Aplysiidae
The superfamily Aplysioidea contains only one family, the Aplysiidae, or sea hares. In Australia they are known as ‘beach blobbies’.
Description
Members of the Aplysiidae have an atrophied inner shell (in constrast with the nudibranchs, which have no shell at all). In Aplysia and Syphonota, this shell is a flattened plate over the visceral rear end, where it is fully or partially enclosed in the mantle skin. In Dolabella auricularia, the shell is ear-shaped. The shell is completely absent in the genera Bursatella and Stylocheilus.
Their length varies between 20 cm and 75 cm (Aplysia vaccaria).
They are cosmopolitan and found in temperate and tropical seas. They inhabit coastal areas, thick with vegetation.
They are herbivorous, eating a variety of red, green or brown algae and eelgrass. Their color is diet-derived from the pigments of the algae; They concentrate the toxins found on algae.
Defenses
Some species spout ink when disturbed or attacked, and then scuttle away with their broad winglike flaps or parapodia.
Sea hares have two main secretory glands in their mantle cavity.
- purple gland : lying on top of the mantle cavity, above the gill. It gives off a red or purple fluid, or, in some species, a white ink.
- opaline gland : situated on the floor of the mantle cavity, beneath the gill. It gives off a white opaque secretion.
Mating habits
Sea hares are hermaphrodites, with fully functional male and female reproductive organs. Their penis is on the right side of the head while the vagina is situated in the mantle cavity, beneath the shell, deep down between the parapodia. It is therefore physically impossible for mating partners to act as both male and female at the same time.
They have strange mating habits. They can mate in pairs with one acting as a male, the other as a female. But they commonly occur in quite crowded numbers and this often leads to chains of three or more sea hares mating together. The one at the front acts as a female and the one at the back as a male. The animal(s) in between are acting as both males and females. The one receiving sperm passes its own sperm to a third sea hare.
Predators
Predators include pycnogonid sea spiders, wrasses and sea turtles.
Reference
Kandel, E.R. (1979) Behavioural Biology of Aplysia. San Francisco, W.H.Freeman & Co. 463pp.