Secondary Metabolites as Mediators of Trophic Interactions Among Antarctic Marine Organisms

Secondary metabolites are widespread among lower phyla and understandingtheir functional role(s) in the producing organism has beenunder study in recent decades. Considerable progress has beenmade in understanding chemical ecological interactions amongterrestrial organisms, and similar research in the marine realmhas been initiated in recent years. Polar regions are more difficultto access and thus progress has been slower. Nevertheless, theextreme and often unique marine environments surrounding Antarcticaas well as the many unusual trophic interactions in antarcticmarine communities might well be expected to select for novelsecondary metabolites and/or novel functional roles for secondarymetabolites. Indeed, recent studies have documented novel, chemically-mediatedinteractions between molluscs and amphipods, between algae,urchins and anemones, and between sponges and their predators.The Porifera are the dominant phylum on the McMurdo Sound benthos,and representatives of this phylum have been shown to elaboratesea star feeding deterrents, inhibitors of fouling or infectiousorganisms, and metabolites which mediate predation via moltinhibition. As a result of studies on Antarctic sponges, newinsights into functional roles of pigments and the ability ofsponges to sequester metabolites have been gained, and a newmechanism of chemical defense has been described. Herein wedescribe recent results of our studies of trophic interactionsbetween sponges and their predators that are mediated by specificsponge secondary metabolites. Moreover, we highlight unusualchemically-mediated interactions in antarctic marine invertebratesother than sponges.