Re: Sacoglossans vs Caulerpa taxifolia

July 21, 2000
From: Kathe R. Jensen

Dear Bill,

Thanks for opening the page on this important issue. Unfortunately bureaucracy may not be enough to prevent the "introduction" of Caribbean sacoglossans to the Mediterranean. Spanish researchers have now collected Elysia subornata (as E. cauze) from the Canary Islands as well as the Cape Verde Islands, so I'm afraid it is only a question of time before Nature starts its own large-scale experiment.

I am not sure I quite understand Cynthia's point about functional or non-functional kleptoplastids. Elysia subornata has functional kleptoplasts, but Oxynoe spp. do not. Oxynoe azuropunctata may be a stronger competitor than O. olivacea, the local Mediterranean species, and this is one of the things I have told the French group of scientists MUST be tested carefully. As all shelled sacoglossans are restricted in diet to Caulerpa spp. (and I have actually tried - in vain - to give them only non-Caulerpa algae for several weeks), I do not fear that O. azuropunctata will switch to other algae (though obviously it will be able to switch to the native C. prolifera). Elysia subornata, on the other hand might be able to switch to feed on Halimeda or Udotea (which have the same cell wall structure as Caulerpa), but it is highly unlikely that they will switch to non-Caulerpales algae. This is another thing I have asked the French group to investigate. What I fear more is that once it has entered the Mediterranean, the road to the Red Sea and the Indian Ocean is wide open, and then we may have a serious problem.

References:
• Ortea, J., Moro, L., Bacallado, J.J. & Espinosa, J. (1998) Catalogo abreviado de las especies del orden Sacoglossa (= Ascoglossa, Mollusca: Opisthobranchia) de las Islas Canarias y de Cabo Verde. Revista Academia Canaria de la Ciencias, 10(4): 85-96.
• Ortea, J., Moro, L. & Espinosa, J. (1997) Nuevos datos sobre el genero Elysia Risso, 1818 (Opisthobranchia: Saccoglossa) en el Atlantico. Revista Academia Canaria de la Ciencias, 9(2-4): 141-155.
• Jensen, K.R. (1997) Evolution of the Sacoglossa (Mollusca, Opisthobranchia) and the ecological associations with their food plants. Evolutionary Ecology, 11: 301-335.

Best wishes,
Kathe

jensen@ait.ac.th

Jensen, K.R., 2000 (Jul 21) Re: Sacoglossans vs Caulerpa taxifolia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/2763

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