The Mating Dance
Mating begins with a courting ritual. For example, in land snails of the genus Helix, including the escargot Helix pomatia, and the common garden snail Helix aspersa (also known as Cornu aspersa and Cantareus aspersus), copulation is preceded by an elaborate tactile courtship.
The two snails circle around each other for up to six hours, touching with their tentacles, and biting lips and the area of the genital pore, which shows some preliminary signs of the eversion of the penis. As the snails approach mating, hydraulic pressure builds up in the blood sinus surrounding the organ housing the dart. Each snail manoeuvres to get its genital pore in the best position, close to the other snail's body. Then, when the body of one snail touches the other snail's genital pore, it triggers the firing of the dart.
The darting can sometimes be so forceful that the dart ends up buried in the internal organs. It can also happen that a dart will pierce the body or head entirely, and protrude on the other side.
After both snails have fired their darts, the snails copulate and exchange sperm.
A snail does not have a dart to fire the very first time it mates, because the first mating is necessary to trigger the process of dart formation. Once a snail has mated, it fires a dart before some, but not all, subsequent matings. A snail often mates without having a dart to use, because it takes time to create a replacement dart. In the case of the garden snail Helix aspersa, it takes a week for a new dart to form.
The dart is shot with some variation in force, and with considerable inaccuracy, such that one-third of the darts that are fired in Helix aspersa either fail to penetrate the skin, or miss the target altogether. Snails have only very simple visual systems and cannot see well enough to use vision to help aim the darts.
Read more about this topic: Love Dart
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