If you've ever wondered about the sex lives of snails, Deep Look has everything you need to know.
Snail sex is interesting in large part because snail are hermaphrodites. When every member of a species is equipped with both sets of reproductive organs, the act of mating gets complicated. Each partner sorts out their sex role on the fly.
In garden snails, the act starts with a "love dart" fired by a potential partner about half an hour before copulation. The dart gets embedded in one or both partners, and it contains hormones that prevent the darted snail from killing incoming sperm. Because sperm is passed in both directions, the snails end up in a battle to determine which one's sperm will live—and thus, which snail has to end up carrying fertilized eggs.
For an Ultra HD look at the sex lives of snails, check out this video:
For more details, check out this blog post from KQED.