Aplysia californica
California seahare

Sea Hares are marine animals that inhabit coastal regions thick with vegetation. This particular species, Aplysia californica, ranges from Northern California to Baja California. (Grzimek, 1968; Meinkoth, 1981)

Aplysia californica are marine animals that inhabit coastal regions thick with vegetation. This particular species ranges from Northern California to Baja California. They can usually be found crawling around the seaweed they use as a source of food. The younger generation live in the deeper waters where they are born while the adult generation lives in shallow, sheltered places with low tide. (Borradaile and Potts, 1963; Grzimek, 1968; Meinkoth, 1981)

The California Black Sea Hare is probably the world's largest gastropod. It can weigh up to 35 pounds! It is typically about 16" long (41 cm) and 8" (20 cm) wide and high. Plump and soft, it has winglike flaps around the top of its head on both sides. Aplysia californica can be reddish, brownish, or greenish, spotted with white or dark circles and lines. The colors reflect the type and color of algae they are prone to eat. They feed with a pair of jaws and a grasping radula. On top of their head, two pairs of antennae are found: one low near the mouth and another behind the eyes. A foot used to help in locomotion extends a little farther than the entire length of the animal. The anterior tentacles are much larger and ear-like (thus its common name- the sea hare) than the second pair which are used more for smelling. They also possess winglike flaps called parapodia that are used for swimming. The mantle folds over and covers a thin, transparent, and flexible shell. In its wall are unicellular glands that secrete a purple dye when the animal is handled. The sea hare does possess a developed nervous and digestive system. In its digestive tract there is an alimentary canal in front of the stomach that ends in a crop lined with horny plates for better mastication before digestion of food. (Borradaile and Potts, 1963; Meinkoth, 1981; Nichols, 1979)

Aplysia californica lives a predominantly quiet life crawling among the bottom of shallow waters and eating seaweed. Two of its behaviors include head waving and ink secretion.

The patterns of head waving are a complex and important behavioral characteristic that can be used for categorizing the sea hares. The patterns can be quite complex and are not constrained by other body parts (joints, muscles, etc.) and thus exhibit much freedom of movement. In the Aplysia californica there are instances of periodicity of movements, but usually the bouts of head waving are made up of more simple movements. Also, Aplysia californica have an important defensive mechanism in the form of an ink gland that processes and secretes a defensive ink pigment. It obtains the pigment from a diet consisting mostly of red seaweed. When irritated, the ink is released from vesicles stored in membrane-bound vacuoles. (Kuenzi and Carew, 1994; Prince, Nolen, and Coelho, May 1998)

Aplysia californica are herbivorous and feed on a variety of algae and eelgrass. Their pair of jaws and broad rasp-like radula help crop the seaweed they eat. The color of the particular animal matches the color of the algae or vegetation they feed on the most. (Buchsbaum et al., 1989; Meinkoth, 1981; Nichols, 1979)

Aplysia californica are used extensively in studies of behavior, reproduction, and development in such fields as chemistry, biology, and psychology. (Buchsbaum et al., 1989)

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