June 27, 2001
From: Paul Young
Here are a few more photos of the White Doris.
Perhaps this will help clear up their identification.
The first shows the gills about half out (They retract the gills when disturbed, so it is hard to photograph them). The grey area to the right is the sponge the animal eats. The animals are cream - white and semi-transparent; I wouldn't call them greenish. The tubercles are yellow.
In checking our files, some of the White Doris shots do show a yellow border to the mantle to some extent. Could they be Cadlina marginata instead of C. laevis?
Young, P., 2001 (Jun 27) More on Cadlina from New England. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4675
The extra photos are very welcome. They certainly show the animal that Sherman Bleakney calls C. marginata in his book. I am not sure why he has resurrected the name Cadlina marginata MacFarland, 1905 which MacFarland replaced with C. luteomarginata in 1966. The name 'marginata' was first used for another species of Cadlina [Doris marginata Montagu 1804] one hundred years before MacFarland and so is unavailable.
As I discuss at the top of the page I think the North Atlantic and North Pacific animals are probably different species but it will need an anatomical study to be sure. The food sponge of your species is interesting as it seems to be a slime sponge, rather than the spiculate sponges the Pacific species eats. Do you know if your sponge has a name? Or can you describe it? Is it smooth, leathery and tough? Does it seem to have sponge spicules? Another interesting point would be a photo of its egg ribbon. Some species have big eggs and the young hatch from them directly as miniature slugs, while in other species there are many small eggs which develop into microscopic veliger larvae which hatch out of the egg ribbon and swim off in the plankton. A photo may give us some clues to the size of the eggs.
As I said before, this is a very interesting find.