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

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.

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

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2012.0052 ◽

2013 ◽

Vol 368 (1613) ◽

pp. 20120052 ◽

Cited By ~ 47

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.

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Sperm competition and sex allocation in simultaneous hermaphrodites

Evolutionary Ecology ◽

10.1007/bf01237878 ◽

1996 ◽

Vol 10 (5) ◽

pp. 457-462 ◽

Cited By ~ 83

Author(s):

Eric L. Charnov

Keyword(s):

Sperm Competition ◽

Sex Allocation ◽

Simultaneous Hermaphrodites

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Sperm Competition and the Dynamics of X Chromosome Drive: Stability and Extinction

Genetics ◽

10.1093/genetics/160.4.1721 ◽

2002 ◽

Vol 160 (4) ◽

pp. 1721-1731 ◽

Cited By ~ 1

Author(s):

Jesse E Taylor ◽

John Jaenike

Keyword(s):

Sex Ratio ◽

Sperm Competition ◽

X Chromosome ◽

Sex Chromosome ◽

Basin Of Attraction ◽

Male Mating ◽

Male And Female ◽

Mating Rate ◽

Female Mating ◽

Balanced Polymorphism

AbstractSeveral empirical studies of sperm competition in populations polymorphic for a driving X chromosome have revealed that Sex-ratio males (those carrying a driving X) are at a disadvantage relative to Standard males. Because the frequency of the driving X chromosome determines the population-level sex ratio and thus alters male and female mating rates, the evolutionary consequences of sperm competition for sex chromosome meiotic drive are subtle. As the SR allele increases in frequency, the ratio of females to males also increases, causing an increase in the male mating rate and a decrease in the female mating rate. While the former change may exacerbate the disadvantage of Sex-ratio males during sperm competition, the latter change decreases the incidence of sperm competition within the population. We analyze a model of the effects of sperm competition on a driving X chromosome and show that these opposing trends in male and female mating rates can result in two coexisting locally stable equilibria, one corresponding to a balanced polymorphism of the SR and ST alleles and the second to fixation of the ST allele. Stochastic fluctuations of either the population sex ratio or the SR frequency can then drive the population away from the balanced polymorphism and into the basin of attraction for the second equilibrium, resulting in fixation of the SR allele and extinction of the population.

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Fertilization dynamics of sperm from different male mating tactics in bluegill (Lepomis macrochirus)

Canadian Journal of Zoology ◽

10.1139/z05-164 ◽

2005 ◽

Vol 83 (12) ◽

pp. 1638-1642 ◽

Cited By ~ 14

Author(s):

Albrecht I Schulte-Hostedde ◽

Gary Burness

Keyword(s):

Sperm Competition ◽

Lepomis Macrochirus ◽

Fertilization Success ◽

Male Mating ◽

Motile Sperm ◽

Mating Tactics ◽

Sperm Activation ◽

Competition Theory ◽

Sperm Density ◽

Over Time

Sperm competition results in the evolution of ejaculate characteristics such as high sperm density, high motility, and fast sperm swimming speed. A fundamental assumption of sperm competition theory is that ejaculates with high motility and fast-swimming sperm have an advantage with respect to fertilization success. We tested this assumption by studying the fertilization dynamics of alternative mating tactics (cuckolders and parentals) of male bluegill (Lepomis macrochirus Rafinesque, 1819). Sneakers (cuckolders) have faster swimming sperm and a higher proportion of motile sperm immediately following sperm activation than do parentals; however, these variables decline more quickly over time in sneaker sperm than in the sperm of parental males. We used a controlled fertilization experiment to test the prediction that parental males will have higher fertilization success than sneakers late in the sperm activation cycle because of the reduced rate of decline in ejaculate quality over time. We found that as the time from sperm activation increases parental sperm fertilizes more eggs than the sperm of sneakers. Our results support the idea that fertilization success is higher when ejaculates contain a higher proportion of either motile sperm or faster swimming sperm, all else being equal. In addition, after controlling for time from sperm activation, we found a significant bias in fertilization success toward parental males, suggesting that cryptic female choice might play a role in fertilization dynamics.

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Relative testis size and mating systems in anurans: large testis in multiple-male mating in foam-nesting frogs

Animal Biology ◽

10.1163/157075511x570312 ◽

2011 ◽

Vol 61 (2) ◽

pp. 225-238 ◽

Cited By ~ 15

Author(s):

Wen Bo Liao ◽

Zhi Ping Mi ◽

Cai Quan Zhou ◽

Ling Jin ◽

Xian Han ◽

...

Keyword(s):

Sperm Competition ◽

Published Data ◽

Male Mating ◽

Data Sets ◽

Testis Size ◽

Data Set ◽

Monogamous Species ◽

Large Testis ◽

Testes Size ◽

Testis Mass

AbstractComparative studies of the relative testes size in animals show that promiscuous species have relatively larger testes than monogamous species. Sperm competition favours the evolution of larger ejaculates in many animals – they give bigger testes. In the view, we presented data on relative testis mass for 17 Chinese species including 3 polyandrous species. We analyzed relative testis mass within the Chinese data set and combining those data with published data sets on Japanese and African frogs. We found that polyandrous foam nesting species have relatively large testes, suggesting that sperm competition was an important factor affecting the evolution of relative testes size. For 4 polyandrous species testes mass is positively correlated with intensity (males/mating) but not with risk (frequency of polyandrous matings) of sperm competition.

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Casanovas are liars: behavioral syndromes, sperm competition risk, and the evolution of deceptive male mating behavior in live-bearing fishes

F1000Research ◽

10.12688/f1000research.2-75.v2 ◽

2013 ◽

Vol 2 ◽

pp. 75 ◽

Cited By ~ 12

Author(s):

David Bierbach ◽

Amber M Makowicz ◽

Ingo Schlupp ◽

Holger Geupel ◽

Bruno Streit ◽

...

Keyword(s):

Mate Choice ◽

Sexual Activity ◽

Sperm Competition ◽

Evolutionary Significance ◽

Behavioral Syndromes ◽

Male Mating ◽

Data Set ◽

Poecilia Mexicana ◽

Audience Effects ◽

Sperm Competition Risk

Male reproductive biology can by characterized through competition over mates as well as mate choice. Multiple mating and male mate choice copying, especially in internally fertilizing species, set the stage for increased sperm competition, i.e., sperm of two or more males can compete for fertilization of the female’s ova. In the internally fertilizing fish Poecilia mexicana, males respond to the presence of rivals with reduced expression of mating preferences (audience effect), thereby lowering the risk of by-standing rivals copying their mate choice. Also, males interact initially more with a non-preferred female when observed by a rival, which has been interpreted in previous studies as a strategy to mislead rivals, again reducing sperm competition risk (SCR). Nevertheless, species might differ consistently in their expression of aggressive and reproductive behaviors, possibly due to varying levels of SCR. In the current study, we present a unique data set comprising ten poeciliid species (in two cases including multiple populations) and ask whether species can be characterized through consistent differences in the expression of aggression, sexual activity and changes in mate choice under increased SCR. We found consistent species-specific differences in aggressive behavior, sexual activity as well as in the level of misleading behavior, while decreased preference expression under increased SCR was a general feature of all but one species examined. Furthermore, mean sexual activity correlated positively with the occurrence of potentially misleading behavior. An alternative explanation for audience effects would be that males attempt to avoid aggressive encounters, which would predict stronger audience effects in more aggressive species. We demonstrate a positive correlation between mean aggressiveness and sexual activity (suggesting a hormonal link as a mechanistic explanation), but did not detect a correlation between aggressiveness and audience effects. Suites of correlated behavioral tendencies are termed behavioral syndromes, and our present study provides correlational evidence for the evolutionary significance of SCR in shaping a behavioral syndrome at the species level across poeciliid taxa.

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