Halgerda batangas from the Solomon Ids

August 29, 2008
From: Barbara Hanchard

Hi Bill,

A joint submission by myself and Tamara Hartwich. Tamara's photo actually shows the egg ribbon bundled around the back of this Halgerda batangas and on my photo [upper ] you can actually see the secretion area beside the gills. I haven't looked through all the entries for this species on the Forum to see if egg laying has been covered in this species and I apologise if this entry is repetitious. This guy was one of two found within a meter of each other. Both very large (90 mm & 50 mm respectively) and probably the largest I have seen here in the Solomon Islands.

Locality: Tulagi Harbour, USS Minniapolis, 13 meters, Florida Islands, Solomon Islands, Pacific Ocean, 24 August 2008, Muddy slope. Length: 90mm. Photographer: Upper Photo: N.Barbara Hanchard ; Lower Photos: Tamara Hartwich.

Regards,
Barbara Hanchard & Tamara Hartwich

barbara.hanchard@ffa.int

Hanchard, N.B., 2008 (Aug 29) Halgerda batangas from the Solomon Ids. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21833

Dear Barbara & Tamara,

I am afraid these animals are engaged in a bodily function which is not quite as romantic as egg-laying, but equally important. The white pellets in your photo and the yellow ones in Tamara's, are faecal pellets. In sponge-eating dorids the colour of the faeces is usually identical to that of the sponge they are feeding on. I may be quite wrong but there appears to be a white sponge at the front of your animal and yellow sponge just in front of Tamara's photo.

You might ask why the anus is found right in the centre of the circle of gills in dorids - it may seem wrong to have faeces so close to the delicate breathing apparatus.  The close proximity of the gills and the anus is a leftover from the evolutionary past when slugs were shelled snails, and the gill, anus and kidney opened together in the mantle cavity. As the shape of the slug evolved, and the position of body openings changed, the anus, for some unknown reason, has retained a close link to the gill.

Best wishes,
Bill Rudman

Rudman, W.B., 2008 (Aug 29). Comment on Halgerda batangas from the Solomon Ids by Barbara Hanchard. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21833

Factsheet

Halgerda batangas

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