Amphipod crustacean mimic (Southern California)

February 4, 2006
From: Matt Segal

On a recent dive in Southern California (Anacapa Island), I came across the following amphipod crustacean, and after running it by a few people that I know, found that it was a Podocerus cristatus (thank you to Leslie Harris and Don Cadien for the ID).

Locality: Backside of Anacapa Island, California, USA. Depth: 25 ft. Length: 6 mm body, ~10 mm w/ front legs. 28 January 2006. High-surge outcrop. Photographer: Matt Segal

I knew that this species had been linked as a mimic amphipod on this website [message #2641] and [message # 2608], but I am curious as to what nudibranch species this colour form would mimic (notice that its legs are bright yellow in contrast to its body), and what substrate is it supposed to live on?

Thanks in advance.
Matt Segal

Segal, M.J., 2006 (Feb 4) Amphipod crustacean mimic (Southern California). [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Matt,
I didn't realise this amphipod had so many different colour forms. Just because two animals are very similarly coloured it does not mean they are mimics in the evolutionary sense of the word. Evolutionary mimics are two species - or one species and a model - which have gradually through evolutionary changes grown to look alike. It is possible that lookalikes can also evolve quite by chance. I don't even know if there are any studies to show that the two examples you mention from the Forum are really true mimics. So even if there are blue and yellow animals from California which look extremely similar to this colour form of the amphipod, it does not necessarily follow that one ins mimicking the other.
Best wishes,
Bill Rudman

Rudman, W.B., 2006 (Feb 4). Comment on Amphipod crustacean mimic (Southern California) by Matt Segal. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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