ASSOCIATION BETWEEN THE SPONGE HALICHONDRIA-PANICEA (PALLAS) AND SCALLOP-CHLAMYS-VARIA (L) - COMMENSAL-PROTECTIVE MUTUALISM

The scallop Chlamys varia (L.) was found associated with an enveloping epizoitic growth of the sponge Halichondria panicea (Pallas). The bivalve was protected against predatory starfishes by the sponge which interfered with the attachment of tube feet and made the vulnerable byssal opening and valve margins inaccessible to the predator's gastric membranes. Protection was partial or complete depending upon the species of starfish and relative sizes of predator, prey, and epizoite. The effectiveness of the pectinid escape response was enhanced by the sponge which enabled the mollusc to dislodge attacking asteroids. The sponge benefited from an increased supply of suspended nutrients generated by the inhalant current of the host. The partnership is a commensal-protective mutualism of an unspecialized and probably facultative nature. The association has not been reported before although it may have a wide distribution, at least on the Atlantic coast of Ireland. © 1979.