Colpodaspis pusilla
M. Sars, 1870

Family: Diaphanidae


Known from south-western Britain, western Ireland and southern Norway from 4-150m.


Village Bay, St. Kilda, Outer Hebrides, Scotland, United Kingdom, 1993. Photos: Daniel Geiger.

Until Greg Brown's report (1979) of this species from southern England it was known only from the original specimen dredged in 150m in Norway (1870) and a second specimen from Plymouth, England in 1894. The lightly calcified globose shell is completely enclosed by a thin mantle layer which has an exhalent siphon on the posterior right side. The head has two prominent enrolled rhinophores which lead to a groove along each side of the head. The posterior foot is very short and cannot be seen from above as it is covered by a foot-like extension of the mantle much as in the haminoeid bubble shells such as Atys semistriata. In the upper photo of colpodaspis, the animal is somewhat contracted, which shows the short foot and the posterior mantle flap or 'pseudofoot'. Its diet is unknown.

Maximum length is about 5mm, and the skin contains secretory glands which produce a milky secretion when the animal is disturbed. An accessory pedal gland on the sole of the foot, in the midline, produces a sticky secretion which apparently helps the animal stay attached to the thin stalks and growths it lives on.

• Brown, G.H. (1979) An investigation of the anatomy of Colpodaspis pusilla (Mollusca: Opisthobranchia) and a description of a new species of Colpodaspis from Tanzanian coastal waters. Journal of Zoology, London, 187: 201-221.

Authorship details
Rudman, W.B., 2000 (June 17) Colpodaspis pusilla M. Sars, 1870. [In] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

Food of Colpodaspis at last?

November 1, 2007
From: Bernard Picton

Hi Bill,

I'm sorting out some photographs and observations from our last two years fieldwork, looking at conservation priority species in Northern Ireland. We've seen quite a few Colpodaspis pusilla and twice photographed it apparently associated with, and almost certainly eating, an unidentified sea squirt. We started seeing this sea squirt in the 1980's, when the Ulster Museum diving team did the Northern Ireland Sublittoral Survey (NISS) for the Environment and Heritage Service, Northern Ireland.

Locality: Maidens, Larne, Co Antrim, 30m, Northern Ireland, Atlantic Ocean, 13 August 2007, offshore rocky reef. Length: 5mm. Photographer: Bernard Picton.

I've put up a page for the seasquirt, Clavelina sp., and one for Colpodaspis on my site at

Interestingly I think I can see the same sea squirt in Jean Pierre's photograph? [message #5911 ]

all the best,

Picton, B.E., 2007 (Nov 1) Food of Colpodaspis at last?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Bernard,

Congratulations! It will certainly be great if this proves to be the food of Colpodaspis. The rolled 'rhinophores' and pallial opening on the right have often made me wonder if Colpodaspis was a primitive pleurobranch. It has usually been associated with Diaphana but I suspect the anatomical differences are greater than the similarities. Certainly feeding on sea squirts is a pleurobranch thing to do.

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Nov 1). Comment on Food of Colpodaspis at last? by Bernard Picton. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Colpodaspis pusilla from Mediterranean

May 15, 2003
From: Eddie Hardy

This shell is now recorded in Microconchas de la Bahía de San Sebastián by Felix Azpilicueta Viguera adding credibility to the report of it in the Mediterranean.
Eddie Hardy

Hardy, E., 2003 (May 15) Colpodaspis pusilla from Mediterranean. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Eddie,
Can you give me details about Viguera's book? I'm afraid I don't have a team of slaves to do the background work. I have no doubt that Jean-Pierre Bielecki's photo is from the Mediterranean, my doubt is whether I have correctly identified it as Colpodaspis pusilla since that species has only been recorded previously much further north. The animal certainly looks the same. I am not sure whether a shell can help, as at present I don't think we know enough about the differences in shell shape between species to confidently identify them from shells alone. The only sure way is to compare living animals, their anatomy and their shells. If anyone has found this species south of the British Isles, or knows of records, it would be interesting to hear about it
Best wishes
Bill Rudman

Rudman, W.B., 2003 (May 15). Comment on Colpodaspis pusilla from Mediterranean by Eddie Hardy. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Colpodaspis pusilla from the Mediterranean

January 9, 2002
From: Jean-Pierre Bielecki

Hi Bill
Here is a photo we suspect to be a juvenile Berthella plumula. Could you confirm ?
Date : 8 July 2000, Dive place : Cerbère, South of France, [Mediterranean coast] Depth : 6m, Size : 5mm.

Jean-Pierre Bielecki

Bielecki, J-P., 2002 (Jan 9) Colpodaspis pusilla from the Mediterranean. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Jean-Pierre,
This is an interesting little animal - Colpodaspis pusilla. In shape and colour it does have similarities to Berthella but it has a large, if fragile, internal shell and a very prominent right-posterior siphon. The white specks on the mantle and foot are skin glands.

I am not sure if it is has been recorded further south than the British Isles so your record from the Mediterranean may be an interesting new find.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (Jan 9). Comment on Colpodaspis pusilla from the Mediterranean by Jean-Pierre Bielecki. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Colpodaspis pusilla

June 19, 2000
From: Bill Rudman

I have added messages on two unnamed species of Colpodaspis today: Colpodaspis sp. 1 and Colpodaspis sp. 2 so it seemed appropriate to include a page on the type species Colpodaspis pusilla. With Colpodaspis thompsoni, which is already on the Forum, that means we pages on all the known species of Colpodaspis.

Bill Rudman.

Rudman, W.B., 2000 (Jun 19) Colpodaspis pusilla. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from