Ichthyodeterrent Properties of Lipophilic Extracts from Bermudian Sponges

Abstract

The feeding deterrent properties of hexane, ethyl acetate, and butanol lipophilic extracts of 16 species of Bermudian sponges presented to the sergeant major,Abudefduf saxatilus, and the Bermuda bream,Diplodus bermudensis, were investigated in the laboratory. The sponges investigated spanned a variety of different color morphs and were representative of patch reef, mangrove, rock wall, soft bottom, seagrass, and cave habitats. Six of the 16 sponges (36%) had at least one extract that deterred feeding byA. saxatilus, while only one of 16 sponges (6%) had an extract that deterred feeding byD. bermudensis. Among those sponges that deterred feeding in one or both fish, deterrence was most frequently associated with compounds extracted in ethyl acetate (moderately polar). Butanol extracts (most polar) were active in only half as many instances, while in only one case was a hexane extract (least polar) active. Both brighly colored (yellow, orange–yellow, gray–blue, purple–brown) and weakly colored (dull brown, pinkish white) sponges had hexane, ethyl acetate, or butanol extracts that were deterrent. Generally the numbers of sponges with bioactive lipophilic extracts that caused feeding deterrence in fish was low. This may be related to Bermuda being located just within or beyond the extreme northern range of many tropical fish and invertebrates, and therefore sponges are exposed to reduced levels of predation.