Symbiotic zooxanthellae in Cinachyra tarentina, a non-boring demosponge

Endosymbiotic zooxanthellae, referred to Symbiodinium microadriaticum, are described in the non-bioeroding sponge Cinachyra tarentina Pulitzer-Finali, 1983, by both light and transmission electron microscopy. The algae are int racellular, included in individual vacuoles of mesohyl cells, inside which they were observed in division. More than one zooxanthella may live in a sp onge cell. The zooxanthellae measured about 8-9 mu m in diameter. No differ ence in their diameter was detected in relation to the location in the spon ge body. Monthly sponge samplings over one year (from January to December 1 996), allowed the presence/absence of the zooxanthellae to be ascertained. A total of 139 sponges were examined, the majority of which (112 specimens) harboured symbionts. The number of sponges lacking zooxanthellae progressi vely decreased with the approach of summer. From August to October all the specimens contained zooxanthellae. Typically, zooxanthellae have been recor ded in clionids and their presence has generally been correlated with the b oring activity and growth of these sponges. The present report shows no evi dence of constraints in the evolution of the association between sponges an d zooxanthellae along with a possible non-vertical transfer of symbionts to the new generations.