This nudibranch (Phyllidia varicosa) feeds on poisonous sponges, and is consequently itself poisonous. If it is provoked, it can secrete toxic mucous that can kill fish and crustaceans.

This nudribranch was photographed in about 40 feet of water on the underside of a lava tube off the south Kohala Coast near the Mauna Lani Resort on the Big Island of Hawaii.