scholarly journals Sperm competition and sex allocation in simultaneous hermaphrodites

1996 ◽  
Vol 10 (5) ◽  
pp. 457-462 ◽  
Author(s):  
Eric L. Charnov
Keyword(s):  
Sperm Competition ◽  
Sex Allocation ◽  
Simultaneous Hermaphrodites

scholarly journals Sex allocation and investment into pre- and post-copulatory traits in simultaneous hermaphrodites: the role of polyandry and local sperm competition

2013 ◽  
Vol 368 (1613) ◽  
pp. 20120052 ◽  
Author(s):  
Lukas Schärer ◽  
Ido Pen
Keyword(s):  
Sexual Selection ◽  
Sperm Competition ◽  
Sex Allocation ◽  
Optimal Allocation ◽  
Recent Theory ◽  
Detailed Knowledge ◽  
Female Reproduction ◽  
Sexually Selected Traits ◽  
Simultaneous Hermaphrodites

Sex allocation theory predicts the optimal allocation to male and female reproduction in sexual organisms. In animals, most work on sex allocation has focused on species with separate sexes and our understanding of simultaneous hermaphrodites is patchier. Recent theory predicts that sex allocation in simultaneous hermaphrodites should strongly be affected by post-copulatory sexual selection, while the role of pre-copulatory sexual selection is much less clear. Here, we review sex allocation and sexual selection theory for simultaneous hermaphrodites, and identify several strong and potentially unwarranted assumptions. We then present a model that treats allocation to sexually selected traits as components of sex allocation and explore patterns of allocation when some of these assumptions are relaxed. For example, when investment into a male sexually selected trait leads to skews in sperm competition, causing local sperm competition, this is expected to lead to a reduced allocation to sperm production. We conclude that understanding the evolution of sex allocation in simultaneous hermaphrodites requires detailed knowledge of the different sexual selection processes and their relative importance. However, little is currently known quantitatively about sexual selection in simultaneous hermaphrodites, about what the underlying traits are, and about what drives and constrains their evolution. Future work should therefore aim at quantifying sexual selection and identifying the underlying traits along the pre- to post-copulatory axis.

No effect of group size on sex allocation in a protandric-simultaneous hermaphroditic shrimp

2007 ◽  
Vol 87 (5) ◽  
pp. 1169-1174 ◽  
Author(s):  
J. Antonio Baeza
Keyword(s):  
Sperm Competition ◽  
Group Size ◽  
Sex Allocation ◽  
Male Gender ◽  
Male Mating ◽  
Gender Preferences ◽  
Female Role ◽  
First Clutch ◽  
Lysmata Wurdemanni ◽  
Simultaneous Hermaphrodites

Lysmata wurdemanni is a protandric-simultaneous hermaphroditic shrimp. Individuals reproduce as males first and late in life as simultaneous hermaphrodites. I examined whether sex allocation (resources devoted to ova vs sperm) varies with group size in shrimps that have just matured as hermaphrodites. Focal males were reared with different numbers of hermaphrodites (1, 2, 5 or 10). Sperm stored in the ejaculatory ducts and eggs brooded underneath the abdomen were retrieved and weighted immediately after focal shrimps matured as hermaphrodites. Hermaphrodites should invest more into sperm with increasing group size to cope with more intense sperm competition. The proportion of focal shrimps that lost their first clutch of eggs after maturing as hermaphrodites increased with group size. This suggests male gender preferences by hermaphrodites experiencing large group sizes. No differences in sex allocation among group sizes were recorded for shrimps that did not lose their first clutch of eggs. Thus, group size does not affect sex allocation in terms of ova and sperm mass. This lack of phenotypic plasticity might be explained if sperm competition is not important in L. wurdemanni. It should not pay in terms of fitness for shrimps to produce and inseminate female-role hermaphrodites with large amounts of sperm when full paternity is assured in the absence of multi-male mating. In agreement with this idea, a second experiment demonstrated that female-role hermaphrodites invariably mated only once with a single other shrimp.

An Evolutionary Ecological Approach to Sex Allocation and Sex Determination in Crustaceans

2020 ◽  
pp. 177-196
Author(s):  
Kota Sawada ◽  
Sachi Yamaguchi
Keyword(s):  
Sex Determination ◽  
Sex Allocation ◽  
Evolutionary Ecology ◽  
Empirical Studies ◽  
Ecological Approach ◽  
Sexual Strategies ◽  
Sexual Systems ◽  
Mating Group ◽  
Simultaneous Hermaphrodites ◽  
Allocation Strategies

This chapter reviews sex determination and sex allocation strategies among crustaceans with different sexual systems (gonochorism, sequential and simultaneous hermaphroditism, and androdioecy), from the perspective of evolutionary ecology. The discussion includes genetic, environmental, and cytoplasmic sex determination in free-living and parasitic crustaceans, timing and frequency of sex change especially in partial protandry, the effects of mating group size on resource allocation by simultaneous hermaphrodites, and sex ratio and determination in androdioecious crustaceans. The fascinating diversity of crustacean reproduction stimulated theoretical biologists to construct models to explain them, and empirical biologists attempted to test hypotheses derived from those models. This review clearly shows that the interaction between theoretical and empirical studies has facilitated understanding of the evolutionary conditions of diverse sexual strategies among crustaceans. Since sexual strategies often interact with other aspects of adaptive strategies such as life history, integrating different aspects into both theoretical and empirical studies will provide further understandings into crustacean sexual systems. In addition, the authors point out the potential of phylogenetic comparative analyses using natural history data as a tool to understand the tempo and mode of evolution of sex allocation strategies.

scholarly journals Sex allocation predicts mating rate in a simultaneous hermaphrodite

2009 ◽  
Vol 276 (1676) ◽  
pp. 4247-4253 ◽  
Author(s):  
Tim Janicke ◽  
Lukas Schärer
Keyword(s):  
Sex Allocation ◽  
Mating Behaviour ◽  
Reproductive Investment ◽  
Mating Strategy ◽  
Species Variation ◽  
Simultaneous Hermaphrodite ◽  
Female Function ◽  
Sexual Selection Theory ◽  
The Relationship ◽  
Simultaneous Hermaphrodites

Sexual selection theory for separate-sexed animals predicts that the sexes differ in the benefit they can obtain from multiple mating. Conventional sex roles assume that the relationship between the number of mates and the fitness of an individual is steeper in males compared with females. Under these conditions, males are expected to be more eager to mate, whereas females are expected to be choosier. Here we hypothesize that the sex allocation, i.e. the reproductive investment devoted to the male versus female function, can be an important predictor of the mating strategy in simultaneous hermaphrodites. We argue that within-species variation in sex allocation can cause differences in the proportional fitness gain derived through each sex function. Individuals should therefore adjust their mating strategy in a way that is more beneficial to the sex function that is relatively more pronounced. To test this, we experimentally manipulated the sex allocation in a simultaneously hermaphroditic flatworm and investigated whether this affects the mating behaviour. The results demonstrate that individuals with a more male-biased sex allocation (i.e. relatively large testes and small ovaries) are more eager to mate compared with individuals with a more female-biased sex allocation (i.e. relatively small testes and large ovaries). We argue that this pattern is comparable to conventional gender roles in separate-sexed organisms.

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