Protandrous Research Articles

Histological evidence of sequential hermaphroditism in Hawaiian sandburrowers Crystallodytes cookei and Limnichthys nitidus

Histological evidence of sequential hermaphroditism in Hawaiian sandburrowers Crystallodytes cookei and Limnichthys nitidus

Catch of the day: Abundance and size data of groupers (Epinephelidae) and combers (Serranidae) from Middle to Late Holocene Levantine archaeological contexts

Groupers (Epinephelidae) are ecologically, commercially, and culturally important carnivorous fishes found throughout the world’s tropical, subtropical, and temperate coastal marine waters. Due to various life history traits (e.g., late maturity, sequential hermaphroditism) and behavior (e.g., sedentary, small home ranges) groupers are susceptible to overfishing, including small-scale and recreational fishing (especially spearfishing), and their populations are declining worldwide. The eastern Mediterranean coast, home to some of the world’s longest continuously occupied urban settlements, hosts important but declining grouper populations. This paper investigates how grouper and comber (fishes in the Serranidae family with similar ecology and osteomorphology, but smaller in size) abundance and catch size changed in the eastern Mediterranean from the Middle to Late Holocene, coinciding with early coastal urbanization, by estimating their relative frequency and reconstructing their size. Size reconstructions have been done from a large sample of bones (Number of Identified Specimens = 1851) recovered from Kinet Höyük in Turkey, and Tell Fadous-Kfarabida and Tell el-Burak in Lebanon, habitation sites along the Levantine coast. Our results imply that groupers in the past reached >100 cm more often than is observed today in areas open to commercial fishing. Furthermore, the apparent lack of large groupers by the Hellenistic Period at Kinet Höyük suggests fishing efforts were intense enough to have either had an appreciable effect on the size structure of local grouper populations or brought about a behavioral change to the fishes of moving to deeper waters.

Comparative demography of three black seabreams found in the Ryukyu Archipelago: implication for the definition of protandrous hermaphrodites

Comparative demography of three black seabreams found in the Ryukyu Archipelago: implication for the definition of protandrous hermaphrodites

Neutral and adaptive loci reveal fine-scale population structure in Eleginops maclovinus from north Patagonia.

Patagonia is an understudied area, especially when it comes to population genomic studies with relevance to fishery management. However, the dynamic and heterogeneous landscape in this area can harbor an important but cryptic genetic population structure. Once such information is revealed, it can be integrated into the management of infrequently investigated species. Eleginops maclovinus is a protandrous hermaphrodite species with economic importance for local communities that are currently managed as a single genetic unit. In this study, we sampled five locations distributed across a salinity cline from Northern Patagonia to investigate the genetic population structure of E. maclovinus. We used restriction site‐associated DNA (RAD) sequencing and outlier tests to obtain neutral and adaptive loci, using FST and GEA approaches. We identified a spatial pattern of structuration with gene flow and spatial selection by environmental association. Neutral and adaptive loci showed two and three genetic groups, respectively. The effective population sizes estimated ranged from 572 (Chepu) to 14,454 (Chaitén) and were influenced more by locality than by salinity cline. We found loci putatively associated with salinity suggesting that salinity may act as a selective driver in E. maclovinus populations. These results suggest a complex interaction between genetic drift, gene flow, and natural selection in this area. Our findings also suggest several evolutionary significant units in this area, and the information should be integrated into the management of this species. We discussed the significance of these results for fishery management and suggest future directions to improve our understanding of how E. maclovinus has adapted to the dynamic waters of Northern Patagonia.

Cyt-C Mediated Mitochondrial Pathway Plays an Important Role in Oocyte Apoptosis in Ricefield Eel (Monopterus albus).

Apoptosis plays a key role in the effective removal of excessive and defective germ cells, which is essential for sequential hermaphroditism and sex change in vertebrates. The ricefield eel, Monopterus albus is a protogynous hermaphroditic fish that undergoes a sequential sex change from female to male. Previous studies have demonstrated that apoptosis is involved in sex change in M. albus. However, the apoptotic signaling pathway is unclear. In the current study, we explored the underlying mechanism of apoptosis during gonadal development and focused on the role of the mitochondrial apoptosis signaling pathway in sex change in M. albus. Flow cytometry was performed to detect apoptosis in gonads at five sexual stages and ovary tissues exposed to hydrogen peroxide (H2O2) in vitro. Then the expression patterns of key genes and proteins in the mitochondrial pathway, death receptor pathway and endoplasmic reticulum (ER) pathway were examined. The results showed that the apoptosis rate was significantly increased in the early intersexual stage and then decreased with the natural sex change from female to male. Quantitative real-time PCR revealed that bax, tnfr1, and calpain were mainly expressed in the five stages. ELISA demonstrated that the relative content of cytochrome-c (cyt-c) in the mitochondrial pathway was significantly higher than that of caspase8 and caspase12, with a peak in the early intersexual stage, while the levels of caspase8 and caspase12 peaked in the late intersexual stage. Interestingly, the Pearson’s coefficient between cyt-c and the apoptosis rate was 0.705, which suggests that these factors are closely related during the gonadal development of M. albus. Furthermore, the cyt-c signal was found to be increased in the intersexual stage by immunohistochemistry. After incubation with H2O2, the mRNA expression of mitochondrial pathway molecules such as bax, apaf-1, and caspase3 increased in ovary tissues. In conclusion, the present results suggest that the mitochondrial apoptotic pathway may play a more important role than the other apoptotic pathways in sex change in M. albus.

Designer clown fishes: Unraveling the ambiguities

The global marine ornamental fish trade is dominated by wild collected fishes, and the contribution from hatchery production is less than 10% of the total. Hatchery production is considered to be the only long-term sustainable option to reduce the fishing pressure on the wild population and also to safeguard the delicate coral reef ecosystem, which houses most of the marine ornamental species. Among the hatchery-produced fishes that are being traded, clown fishes form a dominant group, and a recent addition to this list is the designer clown fishes, which are costlier than other clown fishes due to their rare and attractive color patterns. However, ambiguities about designer clown fish such as its production (wild caught, captive bred, or genetically modified) and taxonomic identity still exist among the general public and hobbyists, as scientific reports on these aspects have not yet been published, even though few aquaculture companies display the photos of designer clown fishes in their websites. The common names for designer clown fishes (such as Platinum, Picasso, and snowflake) have been given by the aquaculture companies/traders solely based on the color patterns or designs on the fish body. The paper describes in detail the production of designer clown fish through captive breeding, followed by elucidating the taxonomic identity of two easily distinguishable designer clown fishes, viz., Picasso and Platinum. Both classical taxonomic tools and molecular methods were employed to elucidate the taxonomic identity. The morpho-merisitic characteristics of Picasso and Platinum were similar to those of Amphiprion percula. The partial cytochrome c-oxidase subunit I (COI) sequences of Picasso and Platinum clown fishes were submitted to the National Center for Biotechnology Information (NCBI) GenBank with accession numbers MT947238 and MT947239, respectively, which had maximum similarity to sequences of A. percula already deposited in the NCBI GenBank. The designer clown fishes exhibited protandrous hermaphroditism with monogamous mating behavior. Their egg incubation period ranged from 7 to 8 days, and the larval rearing was carried out with live feeds such as rotifers and Artemia under the greenwater technique using microalgae, Nannochloropsis oculata. This paper can thus unravel the ambiguities related to the production of designer clown fishes as well as their taxonomy.

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.

Transcriptome Profiling and Expression Localization of Key Sex-Related Genes in a Socially-Controlled Hermaphroditic Clownfish, Amphiprion clarkii.

Clownfish can be an excellent research model for investigating the socially-controlled sexual development of sequential hermaphrodite teleosts. However, the molecular cascades underlying the social cues that orchestrate the sexual development process remain poorly understood. Here, we performed a comparative transcriptomic analysis of gonads from females, males, and nonbreeders of Amphiprion clarkii, which constitute a complete social group, allowing us to investigate the molecular regulatory network under social control. Our analysis highlighted that the gonads of nonbreeders and males exhibited high similarities but were far from females, both in global transcriptomic profiles and histological characteristics, and identified numerous candidate genes involved in sexual development, some well-known and some novel. Significant upregulation of cyp19a1a, foxl2, nr5a1a, wnt4a, hsd3b7, and pgr in females provides strong evidence for the importance of steroidogenesis in ovarian development and maintenance, with cyp19a1a playing a central role. Amh and sox8 are two potential key factors that may regulate testicular tissue development in early and late stages, respectively, as they are expressed at higher levels in males than in females, but with slightly different expression timings. Unlike previous descriptions in other fishes, the unique expression pattern of dmrt1 in A. clarkii implied its potential function in both male and female gonads, and we speculated that it might play promoting roles in the early development of both testicular and ovarian tissues.

Circular RNA expression profiles and CircSnd1-miR-135b/c-foxl2 axis analysis in gonadal differentiation of protogynous hermaphroditic ricefield eel Monopterus albus

BackgroundThe expression and biological functions of circular RNAs (circRNAs) in reproductive organs have been extensively reported. However, it is still unclear whether circRNAs are involved in sex change. To this end, RNA sequencing (RNA-seq) was performed in gonads at 5 sexual stages (ovary, early intersexual stage gonad, middle intersexual stage gonad, late intersexual stage gonad, and testis) of ricefield eel, and the expression profiles and potential functions of circRNAs were studied.ResultsSeven hundred twenty-one circRNAs were identified, and the expression levels of 10 circRNAs were verified by quantitative real-time PCR (qRT–PCR) and found to be in accordance with the RNA-seq data, suggesting that the RNA-seq data were reliable. Then, the sequence length, category, sequence composition and the relationship between the parent genes of the circRNAs were explored. A total of 147 circRNAs were differentially expressed in the sex change process, and GO and KEGG analyses revealed that some differentially expressed (such as novel_circ_0000659, novel_circ_0004005 and novel_circ_0005865) circRNAs were closely involved in sex change. Furthermore, expression pattern analysis demonstrated that both circSnd1 and foxl2 were downregulated in the process of sex change, which was contrary to mal-miR-135b. Finally, dual-luciferase reporter assay and RNA immunoprecipitation showed that circSnd1 and foxl2 can combine with mal-miR-135b and mal-miR-135c. These data revealed that circSnd1 regulates foxl2 expression in the sex change of ricefield eel by acting as a sponge of mal-miR-135b/c.ConclusionOur results are the first to demonstrate that circRNAs have potential effects on sex change in ricefield eel; and circSnd1 could regulate foxl2 expression in the sex change of ricefield eel by acting as a sponge of mal-miR-135b/c. These data will be useful for enhancing our understanding of sequential hermaphroditism and sex change in ricefield eel or other teleosts.

A new species of deep‐sea torquaratorid enteropneust (Hemichordata): A sequential hermaphrodite with exceptionally wide lips

AbstractSpecimens of a new species of torquaratorid acorn worm (Hemichordata, Enteropneusta) were video recorded and subsequently collected at abyssal depths in the eastern North Pacific at sites ranging from Oregon to northern Mexico. These worms are described here as Yoda demiankoopi n. sp. by molecular and morphological methods. The new species differs from its only described congener, Yoda purpurata, in three ways. First, the lips are extremely wide and indented by a deep ciliary groove for ingesting substrate and conveying it to the mouth. Second, a connective tissue bulge of unknown significance runs mid‐dorsally along the hepatic and posthepatic regions of the intestine. Third, the posthepatic intestine is strikingly sinuous and packed with gut contents presumably undergoing digestion for extended periods between infrequent defecations. Yoda demiankoopi n. sp. is hermaphroditic, a character so far known only for the genus Yoda in the entire class Enteropneusta. The gonads of each adult worm comprise hundreds of ovaries (each containing a single oocyte) and hundreds of testes located just beneath the dorsal epidermis of the anterior trunk and associated genital wings. In any given animal, at any given time, gametes of only one sex or the other become fully mature. Thus, the worm is a sequential hermaphrodite, alternately spawning purely as a female or purely as a male.

Potential Impact of Climate Change on Fish Reproductive Phenology: A Case Study in Gonochoric and Hermaphrodite Commercially Important Species from the Southern Gulf of Mexico

In tropical regions, temperature is the fundamental environmental factor controlling the reproduction-related physiological activities of fish. Tropical fish are particularly sensitive to climate change since they develop in a relatively stable thermal environment. A review was done to assess the potential effect of temperature rise on reproduction and population structure in the commercially important hermaphrodite grouper and wrasse species, and in gonochoric snapper species in the southern Gulf of Mexico. Temperature increase can disturb the aromatase synthesis and/or activity, which can affect the reproductive cycle and sexual differentiation in all studied species and the sexual inversion process in sequential hermaphrodites. Moreover, a mistiming or discontinuity in spawning seasonality could occur, with an alteration in the sex ratio in favor of males and a consequent reduction in populations’ fecundity. Furthermore, if the level of fishing exploitation enhances species’ sensitivity to environmental changes, then the stock of red grouper Epinephelus morio would be more affected by temperature increases than other species because it is the only fish population in the Campeche Bank currently assessed as overexploited.

Delayed effect of low rearing temperature on gonadal DNA methylation in juvenile barramundi (Lates calcarifer)

Sex differentiation in many gonochoristic fish is highly responsive to temperature treatment. In some species, exposure to high or low temperatures during primary gonadal development induces phenotypic reversal of an otherwise genetically encoded sex. These changes in sexual phenotype occur in the absence of changes in genotype and are often accompanied by epigenetic modifications, such as DNA methylation. It is unknown if sequentially hermaphroditic fish exhibit similar temperature sensitivity to what has been shown in gonochoristic species; however, sex-specific differences in DNA methylation have been observed. The barramundi (Lates calcarifer) is a protandrous (male-first) sequential hermaphrodite that exhibits sex-specific DNA methylation patterns. To examine the effect of temperature on DNA methylation and primary gonadal differentiation in a sequential hermaphrodite, sexually immature barramundi were exposed to high (34 °C), control (29 °C) low (24 °C) and fluctuating (25–33 °C) temperatures from 10 to 90 days post hatch, and then on-reared at 29 °C for 12 months. At 6 months and 12 months, individuals were sampled, and their gonads examined for evidence of changes in DNA methylation and/or gonadal differentiation. Male-specific DNA methylation patterns and advanced testis development were observed at 12 months but were absent at 6 months, suggesting that low temperature treatment had a delayed effect on the gonads of juvenile barramundi. Additionally, there was an initial, but not lasting, negative effect of low temperature treatment on fish length and weight, indicating that compensatory growth may have occurred. This research provides the first evidence for an effect of temperature on gonadal DNA methylation and primary sexual development in a sequential hermaphrodite. A refinement of treatment timing and intensity could lead to the development of a hormone-free method of sex control for this widely cultured species.

Identification, characterization and functional analysis of gonadal long noncoding RNAs in a protogynous hermaphroditic teleost fish, the ricefield eel (Monopterus albus)

BackgroundAn increasing number of long noncoding RNAs (lncRNAs) have been found to play important roles in sex differentiation and gonad development by regulating gene expression at the epigenetic, transcriptional and posttranscriptional levels. The ricefield eel, Monopterus albus, is a protogynous hermaphroditic fish that undergoes a sequential sex change from female to male. However, the roles of lncRNA in the sex change is unclear.ResultsHerein, we performed RNA sequencing to analyse lncRNA expression patterns in five different stages of M. albus development to investigate the roles of lncRNAs in the sex change process. A total of 12,746 lncRNAs (1503 known lncRNAs and 11,243 new lncRNAs) and 2901 differentially expressed lncRNAs (DE-lncRNAs) were identified in the gonads. The target genes of the DE-lncRNAs included foxo1, foxm1, smad3, foxr1, camk4, ar and tgfb3, which were mainly enriched in signalling pathways related to gonadal development, such as the insulin signalling pathway, MAPK signalling pathway, and calcium signalling pathway. We selected 5 highly expressed DE-lncRNAs (LOC109952131, LOC109953466, LOC109954337, LOC109954360 and LOC109958454) for full length amplification and expression pattern verification. They were all expressed at higher levels in ovaries and intersex gonads than in testes, and exhibited specific time-dependent expression in ovarian tissue incubated with follicle-stimulating hormone (FSH) and human chorionic gonadotropin (hCG). The results of quantitative real-time PCR (qRT-PCR) analysis and a dual-luciferase assay showed that znf207, as the gene targeted by LOC109958454, was expressed in multiple tissues and gonadal developmental stages of M. albus, and its expression was also inhibited by the hormones FSH and hCG.ConclusionsThese results provide new insights into the role of lncRNAs in gonad development, especially regarding natural sex changes in fish, which will be useful for enhancing our understanding of sequential hermaphroditism and sex changes in the ricefield eel (M. albus) and other teleosts.

Transcriptome Analysis Reveals the Role of GA3 in Regulating the Asynchronism of Floral Bud Differentiation and Development in Heterodichogamous Cyclocarya paliurus (Batal.) Iljinskaja.

Cyclocarya paliurus is an important medical plant owing to the diverse bioactive compounds in its leaves. However, the heterodichogamy with female and male functions segregation within protandry (PA) or protogyny (PG) may greatly affect seed quality and its plantations for medicinal use. To speculate on the factor playing the dominant role in regulating heterodichogamy in C. paliurus, based on phenotypic observations, our study performed a multi comparison transcriptome analysis on female and male buds (PG and PA types) using RNA-seq. For the female and male bud comparisons, a total of 6753 differentially expressed genes (DEGs) were detected. In addition, functional analysis revealed that these DEGs were significantly enriched in floral development, hormone, and GA-related pathways. As the dominant hormones responsible for floral differentiation and development, gibberellins (GAs) in floral buds from PG and PA types were quantified using HPLC-MS. Among the tested GAs, GA3 positively regulated the physiological differentiation (S0) and germination (S2) of floral buds. The dynamic changes of GA3 content and floral morphological features were consistent with the expression levels of GA-related genes. Divergences of GA3 contents at S0 triggered the asynchronism of physiological differentiation between male and female buds of intramorphs (PA-M vs. PA-F and PG-F vs. PG-M). A significant difference in GA3 content enlarged this asynchronism at S2. Thus, we speculate that GA3 plays the dominant role in the formation of heterodichogamy in C. paliurus. Meanwhile, the expression patterns of GA-related DEGs, including CPS, KO, GA20ox, GA2OX, GID1, and DELLA genes, which play central roles in regulating flower development, coincided with heterodichogamous characteristics. These results support our speculations well, which should be further confirmed.

Protogynous functional hermaphroditism in the North American annual killifish, Millerichthys robustus

Sex change (sequential hermaphroditism) has evolved repeatedly in teleost fishes when demographic conditions mediate fundamentally different sex-specific returns for individuals of particular age and size. We investigated the conditions for potential sex change in an annual killifish (Millerichthys robustus) from temporary pools in Mexico. In natural populations, we detected adults with intersex colouration and gonads. Therefore, we experimentally tested whether this apparent sex change can be generated by manipulation of ecological and social conditions, rather than being caused by environmental disturbance. We demonstrated functional protogynous (female-to-male) sex change in 60% replicates, when groups of five females interacted and had a visual and olfactory cue of a male. Only one female changed sex in any given replicate. The sex change never occurred in isolated females. Protandrous (male-to-female) hermaphroditism was not recorded. We characterized gradual changes in behaviour, colouration and gonad structure during the sex change process. The first behavioural signs of sex change were observed after 23 days. Secondary males spawned successfully after 75 days. We discuss the adaptive potential of sex change in short-lived annual fishes through the seasonal decline of males, and during colonization of new habitats. This is the first observation of functional hermaphroditism in an annual killifish.

Switches, stability and reversals in the evolutionary history of sexual systems in fish

Sexual systems are highly diverse and have profound consequences for population dynamics and resilience. Yet, little is known about how they evolved. Using phylogenetic Bayesian modelling and a sample of 4614 species, we show that gonochorism is the likely ancestral condition in teleost fish. While all hermaphroditic forms revert quickly to gonochorism, protogyny and simultaneous hermaphroditism are evolutionarily more stable than protandry. In line with theoretical expectations, simultaneous hermaphroditism does not evolve directly from gonochorism but can evolve slowly from sequential hermaphroditism, particularly protandry. We find support for the predictions from life history theory that protogynous, but not protandrous, species live longer than gonochoristic species and invest the least in male gonad mass. The distribution of teleosts’ sexual systems on the tree of life does not seem to reflect just adaptive predictions, suggesting that adaptations alone may not fully explain why some sexual forms evolve in some taxa but not others (Williams’ paradox). We propose that future studies should incorporate mating systems, spawning behaviours, and the diversity of sex determining mechanisms. Some of the latter might constrain the evolution of hermaphroditism, while the non-duality of the embryological origin of teleost gonads might explain why protogyny predominates over protandry in teleosts.

Does the Presence of Boring Sponges Alter Timing of Sex Change in Slipper Shell Snails, Crepidula fornicata?

AbstractThe Atlantic slipper limpet, Crepidula fornicata, is a sequential hermaphrodite whose size at sex change is plastic with respect to social and population cues. As an organism allocates energy between growth, reproduction, and maintenance, the increased cost of one process may affect another. Thus, C. fornicata affected by a stressor might have to alter the balance of energy allocation, potentially leading to changes in the timing of sex change. One such biotic stressor, the boring sponge Cliona celata, has been demonstrated to affect growth and condition of numerous molluscs. In this study, we explored whether the presence of the boring sponge affected the rate of sex change for C. fornicata, using both field surveys and an in situ manipulation. Population surveys suggested that while boring sponges may reduce tissue condition of slipper limpets, this relationship is highly variable and likely confounded by site variables. Using population metrics (size at sex, L50), the presence of a boring sponge did not appear to affect sex change. Likewise, during the in situ experiment where we manipulated stack sex ratios, we did not find any differences in the timing of sex change between male-male and male-female stacks, even though C. fornicata without sponges grew significantly faster. Thus, results from field surveys and our in situ experiment suggest that sex change in this species appears robust to biotic stressors. This study suggests that C. fornicata will undergo sex change when conditions dictate, even if it is experiencing some level of biotic stress, a strategy that likely allows it to maximize lifetime reproductive output.

SEX REVERSAL IN ANIMAL KINGDOM : SPECIAL EMPHASIS ON ROLE OF STEROID HORMONES

Sexual fate is no longer seen as an irreversible deterministic switch set during early embryonic development but as an ongoing battle for primacy between male and female developmental trajectories. That sexual fate is not final and must be actively maintained via continuous suppression of the opposing sexual network creates the potential for flexibility into adulthood. In many Animals, sexuality is not only extremely plastic, but sex change is a usual and adaptive part of the life cycle. Sequential hermaphrodites begin life as one sex, changing sometime later to the other, and include species capable of protandrous (male- to-female), protogynous (female-to-male), or serial (bidirectional) sex change. Natural sex change involves coordinated transformations across multiple biological systems, including behavioural, anatomical, neuroendocrine, and molecular axes. This can be caused by human pollutants, including herbicides, which can act as estrogen promoters or inhibitors, which would respectively increase or decrease the number of female offspring, through controlling aromatase. This review project paper highlights the biological processes underlying this amazing transformation, Gonadal restructuring among germinal and somatic cell interaction, Neuroendocrine control of sex change and Stress response and role of Steroid hormones-balance between 17beta-estradiol & 11- ketotestosterone in sex changes, Endocrine disruption on Changing of Sexual Behaviour, which remains poorly understood, but where new genomic technologies are significantly advancing our understanding of how sex change is initiated and progressed at Hormonal and molecular levels. Knowledge of how a usually committed developmental process remains plastic in sequentially hermaphroditic fishes, Amphibians and Birds are relevant to understanding the evolution and functioning of sexual developmental systems in vertebrates generally, as well as pathologies of sexual development in mammals, some time observed in nematodes and Gastropodes also. Keywords- sex change, hormones, hermaphrodism

Masculinization of Adult Gambusia holbrooki: A Case of Recapitulation of Protogyny in a Gonochorist?

Simple SummaryAlthough gonochoristic fish express one sex or the other in adulthood, some adults display traits similar to those of their opposite sex, suggesting plasticity similar to hermaphrodites. To fully test this potential in the eastern mosquitofish, a gonochorist, two adult stages of females were fed 17α-Methyltestosterone incorporated feed (0–200 mg/kg diet) for 50 days. The hormone (particularly at 50 mg/kg diet) stimulated the formation of complex male copulatory structures and testicular tissue as well as upregulated expression of Anti-Müllerian Hormone gene and altered the behavior from females to males. Collectively, we infer that Gambusia holbrooki retains potential for sex reversal at adulthood, similar to what occurs naturally in hermaphroditic fish and can provide an ideal system to investigate these mechanisms in a regulated fashion.17α-Methyltestosterone (MT) is a synthetic steroid that has been widely used to masculinize many fish species when administered early during larval development, however, reports on its efficacy on adults is limited. To this end, this study investigated the efficacy of MT in the masculinization of the eastern mosquitofish (G. holbrooki) at two adult stages (maiden and repeat gravid females). The treated females were fed control or respective MT incorporated feed (0–200 mg/kg diet) for 50 days. Effects of the hormone on secondary sexual characteristics, internal gonad morphology, expression of the Anti-Müllerian Hormone (amh) gene and sexual behavior of the treated females were investigated. The results showed that MT at the dose of 50 mg/kg feed stimulated secondary sexual character development, upregulated expression of amh, formation of testicular tissue and a shift in the behavior similar to those of normal males, prominently so in treated maiden gravid females. Post-treatment, long-term observations indicated that only two masculinized females reverted back to being females and gave birth to young. Induction of masculinizing effects in most individuals suggests that the sexual phenotype of this species appears to be highly plastic with potential to sex reverse at adulthood. This in combination with its small size and short reproductive cycle could provide an ideal system to explore the mechanisms of sequential hermaphroditism in fish and contribute to genetic control of this pest fish.

Broodstock development, final oocyte maturation and breeding of the newly described sparid fish, Fanged seabream, Sparidentex jamalensis Amir, Siddiqui & Masroor, 2014

Broodstock development, induced maturation and breeding of the newly described seabream, Sparidentex jamalensis collected from Kali estuary, Karnataka, India were achieved successfully for the first time. Taxonomy of the fish was confirmed employing morphological and molecular tools. Majority of the brooders collected were in the 20–30 cm length class (140–510 g) and were ideal for developing matured broodstock. Periodic microscopic observation of ovarian biopsy indicated progressive gonadal development in the broodstock. The broodstock developed for this protandrous hermaphrodite consisted of females having maturing oocytes and males with oozing milt during the breeding season. Final maturation and spawning of the females (520 ± 8 g; ova diameter above 400 µm) was achieved using cholesterol-based LHRH analogue pellets (50 µg/kg fish) and the males (450 ± 54 g) were not treated with hormones. Pelagic fertilized eggs (720 ± 8 µm) with a single oil globule were obtained with an absolute fecundity of 0.42 ± 0.06 million/kg fish and a fertilization rate of 82 ± 2.4%. Major embryological stages were recorded and the fertilized eggs hatched after 18–20 hours with 80 ± 4.6% hatching rate at 28°C. The newly hatched planktonic larvae measured 1.8 ± 0.12 mm in total length. Mouth opening of the larvae was observed on second day post hatch (dph). Resorption of the yolk sac was observed on third dph. These results will act as a baseline for developing a breeding programme for this species.