The effect of inhibitors upon intracellular cyclic AMP levels and chick myoblast differentiation.

The small free-living nematode Caenorhabditis elegans is usually found as a hermaphrodite, but occasionally true males appear in the population. This study provides an account of gonadogenesis in the normal male and in a mutant that is a temperature-sensitive sex transformer.Male and hermaphrodite gonads develop from morphologically identical primordia. The small primordial gonad lies on the ventral side of the worm in the coelomic cavity. The gonadial primordium contains four nuclei at parturition. As this primordium develops in a hermaphrodite, it produces a double-armed, mirror symmetrical gonad that produces first sperm and then eggs. In the male, however, this primordium develops into an asymmetrical structure composed of a ventrally located testis, a loop region, a seminal vesicle, and a vas deferens. The male gonad presents a linear sequence of nuclei in successive stages of spermatogenesis beginning with a mitotic region in the testis, followed by clearly distinguishable stages of meiosis throughout the loop region to the seminal vesicle.A temperature-sensitive sex transformer mutant, tsB202, has been isolated. tsB202 carries an autosomal recessive mutation in linkage group II that at restrictive temperature transforms an XX hermaphrodite into a phenotypic male, complete with a normal male gonad and vestigial external genitalia. These transformed males are classified as pseudomales because they do not exhibit mating behavior. Temperature shift experiments have determined the specific temporal sequences of gonadogenesis, oogenesis, and spermatogenesis. Proper manipulation of the temperature regimen causes the production of intersexes. In one intersex, a male gonad complete with sperm, seminal vesicle, and vas deferens also contains oocytes. In another intersex produced by the complementary temperature shift, a hermaphrodite-shaped gonad develops that produces only sperm and no oocytes.     

Intersex,a temperature-sensitive mutant of the nematode Caenorhabditis elegans

A temperature-sensitive mutation, isx-1(hc17), is reported in the nematode Caenorhabditis elegans which alters the sexual phenotypes of both genotypic sexes. At the restrictive temperature, XX animals are functionally female rather than hermaphroditic due to the absence of spermatogenesis, and XO animals develop as intersexes. These intersexes have normal male head and tail structures and exhibit some mating behavior, but possess hermaphrodite-like gonads which produce no sperm and usually contain a few oocytes. An abortive vulva is usually present and evidence is presented which suggests that the formation of the vulva by the hypodermis is induced by the underlying gonad. The direct effects of the mutation are confined to the descendants of four primordial gonad cells. Gametogenesis and gonad sheath development do not seem to be tightly coupled and are shown to differ in their responses to X-chromosome dosage. The interaction of the intersex mutation with mutant alleles of two transformer genes tra-1 and tra-2 is discussed and a model for the action of these genes in gonad development and sex determination is proposed.     

Hermaphroditism in Meloidogyne hapla

Hermaphrodites were detected in diploid and polyploid isolates of population 86-Va of Meloidogyne hapla. Young hermaphrodites are indistinguishable from normal females. Initially, hermaphrodite ovaries are filled with oocytes at various stages of development. Hermaphroditism is expressed later when young oocytes in the early pachytene region of the growth zone suddenly advance to diakinesis and proceed with maturation divisions, resulting in spermatid production. Spermatogenesis may be initiated shortly after the fourth molt, or later, after a female has produced some eggs. Spermatogenesis may occur in one or both gonads, and it may be initiated in one gonad before the other. Once initiated, spermatogenesis continues for the entire reproductive life of the hermaphrodite. Several thousand spermatozoa accumulate in the ovotestis. Because they do not pass through the oviduct into the spermatotheca, they do not take part in reproduction (nonfunctional hermaphroditism). Among the progeny of hermaphrodites, ca. 50% are hermaphroditic, and the remainder are apparently normal females which, however, produce about 50% hermaphroditic progeny. Two temperature regimes (20-23 C and 27-30 C) did not influence the percentage of hermaphrodites among the progeny. Hermaphroditism could not be transmitted to nonhermaphroditic isolates following attempted crosses between males of hermaphroditic and females of nonhermaphroditic isolates. Although this result suggests cytoplasmic rather than nuclear inheritance, this conclusion is not definitive.     

Mutations Causing Transformation of Sexual Phenotype in the Nematode CAENORHABDITIS ELEGANS

Ten mutations are described that transform genotypic hermaphrodites of the nematode Caenorhabditis elegans into phenotypic males. These fall into three autosomal complementation groups, termed tra-1, tra-2 , and tra-3. Two alleles of tra-1 produce almost complete transformation, to a fertile male phenotype; such transformed animals are useful for analyzing sex-linked genes. All alleles of tra-1 and tra-2 are recessive; the one known allele of tra-3 is both recessive and maternal in effect. Where tested, both XX and XXX hermaphrodites are transformed into males, but XO males (true males) are unaffected by these mutations. It is suggested that these genes are actually involved in hermaphrodite development and have no role in male development.     

Tissue-specific synthesis of yolk proteins in Caenorhabditis elegans

The primary site of yolk protein synthesis in the nematode, Caenorhabditis elegans, has been determined. In animals containing no gonadal cells (obtained by laser ablation of the gonadal precursor cells early in development), yolk proteins are present in abundance. This demonstrates that yolk proteins are made outside the gonad. An examination of proteins present in tissues isolated by dissection, and a comparison of proteins synthesized by isolated tissues incubated in vitro have identified the intestine as the major site of yolk protein synthesis. We propose that yolk proteins are synthesized in the intestine, secreted from the intestine into the body cavity, and taken up from the body cavity by the gonad to reach oocytes. The site of yolk protein synthesis has also been examined in four mutants that have largely male somatic tissues, but a hermaphrodite germ line. Here again, yolk proteins are produced by intestines in a hermaphrodite-specific manner. This suggests that sex determination is coordinately regulated in intestinal and germ line tissues.     

Production of intersexes and the evolution of androdioecy in the clam shrimp Eulimnadia texana (Crustacea,Branchiopoda, Spinicaudata)

Summary

The production of low numbers of offspring that exhibit a mixture of male and female traits (termed “intersexes”) is commonly reported for crustaceans. The production of intersexes has been ascribed to both genetic and non-genetic (e.g., parasitic infections and environmental pollutants) causes. Herein we report on two observed types of intersexes in the clam shrimp Eulimnadia texana: (1) a “morphological” intersex, possessing secondary male characteristics (e.g., claspers) and an eggproducing gonad, and (2) a “gonadal” intersex, possessing primarily male traits (e.g., male secondary sexual characters and male gamete production) but also producing low levels of abortive female gametes. We propose that these intersexes are likely the products of low frequencies of crossing over between the sex determining chromosomes that result in the array of observed mixed sexual phenotypes. Additionally, we suggest that the low-level production of intersexes, combined with the ephemeral nature of the habitats occupied by these shrimp, may explain the preponderance of androdioecy (mixtures of males and hermaphrodites) found in these clam shrimp, and possibly branchiopods more generally.     

The sys-1 gene and sexual dimorphism during gonadogenesis in Caenorhabditis elegans

In wild-type Caenorhabditis elegans, the hermaphrodite gonad is a symmetrical structure, whereas the male gonad is asymmetric. Two cellular processes are critical for the generation of these sexually dimorphic gonadal shapes during early larval development. First, regulatory "leader" cells that control tube extension and gonadal shape are generated. Second, the somatic gonadal precursor cells migrate and become rearranged to establish the adult pattern. In this paper, we introduce sys-1, a gene required for early organization of the hermaphrodite, but not the male, gonad. The sys-1(q544) allele behaves genetically as a strong loss-of-function mutant and putative null. All hermaphrodites that are homozygous for sys-1(q544) possess a grossly malformed gonad and are sterile; in contrast, sys-1(q544) males exhibit much later and only partially penetrant gonadal defects. The sys-1(q544) hermaphrodites exhibit two striking early gonadal defects. First, the cell lineages of Z1 and Z4, the somatic gonadal progenitor cells, produce extra cells during L2, but the regulatory cells that control gonadal shape are not generated. Second, somatic gonadal precursor cells do not cluster centrally during late L2, and the somatic gonadal primordium typical of hermaphrodites is not established. In contrast, the early male gonadal lineage is asymmetric as normal, the somatic gonadal primordium typical of males is established correctly, and the male adult gonadal structures can be normal. We conclude that the primary role of sys-1 is to establish the shape and polarity of the hermaphrodite gonad.     

Body size and symbiotic status influence gonad development in <Emphasis Type="Italic">Aiptasia pallida</Emphasis> anemones

Pale anemones (Aiptasia pallida) coexist with dinoflagellates (primarily Symbiodinium minutum) in a mutualistic relationship. The purpose of this study was to investigate the role of these symbionts in gonad development of anemone hosts. Symbiotic and aposymbiotic anemones were subjected to light cycles that induced gametogenesis. These anemones were then sampled weekly for nine weeks, and gonad development was analyzed histologically. Anemone size was measured as mean body column diameter, and oocytes or sperm follicles were counted for each anemone. Generalized linear models were used to evaluate the influence of body size and symbiotic status on whether gonads were present and on the number of oocytes or sperm follicles produced. Body size predicted whether gonads were present, with larger anemones being more likely than smaller anemones to develop gonads. Both body size and symbiotic status predicted gonad size, such that larger and symbiotic anemones produced more oocytes and sperm follicles than smaller and aposymbiotic anemones. Overall, only 22 % of aposymbiotic females produced oocytes, whereas 63 % of symbiotic females produced oocytes. Similarly, 6 % of aposymbiotic males produced sperm follicles, whereas 60 % of symbiotic males produced sperm follicles. Thus, while gonads were present in 62 % of symbiotic anemones, they were present in only 11 % of aposymbiotic anemones. These results indicate that dinoflagellate symbionts influence gonad development and thus sexual maturation in both female and male Aiptasia pallida anemones. This finding substantiates and expands our current understanding of the importance of symbionts in the development and physiology of cnidarian hosts.     

An unusual hermaphrodite reproductive trait in the Antarctic brooding bivalve Lissarca miliaris (Philobryidae) from the Scotia Sea, Southern Ocean

The Antarctic marine environment is extreme in its low temperatures and short periods of primary productivity. Invertebrates must therefore adapt to maximise reproductive output where low temperature and limited food slow larval development. Brooding is a common reproductive trait in Antarctic marine bivalves; larval development occurs within the mantle cavity, and larvae are released as fully developed young. Lissarca miliaris is a small, short-lived, shallow-water brooding bivalve of circum-Antarctic distribution and found most abundant in the sub-Antarctic Magellan Region and islands of the Scotia Arc. Here, an unusual hermaphrodite reproductive trait is described for L. miliaris from King George Island (62°14′S, 58°38′W) and Signy Island (60°42′S, 45°36′W), Antarctica, using histological and dissection techniques. Specimens demonstrate simultaneous and sequential hermaphrodite traits; male and female gonads develop simultaneously, but the production of oocytes is reduced while testes are ripe. Functional females are more abundant in specimens above 3 mm shell length, although male reproductive tissue persists and functional males are found in all size classes. The number of previtellogenic oocytes produced by far exceeds the number of oocytes extruded and brooded, which may indicate an ancestral link to a planktotrophic past. Hermaphroditism in L. miliaris maximises reproductive efficiency in a short-lived species, in which the female’s capacity to brood its young is limited, and demonstrates a specialised adaptation to a cold stenothermal and food-limited environment prevailing in the Southern Ocean.     

A bias caused by ectopic development produces sexually dimorphic sperm in nematodes

Self-fertile hermaphrodites have evolved independently several times in the genus Caenorhabditis [1, 2]. These XX hermaphrodites make smaller sperm than males [3, 4], which they use to fertilize their own oocytes. Because larger sperm outcompete smaller sperm in nematodes [3-5], it had been assumed that this dimorphism evolved in response to sperm competition. However, we show that?it was instead caused by a developmental bias. When we transformed females of the species Caenorhabditis remanei into hermaphrodites [6], their sperm were significantly smaller than those of males. Because this species never makes hermaphrodites in the wild, this dimorphism cannot be due to selection. Instead, analyses of the related nematode Caenorhabditis elegans suggest that this dimorphism might reflect the development of sperm within the distinct physiological environment of the hermaphrodite gonad. These results reveal a new mechanism for some types of developmental bias-the effects of a novel physical location alter the development of ectopic cells in predictable ways.     

Gonadal development and an indication of functional protogyny in the Indian damselfish (Dascyllus carneus)

The objective of this study was to determine the sexual pattern of the Indian dascyllus Dascyllus carneus . After an initially undifferentiated state, gonads of D. carneus developed an ovarian lumen and primary growth stage oocytes, and subsequently cortical-alveolus stage oocytes. From ovaries with cortical-alveolus stage oocytes and from more developed ovaries, some gonads redifferentiated into testes. From a sample of 163 individuals, two had a gonad containing degenerating vitellogenic oocytes and proliferating spermatogenic tissue, nine had a gonad containing degenerating cortical-alveolus stage oocytes and spermatogenic tissue, and five had a gonad with degenerating primary growth stage oocytes and spermatogenic tissue. The size of these individuals overlapped greatly with the size range of mature females, suggesting that at least in some individuals, redifferentiation toward a testis occurred after spawning as females. This indicates that D. carneus is a functional, diandric protogynous hermaphrodite. Removal of a dominant male(s) did not induce a sex change in any of the ranking females in the laboratory and field groups. There was no difference in the number of chases and signal jumps performed by the ranking female between control and experimental field groups, or before and after removal of the male. However, the sizes of the ranking females were at or beyond the size range of individuals with a mixed-stage gonad, suggesting that the developmental window for female-to-male sex change may not be open ended. In 41 of 43 field groups, in which sex of fish was determined histologically or by the shape of the urogenital papilla, one to several highest size ranks were occupied by males, followed by one to several females. Mature males, however, were not limited to the highest ranks and occurred at various lower size ranks within groups. Individuals with a mixed-stage gonad also occupied various size ranks within groups.     

The C. elegans adult male germline: Stem cells and sexual dimorphism

The hermaphrodite Caenorhabditis elegans germline has become a classic model for stem cell regulation, but the male C. elegans germline has been largely neglected. This work provides a cellular analysis of the adult C. elegans male germline, focusing on its predicted stem cell region in the distal gonad. The goals of this study were two-fold: to establish the C. elegans male germline as a stem cell model and to identify sex-specific traits of potential relevance to the sperm/oocyte decision. Our results support two major conclusions. First, adult males do indeed possess a population of germline stem cells (GSCs) with properties similar to those of hermaphrodite GSCs (lack of cell cycle quiescence and lack of reproducibly oriented divisions). Second, germ cells in the mitotic region, including those most distal within the niche, exhibit sex-specific behaviors (e.g. cell cycle length) and therefore have acquired sexual identity. Previous studies demonstrated that some germ cells are not committed to a sperm or oocyte cell fate, even in adults. We propose that germ cells can acquire sexual identity without being committed to a sperm or oocyte cell fate.     

A Maternal-Effect Sex-Transformation Mutant of the Housefly, MUSCA DOMESTICA L

A maternal-effect sex-transformation mutant, transformer (tra), of the housefly is described. It is located on autosome 4 in close linkage with the Ba locus. Normally, the sex of Musca domestica is determined by the presence or absence of an epistatic factor, M. When produced by tra/tra mothers, a large fraction of the tra/tra genotypic female progeny carrying no M factors are transformed to develop into intersexes or fertile phenotypic males. The tra/+ progeny are also transformed, but less frequently. Aging of the mothers increases the frequency of sex-transformed flies. When produced by tra/+ mothers, tra/tra progeny (but not +/tra) occasionally undergo sex transformation. Thus, tra⁺ is active both maternally and zygotically. Genotypic males carrying the M factor are not affected by the tra mutant. It is concluded that the tra⁺ gene product is required for female determination and/or differentiation. A model is proposed to explain actions of all the known sex-determination genes in M. domestica , and it is discussed in relation to sex-determination mechanisms in several other insect species.     

Nondisjunction Mutants of the Nematode CAENORHABDITIS ELEGANS

The frequency of males (5AA; XO) among the self progeny of wild-type Caenorhabditis elegans hermaphrodites (5AA; XX) is about one in 500. Fifteen him (for "high incidence of males") mutations have been identified that increase this frequency by a factor of ten to 150, as a result of increased X-chromosome nondisjunction. The mutations define ten complementation groups, which have been mapped: nine are autosomal, and one sex linked. Most of the mutants are superficially wild type in anatomy and behavior; however, him-4 mutants display gonadal abnormalities, and unc-86 mutants, which have a Him phenotype, exhibit a variety of anatomical and behavioral abnormalities. All the mutants segregate fertile 3X hermaphrodite progeny as well as XO male progeny. Some produce large numbers of inviable zygotes. Mutants in all ten genes produce diplo-X and nullo-X exceptional ova, and in the four strains tested, diplo-X and nullo-X exceptional sperm are produced by 2X "transformed" males. It appears likely that most of the mutants have defects in both gamete lines of the hermaphrodite. XO males of him strains other than him-4 and unc-86 are similar to wild-type males in anatomy and behavior, and all produce equal or almost equal numbers of haplo-X and nullo-X sperm, and no diplo-X sperm. Male fertility is reduced to varying extents in all him mutants. In four of the strains, nondisjunction during oogenesis has been shown to occur at a reductional division, and in three of these strains, abnormalities in recombination have been demonstrated. One mutant also exhibits autosomal nondisjunction, but many of the others probably do not. Therefore, the X chromosome of C. elegans may differ from the autosomes in the mechanisms controlling its meiotic behavior.——3X hermaphrodites are shorter and less fertile than 2X hermaphrodites, and they produce many inviable zygotes among their self progeny: these are probably 4X zygotes. Haplo-X and diplo-X ova are produced in 2:1 ratio by 3X hermaphrodites. him mutations are expressed in these animals, increasing the frequency of self-progeny males and 2X hermaphrodites.     

Patterns of structural change in gonads of the divine dwarfgoby Eviota epiphanes as they sexually transition

This study documents changes in gonadal structure for the serial hermaphrodite (or bidirectional sex changer) divine dwarfgoby Eviota epiphanes (family Gobiidae) as individuals transition in both directions. To evaluate transitional gonad morphology, individuals actively producing the same gamete type (oocytes or sperm) were set up into pairs and euthanised over a period of 14 days to get a time series of morphological changes during gonad transformation. Results from this study show that rapid changes in the gonad take place at a structural level as individuals change their reproductive function and gamete production. Changing from oocyte production (o-phase) to sperm production (s-phase) starts with the breakdown of vitellogenic oocytes (i.e., atresia) followed by the appearance and proliferation of spermatogenic tissue which, in most cases, was not previously visible. Changing from sperm production to oocyte production included the cessation of sperm production, a reduction in size and number of seminiferous lobules and the maturation of previtellogenic oocytes already present in the gonads. Experimental fish changed from oocyte production to sperm production more readily than from sperm production to oocyte production. The hypothesis that shifts in sexual function among serially hermaphroditic fish species have a similar cost in either direction is not supported in E. epiphanes.     

The postembryonic cell lineages of the hermaphrodite and male gonads in Caenorhabditis elegans

The ancestry of the cells in the hermaphrodite and male gonadal somatic structures of C. elegans has been traced from the two gonadal somatic progenitor cells (Z1 and Z4) that are present in the newly hatched larvae of both sexes. The lineages of Z1 and Z4 are essentially invariant. In hermaphrodites, they give rise to a symmetrical group of structures consisting of 143 cells, and in males, they give rise to an asymmetrical group of structures consisting of 56 cells. The male gonad can be distinguished from the hermaphrodite gonad soon after the first division of Z1 and Z4. However, the development of Z1 and Z4 in hermaphrodites shares several features in common with their development in males suggesting that the two programs are controlled by similar mechanisms. In the hermaphrodite lineage, a variability in the positions of two cells is correlated with a variability in the lineages of four cells. This variability suggests that cell-cell interaction may play a more significant role in organisms that develop by invariant lineages than has hitherto been considered. None of the somatic structures (e.g., uterus, spermatheca, vas deferens) develops as a clone of a single cell. Instead, cells that arise early in the Z1–Z4 lineage generally contribute descendants to more than one structure, and individual structures consist of descendants of more than one lineage.     

Feminization of the Isopod Cylisticus convexus after Transinfection of the wVulC Wolbachia Strain of Armadillidium vulgare

Reproductive parasites such as Wolbachia are able to manipulate the reproduction of their hosts by inducing parthenogenesis, male-killing, cytoplasmic incompatibility or feminization of genetic males. Despite extensive studies, no underlying molecular mechanism has been described to date. The goal of this study was to establish a system with a single Wolbachia strain that feminizes two different isopod species to enable comparative analyses aimed at elucidating the genetic basis of feminization. It was previously suggested that Wolbachia wVulC, which naturally induces feminization in Armadillidium vulgare, induces the development of female secondary sexual characters in transinfected Cylisticus convexus adult males. However, this does not demonstrate that wVulC induces feminization in C. convexus since feminization is the conversion of genetic males into functional females that occurs during development. Nevertheless, it suggests that C. convexus may represent a feminization model suitable for further development. Knowledge about C. convexus sexual differentiation is also essential for comparative analyses, as feminization is thought to take place just before or during sexual differentiation. Consequently, we first described gonad morphological differentiation of C. convexus and compared it with that of A. vulgare. Then, wVulC was injected into male and female C. convexus adult individuals. The feminizing effect was demonstrated by the combined appearance of female secondary sexual characters in transinfected adult males, as well as the presence of intersexes and female biases in progenies in which wVulC was vertically transmitted from transinfected mothers. The establishment of a new model of feminization of a Wolbachia strain in a heterologous host constitutes a useful tool towards the understanding of the molecular mechanism of feminization.     

Reproductive behavior of intersexes of an intertidal amphipod Corophium volutator

Abstract. Intersexes are common in crustaceans. Typically, these intersexes are sterile or function as females, but prior evidence from laboratory experiments suggests that intersexes of a key species of gammaridean amphipod, Corophium volutator , might function as males. We observed that intersexes of C. volutator behaved as males by crawling (mate-searching) on a mudflat during ebb tides and pairing in burrows with female amphipods. In the laboratory, intersexes and males did not differ in aspects of crawling such as movement rate and measures of burrow investigation. I`ntersexuality was costly in that intersexes crawled less often than males on a mudflat, formed fewer pairs with females than males, and remained in tandem less often with receptive females than males. The use of PCR-based identification methods failed to identify the presence of transovarial, feminizing, microsporidian parasites as a major cause of intersexuality in this species in that infected females did not produce broods that contained more intersexes than broods produced by uninfected females. Because intersexes may be mistaken as females, the percentage of functional males in amphipod populations may be underestimated: an important consideration given male limitation in populations of C. volutator. The occurrence of intersexes has significant implications for studies on the evolution and ecology of sex ratios, and the use of crustaceans as indicators of environmental quality.     

Sex Reversal in Zebrafish fancl Mutants Is Caused by Tp53-Mediated Germ Cell Apoptosis

The molecular genetic mechanisms of sex determination are not known for most vertebrates, including zebrafish. We identified a mutation in the zebrafish fancl gene that causes homozygous mutants to develop as fertile males due to female-to-male sex reversal. Fancl is a member of the Fanconi Anemia/BRCA DNA repair pathway. Experiments showed that zebrafish fancl was expressed in developing germ cells in bipotential gonads at the critical time of sexual fate determination. Caspase-3 immunoassays revealed increased germ cell apoptosis in fancl mutants that compromised oocyte survival. In the absence of oocytes surviving through meiosis, somatic cells of mutant gonads did not maintain expression of the ovary gene cyp19a1a and did not down-regulate expression of the early testis gene amh; consequently, gonads masculinized and became testes. Remarkably, results showed that the introduction of a tp53 (p53) mutation into fancl mutants rescued the sex-reversal phenotype by reducing germ cell apoptosis and, thus, allowed fancl mutants to become fertile females. Our results show that Fancl function is not essential for spermatogonia and oogonia to become sperm or mature oocytes, but instead suggest that Fancl function is involved in the survival of developing oocytes through meiosis. This work reveals that Tp53-mediated germ cell apoptosis induces sex reversal after the mutation of a DNA–repair pathway gene by compromising the survival of oocytes and suggests the existence of an oocyte-derived signal that biases gonad fate towards the female developmental pathway and thereby controls zebrafish sex determination.