Further studies on the anatomy and ecology of opisthobranch molluscs feeding on the scleractinian coral Porites

Abstract

Three further species of opisthobranch molluscs are reported to feed on the scleractinian coral Porites in Tanzania. Further information on Cuthona poritophages Rudman, 1979, is also included. The anatomy of the aeolid Phestilla lugubris{Bergh, 1870, = P. sibogae Bergh, 1905) and a new species of Phestilla is described, as is the anatomy of the arminacean Pinufius rebus. The new species of Phestilla, and Pinufius, are, for the first time, reported to feed on Porites. Notes on the anatomy of the type-species of Phestilla, P. melanobrachia Bergh, 1874, are included to make possible a definition of the genus Phestilla. Aspects of the feeding biology, life history, defence mechanisms and habitat specificity of the four Porites-feeding opisthobranchs are described and discussed. The four species are shown to have evolved radular teeth of remarkably similar shape. Each species utilizes a different part of the coral tissue as food. The three aeolids have replaced functional cnidosacs at the tip of their cerata with batteries of large secretory cells. Phestilla lugubris and Pinufius rebus are also reported for the first time from the Great Barrier Reef, Queensland and the new species of Phestilla is reported from Queensland and Hawaii.