The gonadal anatomy and sexual pattern of the protandrous sex-reversing fish, Rhabdosargus sarba (Teleostei: Sparidae)

The gonadal anatomy and sexual pattern of Rhabdosargus sarba (Teleostei: Sparidae) was studied to provide some basic structural information for the subsequent investigations on the endocrinology of protandrous hermaphroditism in this fish. Evidence derived from relating sex to differences in body size, from gonadal histology and from biopsy, revealed the occurrence of natural sex reversal from male to female in this species. The gonad of R. sarba possessed topographically distinct male and female zones that were well separated by connective tissue. Based on gross-anatomical and histological observations, four types of gonad were distinguished and were designated as Types I-IV in the present study. Active spermatogenetic tissue was present in the Type I, II and IV gonads. Dormant oogonia and perinucleolar oocytes were found in the Type I (male) and II (intersex) gonads, respectively. In the Type III (female) gonad, a functional ovarian zone was observed and the testicular tissue was vestigial. The existence of ovarian tissue as an oogonial band in the Type IV (male) gonad, which was found more commonly in large specimens, suggested that these functional males might not undergo sex reversal in their life cycle. The interrelationship of the different types of gonad is discussed with reference to protandrous hermaphroditism.     

Early gonadal development and primary males in the protogynous epinepheline, Cephalopholis boenak

Early gonadal development of the protogynous epinepheline, Cephalopholis boenak, was examined histologically in 289 specimens with standard length (L_S) of 42–130 mm, collected from May 2000 to April 2002 in Hong Kong waters, to determine male developmental pathways and establish its sexual pattern. All juvenile gonads developed an ovarian lumen with primary‐growth stage oocytes and scattered spermatogenic tissue prior to sexual differentiation and first sexual maturation. From this bisexual phase containing both female and male tissues, some gonads differentiated as ovaries with further oocyte growth to cortical‐alveolus and vitellogenic stages, the rest differentiated as testes with the proliferation of spermatogenic tissue and the formation of a sperm sinus. All testes retained the lumen and primary‐growth stage oocytes, and sperm sinuses ran within the gonad wall. Unlike most protogynous species, among functional males it was impossible to distinguish those resulting from juveniles through sexual differentiation (i.e. primary male) from those resulting from functional females through sex change (i.e. secondary male) based solely on testicular morphology. A proportion‐spermatogenic‐tissue index (I_ST) was, therefore, developed and determined to be a reliable quantitative indicator for distinguishing differentiating, primary males before a sperm sinus was evident, from differentiating females during sexual differentiation. Since sexually transitional specimens with the concominant appearance of degenerating vitellogenic, or later, stage oocytes and spermatogenic tissue in the gonads were previously noted from Hong Kong, diandric, protogynous hermaphroditism is confirmed in C. boenak. For species, such as this and other epinephelines, in which all males have the same testicular morphology, a complete analysis of a wide range of body sizes from juveniles to adults is necessary for understanding male developmental pathways, and determining sexual pattern.     

Females of four mole species of genus Talpa (Insectivora,mammalia) are true hermaphrodites with ovotestes

We studied the anatomical, histological, and genetic features of the sexual tract in four European mole species of the genus Talpa (Insectivora, mammalia): T. occidentalis, T. europaea, T. romana, and T. stankovici. All XY individuals had a normal male phenotype, whereas all XX individuals in all four species had features that identified them as intersexes. These individuals were nonetheless presumed to be functionally fertile females. Intersexuality was manifested mainly as gonadal hermaphroditism, with all females possessing bilateral ovotestes. The gonads were composed of a small portion of histologically normal ovarian tissue and a variably sized, generally large mass of disgenetic testicular tissue, accompanied by a small, rudimentary epididymis. The rest of the sexual tract was typically female, including oviducts, uterus, and vagina of normal appearance. Polymerase chain reaction (PCR) and Southern blotting analyses showed that the mammalian testis-determining gene SRY is present in males but not in females. Part of the conserved sequence of the mole SRY gene was cloned and sequenced after PCR amplification in two of the four mole species (T. occidentalis from Spain and T. romana from Italy). Sequences were identical in these two species and were very similar to those of the human and mouse SRY gene. Our findings constitute the first evidence of the existence of a genus-specific case of true hermaphroditism, probably due to a very ancient mutation that fixed in populations of the ancestral species from which contemporary moles evolved. The possible nature of this mutation is discussed with regard to the cytologic, histologic, and genetic features of the gonads in Talpa females. © 1996 Wiley-Liss, Inc.     

Morphological study for understanding the sexual pattern in ghost shrimp Callichirus major (Crustacea: Axiidea)

Callichirus major is a species of ghost shrimp that has burrowing habits, building underground galleries in the intertidal region of beaches. This study aimed to analyse some morphological parameters to verify its type of sexual pattern. A sample of 79 individuals, collected at the beach of Corujão, Espírito Santo, Brazil, was used. Data on the external morphology, presence of gonopores, carapace length (CL) and cheliped lengths (Lch) were obtained. In addition, the gonads were processed for histological analysis. The animals were divided into three categories: A, individuals with male characteristics; B, those presenting exclusively female characteristics; C, animals with characteristics of intersex, which presented supernumerary gonopores. Positive allometries were found for Lch versus CL only for category A, characterizing the group's marked heterochely. Histologically, it was possible to observe the presence of oocytes in category A and one case of male tissue in an intersex individual (category C). However, no genital ducts of both sexes were found in that individual. Callichirus major presents controversial sexual characters, which makes it difficult to understand the reproductive parameters and sexual pattern. However, maybe that species can develop a sexual system of hermaphroditism.     

Protogynous hermaphroditism in the half-banded sea perch, Hypoplectrodes maccullochi (Serranidae)

The half-banded sea perch, Hypoplectrodes maccullochi (Serranidae) exhibits protogynous hermaphroditism, based on the presence of transitional individuals collected from rocky reefs along the coast of New South Wales, Australia. Males dominated the larger size and age classes, whereas females predominated the smaller size and age groups. Histological preparations suggested that sex change occurs between 55–85 mm s.l. and 1 + to 4+ years of age. Three transitional phases were identified which varied according to the proportion of gametogenic tissue and remnant oocytes present within their gonads. All individuals greater than 85 mm s.l. were functional males containing well defined crypts of spermatids and spermatozoa. Remnant oocytes within these testes indicated prior female function. H. maccullochi were sexually monochromatic. The occurrence of some small males derived from pre-spawning females suggested pre-maturational sex change occurred in some individuals. Sex changing individuals were found in all the months of the year that gonads were examined in detail (January, February, April and June 1989). Fish were ripe in August and November. H. maccullochi conforms with the pattern of reproduction evident within the genus Hypopleclrodes .     

Life history of the orange-striped emperor <Emphasis Type="Italic">Lethrinus obsoletus</Emphasis> from the Mariana Islands

The present study investigated the age-based demography of the orange-striped emperor, Lethrinus obsoletus, from commercial samples in the Commonwealth of the Northern Mariana Islands (CNMI), spanning a 24-month market sampling period. Information on growth, life span, mortality, and reproduction was derived through analysis of sectioned sagittal otoliths and gonad material. The species had a moderate longevity of 13 years while females and males reached 50% sexual maturity at 3.8 years (22.9 cm fork length) and 2.8 years (19.9 cm fork length), respectively. Histological examination of gonads and sex-specific age frequency distributions suggest the sexual ontogeny of the species conforms to juvenile hermaphroditism, whereby sexual transition from female to male occurred prior to maturation. No annual spawning periods were identified, but the ubiquitous presence of post-ovulatory follicles in females and spermatogenic material in males coupled with a consistent lunar trend in gonadosomatic index patterns suggests the species spawns every lunar cycle throughout the year with spawning activity potentially increasing around the new moon. Ratios of natural to fishing mortality indicate a moderate level of exploitation (0.37); however, a large portion of harvested females had not reached reproductive maturity, suggesting that formal assessments of stock status are warranted to ensure the sustainable harvest of the species in CNMI.     

Evidence for protogynous hermaphroditism in some lethrinid fishes

An examination of the size/sex relationships and gonadial structure and histology of eight species of the commercially important family Lethrinidae from the North West Shelf of Australia and the Gulf of Carpentaria suggests that protogynous hermaphroditism is the typical mode of sexuality in these fishes. A linear relationship between size and sex ratio, in which females predominate at smaller sizes and males at larger sizes, was demonstrated in five species for which sufficient information was available. All five of these species showed a considerable overlap in the size distribution of the sexes but there was no evidence for the occurrence of primary males in the populations sampled. The tests of all species examined showed typical 'secondary male' morphology and the presence of atretic ovarian material ('brown bodies'). Individuals with intersex gonads were observed in five species. It is suggested that the effects of fishing on such protogynous fish stocks will depend on the precise mechanims, as yet unknown in lethrinids, that control the onset of sex change.     

Sexual and temporal variations in floral scent in the subdioecious shrub Eurya japonica Thunb

In many flowering plants, floral scents are a significant trait for visitors, playing an important role in attracting pollinators and/or detracting herbivores. The evolution of flowering plants from hermaphroditism to dioecy is often accompanied by sexual dimorphism in floral scent. In this study, floral scents emitted by different sexual morphs of the subdioecious shrub Eurya japonica Thunb. were collected using a dynamic headspace method, and sexual and temporal variations were evaluated by gas chromatography–mass spectrometry (GC–MS). Two volatiles, α‐pinene and linalool, were identified as the major components of floral scents in females, hermaphrodites, and males. The males emit higher amounts of floral scents, particularly α‐pinene, compared to females or hermaphrodites. Floral scents emitted by males generally decrease as flowers enter senescence, whereas those from females or hermaphrodites do not significantly differ. Intraspecific variations in floral scents of subdioecious species provided by this study would contribute to better understanding of sexual dimorphism in floral scent.     

Seasonal variations in the intermediate metabolism of Parastacus varicosus (Crustacea, Decapoda, Parastacidae)

The aim of this study was to analyze the seasonal variations in the metabolism of Parastacus varicosus and examine the possible relationships to its reproduction. Animals were sampled (9 h to 10 h) in each month in the Gravataí River, RS, Brazil. Haemolymph samples were collected from each crayfish in the field for determination of glucose, total proteins, total lipids, and total cholesterol. Hepatopancreas, abdominal muscle, and gonads were removed for determination of glycogen, total proteins, total lipids, and total cholesterol. ANOVA revealed significant seasonal differences in the biochemical composition of all tissues studied; when the sexes were compared these parameters did not show any significant difference in the hepatopancreas and muscle. However, in haemolymph we observed significant variation only in cholesterol and lipid levels. The results suggest that the metabolic variability is related to the stage of maturation of the gonads, in females, where the hepatopancreas and other tissue studies can store and transfer reserves to support maturation to complement the food intake. Variations in the gonadosomatic and hepatosomatic indices suggest that reproduction occurs principally in summer. As in other decapods, abiotic factors such as water temperature, oxygen content, etc. influence the intermediate metabolism.     

Sex allocation in a simultaneous hermaphrodite, the zebra goby Lythrypnus zebra: insights gained through a comparison with its sympatric congener, Lythrypnus dalli

Synopsis The sexual pattern of the zebra goby Lythrypnus zebra, is an apparent exception to sex allocation theory. Most L. zebra are simultaneous hermaphrodites (i.e., have active female and male gonadal tissue), yet it appears they do not reproduce as males and females simultaneously. Understanding the maintenance of simultaneous hermaphroditism in L. zebra could expand sex allocation theory. In this study, I used a comparison with the blue-banded goby, Lythrypnus dalli, a sympatric congener with a qualitatively similar sexual pattern, to investigate the role of male spawning rate, body size and sexual flexibility in determining the sexual pattern of L. zebra and to isolate differences between the species that might explain their differing sexual patterns. Using field measurements of male nesting success, I found no differences between the species in the body size of nesting males suggesting that large size is associated with successful male reproduction in both species. In addition, nesting males spawned at approximately three times the rate of females in both species; thus, reproduction via male function can be equally advantageous relative to adopting the female role. However, the nest longevity of L. zebra males was shorter than that of L. dalli males, suggesting reproduction via male function may be less reliable in L. zebra. Finally, under laboratory conditions, L. zebra females tended to prefer large mates, and L. zebra were able to re-allocate in both directions, exhibiting a greater capacity to switch than L. dalli. Given these results, I suggest that switching between the sexes plays a greater role in maintaining simultaneous hermaphroditism in L. zebra than L. dalli, perhaps because male reproduction is not as consistent in L. zebra. Sexual flexibility may be an important factor affecting patterns of sex allocation, generally.     

Steroid hormone profiles and correlative gonadal histological changes during natural sex reversal of sobaity kept in tanks and sea-cages

The gonadosomatic index of sobaity Sparidentex hasta fits well with the natural spawning season of February-March. At 12 and 24 months all the population matured as males. However, during this time, between April-September intersex gonads were seen. From October of the third year of life, females were seen for the first time. These changes in the histology of the gonads were correlated with the hormonal profile. Testosterone showed no significant correlation with sex but 11-ketotestosterone correlated very well with the mature male gonads and thus can be used for sexing. Oestradiol-17β higher in sex reversed individuals (females) in the spawning season than in males. The sequence of events in the protandrous sex change of this fish during the first two spawning seasons is male → intersex → male. However, during the third spawning season (age 36–37 months) this sequence is male →intersex → male or female (10–17%).     

Sex ratios and hermaphroditism in nemipterid fish from northern Australia

Of 13 nemipterid species from coastal waters around northern Australia, nine show size-related differences in sex ratio with males predominating at larger sizes. Histological examination of gonads shows that in Scolopsis monogramma S. taeniopterus and S. bilineatus this size-related skew in sex ratio results from protogynous hermaphroditism and not from sexually differentiated growth rates as has been reported for other nemipterid species. There is also evidence that, in two other species, Nemipterus peronii and Pentapodus porosus , hermaphroditism may occur. Although the mechanism by which the gonads are transformed in S monogramma and S. taeniopterus differ markedly, there is evidence to suggest that in both species sex change is a post spawning event, successful initiation of which may require females to have achieved an advanced stage of vitellogenisis.     

Morphological ontogeny of the gonad of three plectropomid species through sex differentiation and transition

The gonadal ontogeny through sex differentiation and transition of three protogynous coral trout species, Plectropomus leopardus , P. maculatus and P. laevis was described, based on anatomical and germinal differences along the length of the reproductive tract. Gonads of immature and mature females, sex changing individuals (transitionals) and males were examined. Specific anatomical features that were compared between sexual phases included the presence and structure of sperm sinuses, gonadal musculature and germinal cell types. All three coral trout species first differentiated as an immature female. The sexual pattern of P. leopardus and P. maculatus was concluded to be diandric protogynous hermaphroditism (males were derived from the juvenile phase as well as through sex change of mature females). Plectropomus laevis was found to be monandric as males were only derived through sex change in mature females. Structural changes did not occur concomitantly with the germinal changes associated with sex change in these Plectropomus species, which is atypical for protogynous species described to date. Precursory sperm sinuses in the dorso-medial region of the gonad were present, although non-functional, in a proportion of immature and mature females of all three species. These proportions, however, varied between species depending on the sexual pattern. The structural and germinal changes observed were hypothesized as anatomical adaptations that aid in minimizing time spent in the (non-reproductive) sexual transition phase and maximizing flexibility in male development in the diandric species.     

Histological assessment of White Sea cod <Emphasis Type="Italic">Gadus morhua marisalbi</Emphasis> 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.     

Signal trait sexual dimorphism and mutual sexual selection in Drosophila serrata

Abstract The evolution of sexual dimorphism may occur when natural and sexual selection result in different optimum trait values for males and females. Perhaps the most prominent examples of sexual dimorphism occur in sexually selected traits, for which males usually display exaggerated trait levels, while females may show reduced expression of the trait. In some species, females also exhibit secondary sexual traits that may either be a consequence of a correlated response to sexual selection on males or direct sexual selection for female secondary sexual traits. In this experiment, we simultaneously measure the intersex genetic correlations and the relative strength of sexual selection on males and females for a set of cuticular hydrocarbons in Drosophila serrata . There was significant directional sexual selection on both male and female cuticular hydrocarbons: the strength of sexual selection did not differ among the sexes but males and females preferred different cuticular hydrocarbons. In contrast with many previous studies of sexual dimorphism, intersex genetic correlations were low. The evolution of sexual dimorphism in D. serrata appears to have been achieved by sex-limited expression of traits controlled by genes on the X chromosome and is likely to be in its final stages.     

Mating group size and evolutionarily stable pattern of sexuality in barnacles

Barnacles, marine crustaceans, have various patterns of sexuality depending on species including simultaneous hermaphroditism, androdioecy (hermaphrodites and dwarf males), and dioecy (females and dwarf males). We develop a model that predicts the pattern of sexuality in barnacles by two key environmental factors: (i) food availability and (ii) the fraction of larvae that settle on the sea floor. Populations in the model consist of small individuals and large ones. We calculate the optimal resource allocation toward male function, female function and growth for small and large barnacles that maximizes each barnacle's lifetime reproductive success using dynamic programming. The pattern of sexuality is defined by the combination of the optimal resource allocations. In our model, the mating group size is a dependent variable and we found that sexuality pattern changes with the food availability through the mating group size: simultaneous hermaphroditism appears in food-rich environments, where the mating group size is large, protandric simultaneous hermaphroditism appears in intermediate food environments, where the mating group size also takes intermediate value, the other sexuality patterns, androdioecy, dioecy, and sex change are observed in food-poor environments, where the mating group size is small. Our model is the first one where small males can control their growth to large individuals, and hence has ability to explain a rich spectrum of sexual patterns found in barnacles.     

Invasion of unisexuals in hermaphrodite populations of animal-pollinated plants: effects of pollination ecology and floral size-number trade-offs

Abstract.— The most common sexual system in animal-pollinated plants is hermaphroditism, while some species are dioecious or gynodioecious and a very few are androdioecious. In this paper, I attempt to explain this pattern by extending previous models for the evolution of sexual systems to incorporate two main features: (1) a portion of investment in pollinator attraction contributes to only female or male function, because one sexual function of a flower is saturated with pollinator visitation earlier than the other sexual function; and (2) there are trade-offs between the size and number of flowers. The analysis was conducted to determine the conditions when females and males can increase in frequency in a hermaphroditic population, assuming either concave or convex pollinator gain curves (relation between investment to attractive structures of a flower and frequency of pollinator visits to the flower). The results suggest that both of the main factors play important roles in the evolution of plant sexual systems: uneven contribution of pollinator-attractive structures and nonlinear trade-offs between flower size and number can destabilize hermaph-roditism. When a convex pollinator gain curve was assumed, the effect of nonlinear trade-offs can produce accelerating compensation from the elimination of one sexual function, allowing males to increase for large regions of parameter space, where females could not increase. The last prediction obviously conflicts with the observed rarity of androdioecy in nature, indicating the necessity of exploring pollinator gain curves in more detail.     

Sexuality and hermaphroditism in fishes. I. Synchronous functional hermaphroditism in the serranid fish Serranus scriba L

Anatomical and histological examination of Serranus scriba L. showed the existence of primary females (67%), hermaphrodites (31%) and primary males (2%). Synchronous functional hermaphroditism is described on the basis of an anatomical and histological study of the gonads. Although they function simultaneously, the testicular and ovarian parts of hermaphrodite gonads have completely separate ducts. Females and hermaphrodites have the same annual reproduction cycle. In hermaphrodites, the testicular part matures one month sooner than the ovarian part. Cross fertilization between primary females and hermaphrodite individuals and between two different hermaphrodites probably occurs, while self-fertilization is less likely. The testicular tissues of primary males are of the acinar type and those of hermaphrodites are of the radial type. It is possible that primary males do not take part in reproduction. Serranus scriba in Egyptian Mediterranean waters is a longperiod spawner, which spawns from June to the end of October, i.e. it is a summer-autumn spawner.     

Gonadal development and spawning cycle in the digynic hermaphrodite sharpsnout seabream Diplodus puntazzo (Sparidae) off the Canary Islands, northwest of Africa

Diplodus puntazzo is a species characterized by a rudimentary hermaphroditism, with a low level of protandry. The study found that the overall sex ratio was one male to 2.03 females, diverging significantly from 1 : 1, and that there was a ratio of one male to 0.11 transitional fish. The sex ratio varied with season: during the reproductive period the ratio was 1 : 1.86 (male : female), significantly lower than in the non‐reproductive period in which the sex ratio was approximately 1 : 2.26. Both sexes had similar size distributions; however, females were predominant in all size intervals, especially in the larger ones. No significant difference in mean total length (TL) between females (330 mm), males (319 mm) or transitionals (321 mm) was found. The smallest functional female and male analysed were 159 and 157 mm TL, and the largest were 520 and 510 mm TL, respectively. No significant difference in length at first level of maturity, attained at the second year of life, was found between males (281 mm) and females (292 mm), respectively. A protracted spawning season was identified for the species: from September to February, with a peak in November. GSI values followed the same pattern for males and females, with values of females being similar to those of males; the highest values occurred between September and December, with a maximum in November. Occurrence of transitional fish was significantly higher during the month with highest values of GSI than in the resting period. The study found that vitellogenesis did not begin synchronously for all females, and the simultaneous presence of oocytes in all stages of development indicated an asynchronous mode of ovarian development. The presence of postovulatory, together with tertiary yolk vesicle oocytes, indicated that the species is a multiple spawner.