Chemical Signals from Sponges and their Allelopathic Effects on Other Marine Animals

Abstract

In their natural environments, sponges are subject to intense competition for space and for resources such as nutrients. Many of these organisms are soft-bodied, yet inhabit areas of intense predation pressure. Indeed, on coral reefs, sponges are the second most abundant biomass after corals. The ecological success of this group of colourful marine animals may be enhanced by use of a chemical defense strategy. A multitude of structurally-complex natural products representing all the major biosynthetic classes (terpene, alkaloid, polyketide etc) have been isolated from marine sponges¹. Natural chemical signals (allelochemicals) from sponges are likely responsible for inducing or inhibiting the settlement of larvae of coral reef animals. While some of these chemicals are universally toxic to animal larvae, many others may differentially affect the physiology and development of specific types of larvae. One specialised group of marine animals, the nudibranchs, feed on marine sponges and may utilise toxic sponge chemicals as part of their own defensive strategy. In this paper, I discuss recent examples from our laboratory which illustrate the role played by sponge allelochemicals in underwater chemical “warfare”