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Sex determination in Drosophila is controlled by a cascade of regulatory genes. Here we describe hermaphrodite hera new component of this regulatory cascade with pleiotropic zygotic and maternal functions.

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Janet L. Over the last years, research has established that a sexual selection exists and is widespread in the plant and animal kingdoms; b it does not necessarily entail sexual dimorphism; even hermaphrodites have it; c it does not require intelligence or a sophisticated sense of esthetics; even tapeworms and plants choose mates; and d it does not require brawn or even mobility for competition; plants may compete for pollinators, and broadcast spawning invertebrates may also compete for matings. Although discussions of sexual selection often focus on sexual dimorphism, several phenomena that are commonly associated with sexual selection are widespread and highly developed in hermaphrodites. These phenomena include a bizarre and expensive courtship and copulatory behavior, b multiple mating and sperm competition, c rapid evolution of genitalia, d special structures associated with courtship, and e sexual polymorphism. The skewed Looking for hermaphrodite play sex ratios associated with sequential hermaphroditism have long been recognized as contributory to sexual selection.

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Hermaphrodites produce primarily female gametes, with only a limited portion of the ovotestis devoted to sperm production Zucker et al. From: Sexual Biology and Reproduction in Crustaceans, Ramm, in Encyclopedia of Evolutionary Biology Arguably the biggest difference between gonochorists and hermaphrodites is that in the latter each individual has at least potentially access to both the male and female routes to fitness Figure 1.

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Despite this, many existing models for the evolution of anisogamy make assumptions that necessarily lead to the evolution of gonochorism e. From a hermaphrodite perspective, it could be argued that gonochorists are a special case, where some individuals have lost or given up their ability to reproduce via one of the two routes, and an important aspect of understanding hermaphroditism is therefore to understand the conditions under which it may or may not be advantageous for individuals to maintain two routes to fitness.

Figure 1. The two routes to fitness in hermaphrodites. In hermaphrodites, survivorship, fecundity, and mating success will often Looking for hermaphrodite play to fitness separately via the male and female sex functions.


Nevertheless, we can expect important feedback effects between these different fitness components, only some of which are illustrated here. For example, mating success in one sex function may impact upon reproductive success in the other sex function so-called cross-sex effects; stippled arrowsas can occur if mating is reciprocal such that additional matings in the male role automatically correspond to more matings in the female role, with potentially negative consequences see Anthes et al. Note also that for simplicity only a single fecundity component has been plotted, but this could again be split into male and female components and these may often trade off against each other due to a sex allocation trade-off.

Figure 2. The size-advantage model for sequential hermaphroditism. In contrast to Looking for hermaphrodite play, for a simultaneous hermaphrodite each encountered conspecific is a potential mating partner Tomlinson, Moreover, even in the complete absence of access to mating partners, exhibiting both sexes simultaneously — or in short sequence, such as in some Caenorhabditis nematodes — has the additional benefit of permitting self-fertilization Charlesworth and Morgan, ; Jarne and Charlesworth, ; Jarne and Auld, Whilst these adaptive explanations for hermaphroditism are undoubtedly important in understanding how it can evolve, the current taxonomic distribution of the different sexual systems among animals also reveals a strong degree of phylogenetic inertia see Renner and Ricklefs, for data on plants.

While some groups are almost entirely hermaphroditic e. Irrespective of the exact conditions under which hermaphroditism is favored or maintained, once two routes to fitness are present in the same individual, this leaves open the possibility of strategically varying the amount of resources invested into the two sex functions, both in terms of Looking for hermaphrodite play quantity and with respect to the timing during an individual's life history i. Janet L. Hermaphrodites achieve reproductive success as both males and females.

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The extent of their reproductive success is determined by how successful they are in attracting and choosing mates in both sexual roles as well as how they allot their reproductive effort. Hermaphrodites may be sequentially or simultaneously male and female and their mating system is determined to a large extent by the type of sexual system they experience.

A great variety of types of sexual behavior are found in hermaphrodites, with reciprocal mating in simultaneous hermaphrodites being the most notable. Sexual conflict and sexual selection, both pre- and post-mating, play important roles in the evolution of hermaphrodites.

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Gina Broitman-Maduro, Morris F. Maduro, in Methods in Cell Biology Hermaphrodites must be synchronized for in situ experiments because the fixation and freeze-crack techniques work best on animals that are similarly sized, rather than a mixture of adults and larvae. After approximately 3 days the plates should contain gravid hermaphrodites with early embryos. If later-staged embryos are required incubation may be extended a further 5 h, but will depend on incubation temperature, abundance of food, general health of the strain, and tendency of the worms to retain embryos.

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Talbot, Simone Helluy, in Biology of the Lobster Hermaphrodites are apparently very rare in the genus Homarus early literature reviewed by Ridgewood,and both complete and incomplete hermaphrodites are known. The first complete homarid hermaphrodite was described by Nicholls in for H.

This lobster had external and internal female characteristics on the right side and male characteristics on the left side. This pattern of female features on the right and male features on the left has been observed in subsequent reports of H. The most completely described specimen of a Homarus americanus hermaphrodite exhibited bilateral color differentiation as well as hermaphroditism Chace and Moore, The body Looking for hermaphrodite play skewed, probably due to differential growth of the male and female components.

The external features were typical of the respective sexes, except that the seminal receptacle thelycum did not correspond exactly to the structure found in normal females.

Internally, this lobster had a maturing ovary with eggs on the right and a functional testis producing normal sperm on the left. The gon were connected to their respective gonopores by a normal oviduct and vas deferens. It is not known whether this animal was capable of successfully transferring or receiving sperm, since the intromittent organ and seminal receptacle were not complete.

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Reproductive performance has been observed in a bicolored hermaphrodite of Homarus americanus Syslo and Hughes, On two occasions this animal was placed with a normal, freshly molted female, but in neither case did it successfully transfer sperm. However, mating occurred when the gynandromorph molted and was placed with a normal male.

After one such mating, the hermaphrodite extruded eggs that appeared normal and attached them to the pleopods on the right female side. Unfortunately, the eggs were aborted after 1 week and their development could not be followed. Nico K. Michiels, Looking for hermaphrodite play Sperm Competition and Sexual Selection Hermaphrodites might not only attempt to prolong the refractory period of their partner, but also unbalance its sex allocation to make it more female and less male. This not only increases the of eggs it will produce, but may also reduce its mating rate.

Although such a manipulation has not yet been documented, selection on the donor to do so must be high.

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This may be yet another explanation for the importance of prostate products. Hermaphrodites could defend themselves against feminizing products from the partner by a priori biasing allocation to the male function so that, when being feminized by the partner, the resultant sex allocation is still close to optimal for the manipulated individual. This could explain the widespread occurrence of protandry among hermaphrodites.

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Eventually, feminizing agents may result in hermaphrodites that are masculine as long as they are virgin and must receive an ejaculate in order to feminize. In order to keep feminizing factors separate from their own reproductive system, donors could exploit ejaculate resorption by the receiver see earlier and transfer products that become biochemically active when metabolized. Data for snails suggest that young individuals indeed need to metabolize an ejaculate from a partner in order Looking for hermaphrodite play induce egg development Kruglov A major difference with gonochorists is that, when males induce females to produce more eggs, they may only be able to do so by offering her additional resources, which is not in conflict with her interests.

In a hermaphrodite, however, a donor is not interested in topping up the resources of its partner see abovebut may attempt to free resources by reallocation within its receiver instead, resulting in a conflict that is unique to hermaphrodites. Hermaphrodites and males utilize partially different pathways to activate spermatids. The spe-8 class mutant comprises spe-8 L'Hernault et al.

The spe-8 class mutant hermaphrodites are self-sterile.

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Sterility is caused by inability of the mutant spermatids to undergo successful spermiogenesis in the spermatheca of hermaphrodite. As the motility of the sperm depends on successful formation of pseudopod, the mutant spermatids Looking for hermaphrodite play incapable of moving back to spermatheca once they exit from it. Interestingly, mating spe-8 class mutant hermaphrodite with sterile males could restore self-fertility to the hermaphrodite.

When the sterile males inseminate, a male-derived sperm activator is released into the spe-8 class hermaphrodite, which then transactivates spe-8 class mutant spermatids into spermatozoa. This result suggests that hermaphrodite-derived factors s activate spermatids in a SPE-8 class proteins-dependent manner, and activation by male-derived factor s is largely independent of the action of SPE-8 class proteins.

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In other words, SPE-8 class proteins are dispensable for spermiogenesis, as long as male-derived factor s can be supplemented. Hence, the males from spe-8 class mutants are fertile and can be crossed with spe-8 class mutant hermaphrodites to give rise to progeny. The cil-1 mutant spermatids do not fully extend their pseudopods in response to both in vivo and in vitro activators.

As a result, the cil-1 mutant spermatozoa do not move efficiently Bae et al. A genetic screen for male fertility factor uncovered the essential role of protease inhibitor, swm-1 Stanfield and Villeneuve, Looking for hermaphrodite play The seminal vesicle of wild-type male contains spermatids which get activated only after their ejaculation into hermaphrodite reproductive tract.

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In contrast, the seminal vesicle of swm-1 males harbors several activated spermatozoa. These activated spermatozoa are not efficiently transferred by males, presumably because these ectopically activated spermatozoa are more adhesive than spermatids in male reproductive tract. The swm-1 spermatozoa from male successfully fertilize oocytes when introduced into recipient hermaphrodite by artificial insemination, suggesting that swm-1 spermatozoa are functionally active and the sterility observed in swm-1 males is due to sperm-transfer defect.

Consistent with this idea, self-fertility is uncompromised in swm-1 hermaphrodites, as the hermaphrodite is not depend on sperm-transfer from extraneous source for its self-fertility.

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SWM-1 is predicted to function as a secreted serine protease inhibitor. Unknown proteases are capable of activating spermatids in male present in the seminal vesicles. SWM-1 binds and inhibits these protease s to prevent ectopic activation of spermatids in males Stanfield and Villeneuve,