PARTICLE UPTAKE BY A HEXACTINELLID SPONGE , OOPSACAS-MINUTA (LEUCOPSACASIDAE) - THE ROLE OF THE RETICULUM

The discovery of a hexactinellid sponge, Oopsacas minuta, in a Mediter ranean submarine cave provided the opportunity to study its feeding st rategy. Experimental particles (la tex beads and bacteria) are retaine d by a kind of endopinacoderm peculiar to hexactinellids, the reticulu m, which has a great ability of retention, retention. The particle dig estion is performed in this tissue. The choanocytes, responsible for t he uptake of particles in the Demospongiae and the Calcarea, seem, in the Hexactinellida, to mainly provide the water circulation. A develop ed aquiferous system and the retention ability of the hexactinellid ar e interpreted as an adaptation to a scarcity of particles in deep sea.