Chew It Off
When banana slugs get stuck during mating (their penises can be as long as their bodies), one partner may chew off the other's penis to separate.
Banana slugs are hermaphrodites — each individual has both male and female organs. When two slugs mate, they simultaneously fertilize each other. But sometimes things go wrong.
Slugs have penises that can be as long as their entire body (6-8 inches). During mating, these organs can become tangled or stuck. When the slugs can't separate normally, they resort to a drastic solution: apophallation — one slug chews off the other's penis.
The bitten slug doesn't die, but it does lose its male function permanently. From then on, it can only reproduce as a female. Surprisingly, this might not be entirely disadvantageous — producing eggs is often more reliable for passing on genes than producing sperm.
Banana slug mating is elaborate: 1. Two slugs find each other by following slime trails 2. They circle each other, exchanging bites and producing extra mucus 3. They align their bodies and evert their penises 4. Sperm exchange occurs over several hours 5. If they can't separate, apophallation may occur
The reason for getting stuck isn't entirely clear, but it may relate to the unusual shape of the penis, which has a complex, branching structure.