Experiments on the interspecific effect of the hyperglycemic peptidehormone of the eyestalk have been performed in some decapods. Extracts of eyestalks of the crayfish Orconectes limosus injected in doses which are highly hyperglycemic in Orconectes itself were found to be without effect or only slightly hyperglycemic in Cancer pagurus, Carcinus maenas, Portunus holsatus, Maja squinado, Eupagurus bernhardus and Homarus gammarus. Higher doses are hyperglycemic to a certain degree in some species. On the other hand it was found that injection of extract of eyestalks of the species mentioned above and, in addition, Leander serratus and Nephrops norvegicus were in general uneffective in Orconectes, only the extracts of the closely related species Homarus and Nephrops proved to be effective. It was assumed that the hormone might be different in the different groups of decapod crustaceans. This was tested with cross-experiments in which the following species were compared with Orconectes: Squilla mantis, Carcinus maenas, Pagurus arrosor, Scyllarus arctus, Palinurus vulgaris and Astacus leptodactylus. In the dose range applied no interspecific hyperglycemic effect was found with Squilla and Carcinus. A limited degree of interspecific effect was found with Pagurus and a marked interspecific effect was found with the macruran species Scyllarus and Palinurus. With the closely related species Astacus it was found that the eyestalk extract is completely interchangeable in both directions. That a interspecific effectiveness seems to exist also within other systematic groups seems probable since the extract of Carcinus was found to be effective in Maja and that of Palinurus in Scyllarus. These results seem to support the hypothesis that a molecular differentiation of the hormone molecule occurred in the course of the evolution of the Crustacea. This finding is of interest with regard to the evolution of the pituitary hormones in the different vertebrate classes. In the stomatopod Squilla mantis the hyperglycemic eyestalk hormone was found for the first time in a species outside the Decapoda. © 1969 Springer-Verlag.
