|MadSci Network: Zoology|
Relative to the organism's body size (and possibly in terms of absolute size), the sperm of several species of Drosophila (the fruit fly) appear to be the largest, approaching 1 cm in length. Most of the length in these cells is made up of the tail, which normally exists in a tangled state. It is believed this tangled web of sperm tail exists as a means of encumbering sperm from other males in the contest to fertilize the female's eggs. For further details, look in the journal Nature, May 11 and September 21, 1995.
Try the links in the MadSci Library for more information on Zoology.