Tochuina tetraquetra

How to Distinguish from Similar Species: The combination of orange color and white plumose gills around the margin is unique. Of the other orange opisthobranchs in our area,Berthellina engeli is smooth and has rolled rhinophores, Acanthodoris lutea has a circle of gills around the dorsal anus and has many papillae and yellow specks, Triopha maculata has a circle of gills around the dorsal anus and several orange dorsal processes, Aldisia sanguinea and Rostanga pulchra have a circle of gills around the dorsal anus and is 2 cm or less long, Anisodoris nobilis has a circle of gills around the dorsal anus and has black spots, and Dendrodoris fulva and Doriopsilla albopunctata have tubercles with white tips but have a circle of gills around the dorsal anus.

On rocks

Depth Range: Subtidal to 363 m

Members of suborder Dendronotacea do not have an anus on the dorsal midline. They have dorsal outgrowths besides the rhinophores, consisting of branched cerata or gills. The rhinophores are solid, pulpit shaped, and retractable into a cuplike sheath. Tochuina tetraquetra has a large, stout body with white, plumose gill tufts along the undulating dorsolateral margin all the way from the rhinophores to the posterior tip. The anterior border of the oral veil is white and crenulate but does not have papillae. The dorsum is orange or yellowish-orange with white-tipped tubercles. The foot is salmon pink to yellow with a white margin. The rhinophores have 6-10 short, vertical plumose proceesses encircling the main shaft below the tip. Length to 30 cm and weight to 1.4 kg.

Biology/Natural History: This uncommon species feeds on hydroids, sea pens such as Ptilosarcus gurneyi, and other Alcyonaceans such as the soft coral Gersemia rubiformis. In the Kuril Islands this species is eaten raw or cooked as "Tochni". This species is said to be the world's largest nudibranch.

Geographical Range: Kuril Islands, USSR; Alaska to Malibu, CA