Drosophila sperm

Drosophila bifurca is a species of fruit fly. Males of this species are known to have the longest sperm cells of any organism on Earth—an impressive 5. A male can only make a few hundred such cells during its lifetime. The other members of the genus Drosophila also make very few, giant sperm cells, with D. Such sperm gigantism is thought to have evolved via a Fisherian runaway process, with a genetic link between sperm length and the length of the female seminal receptacle length sperm-storage organ combined with an increasing competitive advantage of longer sperm as the seminal receptacle evolves to be longer.

In the animal kingdom, sperm usually are considerably smaller than eggs, which means that males can produce far more of them. Large numbers of tiny sperm can increase the probability of successful fertilization, especially when females mate with several males. This is because the competition among sperm from different males to fertilize the few eggs increases as sperm become more abundant. This sperm competition spurs sexual selection after mating, favoring the best sperm in the female reproductive tract. Therefore, it is astonishing that males of certain animal species produce only very few, but gigantic sperm.

In fact, the sperm of the fruit fly Drosophila bifurca can stretch up to nearly 6 centimeters in length. The D. But what? The phenomenonon is perplexing enough to have garnered its own name.

In the animal kingdom, sperm usually are considerably smaller than eggs, which means that males can produce far more of them. Large numbers of tiny sperm can increase the probability of successful fertilization, especially when females mate with several males. This is because the competition among sperm from different males to fertilize the few eggs increases as sperm become more abundant.