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Splayer with mollusk3/10/2023 Their elaborate mating behaviour may rival the complexity of those of various vertebrates. Both gastropods and cephalopods are unique because of several important features. Studies on sperm competition in gastropods and cephalopods should prove to be particularly rewarding. Several mollusc species may be well-suited for studies on sperm competition, but their potential as experimental organisms has not yet begun to be exploited by behavioural and evolutionary biologists. However, the significance of these structures with respect to sexual selection and sperm competition is, in most cases, unclear. There exists a huge literature on the anatomy and morphology of reproductive systems in molluscs, although not all groups have received the same attention. Sperm competition may occur more frequently among molluscs than commonly assumed. This chapter reviews recent empirical and theoretical advances to discuss various ways in which sperm competition may shape the evolution of sperm and ejaculate traits.īruno Baur, in Sperm Competition and Sexual Selection, 1998 X CONCLUSIONS AND FUTURE RESEARCH DIRECTIONS ![]() The past three decades have seen an explosion of interest in postcopulatory sexual selection that has highlighted the importance of sperm competition and cryptic female choice as engines of evolutionary change. A second consequence of polyandry is the potential for intersexual selection to continue after copulation through mechanisms that enable females (or ova) to bias the outcome of sperm competition in favor of the sperm of certain males, a process known as sperm selection or cryptic female choice. Sperm competition introduces variation in male reproductive success determined by the relative competitive fertilizing efficiency of the ejaculates of different males, and generates postcopulatory, intrasexual selection, which promotes traits that increase the fertilization success of an ejaculate under competitive conditions. As a consequence, the ejaculates of different males may co-occur around a set of ova at the time of fertilization, resulting in sperm competition. In most taxa individual females may copulate (or spawn) with multiple males (i.e., are polyandrous). Charles Darwin (1871) proposed sexual selection as a process that operates on variation in male ability to compete with other males for access to reproductive opportunities, and which promotes traits that confer an advantage in reproductive competition. Sperm competition is the competition between the ejaculates of different males for the fertilization of a given set of ova. Parker, in Sperm Biology, 2009 Publisher Summary ![]() However, the extent to which humans can perform offensive tactics has been sorely understudied and requires considerable further research before firm conclusions can be drawn. Thus, men exhibit behaviors that anticipate and address their partner's infidelity, the success of which may have relaxed selection on physiological and morphological adaptations to tackle sperm competition offensively. ![]() ![]() We conclude that humans have primarily evolved defensive adaptations in response to the risk of sperm competition. This review aims to assess the current evidence for sperm competition in humans, the limitations of that evidence, and directions for future research. Over the past few decades, the extent to which sperm competition has acted as a selective pressure throughout human evolution has been hotly contested. Sperm competition is the competition between the sperm of two or more males to fertilize the ova of a single female. Simmons, in Advances in the Study of Behavior, 2014 Abstract
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