Actinies abyssales d'un site hydrothermal du Pacifique oriental

The Biocyatherm 1 expedition permitted observation of six species of Hexactiniaria, four of which were collected. Three species collected towards the edge of the site, on its basaltic floor, in areas without thermal anomaly, belong to common deep-sea genera (Phelliactis, Chondrophellia, Actinostola ). The sea anemone collected from the active vents belongs to a new genera of the family Actinostolidae. A few Cyananthea hydrothermala were observed on both chimneys. Ultrastructural investigation of this sea anemone reveals a few bacteria in the phagocytic cells of digestive tissues. Their location and the presence of hydrolases suggest that bacteria form part of the diet of sea anemones and are not symbiotic.