Symbiotic association between the plathelminth Convolutrilova longifissura and the alga Tetraselmis sp.
Balzer, I.
I. Zoologisches Institut, Berliner Str. 28, D-37073 Göttingen, Germany
Convolutrilova longifissura has been recently described from the Indonesian coast and belongs to the acoela plathelminths. Its green colour results from symbiotic algae, localised between the bases of epidermal cells, but also in deeper tissue layers. The algal symbionts belong to the taxon Tetraselmis (Prasinophyceae). They were isolated and kept in culture at the SAG collection of algae at the University of Göttingen (SAG B 35.93). Another representative of this taxon, namely Tetraselmis convolutae is known as the symbiont of the acoel Convoluta roscoffensis. Here, algal cells loose the pectinaceous cell wall and are enclosed in vacuoles associated with the body wall musculature projecting into the epidermal host layer. Moreover, Convoluta roscoffensis utilizes photosynthetically produced oxygen from the symbionts for respiration. Convolutrilova longifissura seems to depend more essentially on certain products of their symbionts, since they degenerate within 4 days when kept in darkness. In contrast to Tetraselmis convolutae, symbionts fom Convolutrilova longifissura preserve the cell wall inside the host and are used for nutrition: entire algae are regularly transported into a central resorptive tissue as a dark spot anterior to the pharynx where digestion takes place. C. longifissura shows a remarkable mode of asexual reproduction by longitudinal fission. During this process, algae are equally distributed in both individuals. Microscopical and molecular analysis of the Tetraselmis sp. from C. longifissura suggest a new species distinct from Tetraselmis convolutae (Melkonian, M., pers. commun.) and more related to the newly described Tetraselmis desikacharyi (Marin B, Hoef-Emden K and Melkonian M.: Light and electron microscope observations on Tetraselmis desikacharyi sp. nov. (Chlorodendrales, Chlorophyta) Nova Hedwigia, Beiheft 112, 461-475, 1996).
| LOCATION |
DATE |
TIME |
| Lecture Hall I |
Thursday, April 9 |
02:00 pm |