Cooperative cocktail in a chemical defence mechanism of a trunkfish.

Pahutoxin a quaternary ammonium salt surfactant serves as an active ingredient in the defensive skin secretion of various marine trunkfish (Ostracociidae). In the defensive skin secretion of the Red Sea trunkfish, Ostracion cubicus the effect of PHN is amplified due to the existence of non toxic polypeptides which act as (a) PHN - chelators and (b) potentiators. The secretion of the Red Sea trunkfish includes an additional category of pharmacologically active polypeptides represented by boxin [7] which similarly to PHN they independently kill fish exclusively through medium application. By the aid of radiolabeled PHN and a fish gill membrane preparation a series of equilibrium saturation binding assays were carry out which demonstrate that PHN performs its biological defensive function via receptors and not due to its surface activity. The gill membranes of the trunkfish were shown to be devoid of PHNreceptors. The pharmacological, ecological and environmental implications of the above data are discussed.