Colour variation in Ancula gibbosa

March 6, 2001
From: Bernard Picton

Hi Bill,

I see there is some debate over Ancula gibbosa and A. pacifica, and whether A. gibbosa occurs on the Pacific coast of North America. I enclose pictures of:
UPPER PHOTO: typical A. gibbosa with yellow markings (Millisle, Co. Down, Nthn Ireland) and
LOWER PHOTO: aberrant white form (Kilroot, Belfast Lough) without these markings. The
latter is already represented by Daniel Geiger's picture from Swansea.

I see also that you say Bernard Picton says Ancula feeds on minute animals living on bryozoans - actually I used the name kamptozoans which is a synonym of Entoprocta - so I agree with your conclusions about the food of
Ancula pacifica. I prefer to use Kamptozoa as I get confused between Entoprocta and Ectoprocta - Both used to be in the Phylum Polyzoa (Bryozoa) so Ectoprocta now = Bryozoa - confused yet?

In my earlier messages I have shown that species of Trapania also feed on Entoprocts (Kamptozoans).

Picton, B., 2001 (Mar 6) Colour variation in Ancula gibbosa. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Bernard,
Firstly on feeding. I should have been more precise, 'minute animals' is not very informative. Considering that you have shown that Trapania also eats them [Entoprocta, Kamptozoa], they are definitely important enough to be named so I have changed the reference at the top of the page.

The more photos I see of Atlantic animals the more I wonder if Ancula pacifica is really the same species. The anatomy and radula seem quite similar, but these characters may not be useful in distinguishing species in this genus.

Are Thompson & Brown (1984) the only ones who have considered these species to be synonymous? They say: "Specimens found along the Californian coast, described under the name Ancula pacifica MacFarland, 1905, have extra pigment patches on the dorsum, but apparently lack other morphological differences"

If this is the only argument in favour of synonymising them, it doesn't seem very convincing to me. I would be grateful for anyone else's views or information.
Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Mar 6). Comment on Colour variation in Ancula gibbosa by Bernard Picton . [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Ancula gibbosa

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