Recherche - Observatoire océanologique de Banyuls sur mer
Laboratoire Arago

The enigmatic group of sea slugs (Opisthobranchia) reveals a broad variety of different evolutionary adaptations, including various alimentary strategies, defensive mechanisms and photosynthetic endosymbiosis. Photosynthetic endosymbionts are present in many animals, with the well-known example of corals and their incorporated zooxanthellae. In the sea slug group Sacoglossa, however, a special type of photosynthetic endosymbiosis has evolved. In contrast to other animals with photo-endosymbiosis who integrate whole organism like zooxanthellae, these sea slugs integrate only the chloroplasts as isolated organelles from the algae they feed on. This specialized chloroplast integration shows a wide scale of forms between different sacoglossan species ranging from species with chloroplast retention lasting only several days up to species with long-term chloroplast retention lasting up to several months. It is not clarified yet, in which way the function of the chloroplasts can be maintained over such long periods of time in the animal cell environment and why this specialized system occurs with such variation. Aspects of evolutionary ecology and biology of the photosynthetic endosymbiosis in sacoglossan sea slugs are presented, with the focus on photobehavior, photosynthetic activity, and chloroplast integration in the cells of sea slugs. Possible strategies to maintain long-term retention of functional chloroplasts include evolutionary adaptations in behavior. It is shown that the specific photobehavior of the model species Elysia timida represents a highly specialized and effective evolutionary adaptation in relation to long-term integration of chloroplasts.

Séminaire présenté par Valérie Schmitt (Zoological Research Museum Alexander Koening, Leibniz-Institute for Biodiversity of Animals, University of Bonn, Germany) / Amphithéâtre A.Guille (Bt B 1er étage)