California sea slug

The California sea slug (Aplysia californica), also called the California sea hare, is a species of sea hare which belongs to the class Gastropoda in the phylum Mollusca.

It is a very large sea hare, capable of growing to a recorded length of 75 cm (30 inches) though most are half that size.

The California sea hare is herbivorous. Its diet consists primarily of red and brown seaweed, which gives the animal its typically dark coloration. When disturbed, the sea hare will release reddish-purple ink (much like an octopus also does) from a gland in their mantle cavity.

Life cycle
Like all sea hares, the California sea hare is hermaphroditic, acting as male and female simultaneously, even during mating. The eggs are yellow, but after 8 to 9 days change into a brown color before hatching into larvae. When this annual animal is laying eggs, it has reached the end of its life. Its lifetime depends somewhat on the temperature of the water: 14-25 degrees Celsius is best, but a somewhat cooler temperature delays spawning and extends its life somewhat.

Laboratory use
Aplysia californica has become a valuable laboratory animal, used in studies of the neurobiology of learning and memory, and is especially associated with the work of Nobel Laureate Eric Kandel. Its ubiquity in synaptic plasticity studies can be attributed to its simple nervous system, consisting of just a few thousand large, easily-identified neurons. Despite its seemingly simple nervous system, however, Aplysia californica is capable of a variety of non-associative and associative learning tasks, including sensitization, habituation, and classical and operant conditioning. Study typically involves a reduced preparation of the gill and siphon withdrawal reflex.