Hopkinsia rosacaea

Many people identified our September unknown as a sea anemone. A very reasonable guess, since this lovely pink nudibranch may be a mimic for a sea anemone frequently found in the same habitat - the brooding anemone, Epiactus proliferi.

Hopkins rose is a lovely species belonging to the dorid group of nudibranchs. The tentacle like structures on its dorsal surface are unusual for a dorid nudibranch. Other dorid nudibranchs, such as the sea lemon (Archidoris montereyensis) have a domed body without elongated surface structures. All dorids however, have a set of two elongated receptor organs at the head (anterior) end -- the rhinophores. In this photo, they are located on the right, and are slightly darker than the light pink tubercles covering the body.

A second feature of dorid nudibranchs is the set of gills at the posterior end of the body. Hopkins rose nudibranch ranges from Oregon to Baja California, and is especially common around Monterey, California. It feeds on another pink animal, the bryozoan, Eurystomella bilabiata, a lovely rose-colored bryozoan found under rocks in the low tide zone and below, from Southern California to Alaska.

For a concise and revealing teaching video about the the Phylum Mollusca, get our video: Branches on the Tree of Life: Molluscs. The ecology and diversity of seashores is covered by our program, The Biology of Seashores.