PHYLUM: Mollusca
CLASS: Gastropoda
SPECIES: Hermissenda crassicornis
COMMON NAME: Horned Nudibranch
Nudibranchs are in the same class as snails, gastropoda. They are actually slugs. Hermissenda is one of the more common species found around Monterey.
Hermissenda belongs to the suborder of nudibranchs known as aeolids. The aeolids specialize in eating cnidarians (hydroids, anemones, corals, etc.). They are able to pass the stinging organelles (nematocysts) of their prey into their guts without setting them off. The nudibranchs store them in the cerata, the long projections on their backs, which are extensions of the gut. They can then use the nematocysts to protect themselves from predators.
Hermissenda has a white body with orange areas bordered by bright blue lines on the back. The cerata are long, unbranched, and variable in color, a light golden brown to a brilliant orange, tipped with white. They range from Alaska to Baja, and can be found in the intertidal zone down to 120 feet.
Like all nudibranchs, Hermissenda is hermaphroditic. It was long believed that they fought with one another upon meeting, due to the aggressive appearance of their behavior during mating.