High temperature causes masculinization of genetically female medaka by elevation of cortisol

In poikilothermic vertebrates, sex determination is sometimes influenced by environmental factors such as temperature. However, little is known about the molecular mechanisms underlying environmental sex determination. The medaka (Oryzias latipes) is a teleost fish with an XX/XY sex determination system. Recently, it was reported that XX medaka can be sex‐reversed into phenotypic males by high water temperature (HT; 32–34°C) treatment during the sex differentiation period. Here we report that cortisol caused female‐to‐male sex reversal and that metyrapone (an inhibitor of cortisol synthesis) inhibited HT‐induced masculinization of XX medaka. HT treatment caused elevation of whole‐body levels of cortisol, while metyrapone suppressed the elevation by HT treatment during sexual differentiation. Moreover, cortisol and 33°C treatments inhibited female‐type proliferation of germ cells as well as expression of follicle‐stimulating hormone receptor (fshr) mRNA in XX medaka during sexual differentiation. These results strongly suggest that HT induces masculinization of XX medaka by elevation of cortisol level, which, in turn, causes suppression of germ cell proliferation and of fshr mRNA expression. Mol. Reprod. Dev. 77: 679–686, 2010. © 2010 Wiley‐Liss, Inc.     

Novel evolutionary pathways of sex‐determining mechanisms

Evolutionary transitions between sex‐determining mechanisms (SDMs) are an enigma. Among vertebrates, individual sex (male or female) is primarily determined by either genes (genotypic sex determination, GSD) or embryonic incubation temperature (temperature‐dependent sex determination, TSD), and these mechanisms have undergone repeated evolutionary transitions. Despite this evolutionary lability, transitions from GSD (i.e. from male heterogamety, XX/XY, or female heterogamety, ZZ/ZW) to TSD are an evolutionary conundrum, as they appear to require crossing a fitness valley arising from the production of genotypes with reduced viability owing to being homogametic for degenerated sex chromosomes (YY or WW individuals). Moreover, it is unclear whether alternative (e.g. mixed) forms of sex determination can persist across evolutionary time. It has previously been suggested that transitions would be easy if temperature‐dependent sex reversal (e.g. XX male or XY female) was asymmetrical, occurring only in the homogametic sex. However, only recently has a mechanistic model of sex determination emerged that may allow such asymmetrical sex reversal. We demonstrate that selection for TSD in a realistic sex‐determining system can readily drive evolutionary transitions from GSD to TSD that do not require the production of YY or WW individuals. In XX/XY systems, sex reversal (female to male) occurs in a portion of the XX individuals only, leading to the loss of the Y allele (or chromosome) from the population as XX individuals mate with each other. The outcome is a population of XX individuals whose sex is determined by incubation temperature (TSD). Moreover, our model reveals a novel evolutionarily stable state representing a mixed‐mechanism system that has not been revealed by previous approaches. This study solves two long‐standing puzzles of the evolution of sex‐determining mechanisms by illuminating the evolutionary pathways and endpoints.     

Cell cycle analysis of fetal germ cells during sex differentiation in mice

Background information. Primordial germ cells in developing male and female gonads are responsive to somatic cell cues that direct their sex‐specific differentiation into functional gametes. The first divergence of the male and female pathways is a change in cell cycle state observed from 12.5 dpc (days post coitum) in mice. At this time XY and XX germ cells cease mitotic division and enter G₁/G₀ arrest and meiosis prophase I respectively. Aberrant cell cycle regulation at this time can lead to disrupted ovarian development, germ cell apoptosis, reduced fertility and/or the formation of germ cell tumours. Results. In order to unravel the mechanisms utilized by germ cells to achieve and maintain the correct cell cycle states, we analysed the expression of a large number of cell cycle genes in purified germ cells across the crucial time of sex differentiation. Our results revealed common signalling for both XX and XY germ cell survival involving calcium signalling. A robust mechanism for apoptosis and checkpoint control was observed in XY germ cells, characterized by p53 and Atm (ataxia telangiectasia mutated) expression. Additionally, a member of the retinoblastoma family and p21 were identified, linking these factors to XY germ cell G₁/G₀ arrest. Lastly, in XX germ cells we observed a down‐regulation of genes involved in both G₁‐ and G₂‐phases of the cell cycle consistent with their entry into meiosis. Conclusion. The present study has provided a detailed analysis of cell cycle gene expression during fetal germ cell development and identified candidate factors warranting further investigation in order to understand cases of aberrant cell cycle control in these specialized cells.     

Estrogen rescues masculinization of genetically female medaka by exposure to cortisol or high temperature

Medaka (Oryzias latipes) is a teleost fish with an XX/XY sex determination system. Recently, it was reported that XX medaka can be sex‐reversed into phenotypic males by exposure to high water temperature (HT) during gonadal sex differentiation, possibly by elevation of cortisol, the major glucocorticoid produced by the interrenal cells in teleosts. Yet, it remains unclear how the elevation of cortisol levels by HT causes female‐to‐male sex reversal. This paper reports that exposure to cortisol or HT after hatching inhibited both the proliferation of female‐type germ cells and the expression of ovarian‐type aromatase (cyp19a1), which encodes a steroidogenic enzyme responsible for the conversion of androgens to estrogens, and induced the expression of gonadal soma‐derived growth factor (gsdf) in XX gonads during gonadal sex differentiation. In contrast, exposure to either cortisol or HT in combination with 17β‐estradiol (E2) did not produce these effects. Moreover, E2 completely rescued cortisol‐ and HT‐induced masculinization of XX medaka. These results strongly suggest that cortisol and HT cause female‐to‐male sex reversal in medaka by suppression of cyp19a1 expression, with a resultant inhibition of estrogen biosynthesis. This mechanism may be common among animals with temperature‐dependent sex determination. Mol. Reprod. Dev. 79: 719–726, 2012. © 2012 Wiley Periodicals, Inc.     

Searching for sex‐reversals to explain population demography and the evolution of sex chromosomes

Sex determination can be purely genetic (as in mammals and birds), purely environmental (as in many reptiles), or genetic but reversible by environmental factors during a sensitive period in life, as in many fish and amphibians ( Wallace et al. 1999 ; Baroiller et al. 2009a ; Stelkens & Wedekind 2010 ). Such environmental sex reversal (ESR) can be induced, for example, by temperature changes or by exposure to hormone‐active substances. ESR has long been recognized as a means to produce more profitable single‐sex cultures in fish farms ( Cnaani & Levavi‐Sivan 2009 ), but we know very little about its prevalence in the wild. Obviously, induced feminization or masculinization may immediately distort population sex ratios, and distorted sex ratios are indeed reported from some amphibian and fish populations ( Olsen et al. 2006 ; Alho et al. 2008 ; Brykov et al. 2008 ). However, sex ratios can also be skewed by, for example, segregation distorters or sex‐specific mortality. Demonstrating ESR in the wild therefore requires the identification of sex‐linked genetic markers (in the absence of heteromorphic sex chromosomes) followed by comparison of genotypes and phenotypes, or experimental crosses with individuals who seem sex reversed, followed by sexing of offspring after rearing under non‐ESR conditions and at low mortality. In this issue, Alho et al. (2010) investigate the role of ESR in the common frog (Rana temporaria) and a population that has a distorted adult sex ratio. They developed new sex‐linked microsatellite markers and tested wild‐caught male and female adults for potential mismatches between phenotype and genotype. They found a significant proportion of phenotypic males with a female genotype. This suggests environmental masculinization, here with a prevalence of 9%. The authors then tested whether XX males naturally reproduce with XX females. They collected egg clutches and found that some had indeed a primary sex ratio of 100% daughters. Other clutches seemed to result from multi‐male fertilizations of which at least one male had the female genotype. These results suggest that sex‐reversed individuals affect the sex ratio in the following generation. But how relevant is ESR if its prevalence is rather low, and what are the implications of successful reproduction of sex‐reversed individuals in the wild?     

Genomic characterization of sex‐identification markers in Sebastes carnatus and Sebastes chrysomelas rockfishes

Fish have evolved a variety of sex‐determining (SD) systems including male heterogamy (XY), female heterogamy (ZW) and environmental SD. Little is known about SD mechanisms of Sebastes rockfishes, a highly speciose genus of importance to evolutionary and conservation biology. Here, we characterize the sex determination system in the sympatrically distributed sister species Sebastes chrysomelas and Sebastes carnatus. To identify sex‐specific genotypic markers, double digest restriction site – associated DNA sequencing (ddRAD‐seq) of genomic DNA from 40 sexed individuals of both species was performed. Loci were filtered for presence in all of the individuals of one sex, absence in the other sex and no heterozygosity. Of the 74 965 loci present in all males, 33 male‐specific loci met the criteria in at least one species and 17 in both. Conversely, no female‐specific loci were detected, together providing evidence of an XY sex determination system in both species. When aligned to a draft reference genome from Sebastes aleutianus, 26 sex‐specific loci were interspersed among 1168 loci that were identical between sexes. The nascent Y chromosome averaged 5% divergence from the X chromosome and mapped to reference Sebastes genome scaffolds totalling 6.9Mbp in length. These scaffolds aligned to a single chromosome in three model fish genomes. Read coverage differences were also detected between sex‐specific and autosomal loci. A PCR‐RFLP assay validated the bioinformatic results and correctly identified sex of five additional individuals of known sex. A sex‐determining gene in other teleosts gonadal soma‐derived factor (gsdf) was present in the model fish chromosomes that spanned our sex‐specific markers.     

Sex reversal of genetic females (XX) induced by the transplantation of XY somatic cells in the medaka,Oryzias latipes

In order to investigate the function of gonadal somatic cells in the sex differentiation of germ cells, we produced chimera fish containing both male (XY) and female (XX) cells by means of cell transplantation between blastula embryos in the medaka, Oryzias latipes. Sexually mature chimera fish were obtained from all combinations of recipient and donor genotypes. Most chimeras developed according to the genetic sex of the recipients, whose cells are thought to be dominant in the gonads of chimeras. However, among XX/XY (recipient/donor) chimeras, we obtained three males that differentiated into the donor's sex. Genotyping of their progeny and of strain-specific DNA fragments in their testes showed that, although two of them produced progeny from only XX spermatogenic cells, their testes all contained XY cells. That is, in the two XX/XY chimeras, germ cells consisted of XX cells but testicular somatic cells contained both XX and XY cells, suggesting that the XY somatic cells induced sex reversal of the XX germ cells and the XX somatic cells. The histological examination of developing gonads of XX/XY chimera fry showed that XY donor cells affect the early sex differentiation of germ cells. These results suggest that XY somatic cells start to differentiate into male cells depending on their sex chromosome composition, and that, in the environment produced by XY somatic cells in the medaka, germ cells differentiate into male cells regardless of their sex chromosome composition.     

Phenotypic/genotypic sex mismatches and temperature‐dependent sex determination in a wild population of an Old World atherinid,the cobaltcap silverside Hypoatherina tsurugae

Several New World atheriniforms have been recognized as temperature‐dependent sex determined (TSD) and yet possess a genotypic sex determinant (amhy) which is primarily functional at mid‐range temperatures. In contrast, little is known about the sex determination in Old World atheriniforms, even though such knowledge is crucial to understand the evolution of sex determination mechanisms in fishes and to model the effects of global warming and climate change on their populations. This study examined the effects of water temperature on sex determination of an Old World atheriniform, the cobaltcap silverside Hypoatherina tsurugae, in which we recently described an amhy homologue. We first assessed the occurrence of phenotypic/genotypic sex mismatches in wild specimens from Tokyo Bay for three years (2014–2016) and used otolith analysis to estimate their birth dates and approximate thermal history during the presumptive period of sex determination. Phenotypic sex ratios became progressively biased towards males (47.3%–78.2%) during the period and were associated with year‐to‐year increases in the frequency of XX‐males (7.3%–52.0%) and decreases in XY/YY‐females (14.5%–0%). The breeding season had similar length but was delayed by about 1 month per year between 2014 and 2016, causing larvae to experience higher temperatures during the period of sex determination from year to year. Larval rearing experiments confirmed increased likelihood of feminization and masculinization at low and high temperatures, respectively. The results suggest that cobaltcap silverside has TSD, or more specifically the coexistence of genotypic and environmental sex determinants, and that it affects sex ratios in wild populations.     

Dmrt1 polymorphism and sex‐chromosome differentiation in Rana temporaria

Sex‐determination mechanisms vary both within and among populations of common frogs, opening opportunities to investigate the molecular pathways and ultimate causes shaping their evolution. We investigated the association between sex‐chromosome differentiation (as assayed from microsatellites) and polymorphism at the candidate sex‐determining gene Dmrt1 in two Alpine populations. Both populations harboured a diversity of X‐linked and Y‐linked Dmrt1 haplotypes. Some males had fixed male‐specific alleles at all markers (“differentiated” Y chromosomes), others only at Dmrt1 (“proto‐” Y chromosomes), while still others were genetically indistinguishable from females (undifferentiated X chromosomes). Besides these XX males, we also found rare XY females. The several Dmrt1 Y haplotypes differed in the probability of association with a differentiated Y chromosome, which we interpret as a result of differences in the masculinizing effects of alleles at the sex‐determining locus. From our results, the polymorphism in sex‐chromosome differentiation and its association with Dmrt1, previously inferred from Swedish populations, are not just idiosyncratic features of peripheral populations, but also characterize highly diverged populations in the central range. This implies that an apparently unstable pattern has been maintained over long evolutionary times.     

Female‐specific increase in primordial germ cells marks sex differentiation in threespine stickleback (Gasterosteus aculeatus)

Gonadal sex differentiation is increasingly recognized as a remarkably plastic process driven by species‐specific genetic or environmental determinants. Among aquatic vertebrates, gonadal sex differentiation is a frequent endpoint in studies of endocrine disruption with little appreciation of underlying developmental mechanisms. Work in model organisms has highlighted the diversity of master sex‐determining genes rather than uncovering any broad similarities prompting the highly conserved developmental decision of testes versus ovaries. Here we use molecular genetic markers of chromosomal sex combined with traditional histology to examine the transition of the bipotential gonads to ovaries or testes in threespine stickleback (Gasterosteus aculeatus). Serially‐sectioned threespine stickleback fry were analyzed for qualitative and quantitative indications of sexual differentiation, including changes in gonadal morphology, number of germ cells and the incidence of gonadal apoptosis. We show that threespine stickleback sampled from anadromous and lacustrine populations are differentiated gonochorists. The earliest sex‐specific event is a premeiotic increase in primordial germ cell number followed by a female‐specific spike in apoptosis in the undifferentiated gonad of genetic females. The data suggest that an increase in PGC number may direct the undifferentiated gonad toward ovarian differentiation. J. Morphol., 2008. © 2007 Wiley‐Liss, Inc.     

Cell-autonomous and inductive signals can determine the sex of the germ line of drosophila by regulating the gene Sxl

To investigate the mechanism of sex determination in the germ line, we analyzed the fate of XY germ cells in ovaries, and the fate of XX germ cells in testes. In ovaries, germ cells developed according to their X:A ratio, i.e., XX cells underwent oogenesis, XY cells formed spermatocytes. In testes, however, XY and XX germ cells entered the spermatogenic pathway. Thus, to determine their sex, the germ cells of Drosophila have cell-autonomous genetic information, and XX cells respond to inductive signals of the soma. Results obtained with amorphic and constitutive mutations of Sxl show that both the genetic and the somatic signals act through Sxl to achieve sex determination in germ cells.     

Absence of the candidate male sex-determining gene dmrt1b(Y) of medaka from other fish species

Although the sex-determining genes are known in mammals, Drosophila, and C. elegans, little is known in other animals. Fishes are an attractive group of organisms for studying the evolution of sex determination because they show an amazing variety of mechanisms, ranging from environmental sex determination and different forms of hermaphroditism to classical sex chromosomal XX/XY or WZ/ZZ systems and modifications thereof. In the fish medaka, dmrt1b(Y) has recently been found to be the candidate male sex-determining gene. It is a duplicate of the autosomal dmrt1a gene, a gene acting in the sex determination/differentiation cascade of flies, worms, and mammals. Because in birds dmrt1 is located on the Z-chromosome, both findings led to the suggestion that dmrt1b(Y) is a "non-mammalian Sry" with an even more widespread distribution. However, although Sry was found to be the male sex-determining gene in the mouse and some other mammalian species, in some it is absent and has obviously been replaced by other genes that now fulfil the same function. We have asked if the same might be true of the dmrt1b(Y) gene. We find that the gene duplication generating dmrt1b(Y) occurred recently during the evolution of the genus Oryzias. The gene is absent from all other fish species studied. Therefore, it may not be the male-sex determining gene in all fishes.     

Characterization of a Y‐specific duplication/insertion of the anti‐Mullerian hormone type II receptor gene based on a chromosome‐scale genome assembly of yellow perch,Perca flavescens

Yellow perch, Perca flavescens, is an ecologically and economically important species native to a large portion of the northern United States and southern Canada and is also a promising candidate species for aquaculture. However, no yellow perch reference genome has been available to facilitate improvements in both fisheries and aquaculture management practices. By combining Oxford Nanopore Technologies long‐reads, 10X Genomics Illumina short linked reads and a chromosome contact map produced with Hi‐C, we generated a high‐continuity chromosome‐scale yellow perch genome assembly of 877.4 Mb. It contains, in agreement with the known diploid chromosome yellow perch count, 24 chromosome‐size scaffolds covering 98.8% of the complete assembly (N50 = 37.4 Mb, L50 = 11). We also provide a first characterization of the yellow perch sex determination locus that contains a male‐specific duplicate of the anti‐Mullerian hormone type II receptor gene (amhr2by) inserted at the proximal end of the Y chromosome (chromosome 9). Using this sex‐specific information, we developed a simple PCR genotyping assay which accurately differentiates XY genetic males (amhr2by⁺) from XX genetic females (amhr2by^?). Our high‐quality genome assembly is an important genomic resource for future studies on yellow perch ecology, toxicology, fisheries and aquaculture research. In addition, characterization of the amhr2by gene as a candidate sex‐determining gene in yellow perch provides a new example of the recurrent implication of the transforming growth factor beta pathway in fish sex determination, and highlights gene duplication as an important genomic mechanism for the emergence of new master sex determination genes.     

No evidence that Y‐chromosome differentiation affects male fitness in a Swiss population of common frogs

The canonical model of sex‐chromosome evolution assigns a key role to sexually antagonistic (SA) genes on the arrest of recombination and ensuing degeneration of Y chromosomes. This assumption cannot be tested in organisms with highly differentiated sex chromosomes, such as mammals or birds, owing to the lack of polymorphism. Fixation of SA alleles, furthermore, might be the consequence rather than the cause of recombination arrest. Here we focus on a population of common frogs (Rana temporaria) where XY males with genetically differentiated Y chromosomes (nonrecombinant Y haplotypes) coexist with both XY° males with proto‐Y chromosomes (only differentiated from X chromosomes in the immediate vicinity of the candidate sex‐determining locus Dmrt1) and XX males with undifferentiated sex chromosomes (genetically identical to XX females). Our study finds no effect of sex‐chromosome differentiation on male phenotype, mating success or fathering success. Our conclusions rejoin genomic studies that found no differences in gene expression between XY, XY° and XX males. Sexual dimorphism in common frogs might result more from the differential expression of autosomal genes than from sex‐linked SA genes. Among‐male variance in sex‐chromosome differentiation seems better explained by a polymorphism in the penetrance of alleles at the sex locus, resulting in variable levels of sex reversal (and thus of X‐Y recombination in XY females), independent of sex‐linked SA genes.     

A sex‐linked SCAR marker in Bryonia dioica (Cucurbitaceae), a dioecious species with XY sex‐determination and homomorphic sex chromosomes

Genetic crosses between the dioecious Bryonia dioica (Cucurbitaceae) and the monoecious B. alba in 1903 provided the first clear evidence for Mendelian inheritance of dioecy and made B. dioica the first organism for which XY sex‐determination was experimentally proven. Applying molecular tools to this system, we developed a sex‐linked sequence‐characterized amplified region (SCAR) marker for B. dioica and sequenced it for individuals representing the full geographic range of the species from Scotland to North Africa. For comparison, we also sequenced this marker for representatives of the dioecious B. cretica, B. multiflora and B. syriaca, and monoecious B. alba. In no case did any individual, male or female, yield more than two haplotypes. In northern Europe, we found strong linkage between our marker and sex, with all Y‐sequences being identical to each other. In southern Europe, however, the linkage between our marker and sex was weak, with recombination detected within both the X‐ and the Y‐homologues. Population genetic analyses suggest that the SCAR marker experienced different evolutionary pressures in northern and southern Europe. These findings fit with phylogenetic evidence that the XY system in Bryonia is labile and suggest that the genus may be a good system in which to study the early steps of sex chromosome evolution.     

The ecology and evolution of temperature‐dependent reaction norms for sex determination in reptiles: a mechanistic conceptual model

Sex‐determining mechanisms are broadly categorised as being based on either genetic or environmental factors. Vertebrate sex determination exhibits remarkable diversity but displays distinct phylogenetic patterns. While all eutherian mammals possess XY male heterogamety and female heterogamety (ZW) is ubiquitous in birds, poikilothermic vertebrates (fish, amphibians and reptiles) exhibit multiple genetic sex‐determination (GSD) systems as well as environmental sex determination (ESD). Temperature is the factor controlling ESD in reptiles and temperature‐dependent sex determination (TSD) in reptiles has become a focal point in the study of this phenomenon. Current patterns of climate change may cause detrimental skews in the population sex ratios of reptiles exhibiting TSD. Understanding the patterns of variation, both within and among populations and linking such patterns with the selection processes they are associated with, is the central challenge of research aimed at predicting the capacity of populations to adapt to novel conditions. Here we present a conceptual model that innovates by defining an individual reaction norm for sex determination as a range of incubation temperatures. By deconstructing individual reaction norms for TSD and revealing their underlying interacting elements, we offer a conceptual solution that explains how variation among individual reaction norms can be inferred from the pattern of population reaction norms. The model also links environmental variation with the different patterns of TSD and describes the processes from which they may arise. Specific climate scenarios are singled out as eco‐evolutionary traps that may lead to demographic extinction or a transition to either male or female heterogametic GSD. We describe how the conceptual principles can be applied to interpret TSD data and to explain the adaptive capacity of TSD to climate change as well as its limits and the potential applications for conservation and management programs.     

Evolution of ZZ/ZW and XX/XY sex-determination systems in the closely related medaka species, <Emphasis Type="Italic">Oryzias hubbsi</Emphasis> and <Emphasis Type="Italic">O. dancena</Emphasis>

A DM-domain gene on the Y chromosome was identified as the sex-determining gene in the medaka, Oryzias latipes, and named DMY (also known as dmrt1bY). However, this gene is absent in most Oryzias fishes, suggesting that closely related species have another sex-determining gene. In fact, it has been demonstrated that the Y chromosome in O. dancena is not homologous to that in O. latipes, whereas both species have an XX/XY sex-determination system. Through a progeny test of sex-reversed fish and a linkage analysis of isolated sex-linked DNA markers, we show that O. hubbsi, which is one of the most closely related species to O. dancena, has a ZZ/ZW system. In addition, genetic and fluorescence in situ hybridization mapping of the sex-linked markers revealed that sex chromosomes in O. hubbsi and O. dancena are not homologous, indicating different origins of these ZW and XY sex chromosomes. Furthermore, we found that O. hubbsi has morphologically heteromorphic sex chromosomes, in which the W chromosome has 4,6-diamidino-2-phenylindole (DAPI)-positive heterochromatin blocks and is larger than the Z chromosome, although such differentiated sex chromosomes have not been observed in other Oryzias species. These findings suggest that a variety of sex-determining mechanisms and sex chromosomes have evolved in Oryzias.     

17β-雌二醇诱导斑点叉尾鮰雌性化研究

研究以人工配合饲料为17β-雌二醇(17β-estradiol, 17β-E₂)载体, 对斑点叉尾鮰(Ictalurus punctatus)开口仔鱼连续饲喂27d进行雌性性别诱导, 探究斑点叉尾鮰XY雄鱼雌性化的合适17β-E₂剂量。60日龄测量并统计各组试验鱼的生长数据、存活率, 解剖观察性腺结构, 结合遗传性别鉴定结果计算性逆转率, 并通过组织切片分析各组试验鱼中XX和XY雌鱼卵巢发育情况。270日龄检测XY雌鱼和对照组雌鱼的鳃、心脏、肝脏、肾脏、卵巢和肌肉等组织中17β-E₂含量。研究进一步地采用qRT-PCR检测270日龄雌雄性别分化基因foxl2和dmrt1在XX和XY雌鱼卵巢中的表达水平。结果显示: 各组XY雌鱼的比例和卵母细胞数量均随17β-E₂剂量的提高而增加, 且核仁数量也随之增多, 而核质比相应减小; 各组XY雌鱼的体重和体长随着17β-E₂剂量的提高先增加后减小, 但存活率没有显著性变化; 各组XY雌鱼与对照组雌鱼的鳃、心脏、肝脏、肾脏和肌肉组织中17β-E₂含量均无显著性差异, 卵巢中17β-E₂含量与添加剂量呈正相关; 雌性性别分化基因foxl2在XY雌鱼中的表达量显著升高, 雄性性别分化基因dmrt1在XY雌鱼中的表达量显著降低。研究建立了17β-E₂诱导XY雄性斑点叉尾鮰雌性化方法, 为后续全雄斑点叉尾鮰新品种的培育奠定基础。