Continuing Ed: California Sea Hare

With some really great low tides ahead of us in January, here’s another in our continuing education series, taken from the Cabrillo National Monument Reference Manual (E-binder).  Enjoy!

California Sea Hare (Aplysia californica)

Contributed by Dr. Bonnie Becker

CA Sea Hare
California Sea Hare

Where found:

Low tide zone up to upper tidepools.

Interesting facts:

A sea hare is a mollusc, related to the snails, but without the conspicuous outer shell. They have a tremendous internal shell. When threatened, Aplysia squirts a deep purple “ink”. This substance, as well as parts of the animal, is distasteful to most predators. This species has few natural predators.


Aplysia breathe with the help of two fleshy flaps that extend over the back and are flapped and create currents to force water over the gills.


Aplysia eat algae. They sense the food at a distance and cut it up with their radula. They use three stomachs, two of which have grinding “teeth” inside.

Life history:

Aplysia is hermaphroditic, with both male and female sex organs. Fertilization is internal and copulation lasts several hours to several days. Mating occurs year-round, but concentrated in the late spring to late fall. Eggs are deposited in stringy yellow masses, with on the order of 80 million eggs per mass. One egg mass was unraveled in a lab and was 1/3 of a mile long. Within 12 days the eggs hatch to free swimming larvae that are planktonic for approximately a month. Settlement usually occurs on or near red algae.  The animals grow quickly, and within a year are usually full-grown. They usually don’t
live much longer than a year.

Phylum:    Mollusca (Soft-bodied animals with external shells or modified internal shells)
Class:       Gastropoda (Snails, Limpets, Sea hares, Nudibranchs, etc.)
Subclass: Opisthobranchia (Nudibranchs, Sea hares, Sea slugs, etc.)
Order:       Anaspidea
Family:     Aplysiidae

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