Bisexual Gonad Research Articles

Life-history constraints, short adult life span and reproductive strategies in coral reef gobies of the genus Trimma.

Body size influences many life-history traits, with small-bodied animals tending to have short life spans, high mortality and greater reproductive effort early in life. In this study, the authors investigated the life-history traits and reproductive strategies of three small-bodied coral reef gobies of the genus Trimma: Trimma benjamini, Trimma capostriatum and Trimma yanoi. The authors found all Trimma species studied attained a small body size of <25 mm, had a short life span of <140 days and experienced high estimated daily mortality of 3.0%-6.7%. Furthermore, the pelagic larval phase accounted for 25.3%-28.5% of the maximum life span, and maturation occurred between 74.1 and 82.1 days at 15.2-15.8 mm, leaving only 35%-43% of the total life span as a reproductively viable adult. All mature individuals had gonad structures consistent with bidirectional sex change, with bisexual gonads including both ovarian and testicular portions separated by a thin wall of connective tissue. In the female and male phases, only ovaries or testes were mature, whereas gonadal tissue of the non-active sex remained. One T. benjamini individual and one T. yanoi individual had ovarian and testicular tissue active simultaneously. The results of this study highlight the life-history challenges small CRFs face on their path to reproduction and reproductive strategies that could be beneficial in fishes with high and unpredictable mortality and short reproductive life spans.

Gonadal Changes during the Annual Reproductive Cycle of the Ascidian Halocynthia aurantium (Pallas).

The ascidian Halocynthia aurantium (sea peach), a marine invertebrate, belongs to the same genus of the phylum Chordata along with the ascidian Halocynthia roretzi (sea pineapple), which is one of the model animals in the field of developmental biology. The characteristics of development and reproduction of H. aurantium are not yet known in detail. In order to find out the spawning period of H. aurantium, we investigated development of the gonads during the annual reproductive cycle. Testis and ovary were both in the bisexual gonads (ovotestes) of H. aurantium, which is a hermaphrodite like H. roretzi. In H. aurantium, the right gonad was longer and slightly larger than the left gonad throughout the year. In each gonad, the number of the testis gonoducts was slightly higher than that of the ovary gonoducts. These features were similarly observed in H. roretzi. However, the number of the testis gonoducts and the ovary gonoducts in each gonad of H. aurantium was about half that of H. roretzi. The gonads of H. aurantium contracted during the winter and summer seasons. The gonads decreased to the smallest size around February, and then started to increase again in March. The gonads were most developed in September of the year. Therefore, it is estimated that the spawning of H. aurantium begins around this period.

Expression, localization, and a regulated target gene (ccnd1) of miR-202-5p in the Japanese flounder gonads

MiR-202-5p is identified as the maker microRNA (miRNA) of germplasm in fish. However, the role of miR-202-5p in gonadal development is still unclear. Here we investigated the expression patterns of miR-202-5p in Japanese flounder (Paralichthys olivaceus). Real-time PCR displayed that miR-202-5p was specifically expressed in bisexual gonads, and its transcription in the testis was relatively abundant than that in the ovary. Moreover, it was gradually increased in testis from stage II to stage IV. Fluorescent in situ hybridization (FISH) illustrated that miR-202-5p was co-localized with vasa (a marker gene of germ cells) in testis, and it was predominately expressed in spermatogonia and spermatocytes, implying that miR-202-5p might participate in spermatogenesis. Considering the important role of retinoic acid (RA) on regulating meiosis during spermatogenesis, we treated Japanese flounders by injecting all-trans retinoic acid (ATRA). MiR-202-5p in testis was shown to be up-regulated, and ccnd1, a key cell cycle regulator, was found to be down-regulated after ATRA treatment. Furthermore, ccnd1 was demonstrated to be a direct regulatory target of miR-202-5p using Dual-luciferase assay. In the primary testis cell from Japanese flounder, we further confirmed that ccnd1 was down-regulated by miR-202-5p. The results suggest that miR-202-5p exerts a crucial role in gonadal development by inhibiting ccnd1 in Japanese flounder.

Cloning, pattern of gonadal soma-derived factor mRNA in the orange-spotted grouper, Epinephelus coioides

The orange-spotted grouper (Epinephelus coioides), as a protogynous hermaphrodite, provides a novel model for understanding the mechanisms of sex determination and differentiation in teleosts. Gonadal soma-derived factor (gsdf), involved in early germ cell development, is a new member of the transforming growth factor-beta (TGF-β) superfamily. In this study, a 2364-bp long gsdf gene was cloned from E. coioides and there was further analysis of its tissue distribution and patterns of gene expression during the female phase, bisexual gonads stage and testis stage. The cellular localization of Gsdf during the early sexual differentiation stage was also analyzed. In addition, the expression levels of gsdf, dmrt1, foxl2 and cyp19a1a in gonads during the early sexual differentiation stage were analyzed by real-time PCR. Tissue distribution analysis showed that gsdf was only expressed in the testis and ovary. The gene expression showed that gsdf was expressed significantly higher in testes and bisexual gonads compared to ovaries. The early-stage ovary showed a significant fluorescence signal in the supporting cells surrounding gonium and oogonium, but not pre-vitellogenic oocytes, indicating that gsdf expression was restricted to morphologically undifferentiated supporting cells in the early stages of oogenesis. During the early sexual differentiation stage, Real-time PCR showed that both the expression levels of gsdf and dmrt1 were progressively increased and the expression levels of foxl2 and cyp19a1a were growing slowly. These results suggest that gsdf could have roles in the early sexual differentiation in hermaphroditic, E. coioides.

The first evidence of intersexuality in Atka mackerel Pleurogrammus monopterygius (Hexagrammidae).

Histological examination of Atka mackerel ovotestes reveals the possibility of intersexuality. Individuals with bisexual gonads have been caught in the North Pacific near the south-east coast of the Kamchatka peninsula. While intersex appeared to be normal females with developing ovaries, histological analysis showed the presence of both female and male tissue in the same gonad. Specifically, primary growth, cortical alveolar and primary vitellogenic oocytes were located among spermatogonia cysts. The prevalence of intersexuality in the population was less than 0.1%.

Morphological and histological features of the gonad structure in hermaphroditic walleye pollock Theragra chalcogramma (Gadidae)

Morphology of hermaphroditic gonads is studied in the individuals of walleye pollock Theragra chalcogramma collected in different regions of the seas of the North Pacific from 1987 to 2014. Based on the external morphological characteristics of sexual glands of 17 fishes, the most frequent types of the structure of bisexual gonads are described. Histological analysis shows the absence of differences in the composition and condition of oocytes in the left and right-paired ovaries, and the testes and ovaries of each individual are at the same maturity stage. In the ovigerous lamellae of ovaries in the areas adjacent to testes the zones of oocyte resorption are observed. These zones are located exclusively near the joining of the female and male parts of the gonads. The development of ovaries and testes of bisexual gonads is similar to that in the majority of normally maturing males and females collected during the same period. The occurrence of hermaphrodites is 0.0003–0.0016% from the total number of investigated exemplars.

Histological assessment of White Sea cod Gadus morhua marisalbi gonads in the summer of 2011–2013

In this paper the reproductive status of Gadus morhua marisalbi (White Sea cod) was investigated using histological methods. There was a high prevalence in gonad abnormalities. In 90.0% of females nucleoli hypertrophy and oocyte resorption observed, and in 95.0% of males germ cell were characterized by destruction processes. For the first time a case of hermaphroditism was documented in White Sea cod. The prevalence of individuals with bisexual gonads was 3.8% in the histologically examined specimens. Reproductive disorders are not species-specific, and similar gonads anomalies have been observed in other species of fish, especially near sites with high anthropogenic impact.

Development of the Genital Duct System in the Protandrous Black Porgy, Acanthopagrus schlegeli

Protandrous black porgies, Acanthopagrus schlegeli, have a striking life cycle, which includes early sex differentiation, bisexual gonads, and a male-to-female sex change at three years of age. We found novel features of and insights into the development of the genital duct system in relation to the gonadal stage during early gonadal development and natural sex change. We found that the genital ducts developed at 16-20 weeks of age during sex differentiation. The gonad developed "ovarian cavity cracks" and became "four-stranded" during the first prespawning period and then proceeded to the development of genital ducts before 1 year of age. Two ovarian cavities of the paired gonads combined, developed, and extended caudally to form the oviduct, making up the inner duct of the genital ducts. The testicular main cavities also extended and fused together to form the outer duct of the genital duct system, that is, the sperm duct. The coexistence of an outer sperm duct and an inner oviduct constituted a unique "double cannula genital duct" structure. Gradually the inferior walls of the oviduct intermingled with those of the sperm duct, and the circular lumen of the sperm duct changed into an "M-shaped canal." Finally, the sperm duct and oviduct separated completely at the distal part of genital duct system. During natural sex change, the male reproductive passage regressed and degenerated and was replaced by connective tissue. The oviduct arrested as a blunt end during male phase and, finally, extended and connected to the genital pore during the female phase.

Reproductive characteristics of Spondyliosoma cantharus (Linnaeus, 1758) in the Gulf of Tunis

Summary The reproductive features of Spondyliosoma cantharus were studied in the Gulf of Tunis to contribute to better fisheries management on a regional scale and to broaden knowledge on whether there are actual performance differences compared to others areas. A total of 369 fish were caught by trammel and gill nets in the Gulf of Tunis from January 2005 to June 2006. Sex-ratio, gonad maturation, size and age at maturity, sexual cycle, condition and reproductive strategy were determined. The male : female ratio was initially skewed in favour of females, with males predominating in larger sizes. Length of females at first maturity was 17.8 cm TL (n = 141), which corresponds to 4 years of age. A recommendation is made to increase the length at capture. Spawning season extends from January to May, with a peak in March–April correlated to the lowest sea surface temperatures (14.8–15.6°C); during this period, a dichromatism arises between males and females. The hepatosomatic index and the condition factor present significant monthly changes in relation to the breeding activity. The bimodal size frequency distribution, the biased sex ratio, and the presence of bisexual gonads outline a protogynous hermaphroditism; diandry should be confirmed.

The Expression of amh and amhr2 Is Associated with the Development of Gonadal Tissue and Sex Change in the Protandrous Black Porgy, Acanthopagrus schlegeli1

The protandrous black porgy, Acanthopagrus schlegeli, has a striking life cycle, with sex differentiation at the juvenile stage, mono-male development, a bisexual gonad during the first 2 yr of life, and a male-to-female sex change (with vitellogenic oocytes) at 3 yr of age. In the present study, we investigated the possible roles of amh and amhr2 in gonadal development in a nonmammalian model organism (protandrous black porgy), especially in relation to sex differentiation, testicular and ovarian growth, and sex change. Fish of various ages were treated with estradiol or an aromatase inhibitor to induce the fish to become female. Furthermore, a natural sex change (2(+)-yr-old [>2 yr and <3 yr] fish) and a nonchemical method to surgically remove one of the pair of gonads to examine the possible roles of amh in the natural sex change were conducted. We present integrative in situ hybridization, immunohistochemical, cellular, and molecular data describing these phenomena. During gonadal sex differentiation, an increase in amh and amhr2 expression was detected. Higher levels of amh and amhr2 transcripts were observed in the testicular tissue when compared to the ovarian tissue in the bisexual gonad of 1(+)-yr-old (>1 yr and <2 yr) fish. Transcripts of amh reached peak levels in November (prespermatogenesis period) and then declined to the lowest levels in January (spawning period). Chemical-induced ovarian tissue had very low amh transcript levels but high levels of amhr2. Active testes had significantly higher amh and amhr2 expression levels as compared to inactive testes. In contrast, no difference in the expression of amh and amhr2 between active and inactive ovarian tissues was found. Transcripts of amh were expressed in the somatic cells of the spermatogonia and vitellogenic oocytes, and amhr2 was expressed in the somatic cells of the spermatogonia. Transcripts of amh decreased in the testicular tissue 5 mo before occurrence of the sex change into a female. In contrast, testicular amh expression remained high if the fish remained male. Human chorionic gonadotropin regulated amh and amhr2 expression in the testicular tissue but not in the ovarian tissue. The present results suggest that amh plays important roles in early testicular and ovarian development, late ovarian growth (e.g., vitellogenic oocytes), and natural sex change in the protandrous black porgy.

Sex differentiation and sex change in the protandrous black porgy, Acanthopagrus schlegeli

Protandrous black porgy fish, Acanthopagrus schlegeli, have a striking life cycle with a male sex differentiation at the juvenile stage and male-to-female sex change at 3 years of age. We had characterized the sex differentiation and sex change in this species by the integrative approaches of histology, endocrine and molecular genetics. The fish differentiated in gonad at the age around 4-months and the gonad further developed with a bisexual gonad for almost for 3 years and sex change at 3 year of age. An antagonistic relationship in the testicular and ovarian tissues was found during the development of the gonadal tissue. Male- (such as sf-1, dmrt1, dax-1 and amh) and female- (such as wnt4, foxl2 and cyp19a1a) promoting genes were associated with testicular and ovarian development, respectively. During gonadal sex differentiation, steroidogenic pathway and estrogen signaling were also highly expressed in the brain. The increased expression of sf-1 and wnt4, cyp19a1a in ovarian tissue and decreased expression of dax-1 in the ovarian tissue may play important roles in sex change from a male-to-female. Endocrine factors such as estradiol and luteinizing hormone may also involve in the natural sex change. Estradiol induced the expression of female-promoting genes and resulted in the precocious sex change in black porgy. Our series of studies shed light on the sex differentiation and sex change in protandrous black porgy and other animals.

Gonad development during sexual differentiation in hatchery-produced orange-spotted grouper ( Epinephelus coioides) and humpback grouper ( Cromileptes altivelis) (Pisces: Serranidae, Epinephelinae)

Juvenile sexual differentiation of two commercially important epinephelines, orange-spotted grouper ( Epinephelus coioides) and humpback grouper ( Cromileptes altivelis) (Serranidae, Epinephelinae), produced in hatcheries, was studied until first sexual maturation using gonadal histology. Diandric, protogynous hermaphroditism is confirmed for E. coioides with evidence of primary male differentiation directly from the juvenile phase as well as of secondary male development through the sex-change of functional females. All juveniles developed first an ovarian-phase then entered a bisexual-phase gonad. Sexual differentiation occurred in bisexual gonads at around 105 weeks after hatching (wah), with the growth of oocytes beyond the primary-growth stage for females, and the appearance of sperm sinuses and proliferation of spermatogenic cysts in primary males. The minimum size and age of first sexual maturation for females were 355 mm standard length (SL) and 113 wah. No mature males were found by 141 wah, suggesting that first maturation in males takes longer than in females, at least under mariculture conditions. For C. altivelis, all juveniles developed an ovarian-phase gonad. Minimum body size and age of first sexual maturation for females were 155 mm SL and 83 wah. In contrast to E. coioides, there was no sign of spermatogenic cysts in juvenile gonads and any indication of primary male differentiation in C. altivelis. This study reveals the variation in early gonad development in the epinephelines and highlights the importance of studying juvenile sexual differentiation for fully understanding sexual pattern in this fish subfamily.

Dual Roles of cyp19a1a in Gonadal Sex Differentiation and Development in the Protandrous Black Porgy, Acanthopagrus schlegeli1

Protandrous black porgy fish, Acanthopagrus schlegeli, have a striking life cycle, with male sex differentiation at the juvenile stage, a bisexual gonad during first 2 yr of life, and a male-to-female sex change (with vitellogenic oocytes) at 3 yr of age. The present study investigated the role of aromatase (cyp19a1a/Cyp19a1a) in gonadal development in this species, especially in relation to sexual differentiation and sex change. Fish of various ages were treated with estradiol (E2) or aromatase inhibitor (AI) to determine whether manipulation of the hormonal environment has an impact on these processes. We report an integrative immunohistochemical, cellular, and molecular data set describing these interesting phenomena. During male sex differentiation, high levels of cyp19a1a/Cyp19a1a expression were observed in the undifferentiated gonad (4 mo of age), in marked contrast to the low cyp19a1a/Cyp19a1a levels detected in the differentiated testis at the age of 5-6 mo. A low dose of E2 (0.25 mg/kg feed) stimulated testicular growth and function in sexually differentiated fish, whereas a high dose of E2 (6 mg/kg feed) induced female development. Furthermore, administration of AI suppressed male development and promoted female sexual differentiation. An increased number of figla transcripts (an oocyte-specific gene) were observed prior to cyp19a1a expression, concomitant with the development of oogonia and early primary oocytes in the ovaries of both E2- and AI-treated groups. Immunohistochemical Pcna staining showed that the regression of testicular tissue occurred prior to the development of ovarian tissue in both E2- and AI-induced females. The importance of cyp19a1a in female development was further demonstrated by the increase in cyp19a1a transcripts during the naturally occurring sex change. Transcripts of foxl2 increased in the gonads of 2- to 3-yr-old black porgy during the early stages of the natural sex change, followed by a gradual elevation of cyp19a1a levels. The levels of both genes peaked in the resulting ovarian tissue. Thus, cyp19a1a/Cyp19a1a plays dual roles in the gonadal development, namely, in testicular development during the initial period of sexual differentiation and later in ovarian development during the natural sex change.

Sex steroids and metabolic parameter levels in a seasonal breeding fish (Sparus aurata L.)

The gilthead seabream is a protandrous hermaphrodite seasonal breeding teleost with a bisexual gonad that offers an interesting model for studying the two first reproductive cycles (RCs), in which the specimens develops as males. During the first RC (RC1), 11-ketotestosterone (11-KT) and testosterone (T), the main androgens in fish, play different and specific roles in the testicular physiology as they peak at different stages of RC1. Moreover, the profiles of T serum levels during the second RC (RC2) demonstrated that this androgen is not essential in the testicular regression process that occurs during this cycle. However, changes in serum levels suggest that 17β-estradiol (E2) orchestrates this process during both RCs. Moreover, the E2 serum levels recorded during RC2 indicate that there is a threshold level that determines the initiation of ovarian development during this cycle without promoting complete feminization. We analysed triglyceride, protein, glucose and lactate serum levels in order to establish a relationship between the mobilization and transfer of nutrients, the hormonal changes that take place during the RC and body composition, finding that in vivo serum levels of metabolites change significantly throughout the first two RCs, although the physiological relevance of such changes is still unknown. Triglyceride levels seem to be affected by the beginning of ovary development during RC2 but not by testicular recrudescence during RC1. Moreover, glucose and lactate might be important sources of energy during the resting and testicular involution stages.

Gonadal changes and blood sex steroids levels during natural sex inversion in the protogynous Mediterranean red porgy, Pagrus pagrus (Teleostei: Sparidae)

Changes in gonadal structure and serum levels of sex steroids were investigated during natural sex inversion from female to male in reared populations of the protogynous Mediterranean red porgy, Pagrus pagrus. Four developmental phases were identified by histological observation: female, early transitional (ETr), late transitional (LTr), and male phases. At female phase, a few nests of spermatogonia were observed at the posterior-ventral part of the gonad mainly in females out of the breeding season. At ETr phase, spermatogonial proliferation occurred while perinucleolar oocytes showed signs of degeneration. At LTr phase, seminiferous lobules were formed and spermatogonial proliferation expanded along the ovary which degenerated. All types of male germ cells could be found. At male phase, functional testis underwent active spermatogenesis while small ovarian remnants associated to fat tissue could be detected. Both 17β-estradiol (E2) and estrone (E1) blood levels were significantly lower in fish at transitional and male phases in comparison to breeding females, while levels of 11-ketotestosterone (11-KT) and testosterone (T) gradually increased in the transitional and male phases. In conclusion, the protogynous P. pagrus possess a delimited type bisexual gonad with a medio-dorsal ovarian area and a latero-ventral testicular zone. Sex inversion starts mainly after the female breeding season with an active spermatogonial proliferation. The testis tissues develop while ovarian tissues regress to disappear completely in the functional male. This process is accompanied by a sharp decrease of estrogens levels and a progressive increase of androgens levels. The physiological significance of such endocrine changes is discussed.

Current Status of Genetic and Endocrine Factors in the Sex Change of Protandrous Black Porgy, Acanthopagrus schlegeli (Teleostean)

Black porgy, Acanthopagrus schlegeli Bleeker, a marine protandrous hermaphrodite fish, is functionally male for the first 2 years of life, but begins to sexually change to female after the third year. Testicular tissue and ovarian tissue are separated by connective tissue in the bisexual gonad. This sex pattern provides a unique model to study the mechanism of sex change in fish. The annual profiles of plasma estradiol, vitellogenin, and 11-ketotestosterone concentrations in males were significantly different from those in the 3-year-old females. Oral administration of estradiol stimulated high levels of gonadal aromatase activity, plasma luteinizing hormone (LH) levels, and sex change in the 2-year-old fish. Oral administration with aromatase inhibitors for 1 year further blocked the natural sex change in 3-year-old black porgy and all fish became functional males. Transcripts of estrogen receptor (ER), androgen receptor, and gonadotropin receptors in the ovarian tissue of bisexual gonad were significantly less expressed than those in the bisexual testicular tissue. ER and aromatase transcripts were much higher in the vitellogenic ovary than those in the bisexual ovarian tissue. Plasma LH levels were higher in male fish than sex-changing fish during postspawning and nonspawning season in 2(+)-year-old black porgy. We are also conducting investigations on the role of the genetic factors (Dmrt 1, Sox 9, Sf-1, and Dax-1) in sex development and sex change. An endocrine mechanism of sex change in black porgy is proposed.

An Overview of Cell Renewal in the Testis Throughout the Reproductive Cycle of a Seasonal Breeding Teleost, the Gilthead Seabream (Sparus aurata L)1

The gilthead seabream is a protandrous hermaphrodite seasonal breeding teleost with a bisexual gonad that offers an interesting model for studying the testicular regression process that occurs in both seasonal testicular involution and sex change. Insofar as fish reproduction is concerned, little is known about cell renewal and elimination during the reproductive cycle of seasonal breeding teleosts with asynchronous spermatogenesis. We have previously described how acidophilic granulocytes infiltrate the testis during postspawning where, surprisingly, they produce interleukin-1beta, a known growth factor for mammalian spermatogonia, rather than being directly involved in the elimination of degenerative germ cells. In this study, we are able to discriminate between spermatogonia stem cells and primary spermatogonia according to their nuclear and cytoplasmic diameters and location in the germinal epithelium, finding that these two cell types, together with Sertoli cells, proliferate throughout the reproductive cycle with a rate that depends on the reproductive stage. Thus, during spermatogenesis the spermatogonia stem cells, the Sertoli cells, and the developing germ cells (primary spermatogonia, A and B spermatogonia, and spermatocytes) in the germinal compartment, and cells with fibroblast-shaped nuclei in the interstitial tissue proliferate. However, during spawning, the testis shows few proliferating cells. During postspawning, the resumption of proliferation, the occurrence of apoptotic spermatogonia, and the phagocytosis of nonshed spermatozoa by Sertoli cells lead to a reorganization of both the germinal compartment and the interstitial tissue. Finally, the proliferation of spermatogonia increases during resting when, unexpectedly, both oogonia and oocytes also proliferate. This proliferative pattern was correlated with the gonadosomatic index, testicular morphology, and testicular and gonad areas, suggesting that complex mechanisms operate in the regulation of gonocyte proliferation in hermaphrodite fish.

Neoplastic potential of germ cells in relation to disturbances of gonadal organogenesis and changes in karyotype.

The study consisted of 46 intersexual patients who underwent gonadectomy at the age of 3 months to 19 years because of gonadal dysgenesis (GD; 40 cases) or true hermaphroditism (bisexual gonads; 6 cases). In patients with GD, the incidence of the 46,XY karyotype was 67.5%, whereas the remaining patients exhibited numerical and structural aberrations of sex chromosomes (NSASs), and all patients with bisexual gonads revealed NSAS. Seminoma was diagnosed in 1 patient with the 46,XY karyotype and pure GD (streak gonads). Intratubular carcinoma in situ (CIS) appeared as an exclusive lesion in 61.5% of 13 patients with mixed GD, in 54% of 11 patients with partial GD (bilateral testes), in 16.7% of 6 patients with bisexual gonads, and in none of 13 patients with pure GD. CIS also appeared in tubules in the vicinity of sex cord-derived tumors (gonadoblastoma nests and unclassified mixed germ cell-sex cord-stromal tumor; MGCSCST) and within the tumors. In 3 patients, gonadoblastoma replaced the whole bilateral gonads and is referred to as gonadoblastoma-only GD. The incidence of neoplastic lesions (mostly bilateral) was 90.9% in patients with partial GD, 76.9% (mostly unilateral) in patients with mixed GD, 23.1% (unilateral) in patients with pure GD, and 16.7% (unilateral) in patients with bisexual gonads. Disregarding types of disturbances of gonadal organogenesis, the incidence of lesions was 71.4% in 28 patients with the 46,XY karyotype and 35.3% in 17 patients with NSAS. We conclude, first, that NSAS is not a prerequisite for the appearance of GD and GD is more frequently associated with the 46,XY karyotype. Second, the spectrum of germ cell neoplastic lesions in GD is wider than reported. Besides germ cell carcinoma, CIS, and gonadoblastoma nests, the spectrum also includes a tumor of gonadoblastoma-only in cases of GD and MGCSCST. Third, the incidence of neoplastic lesions is related more to the severity of the disturbances of gonadal organogenesis than it is to aberrations in sex chromosomes. Fourth, less disturbed testicular organogenesis predisposes these patients more toward germ cell neoplastic lesions, which suggests that the testicular environment of a dysgenetic gonad plays an important role in germ cell neoplasia initiation, maintenance, or both.

Estradiol, aromatase and steroid receptors involved in the sex change of protandrous black porgy, Acanthopagrus schlegeli

Black porgy, Acanthopagrus schlegeli, a marine protandrous hermaphrodite, is functionally male for the first 2 years of its life, but begins to sexually change to female after the third year. Testicular tissue and ovarian tissue are separated by connective tissue in the bisexual gonad. This sex pattern provides a unique model for studying the mechanism of sex change in fish. Significantly high levels of plasma estradiol during the prespawning/spawning season, and low levels of plasma 11-ketotestosterone during the spawning season were observed in the inversing females. No difference of plasma testosterone levels was observed in males and females. Oral administration of estradiol stimulated high levels of gonadal aromatase activity, plasma luteinizing hormone levels and sex change in the 2-year-old fish. Oral administration with aromatase inhibitors for a year further blocked the natural sex change in 3-year-old black porgy and all fish became functional males. Transcripts of estrogen receptor and androgen receptor in the ovarian tissue of the bisexual gonad were significantly less expressed than those in the bisexual ovarian tissue. The estrogen receptor transcripts were much higher in the vitellogenic ovary than those in the bisexual ovarian tissue. It was concluded that estradiol, aromatase and steroid receptors in the gonadal tissue play an important role in the natural and controlled sex change in black porgy.

Identification of endocrine-disrupting effects in aquatic vertebrates and invertebrates: report from the European IDEA project

The EU-funded project IDEA aimed to evaluate (a) what parameters and endpoints allow the detection of endocrine-mediated developmental and reproductive effects of (xeno)estrogens in life cycle- and life stage-specific toxicity tests with the zebrafish Danio rerio, a small laboratory fish used in many ecotoxicity test guidelines, and (b) whether substances that act as estrogens in vertebrates may also adversely affect the development, differentiation, and reproduction of aquatic invertebrates. The invertebrate species investigated included Hydra vulgaris, Gammarus pulex, Chironomus riparius, Hyalella azteca, and Lymnaea stagnalis. The animals were exposed to the model estrogenic chemicals ethynylestradiol (EE2), bisphenol A (BPA), and octylphenol (OP), which exert their endocrine activity in vertebrates through the estrogen receptor. As endpoints, developmental and reproductive parameters at the organism level as well as molecular and cellular parameters were measured. Life cycle exposure of zebrafish to (xeno)estrogens induced a specific, partly irreversible response pattern, consisting mainly of (a) induction of vitellogenin (VTG), (b) alterations of gonad differentiation, (c) delay of first spawning, and (d) reduced fertilization success. The effects of EE2 on zebrafish were expressed at environmentally realistic concentrations, while BPA and OP became effective at concentrations higher than those usually found in the environment. The vitellogenic response was equally sensitive as the reproductive parameters in the case of EE2, but VTG was more sensitive in the case of BPA. Partial life cycle exposure of zebrafish had lasting effects on fish development and reproduction only when the fish were exposed during the stage of juvenile bisexual gonad differentiation. In (partial) life cyle and multigeneration studies with invertebrates, (xeno)estrogenic impact was assessed by a range of developmental and reproductive parameters including hatching, growth, moulting, mating behavior, and egg number. Several parameters were found to be responsive to (xeno)estrogens; however, most effects were induced only at higher, probably nonphysiological concentrations. Low-dose effects were observed in full life cycle experiments, particularly in the second generation. It remains to be established whether the estrogen-induced alterations in the invertebrate species indeed do result from disturbances of the endocrine system. The findings of the present research project support the development of appropriate testing methodologies for substances with estrogenic activity.