Commensalism in Californian nudibranchs

July 30, 2005
From: James Lyle & Leslie Harris

Dear Dr. Rudman:
We have recently observed instances of commensal behavior involving nudibranchs from Southern California. Two of the hitchhikers are juvenile scaleworm polychaetes (family Polynoidae) on Tritona festiva [A, D] and Triopha catalinae [B, C]; the other is a juvenile amphipod Podocerus sp. on Tritona festiva [see message #14299 ].

Locality:  Buchannan's Reef, Rancho Palos Verdes. California, USA. Depth: 20 metres. 17 July 2005. rocky reef. Photographer: Jim Lyle

Scaleworms are known for being commensals; some will only attach to a single species while others can live on a variety of other creatures. In Martin & Britayev's 1998 review of all known symbiotic polychaetes (available at ) only two scaleworms are reported on nudibranchs. One is Halosydna brevisetosa on Melibe leonina - that was on this coast - and the other is Hololepidella nigropunctata on Phyllidia varicosa from Hong Kong. So whether this particular association is specific or general it's still fairly novel.

James L. Lyle
Leslie Harris

Lyle, J.L. & Harris, L., 2005 (Jul 30) Commensalism in Californian nudibranchs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Jim & Leslie,
Thanks for these observations. There is definitely a whole world of associations out there that we have still to explore.
Best wishes,
Bill Rudman

Rudman, W.B., 2005 (Jul 30). Comment on Commensalism in Californian nudibranchs by James Lyle & Leslie Harris. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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