Eicosanoids mediate insect cellular immune reactions to bacterial infections.

Abstract

The occurrence of eicosanoids in invertebrate tissues has been recognized for nearly thirty years, beginning with the discovery of certain prostaglandins (PGs) in some species of octacorals1. This discovery attracted more commercial than zoological attention because the large amounts of PGs in the corals represented a natural source of material for research and other pharmaceutical interests2. The initial finding prompted efforts to locate other natural sources of PGs and other eicosanoids, and it is now commonly thought that eicosanoids occur in the tissues of virtually every animal taken under appropriate scrutiny. This idea carries considerable significance, because it suggests eicosanoids were recruited into biological signaling systems before evolution of the Metazoa. I suppose eicosanoids occur in most, if not all, animals, and eicosanoids exert important biological actions in animals. Some eicosanoid actions are limited to a few species. For example, PGs release egg-laying behavior in some, but not all, cricket species3. Similarly, F-series PGs serve as sex pheromone in some, by no means all, fish species4. On the other hand, other eicosanoid actions may be fundamental to animal systems. Eicosanoids seem to be involved in ion transport physiology in every vertebrate and invertebrate suitably studied5. Regulating ion transport physiology may be a fundamental eicosanoid action. In a similar vein, we will suggest in this chapter that mediating cellular defense reactions may also be a fundamental eicosanoid action.