids are the main bioactive compounds in the phytoextracts, which induce sex inversion and fertility impairment in tilapia. The commercialization of plant extracts is, however, hampered by lack of standardized information on extract preparation, optimal dosages, and mechanism of action. Thus, future studies should address these technical limitations and highlight economic incentives for commercial use of plant extracts in tilapia aquaculture.

Effects of environmental factors on changing sex structure of cultivated mussels (Mytilus galloprovincialis, Lamarck, 1819) in the coastal zone of the Black Sea

AbstractAnthropogenically‐induced stressors such as eutrophication and pollution cause fundamental changes of environmental factors in many coastal ecosystems worldwide and may subsequently alter the sex structure of bivalve populations. Such a change of sex structure was observed in the mussel Mytilus galloprovincialis at the Black Sea coast of Crimea, where the sex ratio shifted toward male mussels. This pattern may be caused by the sex inversion in females, higher female mortality, and their falling off to the bottom. Experiments with cultivated mussels M. galloprovincialis were conducted in natural and laboratory conditions to identify the reasons for this phenomenon. The inversion of the mussel sex proceeds in one direction: from females to males. The change of sex occurs under the influence of environmental factors during the post‐spawning restructuring of gonads. Such factors can be adverse hydrological and hydrochemical conditions; environmental pollution; food availability; age and size of mollusks. The sex inversion of mussels in the polluted water area was 20% higher than in the relatively clean water of the mussel farm. The higher mortality of mussel females (69%) in the polluted area as compared to the clean one (19%) was also observed. In a laboratory experiment, the mortality level of females was 34% higher than that of males. The sex ratio on the farm, 1:2.9 (♀:♂), and on the bottom under the farm, 2.6:1 (♀:♂), was found, and the predominance of females at the bottom under the farm was noted. A bias in the sex structure in one direction—from females to males—can have economic implications in aquaculture as well as ecological significance. The increasing anthropogenic impacts on natural mussel populations can cause abnormal bias of sex ratio.

ПРОЯВЛЕНИЕ ПОЛОВОГО ДИМОРФИЗМА В СОМАТОТИПОЛОГИЧЕСКОМ ОБЛИКЕ ЮНОШЕЙ И ДЕВУШЕК СЕВЕРНОГО РЕГИОНА

The article analyzes the data of anthropometric and somatotypological studies of 164 boys and 174 girls of the Khanty-Mansi Autonomous Okrug – Yugra, of diff erent sex somatotypes. It was found that 44% of boys and 15% of girls, according to sexual somatic diff erentiation, correspond to the biological sex, 40% of boys and 58% of girls have mild gender dysplasia in the form of mesomorphism, and 21% of boys and 27% of girls have signs of sex inversion. In young men from the northern region, clear sexual dimorphism anthropometric parameters were revealed. In girls of the Khanty-Mansi Autonomous Okrug – Yugra of diff erent sex somatotypes, no statistically signifi cant diff erences were found in most anthropometric parameters, which is associated with the general tendency of their somatic profi le to asthenization and masculinization

A high-quality de novo genome assembly of one swamp eel (Monopterus albus) strain with PacBio and Hi-C sequencing data.

The swamp eel (Monopterus albus) is one economically important fish in China and South-Eastern Asia and a good model species to study sex inversion. There are different genetic lineages and multiple local strains of swamp eel in China, and one local strain of M. albus with deep yellow and big spots has been selected for consecutive selective breeding due to superiority in growth rate and fecundity. A high-quality reference genome of the swamp eel would be a very useful resource for future selective breeding program. In the present study, we applied PacBio single-molecule sequencing technique (SMRT) and the high-throughput chromosome conformation capture (Hi-C) technologies to assemble the M. albus genome. A 799 Mb genome was obtained with the contig N50 length of 2.4 Mb and scaffold N50 length of 67.24 Mb, indicating 110-fold and ∼31.87-fold improvement compared to the earlier released assembly (∼22.24 Kb and 2.11 Mb, respectively). Aided with Hi‐C data, a total of 750 contigs were reliably assembled into 12 chromosomes. Using 22,373 protein-coding genes annotated here, the phylogenetic relationships of the swamp eel with other teleosts showed that swamp eel separated from the common ancestor of Zig-zag eel ∼49.9 million years ago, and 769 gene families were found expanded, which are mainly enriched in the immune system, sensory system, and transport and catabolism. This highly accurate, chromosome-level reference genome of M. albus obtained in this work will be used for the development of genome-scale selective breeding.

Indicators of chemiluminescent and bioluminescent tests of biological liquids in the assessment of physical health.

The study includes anthropometry of 172 young male, obtained data on the length and body mass, measured the transverse diameters of the shoulders and pelvis, various body types was identified by the J.M. Tanner sexual dimorphism index (andromorphic, mesomorphic, gynecomorphic). The chemiluminescent and bioluminescent study of saliva and blood was conducted in the examined young male. We studied the indicators of the antioxidant defense system under the influence of stress. The antioxidant status of saliva was determined using the H2O2-luminol-dependent chemiluminescence method. Data on the activity of NAD (P) -dependent dehydrogenases in blood lymphocytes was obtained from a bioluminescent method of research. Young male of andromorphic body type had large overall and transverse body sizes. Indicators of antioxidant protection of saliva and blood in men of adolescence, the body type of the sexual dimorphism index J.M. Tanner was different. The persons of the andromorphic body type differed in terms of chemiluminescence in comparison with the young male of gynecomorphic body type. The results of bioluminescent blood tests suggest a violation of the catabolic and anabolic processes of carbohydrate and fat metabolism in young men of mesomorphic and gynecomorphic body types. Indicators of the system of antioxidant protection of saliva and blood reflect the sexual characteristics of the body of young male and can be used as additional criteria for diagnosing sex inversion and assessing the risk of developing socially attributed diseases.

Preliminary experiment on masculinization of mud crab (Scylla tranquebarica) with 17α-methyl testosterone treatments

There is a difference in growth between male and female mud crabs, where males grow faster than females. However, the price of female crabs can be higher than males when female crabs contain eggs which can reach one-third of the whole meat portion. Therefore, the preference for monosex or multi sex cultivation in aquaculture can provide different earnings. Sex reversal has been successfully carried out on various aquaculture fish species, but is yet not common in crustaceans, especially in mud crabs. This preliminary experiment aims to determine the possibility of the masculinization of mud crabs treated with 17α-Methyl Testosterone (MT). The experiments were carried out by the immersion of four-day-old crablets (C-4) with various doses of MT hormones (0, 1, 10, and 100 ppm) for four hours. Following the immersion treatment, crablets reared individually for two months before the male percentage was calculated at the end of the experiments. The result of the experiment showed that immersion with MT hormone solution at a dose of 100 ppm for four hours resulted in total death, whereas no deaths occurred at 0 and 1 ppm. While at 10 ppm treatment, 10% mortality occurred. The MT hormone immersion was found to be ineffective in sex inversion of the C-4 mud crabs where the male sex percentage between treated crab and the control was not significantly different (P>0.05). On the other hand; the second study showed that immersion of C-4 krablet with a dose of 7.5 ppm followed by feeding with MT containing diet for 30 days at 2.5-7.5 mg kg1 feed resulted in 100% male.

Gonadal remodeling and hormonal regulation during sex change of juvenile dusky grouper Epinephelus marginatus (Teleostei, Serranidae), an endangered protogynous hermaphrodite fish.

Sex change was induced in Epinephelus marginatus juveniles using a nonsteroidal aromatase inhibitor (AI), a synthetic androgen (17α-methyltestosterone; MT), and a combination of both (MT + AI) in a 90-day experiment. A detailed remodeling of the gonads, the plasma level of gonadal steroids, and immunostaining of pituitary follicle-stimulating hormone (FSH), luteinizing hormone (LH), and somatolactin (SL) cells were analyzed. Sex inversion reached the final spermatogenesis stages using MT, while AI triggered spermatogenesis, but reaching only the spermatid stage. Estradiol (E2) levels did not change in fish treated with AI but decreased throughout the experimental period in animals treated with MT and MT + AI. Testosterone (T) levels increased in animals treated with MT during the first 60 days (and combined with AI in the first 30 days), decreasing in all experimental groups at 90 days, while AI-treated animals had increased plasma 11-ketotestosterone (11-KT) levels after 90 days. In control fish, FSH- and SL-producing cells (ir-FSH and ir-SL) were restricted to pars intermedia (PI) of the adenohypophysis. Pituitary ir-FSH cells were decreased at the end of the experimental period in all treatments compared with the CT animals. LH-producing cells (ir-LH) were present in proximal pars distalis (PPD) and pars intermedia (PI) of adenohypophysis and did not change after the experimental period. The decreased number of ir-FSH cells at the end of the experiment in all treatments could be related to the negative feedback loop triggered by the increase in natural and/or synthetic androgens.

Steroid Hormones in Reproduction and Roles of GnRH-a in Gonadal Maturation of Marine Fish: A Review

Reproduction in teleosts is regulated by a series of hormones including gonadotropin-releasing hormones (GnRHs), gonadotropins (GTHs) and steroid hormones. To contribute better understanding of steroid hormones in reproduction and GnRH-a in gonadal maturation, this literature review is concerned with the changes of steroid hormone levels in relation with sex inversion, reproductive behavior and gonadal development as well as the application of GnRH-a for inducing maturation of marine fish. The results revealed that in many species of teleost, steroid hormones E2, 11-11-KT and DHP are abundantly produced in gonadal tissues under the control of pituitary gonadotropins, and are essential for critical steps of gametogenesis. Plasma steroid levels have been used as indicators for both of the sex of the fish and its stage in the seasonal reproductive cycle, particularly with regard to induction of spawning. Determination of plasma steroid levels in relation with the sexual status of the gonads over several reproductive seasons might provide valuable information on the mechanisms of sex inversion in ambisexual fish species. In addition, changes of plasma steroid levels in correlation with gonadal development, number of spawning, fecundity, were described clearly in many marine species. The review also indicated that exogenous administration of GnRH-a triggered for final maturation of brood stock of some teleosts. In summary E2, T, 11-KT and C21 steroids are in relation with sex inversion, reproductive processes and GnRH-a is successful for inducing gonadal maturation in some fish species.