THE BIOLOGY OF PROSTAGLANDINS AND RELATED EICOSANOIDS IN INVERTEBRATES - CELLULAR, ORGANISMAL AND ECOLOGICAL ACTIONS

Prostaglandins and related eicosanoids are oxygenated metabolites of C 20 polyunsaturated fatty acids. These compounds have been detected in species representing all major animal phyla, The significance of eicos anoids lies in two broad areas of animal biology. In one, eicosanoids are involved in regulation of many cellular events. In the other, eico sanoids facilitate certain ecological interactions, Eicosanoids are kn own best in the narrow context of their clinical significance in human medicine. In this essay we suggest a new, broader paradigm for unders tanding the meaning of eicosanoids. Under this paradigm, called the bi ological paradigm, we note eicosanoids were recruited into roles as bi ological signal moieties long before the origins of the Metazoa. Durin g the ensuing evolutionary diversification of animals, eicosanoids hav e been used in a vast diversity of biological roles, some of which occ ur only in invertebrates. We think this diversity endows eicosanoids w ith unusual explanatory power in apprehending biological phenomena. In this review, we recount the literature on eicosanoids in protozoans a nd procaryotes, then provide a detailed review of the roles of eicosan oids in invertebrate immunity. We draw upon recent work in parasitolog y to outline an ecological role of eicosanoids in host-parasite relati onships. It appears to us that eicosanoids exert profound effects at t he cellular, organismal and ecological levels of biological organizati on, We suggest that continued inquiry into the biological significance of eicosanoids will yield important new information on invertebrates.