In the animal world, if several males mate with the same female, their sperm compete to fertilize her limited supply of eggs. And
longer sperm seem to have a competitive advantage, but even when it comes to sperm the size of the animals matter.
The larger the animal, the more im-portant the number of sperm is relative to sperm length. That's why elephants have smaller sperm than mice.
the
longer every individual sperm, the fewer of them a testicle of a certain size can produce. Earlier studies sug-gested that the number of sperm might be just as important as sperm length, if not even more so. After all, the more sperm a male fields against his competitors, the greater the likelihood that one of them will win.
In larger species,
sperm length or speed probably comes into effect only if a sufficient number of sperm manage to get near the egg. In smaller species, however, the distance for sperm to cover is shorter and the risk of loss much smaller, allowing the advantage of longer sperm to manifest itself.
As a result, yo
u tend to find the most complex sperm forms in small species, not in large ones. For instance, small fruit flies have the longest sperm ever described, not whales, whose sperm are less than a tenth of a millimeter long and almost a thousand times shorter than those of the flies.
http://www.science20.com/news_articl...ephants-160077
Never knew this
