• Norwegian: sjøharer


The common name, sea hare, is obviously derived from the shape of the head with two dominating rhinophores. The profile tends to resemble a hare. They are rather large species, the largest one is Aplysia vaccaria which may reach a length of 75 cm. The shell, if any, is usually reduced and internal, only visible on juveniles.

Sea hares are hermaphrodites, with both male and female reproduction organs. In dense populations the sea hares may form chains or stacks during mating. Each individual has sex with the the individual behind (on top) as well as the preceding one (below) and thus acting both as a male and a female. The first (bottom) individual is acting solely as a female, while the one at the other end of the chain is only taking use of its male reproduction organs.

Another strange feature of many sea hares is the ability to release ink from the mantle cavity when disturbed. The octopuses do the same when they flee from their enemies. The obvious problem for the sea hares, is that they cannot run away very fast. When the ink cloud vanish, the sea hare will still be there. So what is the point? Nobody knows for sure.


Three sea hares, representing two families, are common in Norway; Aplysia punctata, Elysia viridis and Akera bullata.