Induced Sex Change Research Articles

Assessing the feasibility of exogenous 17β-estradiol for inducing sex change in white snook, C. viridis: From growth, resting and maturation studies

This study evaluated growth, survival, and oogenesis before and after 17β-estradiol (E2) treatments. During the growth period, C. viridis reached a total length of 65 ± 4.2 cm and a weight of 2.5 ± 0.66 kg BW. To induce sex change in males, we implanted silastic tubing loaded with 0 (control), 0.5, or 1.5 mg of E2 kg−1, at days 0, 30, 60, and 90. Blood samples were collected before treatment (day 0) and on days 30, 60, 90, and 120. Initially, 23% of the selected males expressed milt. At 60 days post-treatment 13% in the control and 4.3% in both, 0.5 and 1.5 mg E2 kg−1 BW treatments. After 120 days we observed histological evidence of sex change in 50% of the histology-tagged fish in the 1.5 mg E2 kg−1 treatment. The gonadosomatic index and condition factor did not differ significantly (P > 0.05) between the control and the treatments. However, the mean individual fish weight differed significantly across all sampling times (P < 0.05). The control and 1.5 treatment groups had a 100% survival rate, while the 0.5 treatment showed a 95.6% survival rate. Steroid profiling showed high cortisol levels throughout the experiment but there was no relationship with E2 treatment or sampling point. After the first E2 dose, we observed inhibition of 11-ketotestosterone (11-KT), which persisted until the end of the experiment. At the end of a 150-day rest period, biopsy samples from the fish showed 0%, 29%, and 87% of females with primary growth oocytes in the control, 0.5, and 1.5 treatments, respectively. After 353 days of the maturation period, feminized fish did not reach vitellogenesis. The availability of C. viridis vitellogenic females after induced sex change remains unpredictable. More research is needed to encourage vitellogenesis in hormonally feminized fish of this species.

Induced Sex Reversal in Adult Males of the Protandric Hermaphrodite Centropomus undecimalis Using 17 β-Estradiol: Enhancing Management Strategies for Captive Broodstock

The common snook (Centropomus undecimalis) is a protandric hermaphrodite fish that undergoes a sex change during its life cycle. In nature, common snook females develop directly from males shortly after spawning. However, the factors triggering this process remain unknown. This knowledge gap poses challenges for managing the species in captivity. To address this, we conducted a study on sex change induction in three-year-old males using estradiol and evaluated the potential effects of photoperiod manipulation on early maturation. Four treatment groups were employed: (1) fish with estradiol + natural photoperiod; (2) fish without estradiol + natural photoperiod; (3) fish without estradiol + controlled photoperiod; and (4) fish with estradiol + controlled photoperiod. The effectiveness of these treatments was assessed through histological procedures, which allowed for the examination of the fishes’ gonads. Furthermore, the concentration of alkali labile phosphorus in fish plasma was measured and correlated with the histological results. Our findings revealed that administering 2 mg/kg estradiol implants resulted in a remarkable 100% female population within the estradiol-treated groups. No significant effect on fish maturation was observed due to the manipulated photoperiod conditions. This protocol offers improved management strategies for captive broodstock. Firstly, the concentration of estradiol used in this study proved sufficient to induce sex change in this hermaphroditic species, enabling the production of viable females at an early age and smaller size and facilitating easier broodstock manipulation. Secondly, the implementation of the alkali labile phosphorus technique allows for sex identification without the need to sacrifice the fish. In conclusion, our study provides valuable insights into sex change induction and photoperiod manipulation in common snook. The findings contribute to enhanced management practices for captive broodstock. However, further research is needed to explore the underlying mechanisms triggering sex change and to optimize protocols for long-term maintenance and successful reproduction in captivity.

An in vitro ovarian explant culture system to examine sex change in a hermaphroditic fish.

Many teleost fishes undergo natural sex change, and elucidating the physiological and molecular controls of this process offers unique opportunities not only to develop methods of controlling sex in aquaculture settings, but to better understand vertebrate sexual development more broadly. Induction of sex change in some sequentially hermaphroditic or gonochoristic fish can be achieved in vivo through social manipulation, inhibition of aromatase activity, or steroid treatment. However, the induction of sex change in vitro has been largely unexplored. In this study, we established an in vitro culture system for ovarian explants in serum-free medium for a model sequential hermaphrodite, the New Zealand spotty wrasse (Notolabrus celidotus). This culture technique enabled evaluating the effect of various treatments with 17β-estradiol (E2), 11-ketotestosterone (11KT) or cortisol (CORT) on spotty wrasse ovarian architecture for 21 days. A quantitative approach to measuring the degree of ovarian atresia within histological images was also developed, using pixel-based machine learning software. Ovarian atresia likely due to culture was observed across all treatments including no-hormone controls, but was minimised with treatment of at least 10 ng/mL E2. Neither 11KT nor CORT administration induced proliferation of spermatogonia (i.e., sex change) in the cultured ovaries indicating culture beyond 21 days may be needed to induce sex change in vitro. The in vitro gonadal culture and analysis systems established here enable future studies investigating the paracrine role of sex steroids, glucocorticoids and a variety of other factors during gonadal sex change in fish.

Rapid Induction of Female-to-Male Sex Change in Adult Zebrafish by Injection of an Aromatase Inhibitor.

Previously, we examined whether aromatase inhibitor (AI) treatment induces a sex change in adult female zebrafish. A 5-month AI treatment regime resulted in the retraction of the ovaries and testis formation. Eight weeks after changing the diet to AI-free food, a large number of normal sperm were obtained. Artificial fertilization using sperm from the sex-changed females was successful. These results demonstrated that sex plasticity remains in the mature ovaries of zebrafish. However, >7 months of treatment was necessary; thus, pairing was unsuccessful. In this study, we tried to induce sex change through the injection of an AI to shorten the time course of sex change. When the AI solution was directly injected into the abdomen of zebrafish, retraction of the ovary was induced within 2 months. The natural mating of sex-changed females with normal females was successful at 3 months. Although the fertilization rate was low, juveniles resulting from these matings developed normally. We succeeded in establishing a method for inducing sex changes in adult zebrafish within 3 months. The procedure will support the study of how sexual plasticity persists in adult zebrafish following sex differentiation and the identification of undifferentiated stem cells.

The Administration of Cortisol Induces Female-to-Male Sex Change in the Protogynous Orange-Spotted Grouper, Epinephelus coioides.

In this study, we injected cortisol into the protogynous orange-spotted grouper (Epinephelus coioides) to investigate the role of this hormone in sex change. Following injection, we evaluated gonadal changes, serum levels of steroid hormones, and sex-related gene expression during the processes of cortisol-induced sex change and cortisol withdrawal in the orange-spotted grouper. Cortisol treatment caused the degeneration of oocytes and induced sex change in a dose-dependent manner. Over the long-term, we observed a significant increase in serum 11-ketotestosterone (11-KT) levels in all cortisol-treated groups, although levels of 17β-estradiol did not change significantly. Consistent with the elevation of serum 11-KT levels, the expression of genes related to testicular development was also significantly up-regulated in the cortisol-treated groups. Based on our results, we propose that cortisol may trigger masculinization by inducing the synthesis of 11-KT and by directly activating the expression of sex-related genes. Furthermore, we found that cortisol-induced sex change was not permanent and could be reversed after the withdrawal of cortisol treatment.

A highly efficient method of inducing sex change using social control in the protogynous orange-spotted grouper (Epinephelus coioides)

In this study, a highly efficient method of inducing sex change using social control in the protogynous orange-spotted grouper (Epinephelus coioides) was developed. A series of experiments were carried out to investigate the influence of social unit size and seasonality on the rate of sex change rate in the orange-spotted grouper. The results revealed that the removal of male fish in social units with three females during the pre-breeding and breeding seasons was the fastest method ever recorded for inducing an artificial sex change in orange-spotted grouper. The data indicated that a sex change generally occurred in the largest female in the social unit. A sharp increase in levels of androgen and cortisol in serum are proposed as a marker of the onset of a female-to-male sex change. Using the method described in this study, a sex change from female to male occurred within two to four weeks of removing males from the social unit. To examine sperm fertility, the fertilization rate of males obtained by induced sex change was analyzed. The results revealed that males obtained by this method can successfully fertilize mature eggs. This method could address the scarcity of male groupers required for spawning in captivity, and would promote the development of grouper aquaculture.

Active feminization of the preoptic area occurs independently of the gonads in Amphiprion ocellaris

Sex differences in the anatomy and physiology of the vertebrate preoptic area (POA) arise during development, and influence sex-specific reproductive functions later in life. Relative to masculinization, mechanisms for feminization of the POA are not well understood. The purpose of this study was to induce sex change from male to female in the anemonefish Amphiprion ocellaris, and track the timing of changes in POA cytoarchitecture, composition of the gonads and circulating sex steroid levels. Reproductive males were paired together and then sampled after 3 weeks, 6 months, 1 year and 3 years. Results show that as males change sex into females, number of medium cells in the anterior POA (parvocellular region) approximately double to female levels over the course of several months to 1 year. Feminization of gonads, and plasma sex steroids occur independently, on a variable timescale, up to years after POA sex change has completed. Findings suggest the process of POA feminization is orchestrated by factors originating from within the brain as opposed to being cued from the gonads, consistent with the dominant hypothesis in mammals. Anemonefish provide an opportunity to explore active mechanisms responsible for female brain development in an individual with male gonads and circulating sex steroid levels.

Initiation of sex change and gonadal gene expression in black sea bass (Centropristis striata) exposed to exemestane, an aromatase inhibitor

Many teleost fishes exhibit sequential hermaphroditism, where male or female gonads develop first and later undergo sex change. Model sex change species are characterized by social hierarchies and coloration changes, which enable experimental manipulations to better understand these processes. However, other species such as the protogynous black sea bass (Centropristis striata) do not exhibit these characteristics and instead receive research attention due to their importance in fisheries or aquaculture. Black sea bass social structure is unknown, which makes sex change sampling difficult, and few molecular resources are available. The purpose of the present study was to induce sex change using exemestane, an aromatase inhibitor, and assess gonadal gene expression using sex markers (amh, zpc2) and genes involved in steroidogenesis (cyp19a1a, cyp11b), estrogen signaling (esr1, esr2b), and apoptosis or atresia (aen, casp9, fabp11, parg, pdcd4, rif1). Overall, dietary exemestane treatment was effective, and most exposed females exhibited early histological signs of sex change and significantly higher rates of ovarian atresia relative to control females. Genes associated with atresia did not reflect this, however, as expression patterns in sex changing gonads were overall similar to those of ovaries, likely due to a whole ovary dilution effect of the RNA. Still, small but insignificant expression decreases during early sex change were detected for ovary-related genes (aen, casp9, fabp11, zpc2) and anti-apoptotic factors (parg, rif1). Exemestane treatment did not impact spermatogenesis or testicular gene expression, but testes were generally characterized by elevated steroidogenic enzyme and estrogen receptor mRNAs. Further research will be needed to understand these processes in black sea bass, using isolated ovarian follicles and multiple stages of sex change.

No evidence that the introduced parasite Orthione griffenis Markham, 2004 causes sex change or differential mortality in the native mud shrimp, Upogebia pugettensis (Dana, 1852)

Dramatic, rapid, population declines of the native North American burrowing shrimp Upogebia pugettensis (Dana, 1852) are associated with intense infestations by the introduced Asian bopyrid isopod parasite, Orthione griffenis Markham, 2004. However, expected host weight losses with increasing parasite weights do not occur, even among apparently castrated females. The prevailing assumption that energetic losses cause host castration have thus remained open to question, and the mechanism(s) resulting in castration and consequent population declines of U. pugettensis have remained unclear. Proposed alternative explanations for these declines, which have been based on a dramatically greater prevalence of O. griffenis among U. pugettensis females, include parasite induced sex change, increased male mortality, and differential tidal exposure of sexes to settling O. griffenis larvae. We examined 508 O. griffenis infestations from 2,014 shrimp collected from 26 stations in 5 Oregon estuaries to test these alternative hypotheses. We expected greater infestation frequencies among females than among males and a close association of O. griffenis infestations with intersex shrimp in the overall population if feminization occurs. We also expected covariation in sex ratio with tide exposure if O. griffenis settlement is sex linked. Instead, we found an overall 1:1.07 sex ratio, a lack of association of intersex U. pugettensis with O. griffenis infestations, and an unchanging sex ratio with tidal exposure, precluding parasite induced sex change, male mortality, or tidal immersion effects on infestations. The most likely mechanism driving U. pugettensis declines thus remains castration due to host energetic losses. This energetic interaction is likely to be resolved quantitatively through controlled experiments and increasingly detailed field surveys over time.

Territorial behaviour reflects sexual status in groups of false clown anemonefish (Amphiprion ocellaris) under laboratory conditions

Anemonefishes (genus Amphiprion) are well known as protandrous sex-changing fish. They live symbiotically with sea anemones and form a social unit that consists of a breeding pair and several sexually immature individuals with ambisexual gonads. In general, the hierarchy of the social rank is strictly maintained in a group, and this hierarchy is considered to be one of the critical factors that induce sex change or sex differentiation in anemonefishes. Field observations have shown that behavioural characteristics of anemonefishes vary depending on the environment. In this study we examined the differences in territorial aggression directed at conspecific intruders according to sexual status in the false clown anemonefish, Amphiprion ocellaris, under laboratory conditions. Resident–intruder tests were conducted on groups consisting of three anemonefish: a dominant female, a second-ranked male and a subordinate ambisexual individual. Females and males showed more aggressive behaviour than did ambisexual individuals, and behaviours were specifically directed at intruders of the same sexual status, not at those of the opposite sex. Notably, the female residents displayed fierce aggressive behaviours particularly toward female intruders, whereas male residents engaged more often in side-by-side swimming with male intruders than with female or ambisexual intruders. Ambisexual intruders were threatened by all residents, rarely attacked. We observed only few aggressive acts towards tank mates. These results suggest that sexually mature resident anemonefish in a confined space, such as under laboratory conditions, perceive intruders of the same sexual status as competitors for reproductive status and thus, dominant social rank.

Masculinization in juvenile longtooth grouper, Epinephelus bruneus, with aromatase inhibitor: changes in GtH subunit mRNA expression and steroids hormone levels

We investigated the effects of fadrozol, an aromatase inhibitor (AI), and 17α-methyltestosterone (MT) on the induction of sex change in juvenile longtooth grouper Epinephelus bruneus, via histological observation of gonads. Changes in the mRNA expression of GtH subunits (FSH-β and LH-β) in the pituitary, and estradiol-17β (E2) and 11-ketotestosterone (11-KT) levels in the blood were also surveyed after AI and MT treatment. Juvenile longtooth groupers (113±17 g body weight; 16.2±1.2 cm body length) received intramuscular injections of AI at 3 (3-AI) and 5 (5-AI) mg/kg BW doses and MT at a 5 mg/kg BW (5-MT) dose. At week 7 post-injection, 3-AI and 5-MT oocytes were degenerated, and gonads of the 5-AI group initiated spermatogenesis. At week 21 post-injection, 3-AI- and 5-MT-treated gonads contained spermatogonia and spermatocytes, while 5-AI treatment induced advanced stages of spermatogenesis. The serum E2 level showed no significant differences throughout the experimental period, whereas that of 11-KT was significantly elevated in the 5-AI group at weeks 7 and 21 post-injection. A significant increase in the expression of FSH-β mRNA was evident in the 5-AI group at week 21 post-injection. In contrast, LH-β mRNA expression did not significantly differ among groups during the experimental period. These results imply that sex change has two stages in the longtooth grouper. In the first stage, oocytes are degenerated by the stimulation by 11-KT, and in the second stage spermatogenesis occurs, owing to the co-effects of 11-KT and FSH-β.

Expression profiles of gonadotropins and their receptors during 17α‐methyltestosterone implantation‐induced sex change in the orange‐spotted grouper (Epinephelus coioides)

It is known that the hypothalamic-pituitary-gonadal axis participates in the sex change of hermaphrodite teleosts, and gonadal steroid hormones mediate this physiological process. The secretion of gonadal steroids is directly regulated by signaling pathways involving gonadotropins (GtHs) and gonadotropin receptors (GtHRs) in teleosts. To gain insight into the involvement of GtH/GtHR systems in the sex change process, cDNAs encoding follicle-stimulating hormone receptor (FSHR) and luteinizing hormone receptor (LHR) were firstly isolated from gonads of orange-spotted grouper (Epinephelus coioides), a protogynous hermaphrodite fish. Reverse transcription-PCR (RT-PCR) analysis demonstrated that the expression of the FSHR was confined to the brain, pituitary gland, ovary, and testis, while the LHR was expressed only in the brain, ovary, and testis. Furthermore, the expression profiles of GtH subunits (FSHβ and LHβ) and their receptors were analyzed in parallel with the serum levels of estradiol-17β (E(2) ), testosterone (T), and 11-ketotestosterone (11-KT) during 17α-methyltestosterone (MT)-induced sex change. Quantitative real-time PCR determined that the abundances of FSHβ and FSHR were significantly inhibited after MT treatment for 2 and 4 weeks, but subsequently returned to the control level after 6 weeks. In contrast, the mRNA levels of LHβ and LHR were significantly elevated throughout the sex change process. During MT-induced sex change, serum concentrations of E(2) remained constant while T and 11-KT levels were significantly increased. Taken together, our results suggest that GtH/GtHR systems are involved in MT-induced sex change, and two signaling pathways may have distinct roles in modulating the variations of the corresponding steroid hormones in the orange-spotted grouper.

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.

Expression and localization of forkhead transcriptional factor 2 (Foxl2) in the gonads of protogynous wrasse, Halichoeres trimaculatus.

BackgroundThree-spot wrasse, Halichoeres trimaculatus, is a marine protogynous hermaphrodite fish. Individuals mature either as initial phase (IP) males or females. Appropriate social cues induce the sex change from IP female to terminal phase (TP) male. However, the molecular mechanisms behind such a sex change remain largely unknown. Recently, the forkhead transcription factor 2 (Foxl2) was identified as an essential regulator of vertebrate ovarian development/function/phenotype. Inspired by this information, we characterized the expression patterns of Foxl2 in the protogynous wrasse assuming Foxl2 as the female-specific marker in this species.MethodsFirst, we clonedFoxl2 cDNA from ovary by reverse transcription polymerase chain reaction (RT-PCR) followed by rapid amplification of cDNA ends (RACE). Next, we analysed expression pattern of Foxl2 messenger RNA (mRNA) and protein in gonads of different sexual phases by real time quantitative PCR assay and flour fluorescence immunohistochemical method, respectively. Additionally, we studied the changes in Foxl2 expression pattern during aromatase inhibitor (AI)-induced sex change.ResultsThe amino acid sequence (306 AA) of wrasse Foxl2, especially the forkhead domain, shows high identity with that of other reported teleost Foxl2s. Quite unexpectedly, no sexual dimorphism was observable between the testes and ovary in the expression pattern of Foxl2. In female phase fish, signals for Foxl2 protein were detectable in the granulosa cells, but not the theca cells. Transcript levels of Foxl2 in the testes of IP and TP males were identical to that in the ovaries of females and, further, Foxl2 protein was found to be localized in the interstitial cells including tubules and Leydig cells. Treatment with AI induced sex change in male gonads and an up-regulation was seen in the expression of Foxl2 in these gonads.ConclusionsUnlike in other vertebrates, including teleosts, Foxl2 may have a different role in the naturally sex changing fishes.

Introduction of Trojan sex chromosomes to boost population growth

Conservation programs that deal with small or declining populations often aim at a rapid increase of population size to above-critical levels in order to avoid the negative effects of demographic stochasticity and genetic problems like inbreeding depression, fixation of deleterious alleles, or a general loss of genetic variability and hence of evolutionary potential. In some situations, population growth is determined by the number of females available for reproduction, and manipulation of family sex ratios towards more daughters has beneficial effects. If sex determination is predominantly genetic but environmentally reversible, as is the case in many amphibia, reptiles, and fish, Trojan sex chromosomes could be introduced into populations in order to change sex ratios towards more females. We analyse the possible consequences for the introduction of XX-males (XX individuals that have been changed to phenotypic males in a XY/XX sex determination system) and ZW males, WW males, or WW females (in a ZZ/ZW sex determination system). We find that the introduction of WW individuals can be most effective for an increase of population growth, especially if the induced sex change has little or no effect on viability.

Induced sex change in black sea bass

Experiments were conducted to identify factors involved in sex change in the protogynous black sea bass Centropristis striata. Black sea bass maintained in the ratio of 8 females (F):0 males (M) for 9 months reversed sex while those kept at the ratios of 6F:2M or 4F:4M did not. Female black sea bass implanted with 1·0 mg 11‐ketotestosterone (11‐KT) or 10 mg fadrozole (FAD) changed sex and began spermiating while those implanted with 0·1 mg 11‐KT or 1·0 mg FAD underwent incomplete sex reversal. One fish implanted with 1·0 mg FAD initiated sex change but was not spermiating at the end of the study. One fish in the control group, the largest fish in the study, initiated sex change. These results suggest that the presence of males may restrict sex reversal in black sea bass and that high 17β‐oestradiol:11‐KT is required for maintaining ovarian function.

Induction of sex change within two full moons during breeding season and spawning in grouper

Artificial sex change was induced within two full moons by an aromatase inhibitor (AI; 1 mg/fish) during the breeding season to establish the quickest method of sex change and natural spawning of the honeycomb grouper ( Epinephelus merra). The sex change from female (ovary) to male (testis) occurred during the time between the two full moons (3 weeks) following AI implantation, and the efferent ducts of sex-changed males were filled with sperm. To examine sperm fertility, sex-changed males were mated with natural, normal females and produced fertilized eggs. Most of the hatched larvae grew normally without any morphological deformities. Therefore, the use of this method which is the quickest known sex change method using AI, may contribute to quality sperm production for grouper aquaculture.

Promoter analysis of two aromatase genes in the serial-sex changing gobiid fish, Trimma okinawae

Despite numerous endocrine studies on sex change in teleost, no general mechanism that mediates sex change has emerged. The gobiid fish, Trimma okinawae, can change sex in both directions repeatedly. This phenomenon of sex change in goby assigns it as an excellent animal model to elucidate the understanding mechanisms of sex change. In hermaphrodite fishes, estrogen plays a particularly important role in natural and experimentally induced sex change. To investigate the role of estrogen in the serial-sex changing fish T. okinawae, we cloned and analyzed the 5'-flanking regions of P450arom genes from goby genome DNA. Both regions have consensus sequences of TATA, CRE and ERE. Ad4 binding site was restricted in the region of P450aromA. These findings indicate that different regulators control the expression of the two P450arom genes.

Sex change strategy and the aromatase genes

Sequential hermaphroditism is a common reproductive strategy in many teleosts. Steroid production is known to mediate both the natural and induced sex change, yet beyond this the physiology directing this process has received little attention. Cytochrome P450 aromatase is a key enzyme in the hormonal pathway catalysing the conversion of sex steroids, androgens to oestrogens, and thus is highly relevant to the process of sex change. This study reports the isolation of cDNA sequences for aromatase isoforms CYP19A1 and CYP19A2 from teleost species representing three forms of sexual hermaphroditism: Lates calcarifer (protandry), Cromileptes altivelis (protogyny), and Gobiodon histrio (bi-directional). Deduced amino acid analysis of these isoforms with other reported isoforms from gonochoristic (single sex) teleosts revealed 56–95% identity within the same isoform while only 48–65% identity between isoforms irrespective of species and sexual strategy. Phylogenetic analysis supported this result separating sequences into isoform exclusive clades in spite of species apparent evolutionary distance. Furthermore, this study isolates 5′ flanking regions of all above genes and describes putative cis-acting elements therein. Elements identified include steroidogenic factor 1 binding site (SF-1), oestrogen response element (ERE), progesterone response element (PRE), androgen response element (ARE), glucocorticoid response elements (GRE), peroxisome proliferator-activated receptor α/retinoid X receptor α heterodimer responsive element (PPARα/RXRα), nuclear factor kappaβ (NF-kappaβ), SOX 5, SOX 9, and Wilms tumor suppressor (WTI). A hypothetical in vivo model was constructed for both isoforms highlighting potential roles of these putative cis-acting elements with reference to normal function and sexual hermaphroditism.

Reproduction in context: Field testing a laboratory model of socially controlled sex change in Lythrypnus dalli (Gilbert)

Social interactions can have profound effects on reproduction and the proximate mechanisms involved are just beginning to be understood. Lythrypnus dalli, the bluebanded goby, is an ideal organism for analyzing the dynamics of socially controlled sex change both in the laboratory and field. As with most research species, the majority of its behavioural and physiologic study has been performed in the laboratory. The goal of our study was to induce sex change of L. dalli in a more natural environment and compare field dynamics with our laboratory-based model. Groups of L. dalli, composed of one large male and three females of varying sizes, were introduced into artificial habitats in the field. After male removal, the dominant, largest female underwent protogynous sex change in the majority of the groups. Within 15 days, 9 of 15 of the dominant females (focal fish) successfully fertilized eggs as males, compared to 13 of 17 in the laboratory. Focal fish displayed the distinctive temporal sequence of behaviour changes consisting of a dominance, quiescent, and courtship phase. In addition, focal fish had gonads, genital papillae, and accessory gonadal structures with morphology in between that of females and males. Those fish that fertilized eggs had this transitional morphology, but were functionally male. Steroids of focal fish were assayed by water sample, and morning samples of free 11-ketotestosterone (11-KT) positively correlated with the percent of male tissue in the gonad, with the size of the accessory gonadal structure but not the genitalia (genital papilla), and with aggressive displacement behaviour on the last day before the fish were sacrificed. These morphological, physiological, and behavioural patterns parallel those seen in the laboratory. Lower rates of behaviour and the dramatic effects of ambient temperature in the field provide insights as to how the environmental context modifies the behaviour and, subsequently, the reproductive function of individuals within a social group.