Re: Elysia cornigera from Florida

January 15, 2001
From: Kathe R. Jensen

Dear Bill,

Happy New Year.
Sorry I have taken so long to comment on Anna's Elysia, but first week of classes has been completely chaos, rescheduling and re-rescheduling classes, signing registration forms, plans of study - plus catching up with the huge pile of mail that had accumulated while I was in Denmark for the holidays. And I had to check some references before I could send an answer for the readers of the Forum.
Ortea et al. (1997? - I don't think this was actually published till 1999) compared specimens from the Cape Verde Islands and from Cuba, and tentatively synonymized Elysia timida and E. cornigera. My Spanish is very poor, but I don't think they studied anatomy apart from radular teeth.

In the eastern Mediterranean (Israel) Elysia timida has been described to have encapsulated (direct) development, i.e. the larval shell is lost prior to hatching (Rahat, 1976). In the western Mediterranean a seasonal change from encapsulated to lecithotrophic development (swimming, but non-feeding veligers) has been described (Marin & Ros, 1993). When Nuttall described his E. cornigera (Nuttall, 1989) he also described the larval development, but unfortunately the large larvae died prior to hatching, so either lecithotrophic or encapsulated development was predicted. All this leaves us with a number of possibilities:
•(1) There is only one widespread species with a variable development pattern,
•(2) There are 2 species whose range overlap in the western Mediterranean,
•(3) The population in Florida and Cuba (whether there is one or two species) has been introduced by human activities (ballast water, f.ex.),
•(4) The Mediterranean population could be an early, and higly successful, introduction (not very likely, I think).

These hypotheses should be tested by using phylogenetic analysis, and I hope I have provoked Anna to make the attempt. There are two likely sister species occurring in Australia: Elysia filicauda Jensen & Wells, 1990, which also feeds on Acetabularia, but with unknown development pattern, and Elysia thompsoni Jensen, 1993, with unknown diet, but presumed planktotrophic development (very small egg capsules). Both species have the peculiar teeth with lateral, more or less denticulated flanges.
Thus, I suggest that you move the species to a new page named Elysia cf. timida Risso, 1818. And then we await the progress of science.

References:
• Jensen, K.R. 1993. Sacoglossa (Mollusca, Opisthobranchia) from Rottnest Island and central Western Australia. Pp. 207-253 in: The Marine Flora and Fauna of Rottnest Island, Western Australia (eds. F.E. Wells, D.I. Walker, H. Kirkman & R. Lethbridge). Western Australian Museum, Perth.
• Jensen, K.R. & Wells, F.E. 1990. Sacoglossa (=Ascoglossa) (Mollusca, Opisthobranchia) from southern Western Australia. Pp. 297-331 in: The Marine Flora and Fauna of Albany, Western Australia. Western Australian Museum, Perth.
• Marin, A. & Ros, J. 1993. Ultrastructural and ecological aspects of the development of chloroplast retention in the sacoglossan gastropod Elysia timida. Journal of Molluscan Studies 59: 95-104.
• Nuttall, T.R. 1989. A new Elysia (Opisthobranchia: Ascoglossa) from the Florida Keys. The Veliger, 32: 302-307.
• Ortea, J., Moro, L. & Espinosa, J. (1997?) Nuevos datos sobre el genero Elysia Risso, 1818 (Opisthobranchia: Sacoglossa) en el Atlantico. Revista de la Academia Canaria de Ciencias, 9: 141-155.
• Rahat, M. 1976. Direct development and symbiotic chloroplasts in Elysia timida (Mollusca: Opisthobranchia). Israel Journal of Zoology, 25: 186-193.

Kathe Jensen

jensen@ait.ac.th

Jensen, K.R., 2001 (Jan 15) Re: Elysia cornigera from Florida. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/3515

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