Nudibranch with commensal shrimp

November 14, 1999
From: Erik Schloegl

Dear Bill,

Here's a photo taken at Cabbage Tree Island, off Port Stephens, NSW, at Easter, 1999. Depth: 8m. Sandy Bottom. It's a rather large specimen, close to 10cm, with - as you can see - a commensal shrimp living on it. The pink colour is actually fluorescent (if that's the right word) in the sense that it appears a very bright red to the diver's eye under natural light. When I got the slide developed I was actually quite disappointed how drab it looked. I haven't been able to find the species in any book; my amateur guess would be that it's some Nembrotha or Tambja.

Best regards,
Erik Schloegl

Dear Erik,
I'm pretty sure the shrimp is Periclimenes imperator which is a common commensal of nudibranchs and some sea cucumbers. It is often found with Hexabranchus sanguineus. Over 200 species of the pontoniine shrimps have been reported from the Indo-West Pacific. All seem to have a commensal relationship with other animals ranging from sea anemones and starfish to sea slugs.

The nudibranch it is on is indeed a species of Nembrotha, which is at present unnamed.

Best wishes,
Bill Rudman.

Rudman, W.B., 1999 (Nov 14). Comment on Nudibranch with commensal shrimp by Erik Schloegl. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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