ECOLOGY/EVOLUTION: Size for Breeding

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Science  31 May 2002:
Vol. 296, Issue 5573, pp. 1571b
DOI: 10.1126/science.296.5573.1571b

The function of sperm—the fertilization of eggs—is uniform across the animal kingdom. Nevertheless, there is a bewildering variety of sperm size and morphology. It has been suggested that some of this variation arises via the selective force of sperm competition, whereby sperm from multiple males compete to fertilize eggs. In nematode worms, which have amoeboid sperm, correlative evidence suggests that sperm competition may lead to the evolution of larger sperm, which crawl faster, thereby increasing their chances of a successful fertilization. In an experimental test of this idea, LaMunyon and Ward tracked the evolution of sperm size over 60 generations in populations of the nematode worm Caenorhabditis elegans differing in the level of multiple mating permitted; competition resulted in a 20% increase in the size of the amoeboid sperm. — AMS

Proc. R. Soc. London Ser. B 10.1098/rspb.2002.1996 (2002).

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