Intertidal Invertebrates of the Monterey Bay Area, California

Compiled & photographed by Gary McDonald, Long Marine Laboratory, University of California, Santa Cruz

Onchidoris bilamellata (Linnaeus, 1767)               
Barnacle-eating Dorid
Mollusca: Gastropoda: Opisthobranchia: Nudibranchia: Doridina: Anadoridoidea: Onchidorididae
Geographic Range: Alaska to Baja California, Mexico; Britain; Europe; east coast of USA; Greenland; Circumboreal. Synonyms: Lamellidoris bilamellata, Lamellidoris fusca, Onchidoris fusca
Back to: Doridina Back to: Intertidal Invertebrates of the Monterey Bay Area
Elkorn Slough, Monterey Co., CA; 21 Mar 1972; 17mm total length.

Description: Dorsum brownish-white, with irregular blotches of light rusty brown to dark chocolate brown, occasionally in the form of 2 or 3 irregular longitudinal stripes. Rhinophores with 14-20 lamellae and encrusted with brown except at translucent grayish-white tip. Branchial plumes 16-32 or more, unipinnate, arranged in 2 semi-circles just anterior of the anus, usually encrusted with brown. Similar to the much rarer Acanthodoris brunnea, which has longer rhinophores; higher, pointed papillae on dorsum, and branchial plumes arranged in a circle around the anus.
Size: Typically about 20mm in length.
Notes: Often found with the acorn barnacles upon which it feeds.

Elkhorn Slough, Monterey Co., CA; 10 Feb 1972; 11mm total length.
Moss Landing, Monterey Co., CA; 17 Nov 1971; 7mm total length.
Skipper's Docks, Elkhorn Slough, Monterey Co., CA; 18 Jul 1975; 23mm total length.
North Sunset Palisades, San Luis Obispo Co., CA; 16 Jul 1972; 19mm total length.

Last Updated: