Excerpt from Super sexy snails
http://whyfiles.org/shorties/082snail_dart/But is this whole concept of hermaphroditism sticking in your craw?
Any fan of horse breeding or soap operas knows that the sexes are
designed to mix genes. If hermaphroditism is so useful, how come
they're as rare on the Young and the Restless as infants themselves?
Call it ambi-sexterous
Time for a good word for the evolutionary benefits of switch-hitting.
Plants routinely play both roles, says Chase. Among animals, it's less
common, although 40 percent of 5,600 genera of molluscs are
hermaphrodites -- including all land-dwelling molluscs.
Snails, you'll recall, move along at a snail's pace, and slugs are a
bit sluggish. And if you were a slow-moving member of a rare snail
species, you might never meet a mate (remember, biologically, for
a guy, being marooned with a bunch of he-men equals a life without
offspring -- literally a fate worse than death). If you were colonizing
new terrain, it would certainly help if you could mate with any adult
of your species, not just half of them.
The ultimate ability in these situations would be one that some
hermaphrodites actually have -- to fertilize yourself. That might
seem rather devoid of pleasure, but it's all in a day's work in
the sexual life of snails.
-- David Tenenbaum