Spread your sperm the smart way(maximises the number of offspring he sir...)

Date:7/9/2009

maximises the number of offspring he sires overall. Less attractive males secure fewer matings but value each of them more highly, and by allocating more sperm to each mating make the most of their meagre opportunities. This leads to the rather paradoxical prediction that matings with attractive males may be less fertile than those with unattractive males."

"There are as yet few good examples of this process found in nature, as it has generally been assumed that more attractive or higher quality males will be more fertile. A possible case can be seen in chickens, which in the wild live in groups of varying numbers of males and females. Females mate with many males, so males are subject to sperm competition. However, the attractiveness of a male is determined in large part by his social standing. Males higher up the pecking order find it easier to secure matings with the females, but they transfer fewer sperm to females. In addition, the sperm of dominant birds is less motile and has lower fertilising efficiency than the sperm of subordinate birds. Scientists can artificially change the pecking order, and when this is done, the new dominant male's sperm quickly loses motility, while that of males reduced to subordinate status increases in motility."

"Further work in this area should look at males that are similarly attractive, but have different levels of resources to allocate to sperm production, to see how this alters their sperm number and quality. The model should also be expanded to include the effects of short-term sperm depletion, which is known to affect ejaculate content when males re-mate quickly. We also would like to explore whether the lower fertility of attractive males causes females to start avoiding attractive males that mate too often, as these males reduce their fertility."

"Finally, how this work applies to humans and other primates is not yet known. Human attractiveness is complicated and influenced by a number of facto
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Contact: Jenny Gimpel 44-020-767-99726 University College London Source:Eurekalert

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