Male Sex Change Research Articles

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.

Epigenetics underpins phenotypic plasticity of protandrous sex change in fish.

Phenotypic plasticity is an important driver of species resilience. Often mediated by epigenetic changes, phenotypic plasticity enables individual genotypes to express variable phenotypes in response to environmental change. Barramundi (Lates calcarifer) are a protandrous (male‐first) sequential hermaphrodite that exhibits plasticity in length‐at‐sex change between geographic regions. This plasticity is likely to be mediated by changes in DNA methylation (DNAm), a well‐studied epigenetic modification. To investigate the relationships between length, sex, and DNAm in a sequential hermaphrodite, here, we compare DNAm in four conserved vertebrate sex‐determining genes in male and female barramundi of differing lengths from three geographic regions of northern Australia. Barramundi first mature as male and later sex change to female upon the attainment of a larger body size; however, a general pattern of increasing female‐specific DNAm markers with increasing length was not observed. Significant differences in DNAm between males and females of similar lengths suggest that female‐specific DNAm arises rapidly during sex change, rather than gradually with fish growth. The findings also reveal that region‐specific differences in length‐at‐sex change are accompanied by differences in DNAm and are consistent with variability in remotely sensed sea temperature and salinity. Together, these findings provide the first in situ evidence for epigenetically and environmentally mediated sex change in a protandrous hermaphrodite and offer significant insight into the molecular and ecological processes governing the marked and unique plasticity of sex in fish.

Structural changes in the ovotestis of the bidirectional hermaphrodite, the blue-banded goby (Lythrypnus dalli), during transition from ova production to sperm production

Hermaphroditism is widespread in fishes and has been extensively studied in many groups. The process whereby the gonad changes morphology in sequential hermaphrodites (i.e., female to male sex change or the reverse) is well documented. However, gonadal changes in bidirectional hermaphroditic fishes, in which gamete production can shift repeatedly, has received little attention. Here we examine the transition process in the bidirectional sex-changer Lythrypnus dalli, as it goes from producing eggs to producing sperm. In the ova-producing phase, the majority of the ovotestis consists of vitellogenic oocytes. Gonad transition is initiated with the break-down and reabsorption of mature oocytes. This is then followed by the proliferation of spermatogenic tissue from the dorsal and ventral regions of the ovotestis. The proliferation of spermatogenic tissue continues until it makes up the majority of the ovotestis with the reminder of the gonad comprising previtellogenic oocytes. We were able to define five transitional stages characterized by the relative area of the ovotestis made up of oogenic, spermatogenic, and atretic tissue. In only one other species of bidirectional sex-changing fish, Eviota epiphanes, has similar examination of transitional morphology been performed. Lythrypnus dalli and E. epiphanes are both in the teleost family Gobiidae, and closely related. It has been hypothesized that these two lineages have independently evolved the ability to change sex. Here we provide a comparison of the transition process between L. dalli and E. epiphanes, which highlights the conserved and novel elements and provided insights into differences in their life histories.

Induction of Gonadal Development in Protogynous Grouper with Orally Delivered FSH DNA.

The availability of sexually mature fish often dictates the success of its captive breeding. In this study, we induced reproductive development in juvenile protogynous tiger grouper through oral administration of a plasmid (p) containing an engineered follicle-stimulating hormone (FSH). An expression construct (pcDNA3.1) was designed to express a single-chain FSH consisting of giant grouper FSH β-subunit and glycoprotein subunit-α (CGα), linked by the carboxy-terminal peptide (CTP) sequence from the human chorionic gonadotropin (hCG). Single oral delivery of pFSH encapsulated in liposome and chitosan to tiger grouper yielded a significant increase in plasma FSH protein level after 4days. Weekly pFSH feeding of juvenile tiger groupers for 8weeks stimulated ovarian development as indicated by a significant increase in oocyte diameter and progression of oocytes to cortical alveolar stage. As the pFSH treatment progressed from 20 to 38weeks, female to male sex change was initiated, characterized by oocyte regression, proliferation of spermatogonial cells, and occurrence of spermatogenic cysts. It was also associated with significantly lower mRNA expression of steroidogenic genes (cyp11b, cyp19a1a, and foxl2) and basal plasma levels of sex steroid hormones 17β-estradiol (E2), testosterone (T), and 11-ketotestosterone (11KT). Results suggest that pFSH stimulates ovarian development up to cortical alveolar stage and then initiates sex change in tiger grouper. These findings significantly contribute to our knowledge on the role of FSH in the development of protogynous hermaphroditic fish. This study is the first to demonstrate induction of reproductive development in fish through oral delivery of plasmid gonadotropin.

Endoscopic submucosal dissection for gastric indefinite for neoplasia: which lesions should be resected?

The management plan for gastric indefinite for neoplasia is undetermined, and endoscopic forceps biopsy might be inconclusive in ascertaining whether a resection is required. This study aimed to evaluate the clinical outcomes of endoscopic submucosal dissection (ESD) for gastric indefinite for neoplasia and to identify the factors highly predictive of true neoplasia. This retrospective study was conducted in a single, tertiary, referral hospital between November 2008 and December 2015. A total of 109 gastric indefinite for neoplasia lesions from endoscopic forceps biopsy that were resected by ESD were included in the study. The clinical outcomes and endoscopic factors for prediction of true neoplasia were analyzed. A total of 99 patients (90.8%) were diagnosed with definite neoplasia after ESD and were classified as category 3 (n = 42), category 4 (n = 50), and category 5 (n = 7) according to the revised Vienna classification. The mean age of the patients was 65.8 ± 9.8years. The mean lesion size was 10.7 ± 6.1mm. The patient population predominantly consisted of male patients (70.6%). The en bloc and complete endoscopic resection rates were 98.2% and 94.5%, respectively. Factors associated with true neoplastic lesions were male sex (odds ratio [OR] 8.596, p = 0.008) and lesion size ≥ 5mm (OR 11.355, p = 0.003). Factors associated with category 4-5 were male sex (OR 3.165, p = 0.021) and erosive change (OR 2.841, p = 0.031). Endoscopic resection for indefinite for neoplasia with larger lesions size and erosive changes, especially in males, should be considered when possible.

Cloning, expression and functional characterization of a novel luteinizing hormone receptor in the orange-spotted grouper, Epinephelus coioides

Luteinizing hormone receptor (LHR) plays a critical role in reproduction by mediating LH signaling in the gonad. In this study, we cloned a novel lhr gene from the orange-spotted grouper, named glhr2. The cloned complete open reading frame sequence of glhr2 was 2082 bp in length, encoding a protein of 693 amino acids, sharing approximately 50% amino acid identity with glhr1. glhr1 and glhr2 were primarily expressed in gonad, brain and hypothalamus with low expression in other tissues such as gill, spleen, etc. The expressions of both glhr1 and glhr2 increased during vitellogenesis, while decreased during natural female to male sex change. The two gLHRs both could be activated by equine LH or human chorionic gonadotropin, but not by human follicle stimulating hormone. Both gLHR1 and gLHR2 activation stimulated the expression of cAMP response element driven reporter gene in a dose-dependent manner, while gLHR2 but not gLHR1 also activated serum response element driven reporter gene expression. This was the first study to demonstrate that two active LHRs exist in fish with possible different functional roles.

Gender reassignment surgery: Our experience of 20 cases

IntroductionGender Reassignment Surgery is a general term used to describe all procedures related to surgically converting patients of Gender identity disorder into their desired sex. This may be mastectomy, vaginectomy, penile reconstruction etc in female to male, or breast augmentation, vaginal reconstruction etc in male to female. Material and methodWe share our experience of twenty cases of Gender identity disorder operated over a period of seven years at our hospital with a minimum follow up of six months ResultsThe most commonly done procedure was mastectomy in female to male sex change followed by vaginal reconstruction in male to female. ConclusionGender identity disorder is becoming increasingly common nowadays with patients coming forward for surgical intervention. These patients need a sensitive approach and teamwork between the Plastic Surgeon, Psychiatrist, Gynecologist and the Endocrinologist.

Reproductive life history of the introduced peacock grouper Cephalopholis argus in Hawaii.

This research investigated the reproductive biology (sex ratio, hermaphroditic pattern, size and age at maturity) of Cephalopholis argus, known locally in Hawaii by its Tahitian name roi. The results suggest that C. argus exhibits monandric protogyny (female gonad differentiation with female to male sex change) with females reaching sexual maturity at 1.2 years (95% c.i.: 0.6, 1.6) and 20.0 cm total length (LT ; 95% c.i.: 19.6, 21.2). The female to male sex ratio was 3.9:1. The average age and LT at sex change was 11.5 years (95% c.i.: 11.1, 12.9) and 39.9 cm (95% c.i.: 39.5, 41.2), respectively. Current information on spawning seasonality of this species is incomplete, but based on the occurrence of spawning capable and actively spawning females, spawning probably takes place from May to October. Evidence of lunar spawning periodicity was found, with an increased proportion of spawning capable and actively spawning females, and an increased female gonado-somatic index during first quarter and full-moon phases. This information fills a valuable information gap in Hawaii and across the species' native range.

Induction of Primary Male in Juvenile Red Spotted Grouper Epinephelus akaara by Immersion of 17α-Methyltestosterone

We investigated the androgenic effects of 17α- methyltestosterone (MT) on gonadal sex reversal in juvenile red spotted grouper Epinephelus akaara. The fish were immersed in 17α-MT at 1 and 5 mg/L. Treatment method of 17α-MT was once weekly for 4 and 8 weeks. Fish were sampled at 12 months after end of the treatment period in order to histological analysis. At the initiation of an experiment (70 day after hatching), juvenile red spotted grouper have the paired primordial gonads with somatic cells bellow kidney in the posterior portion of the body cavity. Formation of ovarian cavity indicates that the ovarian differentiation beginning at 70 DAH in red spotted grouper. At 12 months after end of the treatment period, control group, 17α-MT 1 mg/L treatment group for 4 and 8 weeks, and 17α-MT 5 mg/L treatment group for 4 weeks were all female. However, sex-changed males without ovarian cavity were observed in the 17α-MT 5 mg/L treatment group for 8 weeks. In grouper, we firstly reported that the red spotted grouper be able to induce the primary males by hormone treatment prior to gonadal sex differentiation.

Bidirectional sex change in the magenta dottyback Pictichromis porphyrea: first evidence from the field in Pseudochromidae

Protogyny and protandry are well known among fishes, but bidirectional sex change has been reported from only 25 species in six families; field evidence is limited to nine species in four families. The present study confirmed bidirectional sex change of the magenta dottyback Pictichromis porphyrea in the field, the first field evidence for this phenomenon in the family Pseudochromidae. Field experiments were conducted on the patch reefs of Sesoko Island, Okinawa. The sex ratio was female-biased, and males were significantly larger than females. These features are common to protogynous species with a polygynous mating system, although mating behavior was not observed. When members of the opposite sex were removed from a certain area, nearly half of the tagged fish moved to different sites. Among the fish that moved from the original site, four females changed to male, and two males changed to female. Gamete release was confirmed both before and after the sex change. The sex-changed males were larger than their neighbors, whereas the sex-changed females were smaller than their neighbors, suggesting that the sex change was socially controlled in both directions.

DSD Due to 5α-Reductase 2 Deficiency - from Diagnosis to Long Term Outcome

Most of the patients with 5α-RD 2 deficiency are reared in the female social sex due to their severely undervirilized external genitalia but ~60% who have not been submitted to orchiectomy in childhood undergo male social sex change at puberty. In our cohort of 30 cases from 18 families, all subjects were registered in the female social sex except for two children-one who had an affected uncle and the other who was diagnosed before being registered. The majority of the patients were satisfied with the long-term results of their treatment and surprisingly, penile length was not associated with satisfactory or unsatisfactory sexual activity. Steroid 5α-RD2 deficiency should be included in the differential diagnosis of all newborns with 46,XY DSD with normal testosterone production before gender assignment or any surgical intervention because these patients should be considered males at birth.

Sexual patterns and protogynous sex reversal in the rusty parrotfish, Scarus ferrugineus (Scaridae): histological and physiological studies

Gonadal histology confirmed that Scarus ferrugineus is a diandric protogynous fish. The process of protogynous sex reversal was investigated through histological observations on the gonads of females changing sex to male. This process was divided into three stages on the basis of changes in the structure of the germinal and somatic elements. Ovaries of functional females (stages IV-V) were filled with vitellogenic oocytes during the breeding season but contained no trace of spermatogenic tissue. During post-spawning period, the remaining vitellogenic oocytes began to degenerate and accompanied by a drop in plasma levels of estradiol-17β. At the commencement of sex change, previtellogenic oocytes began to degenerate and stromal cell aggregation was observed in the central region of the lamellae. At mid-reversal stage, steroid-producing cells (Leydig cells) developed at the border of the stromal aggregate and spermatogonial cysts appear at the periphery of lamellae. Finally, sex change to secondary males was considered complete, with the beginning of active spermatogenesis and spermiation. Plasma levels of testosterone remained low throughout the sex change, but II-KT increased rapidly parallel to the increased number of Leydig cells while the level of estradiol-17β decreased. The results indicate also that the sex-changed males had higher level of II-KT than primary males, while primary males had higher level of testosterone. Histological examination revealed that testes of primary and secondary males are almost identical in organization of the spermatogenic cysts, association of sertoli cells, and developing germ cells but differ in clustering and development of Leydig cells.

Effects of 17α-Methyltestosterone on Growth and Induced Sex Change in Longtooth Grouper Epinephelus bruneus (Bloch)

We examined the effects of 17<TEX>${\alpha}$</TEX>-methyltestosterone (MT) on growth and induced sex change in the longtooth grouper Epinephelus bruneus. The growth rate for body weight (GRW) and specific growth rate (SGR) of the group injected with MT over 8 weeks were significantly higher than those of the sham-injected control group, the group injected over 4 weeks, and the control group. Of the orally administrated groups, the GRWs of the control group and the group given 1 kg of feed with 2.0 mg of MT were highest and did not significantly differ from one another. For SGR, the treatment groups differed significantly, and the SGR of the control group was higher than those of the other groups (P<0.05). The condition factor (CF) of the group injected over 4 weeks was higher than those injected over 8 weeks, the sham-injected control group over 8 weeks, and the control group. The CF did not significantly differ between the sham-injected control group over 8 weeks and the injected group over 8 weeks, but these two groups differed from the control group (P<0.05). The CFs of the groups given 1 kg of feed with 0.5, 1.0, and 2.0 mg of MT were significantly higher than that of the control group (P<0.05). The feed efficiency ratio was not significantly affected by MT administration. Most of the experimental groups receiving MT developed many unidentified germ cell cysts and perinucleolus oocytes, although neither spermazoa cells nor sex-changed males were observed in any of the treatments.

Reproductive biology and implications for management of the spangled emperor Lethrinus nebulosus in the southern Arabian Gulf

The reproductive biology of the spangled emperor Lethrinus nebulosus in the southern Arabian Gulf was determined from the examination of 781 individuals collected between September 2008 and August 2009. There was no histological evidence of adult sex change, and sex ratios did not differ significantly from unity across all size and age classes. Testes had an ovarian structure and a remnant lumen which was not used for sperm transport; furthermore, residual oocytes were observed in the testes of some immature, resting and developing males. A dramatic change in the sex ratio of the smallest and youngest size and age classes suggested that juvenile female to male sex change occurred between 21·0 cm fork length (L(F)) and 24·0 cm L(F) at 1 year of age. The combination of histological evidence with the sexual composition of the size and age structures suggests a non-functional protogynous hermaphroditic sexual pattern, which is analogous to functional gonochorism. The spawning season was well defined, occurring once a year during March, April and early May. Peaks in spawning occurred after full moons, there was a cessation in spawning activity after new moons and spawning was completed within three lunar cycles. The distribution of males over the entire size and age ranges and the absence of inactive mature females during the spawning season suggested that the population was not constrained by sperm limitation. Size-specific and age-specific reproductive potential indicated that conventional regulations that equate the mean size at first capture to sexual maturation are unsuitable for the management of L. nebulosus. The maximum recorded age (11 years), small mean size and young age at sexual maturation (L(m50) = 26·7 cm L(F), 2·1 years, for females and 19·4 cm L(F), 0·5 years, for males) may be a direct result of intensive demersal fishing in the southern Arabian Gulf.

Isolation, characterization and expression analyses of FSH receptor in protogynous grouper

Follicle-stimulating hormone (FSH) and its receptor (FSHR) play important roles in spermatogenesis. We cloned and characterized the honeycomb grouper Epinephelus merra FSHR ( EmFSHR) to elucidate its role in the protogynous sex change in groupers. Reverse transcription-polymerase chain reaction (RT-PCR) analysis suggested that EmFSHR was expressed exclusively in the gonads. In situ hybridization showed the distribution of EmFSHR in the granulosa cells of previtellogenic oocytes and Leydig cells in the testis. Quantitative reverse transcription PCR (RT-qPCR) analysis of gonadal EmFSHR transcripts during the process of sex change indicated that the lowest levels were found in the female phase before sex change. EmFSHR transcripts increased during the early transitional phase, when oocytes began to degenerate in parallel with the initiation of gonial germ cell differentiation into spermatogonia. A dramatic increase in EmFSHR transcription occurred during the late transitional phase, when the gonad contained numerous proliferating male germ cells and many degenerated oocytes. EmFSHR expression remained high until the transformation from ovary to testis was complete. The data reveal that female to male sex change is associated with the upregulation of EmFSHR transcripts, and that this upregulation may be responsible for the development of testicular tissue and the progression of spermatogenesis. Furthermore, how the upregulation of EmFSHR is controlled in the initiation of sex change remains to be elucidated.

Life history characteristics of the protogynous parrotfish Calotomus japonicus from northwest Kyushu, Japan

In this study, we examined the life history characteristics of the parrotfish Calotomus japonicus, using individuals collected between May 2003 and May 2008 off the Nagasaki Peninsula in northwest Kyushu, Japan. Age determinations were performed using scales. Marginal increment analysis revealed that growth rings were formed annually around July. Growth in both sexes was fitted to the von Bertalanffy growth function (L∞ = 513, k = 0.28, t0 = 0.03, where L∞ is the theoretical asymptotic total length in mm, k is the growth rate coefficient and t0 is the theoretical time at zero length). Observed maximum age for both sexes was 8 years. We also characterized the reproductive biology of this species based on a gonadosomatic index and histological examinations of the gonads. The spawning season extends from July to October, with peak spawning activity occurring during July and August. Fish reach sexual maturity by the second year of life. Females are assumed to be multiple spawners, since we observed specimens with postovulatory follicles in ovaries containing either yolk globule oocytes or migratory nucleus oocytes. All males had secondary testes, which were characterized by the presence of an ovarian lumen structure and sperm sinuses in the gonadal wall. This indicates that all males, irrespective of whether they were initial or terminal phase males, had undergone a sexual transition. Sex change appears to occur during the spawning season, and thereafter sex-changed males are able to fertilize female eggs throughout the remainder of the current spawning season.

A Phylogenetic Test of the Size‐Advantage Model: Evolutionary Changes in Mating Behavior Influence the Loss of Sex Change in a Fish Lineage

The size-advantage model asserts that mating behavior influences the incidence and direction of sex change in animals. Selection for protogyny (female to male sex change) occurs in mating systems in which large males monopolize and pair spawn with females; however, gonochorism (no sex change) is favored when adults spawn in groups and sperm competition is present. Despite widespread empirical and theoretical support for the model, these predictions have not been tested within a phylogenetic context. Here we show that the loss of sex change within a lineage of reef fishes is influenced by evolutionary changes in two traits related to their mating behavior: mating group structure and sperm competition intensity. Phylogenetic reconstructions of the reproductive evolution of groupers (Epinephelidae) indicate that protogyny and paired spawning are the ancestral conditions for the lineage; both gonochorism and group spawning evolved independently at least four times in three different genera. Evolutionary transformations from protogyny to gonochorism (loss of sex change) are associated with equivalent transformations in mating group structure from paired to group spawning, and sperm competition is considerably higher in gonochoric species than in protogynous species. These results provide explicit phylogenetic support for predictions of the size-advantage model, demonstrating that selection for protogynous sex change decreases as mating group size and sperm competition intensity increase.

Growth acceleration, behaviour and otolith check marks associated with sex change in the wrasse Halichoeres miniatus

In protogynous sex-changing fishes, females are expected to compete for the opportunity to change sex following the loss of a dominant male and may exhibit growth and behavioural traits that help them maintain their dominant status after sex change. A male removal experiment was used to examine changes in female growth and behaviour associated with sex change in the haremic wrasse Halichoeres miniatus and to test whether any changes in growth associated with sex change were recorded in otolith microstructure. Dominant females began displaying male-characteristic behaviour almost immediately after the harem male was removed. The frequency of interactions between females increased following male removal. In contrast, feeding frequency of females decreased. The largest one to three females in each social group changed sex following male removal and exhibited an increase in growth associated with sex change. Sex changers grew more than twice as fast as non-sex changers during the experimental period. This growth acceleration may enable new sex-changed males to rapidly reach a size where they can defend the remaining harem from other males. An optical discontinuity (check mark) was present in the otoliths of sex-changed fish, and otolith accretion rate increased significantly after the check mark, corresponding with the increased growth rate of sex-changing females. Wild caught males, but not females, exhibited an analogous check mark in their otoliths and similar increases in otolith increment widths after the check. This indicates that an increase in growth rate is a regular feature of sex-change dynamics of H. miniatus.

Short term treatment with aromatase inhibitor induces sex change in the protogynous wrasse, Halichoeres trimaculatus

The purpose of this study was to specify the time when individuals are committed to female to male sex change in the protogynous wrasse, Halichoeres trimaculatus, induced by treatment with the nonsteroidal aromatase inhibitor (AI) Fadrozole. In this study, treatment with AI was carried out by providing adult females with a diet containing 500 μg AI/g food for 3 (AI-3), 5 (AI-5), and 10 days (AI-10). We examined the gonadal structure of the fishes histologically at the end of the AI treatment and 30 days after the start of the experiment. At the end of the AI treatment, all individuals in the AI-3 treated group had gonads with degeneration of yolky oocytes, indicating the onset of sex change. Most individuals in the AI-5 treated group had gonads with atretic vitellogenic oocytes, like those in AI-3 treated group, whereas most individuals in the AI-10 treated group had gonads with testicular tissue. At 30 days after the onset of the experiment, approximately 70% of the individuals in the AI-3 treated group had mature ovaries, whereas all fishes in AI-5 and AI-10 treated groups had mature testes, indicating sex change. Therefore, treatment with AI for only 5 days resulted in complete sex change. Our results also indicate that crucial events for testicular differentiation occur within 5 days from the start of AI treatment. Thus, we conclude that females are committed to change into males after 5 days of AI treatment.

Sex change of adult initial-phase male wrasse, Halichoeres trimaculatus by estradiol-17β treatment

Sex steroids are considered major regulators of sex change processes in fish. Estrogen depletion is shown to be crucial for female–male sex change initiation; however, its role in male–female sex change is largely unknown. In the present study, we examined the effects of estradiol-17β (E2) treatments on testes of initial-phase (IP) males of the three-spot wrasse (Halichoeres trimaculatus), which naturally do not undergo male–female sex change. Sexually mature IP males were fed a diet containing E2 (low, 20μg/g feed; high, 200μg/g feed) for 6 or 12 weeks, and changes in gonadal structures were examined. Percentage of sex change varied with the dosage of E2 and the duration of treatment. All individuals treated with high-dose E2 for 6 weeks had ovaries with many immature oocytes; whereas 75% of individuals treated with low-dose of E2 for 6 weeks and sampled on the 12th week had ovaries with yolky oocytes and an ovarian cavity indicating a typical mature ovary. No testicular tissue was observed in sex-reversed gonads in both treatment groups. Contrary to the previous assumptions, present results suggest that IP male wrasses have the potential to undergo male–female sex change in response to exogenous estrogen. How the presence or absence of estrogen creates sexual plasticity in gonadal germ and somatic cells remains to be clarified.