CHEMICAL SIGNALS IN THE SEA: MARINE ALLELOCHEMICS AND EVOLUTION 1

Abstract

Ohservations in ~hemi~al ecology suggest the ~oevolution of natural produ~ts of plants and the ~hemore~eptors of herhivorous inse~ts. We have reviewed eviJen~e whi~h suggests that this ~oevolution extends ha~k to the primordial protistans. Thus, the evolutionary pressure for the development of a chemosensory ~apahility piOhahly derived from the presence of metaholi~ in the milieu. These produels are ~onsidered to have heen hoth ~ues to the lo~ation of prey and memhrane irritants evolved in the initial phase of ~hemi~al prote~tion. Sometime later this ~hemosensory ~apahility provided several fun~tions in the evolution of metazoans, i.e. the pre~ursors of developmental signals. hormone fun~tion. and synapti~ transmission. We ~onsider that most of the extant natural products of plants and marine invertehrates are protective all omones. A feature of allomone fun~tion that has heen termed antifeedant or feeding inhihitor may represent the ~rypti~ odors of Haldane. We provide eviden~e that the naphthoquinones with a juglone or naphthazarin stru~ture have this activity. O~to­ pus ink has a crypti~ odor effe~t on moray eels. Marine Crusta~ea have, however, evolved an ahility to per~eive the orthoquinone pre~ursors of the ink, a warning signal. Evidence for an array of sex pheromones in a crah and a ~ycloid swimming pattern in a ~opepod that may enahle it to follow a ~hemi~al gradient indicate the ~omplexity of hehavioral responses to ~hemi~al ~ues.