Predation by asteroids, escape response, and morphometrics of scallops with epizoic sponges

Abstract

The asteroid predator Coscinasterias calamaria (Gray) was caged with the scallops Chlamys asperrima (Lamarck), with and without epizoic sponges, and Chlamys bifrons (Lamarck) which lacks epizoic sponges. The sponges inhibited predation on host C. asperrima apparently by camouflaging the scallop and interfering with adhesion of the predators' tube feet. This enabled the scallops to escape easily. C. bifrons, which is heavily constructed and swims more readily, was not significantly more susceptible to predation than sponge-covered C. asperrima. The sponge clad C. asperrima were less responsive to the presence of Coscinasterias, and made fewer repeated escapes, than both Chlamys asperrima without sponge and C. bifrons. The shells of C. asperrima with sponge were thinner than those without, possibly a result of the latter having to repair damage caused by borers. The growth of sponge-covered scallops was enhanced, their shells were higher, heavier, and contained more soft tissue for their number of growth rings than those without sponge. The scallops appeared to facilitate recruitment of the sponges which were uncommon on other substrata.