Defenses of Caribbean sponges against invertebrate predators. II. Assays with sea stars

Sea stars are dominant predators in many marine habitats, and spongivory by sea stars has been documented from polar seas to the tropics. Feeding assa ys of whole tissue and artificial foods containing organic extracts, spicul es, and spiculated skeleton of sponges were performed with the Caribbean se a stars Echinaster echinophorus (from the Bahamas) and Echinaster sentus (f rom Florida, USA) to determine whether sponge secondary metabolites or skel etal constituents affect feeding by sea stars. Whole tissue assays of 6 spe cies of mangrove sponges yielded similar preference hierarchies for both se a star species: for E. echinophorus, Tedania ignis = Haliclona hogarthi? Ir cinia felix = Dysidea etheria > Chondrilla nucula = Chondrosia collectrix; for E. sentus, T. ignis = H. hogarthi > I. felix = D. etheria = C. nucula = C. collectrix. Whole tissue assays of 5 species of reef sponges yielded id entical hierarchies for both E. echinophorus and E. sentus: Geodia neptuni > Callyspongia vaginalis > Amphimedon compressa = Ectyoplasia ferox = Agela s clathrodes. Crude organic extracts of the same 6 mangrove sponge species were assayed, and only the crude organic extracts of Dysidea etheria deterr ed feeding by E. echinophorus, Extracts of I. felix, which consistently det erred both fishes and hermit crabs in previous studies, did not deter E. ec hinophorus. Extracts of the same reef sponge species were assayed, and only A. clathrodes, E. ferox, and A. compressa deterred feeding by E. echinopho rus. In whole tissue assays with E. sentus of chemically non-defended speci es (sponges that yielded organic extracts palatable to E. echinophorus) fro m both reef and mangrove habitats, all species were consistently preferred over C. nucula. The preferences of E. sentus for chemically non-defended sp ecies did not correlate with sponge nutritional or skeletal content, sugges ting that other characteristics of these sponges influence sea star prefere nces. Spicules from 5 species of reef sponges (G. neptuni, C. vaginalis, A. clathrodes, E. ferox, and A. compressa) and 3 species of mangrove sponges IT. ignis, H. hogarthi, and C. nucula), and whole sponge skeleton from 4 sp ecies of mangrove sponges (T. ignis, I. felix, C. nucula, and C. collectrix ) did not deter feeding by E. echinophorus. These results, when considered with the data from previous studies employing fishes and hermit crab assays , further illustrate the importance of secondary metabolites as antipredato ry defenses for Caribbean sponges.