This beautiful nudibranch, about 35 mm long, feeds on the polyps of hydroids storing their stinging cells in its dorsal processes. These cells will serve in its defense. The brilliant colors may be a warning signal. When disturbed it swims by rapidly flexing its body laterally. It has a complex hermaphroditic reproductive system.
Note the graze marks left by this little herbivorous limpet that lives only on eel grass, Zostera marina. In recent years this invasive species has wiped out most of the Zostera beds in Monterey Bay by grazing the leafs' epidermis with its chloroplasts and chlorophyll .
We are fortunate that the little goby posed for us on this keyhole limpet. These limpets include seaweeds and colonial tunicates in their diet. Coastal Indians used the shells of these and other limpets as wampum. Subclass Prosobranchia.