Limapontia capitata on Vaucheria

November 5, 2009
From: Ian Smith

Note added 9 November 2009: The animals in the lower 3 photos are most likely L. depressa. See message #22763.

Dear Bill

I attach some pictures of Limapontia capitata. The rhinophoral crests can be seen fairly clearly on the brownish specimens, and the elongated pale metapodium is well extended on the dark specimen.

I found these in October 09 ,and others in Sept 09, in a bay adjoining the Swellies section of the Menai straights between Anglesey and mainland Wales.

They were found in conditions more usually associated with Limapontia depressa, except that the water in the Menai has full salinity. They were on Vaucheria. At least I think it is that; fine filaments forming a mat in mud pools among Salicornia europaea and on damp mud flats high on the shore. A couple of L. capitata were on it in a mud pool, but most were on the mat of "Vaucheria" lying on damp mud; a situation reported by T.E. Thompson (Biol. Opisth. Moll. vol.1,1976) as suited for L. depressa, while he gave coralline pools as the habitat of L. capitata, which he said is reluctant to leave water.

One of the attached pictures is of a L. capitata in situ on "Vaucheria" lying on damp mud.

I'll send a further message [#22753 ] with pictures of the "Vaucheria" in the hope that another member can tell me if I am right, and that it is not a fine Enteromorpha, which was reported by T.E. Thompson, along with Cladophera and Bryopsis, as pablum of L. capitata.

Locality: Church Island, Menai, Anglesey, intertidal, Wales, U.K., Irish Sea, 17 October 2009, intertidal mud flat, full salinity. Length: 3 mm. Photographer: Ian F. Smith.

Best Wishes
Ian (Smith)

ifsmith@bethere.co.uk

Smith, I.F., 2009 (Nov 5) Limapontia capitata on Vaucheria. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22752

Dear Ian,

Thanks for these interesting photos. As I said in your recent message on L. depressa [message #22743], differentiating between L. depressa and L. capitata could be tricky. Did you look at these animals with a binocular microscope? It would be interesting to know where the anus and renal openings were. Tom Thompson also mentions a pale yellowish variety of L. depressa [var pellucida Kevan] in which the mantle skin is devoid of most pigment and the branched digestive gland shows through as a dark shadow. Two of you photos show this quite clearly, but I don't know if L. depressa is the only species which has this variation. If it is then your animals may be that species.

Unfortunately I am not very familiar with these common northern hemisphere species. Perhaps Kathe Jensen, who worked on these animals some years ago can give her views.

Best wishes,
Bill Rudman

Rudman, W.B., 2009 (Nov 5). Comment on Limapontia capitata on Vaucheria by Ian Smith. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22752

Factsheet

Limapontia capitata

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