Protogynous Hermaphrodite Research Articles

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.

Age, Growth, and Functional Gonochorism with a Twist of Diandric Protogyny in Goliath Grouper from the Atlantic Coast of Florida

The lack of data on the age, growth, and reproduction of the Atlantic Goliath Grouper Epinephelus itajara off the coasts of Florida (USA) makes it difficult to estimate the extent of their population recovery following the 1990 fishery closure, as well as the potential effects of the recent (2023) opening of a fishery for juveniles. Goliath Grouper from the Atlantic coast of Florida were non-lethally sampled for size (total length, TL), age (via fin rays), and sex and reproductive stage (via gonad biopsies, milt/egg expression, gonopores) from May to October 2010–2016. Of 653 unique fish captured (not including 118 recaptures), 257 (39.4%) were females (122–228 cm TL; 5–20 years old), 264 (40.0%) were males (104–225 cm TL; 4–22 years old), 100 (15.3%) were unsexed (82–211 cm TL; 3–15 years old), and 32 (4.9%) were protogynous hermaphrodites (108–209 cm TL; 5–20 years old). Protogyny was conclusively determined in two fish recaptured and re-biopsied that had transitioned from female to male. However, an overlap in the age and size of males and females, a 1:1 sex ratio, and the presence of relatively small, young, mature males, in combination with an apparently low functional sex change rate, all indicated that the sexual pattern of Goliath Grouper was functionally gonochoristic with the potential for diandric protogyny. Females > 10 years old were larger-at-age than males, and Goliath Grouper from the Atlantic coast were larger-at-age than fish from the Gulf of Mexico. These differences in age, growth, and reproductive strategy—as well as the nascent fishery for juveniles—need to be monitored closely so that the current and future reproductive capacity of the population continues to ensure growth and sustainability.

Length and age compositions, hermaphroditic traits and reproductive characteristics vary among five congeneric species of labrid in a large embayment

This study explored the extent to which the hermaphroditic and reproductive characteristics vary among five congeneric (Choerodon) and co-occurring species of the Labridae, a family in which hermaphroditism is widespread. Sampling was located in the large sub-tropical Shark Bay (26° S, 113° E), one of only twenty World Heritage Properties in Australia. Choerodon cephalotes, C. cyanodus, C. cauteroma and C. schoenleinii live within the main body of the embayment, which approaches the southern limit of their tropical, geographical ranges, whereas C. rubescens lives along its outer western boundary, close to the northern limit of its warm, temperate distribution. A combination of comprehensive length and age compositions, histological analyses of gonads and logistic regressions of lengths and ages at maturity and sex change are consistent with all five species being monandric protogynous hermaphrodites. Choerodon cephalotes, C. rubescens and C. schoenleinii are sexually dichromatic, with the lengths and ages of males at the extreme upper end of those of females and low proportions of males among adults (adult sex ratios, ASR: 11–33%). It is proposed that these species have polygynous mating systems, such as leks or harems. Although C. cauteroma has an ASR of essentially parity, its pronounced sexual dichromatism and the ages of its males typically lying at the upper end of those of its females indicate that this species also has a polygynous mating system. Limited sexual dichromatism and an ASR as high as 71% suggest that C. cyanodus is not polygynous. As the timing of the main spawning period of the four species within Shark Bay increases sequentially between early spring and late summer, the temperature trigger for spawning by those species also presumably increases progressively. This phasing of spawning, allied with some interspecific spatial variation, reduces the potential for competition among the larvae and early juveniles of the five Choerodon species. Choerodon rubescens spawns earlier in Shark Bay than in the cooler waters of the Abrolhos Islands, 230 km further south. The management implications of data for Choerodon species, and particularly of the size compositions and the ASRs of the two largest species, C. rubescens and C. schoenleinii, are discussed. The variations in the hermaphroditic and reproductive features of five congeneric species of labrid, in the region in which their distributions overlap, highlight the evolutionary/biological plasticity of this family and thereby contributes to its diversity and success.

Life-history characteristics and mortality of the protogynous hermaphroditic frostback rockcod (Epinephelus bilobatus) from the eastern Indian Ocean

The frostback rockcod, Epinephelus bilobatus, is a small epinephelid (<50 cm total length) with a limited distribution in the tropical eastern Indian Ocean (i.e., north-western Australia and parts of Indonesia). Although its fishery harvest in Western Australia is low (<6 t year−1), its life history is not well known (i.e., reproductive biology, growth, and natural mortality) preventing assessment of its inherent vulnerability to overfishing. Samples of E. bilobatus were collected from ∼2000 km of the north-western Australian coast, comprising the Kimberley, Pilbara, and Gascoyne regions, between 2012 and 2022 to determine its life-history characteristics. Detailed histological analysis of gonads (n = 1460) identified that E. bilobatus is a monandric protogynous hermaphrodite. The length and age at which females matured was 278 mm LT and 2.5 years in the Pilbara region, and the lengths and ages at which they changed to males was 336 and 342 mm LT and 6.2 and 6.5 years in the Kimberley and Pilbara, respectively (i.e., less than 5% variation between regions). Based on histology, female E. bilobatus were in spawning condition in all months. However, the mean monthly gonadosomatic indices and proportions of developed/spawning females were highest (i.e., >0.95 and 40%, respectively) for 5 months of the year (i.e., January to April and September). Marginal increment analysis confirmed the annual formation of one opaque and one translucent zone in the sagittal otoliths of this species. Epinephelus bilobatus had a moderate longevity (∼20 years) and attained a larger mean length-at-age in the cooler southern Gascoyne region compared to the more northern Kimberley and Pilbara regions. Three values of natural mortality (M) were used to assess the sensitivity of fishing mortality (F) in the Kimberley and Pilbara commercial trap fisheries, with all point estimates of F < M, indicating that at the time of sampling, the harvest of this species over a long period (>20 years) was sustainable for these contemporary fisheries.

Life history of the endemic Hawaiian hogfish Bodianus albotaeniatus: age, growth, and reproduction.

Growth rate, longevity, maturity, and spawning seasonality were estimated for the endemic Hawaiian hogfish Bodianus albotaeniatus. The sex-specific von Bertalanffy growth parameters are L∞ = 339 mm fork length (LF ) and K = 0.66 year-1 for females; L∞ = 417 mm LF and K = 0.33 year-1 for males. The maximum age is 22 years. Histological gonad analysis and the absence of small and young males indicate a monandric protogynous hermaphrodite. Size and age at maturity for combined sexes are L50 = 238 mm LF and A50 = 1.6 years. This article is protected by copyright. All rights reserved.

Age, growth, and reproduction of the yellow-edged lyretail Variola louti (Forssakal, 1775)

Groupers (Family Epinephelidae) are important to commercial, subsistence, and recreational fisheries throughout the world. Grouper species have complex life histories that make them more vulnerable to exploitation. While there has been extensive research on some, the majority of groupers lack sufficient life history information for proper management. The yellow-edge lyretail grouper, Variola louti, has life history gaps that need to be filled and lacks regional life history information for Guam. Age, growth, and reproduction were assessed from fishery-dependent samples collected from around Guam from 2010 to 2017. Variola louti ranged from 19.4 to 49.7 cm fork length (FL) and 2 to 17 years old. Due to the size selectivity of the fishery, a Bayesian von Bertalanffy growth model was applied. The von Bertalanffy growth parameters were L∞ = 43.7 cm FL, k = 0.28, and t0 = − 0.2. Protogynous hermaphroditism was confirmed with females reaching reproductive maturity at 26.0 cm FL (L50) and 2.6 years (A50) and female to male sex change at 35.3 cm FL (LΔ50) and 6.1 years (AΔ50). Sex ratio was 1.5 females per male, excluding transitional individuals. Using Hoenig’s method, natural mortality was estimated at 0.37 year−1. The life history of Variola louti suggests that it is a relatively fast growing and early maturing grouper that is not as vulnerable to exploitation as larger bodied, slower growing groupers. However, future monitoring of sex ratio, size at maturity, and size at sex change is recommended to track and manage fishery effects, such as the recent scuba spear ban in Guam, on the life history and population status of this species.

Gametic cycle and gonadal maturity of Bulimulus bonariensis (Rafinesque, 1833) (Gastropoda: Bulimulidae), in a rural area of Buenos Aires, Argentina.

Bulimulus bonariensis, a snail distributed over a large part of Argentina, has generated negative effects on the agribusiness. We accordingly conducted a seasonal sampling during 2018-2019 in order to characterize the gametic cycle and establish the size of this gastropod at gonadal maturity. Three reproductive stages were identified: the mature in autumn; the spawn, which begins in winter but occurs mainly in the spring, followed by the post-spawn in summer, where an absence of gonadal rest was evidenced. In the fall, in maturity resorption was observed in addition to abundant primary spermatocytes, secondary spermatocytes, and growing vitellogenic oocytes. At the same time, could correlate the degree of spermioviduct development with the stage of gonadal development. Moreover, we used a logistic regression to calculate the size at gonadal maturity, which was established at the total shell length of 12 mm. In addition, we found that at the beginning of reproductive development those gastropods are protogynous hermaphrodites, but after reaching gonadal maturity became simultaneous hermaphrodites. Finally, B. bonariensis also proved to be an iteroparous species. The information provided here will be essential for delineating and establishing population control strategies.

Mechanisms of sex differentiation and sex reversal in hermaphrodite fish as revealed by the Epinephelus coioides genome.

Most grouper species are functional protogynous hermaphrodites, but the genetic basis and the molecular mechanisms underlying the regulation of this unique reproductive strategy remain enigmatic. In this study, we report a high-quality chromosome-level genome assembly of the representative orange-spotted grouper (Epinephelus coioides). No duplication or deletion of sex differentiation-related genes was found in the genome, suggesting that sex development in this grouper may be related to changes in regulatory sequences or environmental factors. Transcriptomic analyses showed that aromatase and retinoic acid are probably critical to promoting ovarian fate determination, and follicle-stimulating hormone triggers the female-to-male sex change. Socially controlled sex-change studies revealed that, in sex-changing fish, the brain's response to the social environment may be mediated by activation of the phototransduction cascade and the melatonin synthesis pathway. In summary, our genomic and experimental results provide novel insights into the molecular mechanisms of sex differentiation and sex change in the protogynous groupers.

Divulging the social sex change mechanism in a unique model system for studying the sexual plasticity of protogynous hermaphrodite fish, three bamboo leaf wrasse (Pseudolabrus sieboldi)

The gonadal sexual fate of vertebrates is either defined by genetics or environment, or a combination of both factors. Interestingly, in sequential hermaphroditism, the animal can undergo natural sex changes from female-to-male, male-to-female, and bidirectional way throughout their lives. This change exhibits the process which shifts between oogenesis and spermatogenesis and is regarded as an ideal instance of sexual plasticity. To develop the experimental model for studying the sexual plasticity of protogynous fish, the social conditions that induce sex changes were defined in wrasse, Pseudolabrus sieboldi. When six females were kept together in a tank, the largest female became a male, whereas a similar conversion did not occur when only two females were present in a tank. A semi-gonadectomy analysis developed in the present study verified the direct relationship between gonadal sex and body coloration. In P. sieboldi, the sex change is controlled by the relative body size of an individual within a group, rather than by absolute body size. When six females were kept in smaller sized tanks, delayed sex change or unchanged individuals was observed. Overall, more than 90% of the largest females demonstrated sex change after being housed with five smaller females in different sizes of tanks ranging from 80 to 500 L. Furthermore, the experiment using a transparent barrier suggested that visual stimuli are one of the major cues to initiate sex change. Our findings on the laboratory conditions leading to the initiation of sex change in wrasse suggest the usefulness of this species as a model organism for comparative studies in molecular, cellular, and physiological mechanisms of sexual plasticity, as well as on social and reproductive behaviors.

The ontogenic gonadal transcriptomes provide insights into sex change in the ricefield eel Monopterus albus

BackgroundThe ricefield eel is a freshwater protogynous hermaphrodite fish and has become an important aquaculture species in China. The sex change of ricefield eel is impeding its aquaculture practice, particularly the large-scale artificial breeding. Many studies including transcriptomes of mixed gonadal samples from different individuals have been aimed to elucidate mechanisms underlying the sex change. However, the key physiological factors involved in the initiation of sex change remain to be identified. ResultsThe present study performed transcriptomic analysis on gonadal samples of different sexual stages obtained through biopsy from the same fish undergoing sex change. A total of 539,764,816 high-quality reads were generated from twelve cDNA libraries of gonadal tissues at female (F), early intersexual (EI), mid-intersexual (MI), and late intersexual (LI) stages of three individual sex-changing fish. Pairwise comparisons between EI and F, MI and EI, and LI and MI identified 886, 319, and 10,767 differentially expressed genes (DEGs), respectively. Realtime quantitative PCR analysis of 12 representative DEGs showed similar expression profiles to those inferred from transcriptome data, suggesting the reliability of RNA-seq data for gene expression analysis. The expression of apoeb, csl2, and enpp2 was dramatically increased and peaked at EI while that of cyp19a1a, wnt4a, fgf16, and foxl2a significantly downregulated from F to EI and remained at very low levels during subsequent development until LI, which suggests that apoeb, csl2, enpp2, cyp19a1a, wnt4a, fgf16, and foxl2a may be closely associated with the initiation of sex change of ricefield eels.ConclusionsCollectively, results of the present study confirmed that the down-regulation of female-related genes, such as cyp19a1a, wnt4a, fgf16, and foxl2a, is important for the sex change of ricefield eels. More importantly, some novel genes, including apoeb, csl2, and enpp2, were shown to be expressed with peak values at EI, which are potentially involved in the initiation of sex change. The present transcriptomic data may provide an important research resource for further unraveling the mechanisms underlying the sex change and testicular development in ricefield eels as well as other teleosts.

Life history traits vary between geographically distinct populations in a protogynous hermaphrodite

Sequential hermaphroditic species, such as blue cod (Parapercis colias), are particularly vulnerable to selective harvesting as it can directly influence the sex ratio, timing of sex change, and consequentially recruitment success. We analyzed the population structure, at which males dominate the populations, and modeled fecundity of blue cod from the Marlborough Sounds in the north of New Zealand's South Island, and compared these results with previously collected data from a blue cod population in Fiordland on the southwest coast of the South Island. In addition to the geographical difference, there were differences in the time the two populations were sampled, and the fisheries management regime between regions. Within the Marlborough Sounds population, the length-frequency distribution was skewed toward high numbers of smaller individuals with an average length of 290 ± 59 mm. In Fiordland, the average length of blue cod was 380 ± 78 mm. Larger proportions of males within each length class were observed in the Marlborough Sounds, whereas females were the dominant sex in the Fiordland population. The estimated length at which males dominate the population was significantly smaller for the Marlborough Sounds population (182 mm) than for blue cod from the Fiordland population (419 mm). Geographical and temporal differences in sampling likely played important roles in the observed life history differences, particularly in the observed differences in growth. However, when compared to length and age data from national surveys, the life history traits of both sampled populations have remained relatively stable over the past 15 years, indicating that differences in population management and fishing pressure are the most likely explanation for the observed differences in length frequency and length-at-sex-change. For effective and sustainable management of species with sequential hermaphroditism, size-sensitive management, particularly protecting larger individuals, is required to avoid declines in length structure and recruitment limitations.

Effects of cortisol on female-to-male sex change in a wrasse.

Sex change occurs as a usual part of the life cycle for many teleost fish and the modifications involved (behavioural, gonadal, morphological) are well studied. However, the mechanism that transduces environmental cues into the molecular cascade that underlies this transformation remains unknown. Cortisol, the main stress hormone in fish, is hypothesised to be a key factor linking environmental stimuli with sex change by initiating gene expression changes that shift steroidogenesis from oestrogens to androgens but this notion remains to be rigorously tested. Therefore, this study aimed to experimentally test the role of cortisol as an initiator of sex change in a protogynous (female-to-male) hermaphrodite, the New Zealand spotty wrasse (Notolabrus celidotus). We also sought to identify potential key regulatory factors within the head kidney that may contribute to the initiation and progression of gonadal sex change. Cortisol pellets were implanted into female spotty wrasses under inhibitory conditions (presence of a male), and outside of the optimal season for natural sex change. Histological analysis of the gonads and sex hormone analyses found no evidence of sex change after 71 days of cortisol treatment. However, expression analyses of sex and stress-associated genes in gonad and head kidney suggested that cortisol administration did have a physiological effect. In the gonad, this included upregulation of amh, a potent masculinising factor, and nr3c1, a glucocorticoid receptor. In the head kidney, hsd11b2, which converts cortisol to inactive cortisone to maintain cortisol balance, was upregulated. Overall, our results suggest cortisol administration outside of the optimal sex change window is unable to initiate gonadal restructuring. However, our expression data imply key sex and stress genes are sensitive to cortisol. This includes genes expressed in both gonad and head kidney that have been previously implicated in early sex change in several sex-changing species.

Sexual Reproduction in Zoanthus kuroshio and Isaurus tuberculatus (Cnidaria: Anthozoa: Zoanthidae) in Southern Japan.

Among family Zoanthidae (Anthozoa: Hexacorallia: Zoantharia), Zoanthus and Isaurus are widespread benthos on coral reefs, but the reproductive biology of both genera is generally unknown. Accordingly, sexual reproduction of two Zoanthidae species in Japan, Zoanthus kuroshio in Okinawa, and Isaurus tuberculatus in Okinawa and Kochi, was investigated by annual sampling. Between 2012 and 2013, polyps of tagged colonies of Z. kuroshio and I. tuberculatus were sampled monthly, and gonads in mesenteries were examined under a stereomicroscope. In Z. kuroshio, sizes of oocytes were estimated and in situ spawning observations were conducted at night at Okinawa sites. Monthly sampling indicated that gametogenesis periods of both species in Okinawa were from May to August, and oogenesis set in earlier than spermatogenesis, and thus both species can be considered protogynous functional hermaphrodites. On the other hand, I. tuberculatus in Kochi had hermaphroditic polyps in July and August. Notably, fertile colonies of Z. kuroshio were not only hermaphrodites but also included exclusively male and female colonies. Overall, four sexual types were identified in Z. kuroshio: male, female, functional protogynous hermaphrodites, and unclassified sterile colonies. In situ gamete release of Z. kuroshio was observed in August 2012 and July to August 2013. First spawning of the year occurred 1 day after the new moon; colonies shed their bundles 3.5-4 h after sunset. We speculate that lunar phase and time after sunset influence spawning timing in Z. kuroshio. Basic knowledge on sexual reproduction of Zoanthidae is critically needed to better understand the basic biology of these benthic cnidarians.

Growth, sexual transition, and maturation of blacktip grouper Epinephelus fasciatus under long-term artificial rearing: Puberty and its associated physiological and endocrine changes

The blacktip grouper Epinephelus fasciatus is considered a valuable marine fish for aquaculture. This study was conducted to obtain information on its age of puberty, growth performance, gonadal development, sexual transition pattern, and plasma sex steroid levels from juvenile stage to maturity in specimens reared in captivity. The stages of gonadal development were identified by histological analysis, and plasma sex steroid levels were measured using an enzyme-linked immunosorbent assay. Our results show that maturation and spawning in blacktip groupers occurred at almost 3 years of age; although some females matured at 2 years. Plasma 17β-estradiol (E2) levels increased rapidly to high levels during puberty at 3 years of age, especially during the late stage of vitellogenesis at the tertiary yolk stage, and reduced at the ripe and ovulated stages prior to spawning. The gonadal somatic index also showed an increase consistent with the rise in plasma E2 levels. Plasma 11-ketotestosterone (11-KT) levels increased dramatically during sex change and in males. The significant decrease in plasma E2 levels and remarkable increase in plasma 11-KT were the key factors for the progress of sex change in these fish. Interestingly, there were the concomitant appearances of spermatocytes in ovaries of immature females at 1 year 3 months of age. The earliest appearance of sex-transitioning and male fish in blackfish groupers was observed at 2 years, although no mature females were observed below this age. This indicated that the sex change and male transformation in these fish took place without them undergoing the mature female stage. In conclusion, this species had the ability to reach puberty at 2 years of age, but most individuals matured and were functional at 3 years old. Puberty might be affected by age rather than size. In addition, although this species had a protogynous hermaphrodite pattern, when individuals born in the same year were reared together, some individuals were capable of directly becoming males without experiencing a mature female stage. This was due to the lack of socialization in captivity wherein individuals of various ages do not coexist, unlike that in the wild.

Molecular Cloning and Expression Analysis of Thyrotropin-Releasing Hormone, and Its Possible Role in Gonadal Differentiation in Rice Field eel Monopterus albus.

Simple SummaryThyrotropin-releasing hormone (TRH) is an important upstream regulator in the hypothalamus-pituitary-thyroid (HPT) axis in mammals. In this study, we isolated and characterized trh gene from a protogynous hermaphrodite fish rice field eel Monopterus albus. TRH had no significant effect on serum thyroid hormone levels in rice field eel. However, we found that TRH was involved in the regulation gonadal differentiation-related gene expression and serum sex steroid hormone secretion. Our results indicated that TRH may play a novel role in gonadal differentiation in rice field eel.Rice field eel (Monopterus albus), a protogynous hermaphrodite fish, is a good model for the research of sex determination and gonadal differentiation in teleosts. In this study, we cloned the full-length cDNA sequence of trh, which encoded a predicted protein with 270 amino acids. Trh mainly expressed in the brain, followed by the ovary, testis, muscle and pituitary, and had low levels in other peripheral tissues. During natural sex reversal, trh mRNA expression levels exhibited a significant increase at the late intersexual stage in the hypothalamus. In the gonad, trh mRNA expression levels showed a trend of increase followed by decrease, and only increased significantly at the middle intersexual stage. No matter static incubation or intraperitoneal (IP) injection, TRH had no significant effect on trh and thyroid-stimulating hormone β subunit (tshβ) mRNA expression levels, and serum T3, T4 and TRH release. After static incubation of ovarian fragments by TRH, the expression of gonadal soma derived factor (gsdf) was up-regulated significantly at both the doses of 10 and 100 nM. IP injection of TRH stimulated the expression of gsdf, and inhibited the expression of ovarian aromatase gene (cyp19a1a), accompanied by the increase of serum 11-KT levels. The results indicated that TRH may play a novel role in gonadal differentiation by the regulation of gonadal differentiation-related gene expression and sex steroid hormone secretion in rice field eel.

Demography of the black grouper, Mycteroperca bonaci (Poey, 1860) (Teleostei: Epinephelidae) from the North Brazil Shelf.

Mycteroperca bonaci (black grouper) is one of the most sought species of grouper along its entire distribution, being a prime target for demersal line fisheries because of its high commercial value. Nonetheless, because of population declines the species is considered near threatened according to the IUCN red list. The present study aimed to determine the population parameters of M. bonaci, including growth, reproduction and mortality, and thus contributes to measures towards its conservation and management in the southwestern Atlantic. The sampling area is in the North Brazil Shelf, off Maranhão State, an area of intense fisheries development and yet poorly known. The large continental shelf harbours unique coral reef formations and has been declared an ecologically or biologically significant marine area (EBSA). Sampling on landing sites was carried out monthly between May 2017 and January 2019. A total of 137 black grouper specimens were sampled from commercial landings of artisanal fisheries. The size of the specimens ranged from 44 to 157 cm, and the weight varied from 0.976 to 54 kg. The length-weight was established: log(TW)=-11.26 + 3.01log(TL). Histological analysis of the gonads confirmed only the presence of female individuals, and the occurrence of individuals in the sexual transition was not recorded. Higher GSI values and higher frequency of spawning capable staged individuals occurred during the months of June to August, indicating spawning peaks. The estimated age of sexual maturity A50 for females was 4.62 years ( 93 cm-TL). The growth parameters for the Von Bertalanffy model were TL∞ (cm): 185.5, k: 0.04, t0 (year): -4.75 (t0 not fixed) and TL∞ (cm): 141, k: 0.11 (t0 = 0 fixed). The total estimated mortality rate (Z) according to catch length presented a Z value=0.11, and the natural mortality was M= 0.04 year-1 . This is the first study on the age and growth of M. bonaci in the SWA, a region where the species is considered as endangered according to Brazil's red list regional assessment. Only females were present in the samples, results that suggest either differential capturability of sexes because of distinct patterns of behaviour or distribution or an effect of selective mortality upon larger and older individuals, as the species is described as a protogynous hermaphrodite. This indicates the need to closely manage this population to avoid collapses. Recovery plans that have been planned by the Brazilian government but not yet implemented for the species must be put into practice to avoid progressive decline as fisheries target more remote areas.

Protogynous sex change in ricefield eel Monopterus albus (Zuiew, 1793) by hormonal induction using javanese chili extract (Piper retrofractum Vahl)

The ricefield eel Monopterus albus (Zuiew, 1793) is a protogynous hermaphrodite that undergoes sex change from female at the beginning of its life cycle to becoming male after going through the intersex phase. This study aims to evaluate the sex status of ricefield eels measuring 18–55 cm and the development of protogynous sex change by hormonal induction using Javanese chili extract (Piper retrofractum Vahl) through injection. One hundred and twenty eels averaged 24.86 ± 0.76 cm of length and 10.65 ± 0.83 g of weight was used in this research. A completely randomized experimental design consisted of four treatments (different doses of Javanese chili extract) and three replications were applied in this research. The dose of Javanese chili extract given was 187.5 g.kg-1 fish (P1) and 375 g.kg-1 fish (P2) compared to the control with injection using NaCl 3 mL.kg-1 fish (P0) and without injection (K). Injections through intramuscular were given 5 times with an interval of 7 days and observations of sex status were carried out every 14 days based on the development of the gonads. In the normal conditions, the sex status of ricefield eels measuring 20-33 cm in length indicates females, while intersex has a length ranging from 33–43 cm, and males with a length range of 43–55 cm. Hormone induction by injection of Javanese chili extract at a dose of ECJ 375 g.kg-1 fish produced a sex change percentage of eels with 75% male sex status and 25% intersex with an average length of 24.88 ± 0.35 cm and a weight of 10.22 ± 0.14 g.

Isolation and Characterization of Germline Stem Cells in Protogynous Hermaphroditic Monopterus albus.

Germline stem cells (GSCs) are a group of unique adult stem cells in gonads that act as important transmitters for genetic information. Donor GSCs have been used to produce offspring by transplantation in fisheries. In this study, we successfully isolated and enriched GSCs from the ovary, ovotestis, and testis of Monopterus albus, one of the most important breeding freshwater fishes in China. Transcriptome comparison assay suggests that a distinct molecular signature exists in each type of GSC, and that different signaling activities are required for the maintenance of distinct GSCs. Functional analysis shows that fGSCs can successfully colonize and contribute to the germline cell lineage of a host zebrafish gonad after transplantation. Finally, we describe a simple feeder-free method for the isolation and enrichment of GSCs that can contribute to the germline cell lineage of zebrafish embryos and generate the germline chimeras after transplantation.

Protogynous hermaphroditism in Crustacea: a new example from Tanaidacea

Hermaphroditism has been widely reported in the Crustacea, but protogyny, in which females change to males, is apparently rare and restricted to the peracarid orders Isopoda and Tanaidacea. In the latter, protogyny has been demonstrated in only seven species representing six genera by rearing experiments and indicated for several other genera and species through morphology. Here, we show through rearing experiment and histological observations, protogynous hermaphroditism in the tanaidacean species Nesotanais sp. aff. ryukyuensis Kakui, Kajihara and Mawatari, 2010. Our rearing experiment and size distribution data for wild individuals showed that females can change sex at various sizes (= ages). We found one individual identified externally as a female containing both ovaries and testes, indicating that overt female individuals undergo a short transitional phase as simultaneous hermaphrodites before the sex-change molt. We discuss the relationship among the wide size distribution of sex-changing females, the short life span of males, and the tube-dwelling mode of life.

A review of the world wide work on the breeding and production of Groupers

The Groupers fishes consist many important marketable species, in the world and the Gulf region, but it's populations were gravely reduced. The production of Groupers was either by fisheries- based aquaculture, or by artificial breeding. The baby Groupers were caught during early summer from the costal waters, estuaries and tidal pools. The Groupers are mostly Protogynous hermaphrodites, and the hormones implantation were used for sex reverse. The enrichment of the brooders diet must be done with polyunsaturated fatty acids, that to amelioration the eggs quality and increasing larval quality and survival rate. The hormone injection was used either for artificial insemination or semi-natural breeding. The induced brooders were placed in spawning tanks, and then the floating fertilized eggs were collected by collecting funnel. The hatching troughs were used for hatching the fertilized eggs. The larvae could be produced in raceways, earthen ponds, and outside cement tanks. The live food must produce in the hatchery for the feeding of the newly hatching larvae. Then the fingerlings could be reared to marketing size for a period of 6-8 months.