Tambutté S., 1996. Le tissu oral des anthozoaires : fonctionnement et rôle dans l'association symbiotique. PhD from Aix-Marseille II University, Ocanology Center of Endoume.

ABSTRACT

The aim of this work was to characterize the permeability properties of the oral epithelial layers which are at the interface between the coelenteric fluid and the external sea water in a scleractinian, Heliofungia actiniformis, and a sea anemone, Anemonia viridis. Permeability characteristics of this tissue led us to classify it among leaky epithelia where paracellular diffusion is the major pathway for Ca2+, Na+ and Cl- ions. Permeability depends on the size of molecules. Alanine is absorbed by the ectoderm but does not cross the two epithelial layers due to the presence of ectodermal junctions. The tissue is not permeable to large molecules like inulin. The tissue has a low water permeability allowing the maintenance of an hydrostatic skeleton. We have also determined the mechanisms of inorganic carbon transport for supplying zooxanthella photosynthesis. Paracellular transport is not sufficient for photosynthesis. Not only the endodermal but also the ectodermal cells are involved in the transport of inorganic carbon. The transport occurs via Cl-/HCO3- exchangers, H+-ATPases and carbonic anhydrases. In addition to being morphologically polarized, the tissue is physiologically polarized too with an intratentacular medium more basic than external seawater. We have also made a cellular approach consisting in the isolation of endodermal cells and their observation with a confocal microscope. Taking into account the constraints of our biological and experimental materials, we have set up a procole to measure the internal pH thanks to a vital fluorescent dye, SNARF1, and to appropriate filters.

Key words : sea anemones - corals - permeability - transepithelial transport -bicarbonate - photosynthesis -confocal microscope