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Sex, Violence, and Garden Snails

If you think dating is tough, just be glad you aren’t a garden snail. When you live life at a snail’s pace, you’d better be able to mate with the next snail you meet without worrying if it’s male or female. That’s why garden snails are hermaphrodites and can take on both the male and female roles in reproduction.

But here’s where things get tricky. A successful male reproductive strategy is to mate with lots of females; while a successful female strategy is to be choosy since producing eggs uses up more energy than producing sperm. In order to help weed out bad seeds, each snail’s female reproductive tract contains a gland that digests more than 99.98 percent of incoming sperm. The sperm that survive are stored until the snail lays its eggs.

Now, since the garden snail is promiscuous and fertilization may be delayed, by the time the garden snail lays its eggs there may be sperm from multiple partners in the reproductive tract. So how can a garden snail up the odds that its sperm will be the first to reach the eggs? By making sure as many sperm as possible survive. To do that, garden snails resort to violence.

Before depositing sperm in their partners, garden snails shoot mucus-covered darts at each other. If the dart hits the partner, it temporarily disables the gland that digests sperm, allowing twice as many sperm to make it to storage. And if the dart misses, the snail will release an extra-large amount of sperm into its partner. With a little luck, all these extra sperm will end up giving the snail a reproductive edge.

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