Search

Abstract. The caridean shrimp Lysmata wurdemanni is a protandric simultaneous hermaphrodite. These individuals go through a male phase (MP) before changing sex to become female-phase simultaneous hermaphrodites (FPSH). The latter [...]

Abstract. The hypothesis of protandrous (male to female) sex change was tested for the first time in a rhynchocinetid shrimp, Rhynchocinetes uritai, with an analysis of life-history traits. Samples were [...]

External parental care is uncommon among actiniarians but common in Epiactis species. Here, several aspects of reproduction are analyzed for of one of them, Epiactis georgiana. Samples were collected in December, January, February, March, and April in the Antarctic Peninsula and the eastern Weddell Sea, during 1998, 2000, 2002, and 2003. Most sexually mature individuals of E. georgiana are male or female, but some are hermaphrodites. This is the first report of hermaphroditism in E. georgiana, which is the third species of the genus with this sexual pattern. The results suggest that oogenesis starts in December and that at least two generations of oocytes overlap; a third generation is often brooded externally. Putative fertilization is likely internal, and larvae and/or embryos are externally brooded on the distal part of the adult column until an advanced developmental stage. Apparently E. georgiana reproduces seasonally, probably releasing the embryos/larvae in the last months of the austral spring (December). Inter-individual variability was observed in gametogenesis. In addition, specimens from the Antarctic Peninsula were larger than those from the Weddell Sea. This study represents the first step in understanding the reproductive mode of E. georgiana., Introduction The diversity and number of clades of marine benthic invertebrates employing parental care in the Southern Ocean is unusually high, leading to a wide array of hypotheses to explain [...]

We report the incidence of male intersex in adult Pacific lamprey (Entosphenus tridentatus (Richardson, 1836)) during their pre-spawning migration in fresh water. Although 'hermaphrodites' have been suggested in other adult lampreys, this is the first detailed description and discussion of this phenomenon. A total of 0.5% of our adult Pacific lamprey from Willamette Falls (2 out of 427 adults) were intersex, with oocytes in the testes. This phenomenon was identifiable only by histological examination. The testes of the intersex males were immature, in the beginning stages of meiosis. One intersex male possessed primary growth or perinucleolar stage oocytes loosely interspersed throughout the testes, and the other possessed at least 6 mid-vitellogenic oocytes (0.6 mm, mean long diameter) separate from the testes. Because premetamorphic lamprey can possess both female and male gonial cells, we hypothesize that intersex is a remnant larval trait and that these fish failed to fully develop into males during metamorphosis. Key words: intersex, gonochoristic, primitive fish, reproduction, maturation, cyclostomes. Nous rendons compte de l'incidence d'intersexualite chez des males adultes de lamproie du Pacifique (Entosphenus tridentatus (Richardson, 1836)) durant leur migration en eau douce precedant le frai. Bien que la presence << d'hermaphrodites >> ait ete suggeree chez d'autres lamproies adultes, il s'agit des premieres description et discussion detaillees de ce phenomene. Au total, 0,5 % des lamproies du Pacifique adultes de Willamette Falls recensees (2 individus sur 427 adultes) etaient intersexuelles, presentant des oocytes dans les testicules. Ce phenomene n'est observable que par un examen histologique. Les testicules des males intersexuels etaient immatures, aux stades initiaux de la meiose. Un male intersexuel possedait des oocytes au stade de croissance primaire ou perinucleolaire dissemines ca et la dans les testicules et l'autre possedait au moins six oocytes a des stades intermediaires de la vitellogenese (diametre long moyen de 0,6 mm) separes des testicules. Etant donne que la lamproie premetamorphique peut presenter des cellules goniales femelles et males, nous avons emis l'hypothese que l'intersexualite est un caractere larvaire residuel et que ces poissons ne se sont pas developpes completement en individus males durant la metamorphose. Mots-cles : intersexualite, gonochoriste, poisson primitif, reproduction, maturation, cyclostomes. [Traduit par la Redaction], Introduction Hermaphroditism, either sequential or synchronous, exists in approximately 5% to 6% of all animal species (Grober and Rodgers 2007) and approximately 2% of all extant teleost fishes, across 20 [...]

Protandrous hermaphrodites are predicted to change sex from male to female when relative reproductive fitness of females surpasses that of males. How size at sex transition varies with population, mating group and individual parameters was investigated for five populations of the protandrous hermaphrodite slipper snail, Crepidula fornicata. The populations varied for density, size distribution, average mating group size and sex ratio. Size at sex-change was correlated with the population sex ratio. Comparisons of multiple hypotheses revealed that variables predicting the sex of a snail vary among positions in the mating group. The variables included body size, the relative size of the snail sitting atop the focal snail and population density. Our data support the conclusions that size at sex-change (and by inference, the size at which one sex has relatively greater fitness) is not fixed for these hermaphrodites and that individual size, social conditions and population differences all influence variation in relative fitness., Introduction Sequential hermaphroditism is a reproductive strategy whereby organisms change sex at some point in their lifetime. The size-advantage hypothesis for sequential hermaphroditism posits the existence of a threshold size [...]

One of the main goals of sex allocation theory is understanding sex ratio evolution. However, theoretical studies predicting sex ratios in species with unusual sexual systems, such as protandric simultaneous (PS) hermaphroditism, are rare. In PS hermaphrodites, juveniles first develop into functional males that mature into simultaneous hermaphrodites later in life. Here, we report on the sex ratio (males/males + hermaphrodites) in the PS hermaphroditic shrimp Exhippolysmata oplophoroides. A 2-year study demonstrated that hermaphrodites dominated the population in two different bays. This skewed sex ratio may be explained by limited encounter rates among conspecifics. In agreement with this idea, the density of shrimps was extremely low ([less than or equal to]1 shrimp km.sup.-2) at the two study sites. Size at sex phase change and sex ratios remained relatively stable through time at the two bays. The stability of these parameters might be explained by the rather steady population structure of this species during the study period. A review of sex ratios in PS hermaphroditic shrimps (Lysmata and Exhippolysmata) revealed considerable variation; some species have male- and others hermaphrodite-skewed sex ratios. The conditions explaining inter- and intra-specific sex ratio variation in protandric simultaneous hermaphroditic species remain to be addressed., Author(s): J. A. Baeza [sup.1] [sup.2] [sup.3] , A. A. Braga [sup.4] , L. S. López-Greco [sup.5] , E. Perez [sup.3] [sup.6] , M. L. Negreiros-Fransozo [sup.7] , A. Fransozo [...]

Introduction Barnacles (Cirripedia: Thoracica) exhibit diverse patterns of sexuality (Darwin, 1851). Individuals of most species are simultaneous hermaphrodites. However, coexistence of pure males and hermaphrodites (androdioecy) is known in some [...], In the lepadomorph barnacle Octolasmis warwickii, individuals are often found attached to the scutum of conspecifics living externally on the crab hosts. To test whether these conspecific-attached individuals are dwarf males, as are known to occur in other suborders of barnacles, we compared the pattern of attachment, size-frequency distribution, and reproductive status of the conspecific-attached (Con-A) and crab-attached (Crab-A) individuals. Con-As were smaller than Crab-As. There was a positive relationship between the body size of Crab-As and the number of individuals on them. Con-As had longer penises than Crab-As of the same body size, and their testes were better developed. The four largest Con-As examined were brooding eggs. These results indicate that Con-As of O. warwickii are dwarf males, with a potential to become hermaphroditic. This represents the first known example of coexistence of males and hermaphrodites in the suborder Lepadomorpha. The mating group size of O. warwickii was smaller than in its hermaphroditic congeners but larger than in barnacles with dwarf males and females, which supports the current theories that group size is important for the evolution of sexuality patterns in barnacles.

Although the nematode Caenorhabditis elegans produces self-fertile hermaphrodites, it descended from a male/female species, so hermaphroditism provides a model for the origin of novel traits. In the related species C. remanei, which has only male and female sexes, lowering the activity of tra-2 by RNA interference created XX animals that made spermatids as well as oocytes, but their spermatids could not activate without the addition of male seminal fluid. However, by lowering the expression of both tra-2 and swm-1, a gene that regulates sperm activation in C. elegans, we produced XX animals with active sperm that were self-fertile. Thus, the evolution of hermaphroditism in Caenorhabditis probably required two steps: a mutation in the sex-determination pathway that caused XX spermatogenesis and a mutation that allowed these spermatids to self-activate. 8 May 2009; accepted 16 September 2009 10.1126/science.1176013

Male mating tactics can vary according to the potential for scramble or contest competition but also as a consequence of individual characteristics, such as body condition and previous experience. The influence of experience, i.e., residency, on male recapture rates and reproductive success was studied in a population of free-living grey mouse lemurs. Long-term capture data from 320 individuals revealed that both sexes had very low recapture probabilities within their first year in the study population, but recapture rates declined less sharply during the following years. Capture results and telemetric analyses on 12 focal males revealed that resident males had larger body mass and larger home ranges than new males. Home range size correlated with the number of accessible females, indicating that resident males had higher probabilities to meet mates than new males. The reproductive success of 132 candidate fathers, representing both resident and new males, was determined by means of molecular genotyping. Paternity determination was successful in 38 cases (success rate: 19%). Sixteen resident males and seventeen new males sired offspring. However, in relation to the number of candidate fathers being present in the mating season, resident males were twice as likely to reproduce successfully as new males. These findings suggest experiencedependent reproductive tactics that most likely correspond to a differential spatial knowledge of resources, mates and potential threats. The results generally agree with the predictions made for a scramble competition regime and demonstrate substantial behavioral plasticity in a nocturnal primate species with a dispersed multi-male/ multi-female mating system. KEY WORDS Sexual selection; intrasexual competition; survival analysis; mating tactics

An investigation of whether hermaphrodites also posses facultative sex allocation, that is, a phenotypic flexibility, allowing them to distribute resources to either sex in an opportunistic way during their adult lifetime, is conducted. It is revealed that the findings are found to be consistent with theory for the evolutionary adjustment of sex allocation in simultaneous hermaphrodites.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2006.06.011 Byline: Roumen Voutev, Darrell J. Killian, James Hyungsoo Ahn, E. Jane Albert Hubbard Keywords: Gonadogenesis; Proximal germline tumor; Ribosome biogenesis; LIN-35/Rb Abstract: Ribosome biogenesis is a cell-essential process that influences cell growth, proliferation, and differentiation. How ribosome biogenesis impacts development, however, is poorly understood. Here, we establish a link between ribosome biogenesis and gonadogenesis in Caenorhabditis elegans that affects germline proliferation and patterning. Previously, we determined that pro-1(+) activity is required in the soma - specifically, the sheath/spermatheca sublineage - to promote normal proliferation and prevent germline tumor formation. Here, we report that PRO-1, like its yeast ortholog IPI3, influences rRNA processing. pro-1 tumors are suppressed by mutations in ncl-1 or lin-35/Rb, both of which elevate pre-rRNA levels. Thus, in this context, lin-35/Rb acts as a soma-autonomous germline tumor promoter. We further report the characterization of two additional genes identified for their germline tumor phenotype, pro-2 and pro-3, and find that they, too, encode orthologs of proteins involved in ribosome biogenesis in yeast (NOC2 and SDA1, respectively). Finally, we demonstrate that depletion of additional C. elegans orthologs of yeast ribosome biogenesis factors display phenotypes similar to depletion of pro genes. We conclude that the C. elegans distal sheath is particularly sensitive to alterations in ribosome biogenesis and that ribosome biogenesis defects in one tissue can non-autonomously influence proliferation in an adjacent tissue. Author Affiliation: Department of Biology, New York University, 1009 Silver Center, 100 Washington Square East, New York, NY 10003-6688, USA Article History: Received 30 April 2006; Revised 21 May 2006; Accepted 2 June 2006

The changes in ribosome biosynthesis in the Caenorhabditis elegans embryo which leads to defects in gonadogenesis in the hermaphrodite is studied.

Hermaphroditic animals often exhibit mating mechanisms that seem more damaging than those in species with separate sexes. Our analyses indicate that this difference is real. While females only remate when the benefit is positive, hermaphrodites remate even when this implies losing female fitness. This occurs because hermaphrodites can outweigh losses in the female function by gaining paternity. In an extended model we ask whether this favors the evolution of more male harm in hermaphrodites. When male harm only suppresses remating in the receiver it neither evolves in hermaphrodites nor in gonochorists. However, when male harm is coupled to a fertilization advantage, it evolves in both forms of gender expression with the highest levels in hermaphrodites. Hence, hermaphrodites are more prone to be caught in costly escalations than gonochorists. We discuss the implications for the evolution of gender expression in animals and plants.

Mating behavior in simultaneously hermaphroditic seabasses has been often cited as an example of cooperation among unrelated conspecifics. The predominant mating behavior in this group involves egg trading, where individuals reciprocally fertilize parcels of eggs from a partner. Egg trading has been suggested as a good example of a tit-for-tat cooperative mating strategy. Although simultaneous hermaphroditic fishes are often held up as strong examples of cooperation in mating behavior, a closer examination reveals significant sexual selection and sexual conflict between male and female roles among individuals. In the 7 species where data exist, there is a significant increase in male reproductive success with individual size, and in all but 1 species success through male function increases faster than reproductive success through female function. Despite this male-size advantage in simultaneous hermaphrodites, most species maintain their hermaphroditism for their entire life, and the increased male allocation while engaging in biased forms of reciprocation appear to increase the evolutionary stability of hermaphroditism in these species. Thus, egg-trading behavior is probably more complicated than was initially recognized, with individuals releasing different numbers of eggs in spawns, spawning at different rates as males and females, and partitioning male effort between pair and alternative mating tactics. The departures from equal reciprocity can probably be best understood by including aspects of traditional mating-system theory, with individuals increasing male mating success through a variety of behavioral tactics.

Androdioecy (populations consisting of males and hermaphrodites) is a rare mating system in plants and animals: up to 50 plants and only 36 animals have been described as being androdioecious, with most of the latter being crustaceans. To date, a thorough comparative analysis of androdioecy in animals has not been undertaken. Herein we present such an analysis. Androdioecy has only been extensively surveyed in 2 animal taxa: the nematode Caenorhabditis and the clam shrimp Eulimnadia. The other major taxon having androdioecious species is the Cirripedia (barnacles), but there are only limited studies on androdioecy in this group. In animals, androdioecy is found either in species that have morphologically and ecologically distinct sexes (that is, hermaphrodites and small, 'complemental' males) that are derived from hermaphroditic ancestors (that is, the barnacles) or in species that have similarly-sized males and hermaphrodites that have been derived from dioecious ancestors (the remaining androdioecious species). We suggest that the barnacles have evolved a sexual specialization in the form of these complemental males that can more efficiently use the constrained habitats that these barnacles often experience. For the remaining species, we suggest that androdioecy has evolved as a response to reproductive assurance in species that experience episodic low densities. Additionally, we hypothesize that the development of mechanisms allowing reproductive assurance in species with a number of sexually differentiated traits is most likely to result in androdioecy rather than gynodioecy (mixtures of females and hermaphrodites), and that these species may be developmentally constrained to stay androdioecious rather than being capable of evolving into populations solely consisting of efficient, self-compatible hermaphrodites. We conclude by suggesting several areas in need of further study to understand more completely the evolution and distribution of this interesting mating system in animals.

The sexual system of the decapod (caridean) shrimp Lysmata is protandric simultaneous hermaphroditism (PSH). Individuals first mature as males (male phase = MP) and then when older (larger) change to the external phenotype of female carideans (female phase = FP). However, unlike purely protandric carideans, Lysmata FPs retain reduced male gonadal tissues and ducts, and are able to mate nonreciprocally as males as well as to reproduce as females. Thus, FPs of Lysmata species are functional simultaneous hermaphrodites although most reproductive effort is devoted to embryo production and incubation. The question explored here is, given the propensity of carideans to protandry, the apparent low cost, and high reproductive advantage of PSH, why has not PSH evolved more frequently? The mating systems and sexual selection of caridean shrimps, the original sex of protandric individuals, the cost of maleness, and sex allocation theory are discussed in relation to protandry and PSH. None of these factors adequately explains the evolution of PSH of Lysmata species. Lysmata has at least 2 species groups with very different sociobiologies; these groups do not appear to share current selective pressures that would explain PSH in both. A historical contingency hypothesis, testable in part with a phylogenetic analysis, may explain the evolution of PSH in Lysmata.

Biomphalaria glabrata are simultaneous hermaphroditic freshwater snails that act as intermediate hosts for the macroparasitic trematode Schistosoma mansoni, a causative agent of schistosomiasis. Heritability and strain-specificity of both snail resistance and susceptibility to schistosome infection have been demonstrated, genetic variability for which is maintained, in part, through trade-offs between high fitness costs associated with infection and those associated with resistance. However, despite such a high cost of resistance and a low prevalence of infection in natural snail populations, genes for resistance are maintained within snail populations over successive generations, including in the complete absence of parasite pressure in laboratory populations. This may he indicative of alternative benefits of resistance genes, in addition to parasite defense, such as differential mating success between genotypes. Here we examined the mate and gender choice of snails across a multi-factorial range of potential partner combinations. These included host-resistance or susceptibility genotype, host genotype frequency within the population, current parasite infection status, and parasite genotype. We demonstrate recognition and discrimination by host snails depending on host and/or parasite genotype for each of these factors. In particular, our results suggest that a rare mating advantage to resistant genotypes may be a potential explanation for the maintenance of highly costly resistance genes within intermediate host populations under conditions of low or zero parasite pressure.

The mangrove killifish (Kryptolebias marmoratus) is the only vertebrate known to be capable of self-fertilization. Its gonad is typically an ovotestis that simultaneously produces eggs and sperm, and fertilization is internal. Although most populations of this species consist primarily or exclusively of hermaphroditic individuals, gonochoristic males occur at [approximately equal to] 20% frequency in a natural population at Twin Cays, Belize. Here we use a battery of 36 microsatellite loci to document a striking genetic pattern (high intraspecimen heterozygosities and low within-population linkage disequilibria) that differs qualitatively from the highly homozygous (or 'clonal') genetic architecture characteristic of killifish populations previously studied in Florida, where males are much rarer. These findings document that outcrossing (probably between gonochoristic males and hermaphrodites) is common at the Belize site, and, more importantly, they demonstrate the dramatic impact that functional androdioecy can have on the population genetic architecture of this reproductively unique vertebrate species. heterozygosity | inbreeding | Kryptolebias | linkage disequilibrium | selfing

Some possible effects of the ovotestis on evolution are considered. The effects hypothesized that the accumulated mutation frequency of nuclear genes in hermaphrodites may reach twice that compared with gonochorists.

The various conditions under which male or female sterility mutations might invade and spread in a heterodichogamous population which is a dimorphic population consisting of protandrous and protogynous individuals is discussed. It was found that under many circumstances conditions for the evolution of gynodioecy and androdioecy in a heterodichogamous population were the same as those for their evolution from populations that are monomorphic.

Abstract Introduction Gender-Biased Nectar Production (GBNP) in Dichogamous Plants Commonalities among Dichogamous Plants with GBNP GBNP is Male-Biased as Often as Female-Biased Nectar Production Biases Are Modest in Most Plants [...]

One of the major evolutionary trends in flowering plants is the evolution of unisexual flowers (male or female) from perfect flowers. This transition has occurred repeatedly in many taxa and has generated a wonderful array of variation in sexual expression among species. Theoretical studies have proposed a number of mechanisms to explain how this level of variation could be maintained in natural systems. One possible mechanism is the female compensation hypothesis, which predicts that female mutants require an increase in their seed fitness in order to invade a hermaphroditic system. Using Geranium maculatum, I tested this hypothesis and showed that female mothers produced more and larger seeds than hermaphroditic mothers even though they were indistinguishable in their vegetative traits and the flower production. Seeds from females were also more likely to germinate and produced seedlings with larger above-and below ground biomass. These seedlings were more likely to flower than those from hermaphrodites in at least one of the two populations studied. Combined, these results indicated that females in G. maculatum did compensate for their loss of male function by producing more and better seeds than hermaphrodites. This provides a mechanism for the maintenance of female plants in this species. Key words: female compensation; fitness; Georgia; Geraniaceae; gynodioecy; male sterility; progeny quality; spring ephemeral.

People born with intersex conditions experience trauma and stigma that have not been fully recognized by the medical and therapeutic professions. Current treatment protocols require rapid diagnosis followed by surgical alteration of infants born with ambiguous genitalia which has led to a lack of thorough attention to the psychosocial issues faced by these children and their families. Histories of surgery and silence have left children and families unable to address many of the traumas associated with intersexuality, including stigma, shame, surgical complications, and potential questions about sexual and gender identity. This article outlines recommendations for alternative treatment protocols. In addition to withholding unnecessary surgeries until children born with disorders of sex development are old enough to be involved in decisions regarding their medical treatment, this approach calls for the inclusion of social workers and other mental health experts as part of an interdisciplinary treatment team to serve as advocates, educators, psychotherapists and family systems experts, addressing ongoing issues in the lives of families and children living with intersex conditions. KEYWORDS. Ambiguous genitalia, genital surgery, family, intersex, intersexed, psychotherapy, stigma, shame, sex assignment, therapy, trauma, disorders of sex development

The literature is unclear regarding the appropriate medical and psychological treatment of intersexuality: people who have genital, gonadal, or chromosomal characteristics that are neither all female nor all male. Medical and psychosocial management of such individuals is being reevaluated. Congenital adrenal hyperplasia (CAH), the most common cause of intersexual development among genetic females, is an inherited disorder that leads to varying degrees of masculinization of the external genitalia while internal genitals (ovaries, Fallopian tubes, and uterus) are typically female. The purpose of this study was to explore self-perceptions of adult women who have CAH and the impact of the condition on their relationships, sexuality, gender identity, gender roles, and self-concept. In addition, their perceptions of medical treatment were examined. Five women with CAH chose to participate. Participants reported: (a) a sense of isolation and embarrassment about sharing information concerning their condition with others; (b) discomfort and embarrassment about certain aspects of their medical treatment; and (c) varying experiences and perceptions of their gender identity and gender roles. Recommendations are provided to assist psychotherapists in their work with people who have intersex conditions and their families. KEYWORDS. Congenital adrenal hyperplasia, sexuality, gender, gender role, gender identity, genetics, intersexuality, medical treatment, psychoeducation, psychotherapy, self-concept, sex assignment, sexuality, sexual orientation, stigma, virilization

Intersexuality is not rare. In its traditional definition--the impossibility of distinguishing whether the individual is male or female--the incidence is estimated at 1/4,500 births. If all minor variants of the shape of genitalia are included in the definition of intersex, the incidence rises to close to 1%. These numbers show that, although not spoken about as openly as other conditions, intersexuality is present at a high frequency throughout the world. Understanding intersexuality from a biological perspective has been a challenge. The main cause of the slow rate of progress in this field is the tremendous genetic heterogeneity that may correspond to an intersex situation. More than a dozen medical diagnoses can be associated with the same appearance of genitalia, which taken alone may give the observer little or no clue to the pathophysiology. Dissecting the various causes of intersexuality is essential at many levels: to understand the fundamental biological events of sexual development, to better interpret long-term follow-up studies on intersex patients, and to better predict psychosexual outcome and therefore improve the clinical management of intersex patients. This paper illustrates that the biological mechanisms of intersexuality are complex, and for the most part, understanding them is still a work in progress. Despite understanding the embryology of the genitalia, the mechanisms of action of sex hormones and of a number of sex-determining genes, many intersex babies are born without a clear biological explanation. The pressing question in this field is the social issue of gender assignment and early genital surgery. The author argues that the most important criteria in assigning a gender to an intersexed newborn is the future gender identity, regardless of the chromosomal constitution, gonadal secretions, and aspect of the genitalia. KEYWORDS. Ambiguous genitalia, endocrinology, genetics, gender, gender assignment, gender determination, hermaphroditism, intersex, intersexuality, sex determination, sex differentiation, sexual dimorphism

The wide spread production of pollen by triploid asexual dandelions, Taraxacum sect is studied by comparing rare male sterile individuals with pollen producing asexuals. Individuals are found to show plasticity in the production in the production of pollen, but it is nevertheless possible to distinguish between male sterile asexuals and male fertile asexuals.

Bateman's principle states that reproductive success is limited a) in females by the resources available for egg production; and b) in males, only by access to females and/or eggs. The principle has been used to generate predictions for two aspects of hermaphroditism; a) the advantage of hermaphroditism and b) sexual conflict. Comparing these predictions to the empirical data offers tests of Bateman's principle. Charnov's prediction that hermaphroditism would occur under circumstances where Bateman's principle does not apply is found to be largely correct. However, the prediction as to the association of hermaphroditism and low fixed costs is inconsistent with the data. Alternative explanations that predict that hermaphroditism is a strategy for reducing variance in reproductive success may better explain the data. Probability theory demonstrates that where two strategies have equal mean fitness, which must be the ease for male and female function, the strategy with the lower variance in reproductive success must have higher fitness (Gillespie's principle). Bateman's principle predicts that this will be the female role in hermaphrodites. However, Charnov, assuming Bateman's principle, predicted that sexual conflict stemming from a preference for the male role would be important in hermaphrodite mating systems, creating a paradox. Many hermaphrodite mating systems are based on conditional reciprocity with a preferred sexual role indicating sexual conflict. The data demonstrate that the preferred role varies among taxa, contrary to the predictions of Bateman's principle. It has been suggested that Bateman's principle can explain eases in which the female role is preferred (sperm-trading) as involving energy rather than gamete trading. However, energetic considerations suggest that energy trading would only be adaptive if Bateman's principle does not apply, paradoxically. The gamete trading model, based on the prediction that the role that offers control of fertilization will be preferred, is more consistent with the data. Application of Bateman's principle to hermaphrodites leads to contradictory predictions and does not offer the basis for a coherent theory of sexual selection, as Bateman proposed.

The protandric simultaneous hermaphrodite shrimp Lysmata wurdemanni (Gibbes 1850) has a pure searching mating system, i.e., males are continually searching for receptive females and copulation is brief. To examine whether size-based advantage in male--male competition occurs and whether the mating ability of male-phase (M) shrimp equals that of euhermaphrodite-phase shrimp serving as males (Em), mating performance, including mating frequency and precopulatory behavior, of M and Em shrimp was compared using two M:Em ratios. Two experiments were carried out from March 2004 to August 2004 at Florida Institute of Technology's Vero Beach Marine Laboratory using laboratory-cultured shrimp that originated from Port Aransas, TX, USA. In the two experiments, one parturial euhermaphrodite-phase shrimp acting as a female (Ef) was maintained with one M and two Em shrimp (one with and one without an egg mass), and two M and two Em shrimp, respectively. The M shrimp used were always smaller than the Em shrimp. Experiment 1 showed that there was no significant difference in mating ability between Em with and without egg mass. In both experiments, the M shrimp gained mating partners more frequently than the Em shrimp did. In the experiment with two M and two Em shrimp, mating frequencies of the small M and large M shrimp were similar. Precopulatory behaviors of the M shrimp were more active than those of the Em shrimp. Mating between the small M and larger Ef shrimp was sometimes successful even when the size difference was 20.0 mm total length (TL). Mating between a larger M shrimp and smaller Ef shrimp sometimes failed when the size difference was only 13.0 mm TL. Mating frequency of M shrimp over that of Em shrimp with Ef shrimp increased significantly with increasing density and operational sex ratio. The advantage of M over Em shrimp in obtaining mating partners is probably a result of sexual selection and adaptation, and may partially explain the observed delayed sex change in some L. wurdemanni, i.e., some male-phase shrimp grow very large and never become hermaphrodites.

Introduction Hermaphroditism is a universal character of ascidians (Satoh, 1994). In solitary ascidians, gametes of both sexes are often released to the environment simultaneously. In some species, such as Halocynthia [...], Solitary ascidians are hermaphrodites that release sperm and eggs simultaneously. However, many species are self-sterile, owing to a self/non-self recognition system operating at the outer surface of the chorion during sperm-egg interaction. In Ciona intestinalis, self-incompatibility is thought to have a genetic basis. Here, we report a survey of the self-fertilization potential of a Santa Barbara. California, population of Ciona savignyi, a close relative of C. intestinalis. We found that, in contrast to reports on C. intestinalis, C. savignyi is highly self-fertile. However, using two nonlethal recessive mutant strains, aimless (aim) and immaculate (imc), and a stable transgenic strain that expresses green fluorescent protein (GFP) in the notochord to follow offspring genotype, we demonstrate that non-self sperm outcompete self-sperm in fertilization competition assays. When the chorion was removed, both self- and non-self sperm performed equally well in the competition assay. Thus the non-self/self gamete recognition in C. savignyi is not absolute but relative, and is mediated by one or more components in the chorion. We discuss the significance of this finding in the context of natural populations in the wild, where individuals of C. savignyi are typically found growing in large groups that spawn in unison and where self-fertilization would be expected to be very rare.

Recent reports have demonstrated a cost associated with intersexuality in Amphipoda, including reduced fecundity and fertility. In this study, the gross morphology of the gonads in normal and intersex Echinogammarus marinus (Amphipoda) were compared to determine whether resource allocation to gonadal tissue accounted for this reduced fitness. Evidence for the presence of the male sex-determining hormone, androgenic gland hormone (AGH), was compared between sexual phenotypes using MALDI mass spectrometry. Two distinct intersex phenotypes ('male' intersex and 'female' intersex) were found, with variation in gonadal structure corresponding with external phenotype. Examination of male intersexes revealed normal testicular development (testes, seminal vesicles and vas deferens), but also revealed the formation of an oviduct. Ovaries of intersex females showed normal ovarian development, but were reduced in length by approximately 20% due to the presence of vas deferens. The number of vas deferens in intersex females was equal to the number (one or two) of genital papillae. We hypothesise that the reduced ovarian length observed in intersex females is a likely cause of the reduced brood size previously reported in intersex females of this species. Variation in the sexual phenotype corresponded both to development of the androgenic gland and to expression of a peptide fragment corresponding to the A chain of androgenic gland hormone (AGH). Androgenic glands and a putative AGH peptide were present in males. However, in both normal and intersex females, the androgenic glands were only present in a rudiment form and the peptide was not detected. Intersex males were found to possess abnormal glands that appeared hypertrophied. However, AGH peptides were not detected, supporting the suggestion that the intersex phenotype is manifested via perturbations of AGH., Introduction Intersexuality is widespread throughout the Amphipoda, having been reported in many families (Sexton and Huxley 1921; Sexton 1924; Ginsberger-Vogel 1975; Hastings 1981; Ford et al. 2003). Recent reports demonstrate [...]

The reproductive biology of the Mediterranean vermetid gastropod Serpulorbis arenarius, a subtidal sessile solitary species that lives in shady rocky communities, was studied at two localities south-east of the Iberian Peninsula. Its population density is usually low, with specimens sometimes sparsely distributed. Its shell often appears to be covered by epibiotic organisms. The sex ratio is biased toward males (63%) in the populations of SE Spain, and the results point towards hermaphroditism with alternating sexuality. The results obtained suggest that all specimens are first males, change to females under some as yet unknown condition and, after the ovogenesis cycle has been completed, revert to the original sexual state (male). The possible adaptive forces that favour hermaphroditism in this species are discussed, and we hypothesise that the seizure of a spermatophore by males may stimulate sex change to female. Brooding females (51% of females studied) were found from March to December. In males, histological study of testes revealed that spermatogenesis seems to occur throughout the year. Females brooded between 5 and 28 ([bar.x]= 15) egg capsules, which were attached by stalks to the inner surface of the shell. It is noteworthy that the gonads of two of the specimens brooding egg capsules were developing testes. The newly laid egg capsules were filled with an organic intracapsular matrix, in which 40-153 (2=94) eggs were embedded. The mean diameter of the uncleaved ova was 352.5 [micro]m. The organic intracapsular matrix and some nurse eggs were used as an extra-embryonic food source. Hatching occurred at an advanced veliger stage, immediately followed by metamorphosis. Therefore, the larval development of S. arenarius is of a lecithotrophic intracapsular type, with a short, free-swimming/crawling phase.

Increasing concerns over rising intersexuality in the animal kingdom and the ability of certain chemicals to disrupt the endocrine system have demanded a better understanding of the costs associated with such conditions. Whilst intersexuality appears relatively wide-spread throughout gonochoristic crustaceans, i.e. those crustacean species with two separate sexes, the 'fitness' costs have rarely been reported. Through comparable investigation of normal and intersex specimens of the highly abundant marine/estuarine amphipod Echinogammarus marinus (Leach) these 'fitness costs' were determined. Measurements taken to assess fitness costs included fecundity, fertility and embryonic development, maturation period, and any morphological deformities that might result in reduced pairing success. Results from this study suggest that intersex E.marinus suffer from reduced fecundity and fertility, and mature at a larger size than normal specimens. These fitness costs can also, to a certain extent, be related to the degree of intersexuality. It is suggested that the increased size and morphological abnormalities observed in intersexes may result in reduced pairing success. Investigations into intersex organisms, i.e. those organisms with known dysfunctional endocrine systems, and the costs associated with such conditions, should aid researchers in assessing effects at the population and community level.

Byline: R. Wiersma (1) Keywords: Abnormal genitalia; Infertility; True hermaphroditism Abstract: This is an 18-year (1985--2001) retrospective review of 85 patients with true hermaphroditism, with the aim of facilitating early recognition of this condition. Presentation of neonates and infants 6 months or younger, constituting 54% of this cohort, were different from the older children. The presentation, clinical features and investigative results of all patients diagnosed with true hermaphroditism at a single South African paediatric surgical unit were reviewed. This paper highlights the previously reported high incidence (51%) of this condition, as well as some of the unusual features of true hermaphroditism in this region. Diagnosis of true hermaphroditism requires a high index of suspicion for subtle anomalies of the genitalia. Although there were no pathognomonic clinical features, the true hermaphrodite presents as a patient of either gender with a congenital anomaly of the genitalia. The child is likely to have a normal male phallus, bifid labio-scrotal folds, a perineal hypospadias and in 53% of patients there was a palpable gonad. The method of investigation, together with the results and some of the management dilemmas associated with true hermaphroditism in a Third World population are presented. Author Affiliation: (1) Department of Paediatric Surgery, University of Natal, Private Bag 7, 4013 , Congella Durban, South Africa Article History: Registration Date: 30/03/2004 Accepted Date: 16/02/2004 Online Date: 26/05/2004

Byline: Josiane Courteau (1), Sabin Lessard (2) Keywords: Optimal sex ratio; Diffusion approximation; Stationary distribution; Group competition Abstract: We consider a haploid, hermaphrodite population subdivided into an infinite number of demes of finite size N. Assuming recurrent mutation, random union of gametes, partial dispersal, genetic drift, and incorporating group competition, a diffusion approximation is used to describe the evolution of sex ratio, corresponding to sex allocation to male versus female functions. The stationary distribution is deduced. In presence of group selection, a female-biased sex ratio in the whole population is found to be optimal in the sense that an allele coding for this sex ratio is always more frequent at equilibrium when segregating with another allele coding for a different sex ratio than for the same sex ratio. Numerical studies are presented to check the validity and accuracy of this prediction. Author Affiliation: (1) Centre de recherche clinique, Centre hospitalier universitaire de Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4 (2) Departement de mathematiques et de statistique, Universite de Montreal, Montreal, Quebec, Canada H3C 3J7 Article History: Registration Date: 01/01/2003 Received Date: 19/03/2003 Online Date: 27/10/2003 Article note: Research supported in part by grants from NSERC of Canada and FCAR of Quebec. This work is part of the first author's Ph.D. thesis at the Universite de Montreal under the supervision of the second author. Send offprint requests to: Sabin Lessard

Byline: J.A. Vargas (1), R.F. del Castillo (2) Keywords: aAndrodioecy; Gynodioecy; Fitness; Pollen discounting; Rational map; Projective plane Abstract: We formulate two single-locus Mendelian models, one for androdioecy and the other one for gynodioecy, each with 3 parameters: t the male (female) fertility rate of males (females) to hermaphrodites, s the fraction of the progeny derived from selfing and g the fitness of inbreeders. Each model is expressed as a transformation of a 3 dimensional zygotic algebra, which we interpret as a rational map of the projective plane. We then study the dynamics for the evolution of each reproductive system and compare our results with similar published models. In this process, we introduce a general concept of fitness and list some of its properties, obtaining a relative measure of population growth, computable as an eigenvalue of a mixed mating transformation for a population in equilibrium. Our results concur with previous models of the evolution of androdioecy and gynodioecy regarding the threshold values above which the sexual polymophism is stable, although the previous models assume constant the fraction of ovules from hermaphrodites that are self pollinated, while we assume constant the fraction of the progeny derived from selfing. A stable androdioecy requires more stringent conditions than a stable gynodioecy if the amount of pollen used for selfing is negligible in comparison with the total amount of pollen produced by hermaphrodites. Otherwise, both models are identical. We show explicitly that the genotype fitnesses depend linearly on their frequencies. Simulations show that any population not at equilibrium always converges to the equilibrium point of higher fitness. However, at intermediate steps, the fitness function occasionally decreases. Author Affiliation: (1) Independent scholar, Constitucion 204, (centro), Oaxaca, Oaxaca, Mexico, 68000 (2) CIIDIR IPN Oaxaca, Calle Hornos 1003, Xoxocotlan, Oaxaca, Mexico, 71230 Article History: Received Date: 07/05/1999 Online Date: 23/04/2003

The unc-52 gene of Claenorhabditis elegans encodes a homologue of the basement membrane heparan sulfate proteoglycan perlecan. Viable alleles reduce the abundance of UNC-52 in late larval stages and increase the frequency of distal tip cell (DTC) migration defects caused by mutations disrupting the UNC-6/netrin guidance system. These unc-52 alleles do not cause circumferential DTC migration defects in an otherwise wild-type genetic background. The effects of unc-52 mutations on DTC migrations are distinct from effects on myofilament organization and can be partially suppressed by mutations in several genes encoding growth factor-like molecules, including EGL-17/FGF, UNC-129/TGF-[beta], DBL-1/TGF-[beta], and EGL-20/WNT. We propose that UNC-52 serves dual roles in C. elegans larval development in the maintenance of muscle structure and the regulation of growth factor-like signaling pathways. Keywords: UNC-52; Perlecan; Organogenesis; Netrins; Cell migrations; C. elegans

Anne Fausto-Sterling's suggestion that the prevalence of intersex might be as high as 1.7% has attracted wide attention in both the scholarly press and the popular media. Many reviewers are not aware that this figure includes conditions which most clinicians do not recognize as intersex, such as Klinefelter syndrome, Turner syndrome, and late-onset adrenal hyperplasia. If the term intersex is to retain any meaning, the term should be restricted to those conditions in which chromosomal sex is inconsistent with phenotypic sex, or in which the phenotype is not classifiable as either male or female. Applying this more precise definition, the true prevalence of intersex is seen to be about 0.018%, almost 100 times lower than Fausto-Sterling's estimate of 1.7%., Sometimes a child is born with genitalia which cannot be classified as female or male. A genetically female child (i.e., with XX chromosomes) may be born with external genitalia which [...]

Gonad morphology and colony composition support the existing supposition that the obligate coral-dwelling damselfish Dascyllus aruanus has a protogynous hermaphroditic sexual pattern. Adults had either an active ovary containing vitellogenic oocytes, an ovotestis, or a spermiated testis and were classified as adult female, hermaphrodite, or adult male, respectively. Among individuals having male function, the testis (or testis portion of the ovotestis) takes the form of an unrestricted spermatogonial lobular testis. Among hermaphrodites having an ovotestis, a small proportion of individuals had a gonad in which both the ovarian and testicular portions were inactive (inactive hermaphrodites), whereas the majority had a predominantly testicular ovotestis that contained spermatozoa (male-active hermaphrodites). The size range of individuals within gonadal classes indicates that all D. aruanus first develop an ovariform gonad. Some individuals then undergo ovarian maturation to become adult females while others develop testicular tissue to form an ovotestis and become male-active hermaphrodites. Subsequently, progressive loss of ovarian tissue results in the development of a secondary testis from an ovotestis with the retention of a residual, afunctional lumen among adult males. The wide size range of individuals having an ovotestis suggests that some hermaphrodites function as adult females before developing testicular tissue while other individuals do not pass through an adult female stage. If this is the case, D. aruanus exhibits a diandric protogynous hermaphroditic sexual pattern. The apparent prolonged retention of an ovotestis with both healthy oocytes and an ovarian-type lumen in a spermiated ovotestis, as well as a functional sex ratio of 1:1 for adult females:adult males plus male-active hermaphrodites also raises the possibility that D. aruanus may be capable of bidirectional sex change during the hermaphroditic stage. Such a capability would be highly adaptive for a species having limited mobility and unpredictable recruitment of new colony members resulting in unpredictable mating opportunities.

The caridean shrimp Lysmata wurdemanni (Gibbes) displays protandric simultaneous hermaphroditism with out-crossing, but not all males become simultaneous hermaphrodites (euhermaphrodites). In this laboratory study, we attempted to determine why some shrimp remain males. In our experiment, we grew L. wurdemanni from postlarvae to adults in several group sizes and observed their reproductive function. We found that all shrimp reared in isolation become euhermaphrodites. When cultured in a group, the proportion of shrimp remaining male decreased with increasing group size. Except for those that mated within a day, inter-molt euhermaphrodite-phase shrimp (with or without embryos) and inter-molt male-phase shrimp fertilized eggs successfully. On the other hand, euhermaphrodite shrimp can only mate as females and have their eggs fertilized during a narrow post-molt window (less than 12 h) in each molt cycle (10 days). The fertilization rate of male-euhermaphrodite pairs was similar to that of euhermaphrodite-euhermaphrodite pairs. There are at least two non-exclusive explanations for the persistence of male shrimp in a group. In certain group compositions, an individual may gain more reproductive fitness as a large male with multiple mating partners than as a small female with low clutch size. Alternatively, the presence of male-phase individuals, with variable molt-cycle duration (5-8 days), may be necessary to ensure mating. This study is the first direct experimental demonstration of social control of sex change in the decapod crustaceans.