Hermissenda crassicornis

Hermissenda crassicornis is a species of brightly coloured, sea slug or nudibranch, a marine gastropod mollusc in the family Facelinidae. This nudibranch lives from Kodiak Island, Alaska, to Northern California. It is replaced by Hermissenda opalescens to the south of Northern California. This species is found in various habitats, including the intertidal zone of rocky shores, but also in bays and estuaries. The species grows to be about 50 mm, or about 2 inches. The colour of this nudibranch varies from one locality to another, but it is always easily recognizable by the orange stripe along its head area and the white stripes on the cerata. This nudibranch feeds on hydroids and other marine organisms such as ascidians and sea anemones. It sometimes attacks other nudibranchs, and will eat smaller specimens of its own species.