Re: Halgerda dichromis

December 1, 1999
From: Valda Fraser

Dear Bill
You suggested that this animal may be a variation of Halgerda dichromis or possibly, another species altogether. I have found another one. This makes me think that your second suggestion is more plausible.
Locality: South Coast KwaZulu-Natal, SOUTH AFRICA. Scottburgh - 28m, 28 November 1999
Size: 40mm.

Look at all the shrimps on the poor thing!

Valda Fraser

Fraser, V., 1999 (Dec 1) Re: Halgerda dichromis. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Valda,
It wasn't this colour form I thought was possibly different but the one on the bottom left of your message with the more yellow lines and more sharply angled complete ridges. But perhaps all three in that message are different. Now that you are aware that such differences could be significant you will develop an instinct for noticing them. Internal anatomy is the best way to be sure if two animals are different, but we can't cut up every animal we see. Keep an eye out for egg laying, mating, - any little biological activity which might be a useful clue to differences.

Concerning the shrimps crawling over its back - you certainly seem to be in an area rich in crustacea. It looks like they have just hopped on as the slug has crawled through their territory rather than being commensals.

Best wishes,
Bill Rudman.

Rudman, W.B., 1999 (Dec 1). Comment on Re: Halgerda dichromis by Valda Fraser. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


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