Aldisa erwinkoehleri from the Andaman Sea

March 23, 2007
From: David Scheel

Bill,
I have been unable to identify the Dorids in this photograph. Are you able to? They seem likely to be Phyllidiidae based on over-all appearance (perhaps Phyllidiella or Phyllidiopsis, judging by bi-colored white and black rhinopores, orange and white tubercules, blue ground with black stripes). Unfortunately, I did not turn them over to check for medial stripe on the foot.

I have looked through images of that family on your site, however, and was unable to find a match. Phyllidia and Phyllidiella species were common on other dives I did in the Similans around the same time.

Place: Deep Six, Koh Payoo, Similan Islands, Thailand, Andaman Sea. Depth: 30 feet. Length: approximately 1-2 cm. 8 February 2007. Rocky reef
Photographer: D. Scheel

Thanks for any information you can provide.
Cheers,
David Scheel
Alaska Pacific University

dscheel@alaskapacific.edu

Scheel, D., 2007 (Mar 23) Aldisa erwinkoehleri from the Andaman Sea. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19740

Dear David,
You seem to have made a good attempt to identify these animals but you have missed one vital clue - dorsal gills. In the close-up alongside we can see a circle of gills in the posterior dorsal midline - a common feature in dorid nudibranchs, but one which is missing in all members of the Phyllidiidae.

This is the recently named Aldisa erwinkoehleri, one of a growing number of phyllidiid mimics which are being discovered [see mimicry Fact Sheet]. One reason that phyllidiids are often the most commonly seen nudibranchs - especially during daylight hours - is that they contain extremely disasteful chemicals in their mantle, which deter fish from eating them. As often occurs in nature when someone comes up with a good survival strategy, a number of dorids, often unrelated to each other, have decided to mimic phyllidiids so that they also look distasteful to hungry fish.

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Mar 23). Comment on Aldisa erwinkoehleri from the Andaman Sea by David Scheel. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19740

Factsheet

Aldisa erwinkoehleri

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