Aplysia californica is found along the coast of California, United States, and northwestern Mexico. Aplysia species inhabit the photic zone to graze on algae, mainly the intertidal, usually not deeper than.
Description
The maximum length recorded for the California sea hare is when crawling and thus fully extended, although most adult specimens are half this size or smaller. Adult animals can weigh up to. A closely related species, Aplysia vaccaria, the black sea hare, can grow to be larger still.
Life cycle
Like all sea hares, the California sea hare is hermaphroditic, acting as male and female simultaneously during mating. Aplysia are known to form mating chains with up to 20 animals. The eggs are yellow-green, and change after 8 to 9 days into a brown color before larvae hatch. Mating is most prominent during the summer month following the rise of the water temperature to 17 degrees Celsius. Aplysia has a generation time of 19 weeks: Day 1-37 after hatching from the egg planktonic stage, day 34-37 Metamorphic stage, day 45-80 juvenile stage. Reproductive maturity is reached 85 days after hatching. The development of the nervous system lasts for a total of 140 days The life span is assumed to be around a year, yet older animals have been found. Cooler temperature delays spawning and has been shown to extend the lifespan.
Sexual reproduction
At the base of the right anterior tentacle is the aperture from which the penis can protrude. The genital aperture lies at the anterior end of the mantle cavity, a seminal grove arises from it and runs forward to the penis, at the base of the anterior tentacle. Coupling lasts for hours or sometimes for days, although the actual passage of the sperm may take only a few minutes. Egg laying normally has to be triggered by copulation, but it occurs spontaneously in individuals kept in isolation for up to 3–4 months. Copulation occurs most frequently in the early morning, and only rarely after 12:30 pm. An individual animal weighing 2,600g was recorded to have laid about 500 million eggs at 27 separate times during less than five months.
Feeding habits
Like all Aplysia species, the California sea hare is herbivorous. Its diet consists primarily of red algae like Laurencia pacifica, Plocamium pacificum, and Ceramium eatonianum, which gives the animal its typically reddish or pinkish coloration. Aplysia resembles the food it grazes on and cannot be distinguished easily from the seaweed unless the animal is moving.
Predators
Because of the toxins in its body that come from consuming algae, the California sea hare has very few predators. Other predators include starfish, lobsters, and the ophistobranch Navanax inermis which will take juveniles. When it is considerably disturbed, the sea hare is capable of releasing two different kinds of ink from different locations within its mantle cavity, much in the way an octopus does. One ink is reddish-purple and comes from what is called the purple ink gland, while the other is milky white, comes from what is called the opaline gland, and contains the aversive chemical opaline.
Protective mechanisms
Inking provides protection from spiny lobsters, a major predator of sea hares, by means of three mechanisms: chemical deterrence, sensory disruption, and phagomimicry. The typical defence response of the sea hare to a predator is the release of chemicals such as free amino acids, ink from the ink gland and opaline from the opaline gland. Chemical deterrence involves the release of toxic chemicals that are noxious to predators and rapidly dissuades them from feeding. Ink creates a dark, diffuse cloud in the water that disrupts the sensory perception of the predator by acting as a smoke screen and as a decoy. The opaline, which affects the senses dealing with feeding, causes the predator to instinctively attack the cloud of chemicals as if it were indeed food.
