Courtship behavior of snails, featured on cover of Issue 6, Volume 12 in Behavioral Ecology, taken by Michael A. Landolfa.
Dart shooting is a fascinating sexual behavior performed by many species of hermaphroditic land snail. All snails of a hermaphroditic species possess both female reproductive tracts and sperm, so both partners attempt to fertilize one another's eggs during mating. As the two snails mate, pointed calcerous structures, the "love darts," begin to emerge a bit behind the snails' eyestalks. The snails then attempt to pierce their partner with the dart, usually leaving the dart inside of their partner once they've hit their mark. The exact purpose of this behavior is unknown, but we will discuss several of the most popular theories as to why this occurs.
We will use Niko Tinbergen's "four questions" to guide our exploration of this behavior. The dart shooting behavior's evolutionary history (phylogeny), the behavior's development over the lifetime of a single snail (ontogeny), the behavior's physical and chemical basis (mechanism), and how the behavior affects a snail's fitness (adaptation) will all be discussed.