Orange slug-like species from Sydney, Australia

May 15, 2009
From: Roland Bircher

Dear Bill,

I found this orange species on a night dive yesterday. It was living on an isolated overgrown rock at the edge of a little overhang, in close proximity to three specimen of Aphelodoris varia. It was sensitive to/disturbed by the light of my diving torch and the red modeling light of my strobe and moved in reasonable speed under the overhang.

Locality: Bare Island, La Perouse, Sydney, 10 m, New South Wales, Australia, Botany Bay, Pacific Ocean, 14 May 2009, Overgrown rock (weed, sponges) on sand, close to rocky reef. Length: 5 cm. Photographer: Roland Bircher.

I couldn't make out any external gills. The two tube-like extensions (presumably sensing organs) looked like rolled sheets. The back tip of a foot was showing under the mantle (image 2). The body was bright orange-red, the mantle was semi-transparent. All of this doesn't look like the typical nudibranchs I see around here, but the specimen was definitely of slug-like appearance. Could you tell me what family this species belongs to?

The pictures are far from perfect due to heaps of particles and a mishandling of the strobe. The colour of the first photo is reproducing the natural colour best.

Kind regards,
Roland

roland.bircher@gmx.net

Bircher, R., 2009 (May 15) Orange slug-like species from Sydney, Australia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22469

Dear Roland,

The slug shape has evolved many times among the snails. This is Berthellina citrina, one of the pleurobranch or side-gilled slugs.  They get the name from the single gill which is attached to the right side of the body below the mantle skirt.

The tube-like extensions you mention are tentacles which suck water down over chemosensory organs so they can check for food 'smells' or danger.

If you look at earlier messages attached to the species' Fact Sheet you will find other information on the natural history of ths species.

Best wishes,
Bill Rudman

Rudman, W.B., 2009 (May 15). Comment on Orange slug-like species from Sydney, Australia by Roland Bircher. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22469

Factsheet

Berthellina citrina

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