Halgerda formosa? from Mayotte

November 26, 2003
From: Marina Poddubetskaia


Note added 7 January 2004. This is almost certainly a form of H. wasinensis. See relevant discussion.

Dear Bill,
I'm just back from Mayotte (the Comoro Islands) where I realised a collecting mission to better know local opisthobranchs. The large lagoon of Mayotte proved to be very rich in sea slugs species.

I'd like to begin my contribution with these Halgerda formosa which have many more black spots than the animal I photographed in Mauritius. This ID was kindly confirmed by Shireen Fahey.

NB. The second animal seems to be on a pink sponge, but in fact it was moved for the photo from under the dead coral where it was found.

Location : Mayotte Island, France, Indian Ocean

Upper Photo: Passe en S, buoy n° 7bis
Depth: 13.5m, Size: 13-15mm. November 04, 2003
Lower Photos: Passe en S, buoys n° 6&7. Depth: 15m. Size: 15mm. November 15, 2003. Photos: Marina Poddubetskaia

Best wishes,
Marina.

nembro@nembro.info

Poddubetskaia, M., 2003 (Nov 26) Halgerda formosa? from Mayotte. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/11477

Dear Marina,
Thanks for these photos which help clarify my ideas about this group of species. This animal is clearly the one I incorrectly identified as Halgerda punctata some years ago (Rudman, 1978). It differs from Halgerda formosa In having the yellow lines [and ridges] arrange diagonally and forming a network over the mantle. Only the upper two-thirds of the rhinophore club is black, rarther than all the club in typical H. formosa and the upper third of the gills are black, rather than in H. formosa where there is a black line along the whole of the upper edge of the gills. Also in this species there are many black spots on the mantle while in H. formosa the spots, if present, are few in number.

See Terry Gosliner's message where he discusses the possibility of this animal being an unnamed species, a proposition which I totally agree with. To save confusion I should really sort out the examples of this species which are at present mixed up with 'typical' H. formosa on this page.

• Rudman, W.B. (1978) The dorid opisthobranch genera Halgerda and Sclerodoris from the Indo-West Pacific. Zoological Journal of the Linnean Society, 62: 59-88.

Best wishes
Bill Rudman

Rudman, W.B., 2003 (Nov 26). Comment on Halgerda formosa? from Mayotte by Marina Poddubetskaia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/11477

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