Halgerda maricola? from Rottnest Is, W. Australia

Dear Mark,
Sorry for the delay in answering this but I have been trying to get a name for you without success. It has some similarities to Halgerda maricola, which was described from Rottnest Island. That species has very low ridges with a narrow yellow line along the edge, just like your animal, but in that species there is a black spot in ech of the 'valleys' between the yellow ridges, and there are no large black spots around the mantle edge, while your animal has the opposite. In Halgerda maricola there is also a thin yellow line at the edge of the mantle and the foot. I can't see either in your photo so if you have other photos could you check what the edge of the foot and the mantle looks like?

So very tentatively I am calling it H. maricola but I am probably wrong. There is one other possibility, and that is that both this animal and the photo of 'true' H. maricola are colour forms of Halgerda wasinensis. I have recently discussed that species [message #11828] and suggested it has quite a colour shift across the Indian Ocean. If that is so then your photo here looks very similar to one in an earlier message [#8905] from the Similan Ids, Andaman Sea, and the photo of typical Halgerda maricola from Rottnest Island [#5476] looks very like photos from Mayotte [#11477] of a spotted form of H. wasinensis.

So basically the best I can say is that your animal is interesting, and it would be useful to look our for other similar coloured animals.

Best wishes
Bill Rudman