Chemical defense mechanisms on the Great Barrier Reef, Australia.

Seventy-three percent of all exposed common coral reef invertebrates, from four phyla (42 species) tested, are toxic to fish. This represents the first evidence of the high incidence to toxicity in the marine tropics among several phyletic groups comprising dominant species. Most of the remaining exposed species have structural defense mechanisms against predation by fish. Of cryptic invertebrates, 25 percent are toxic to fish. The relation between toxicity, fish feeding behavior, community structure, and evolutionary theory is discussed.