Studies on Crustacean Eyestalk Neuropeptides by Use of High Performance Liquid Chromatography

Abstract

The neurosecretory system in the eyestalk of decapod crustaceans, comprising groups of perikarya and a conspicuous, “classical” neurohemal organ, the sinus gland, is widely believed to be the most important component of the endocrine system of this animal group. Largely on the basis of deficiency and replacement experiments, a considerable number of active “factors”, regulating a large variety of physiological processes, have been postulated to be synthesized, stored, and released in the eyestalk (reviews [1,2]). It is not known how many individual active substances are responsible for the many biological effects of eyestalk or sinus gland extracts. Despite many attempts at isolation and characterization, thus far only two eyestalk neuropeptides have been completely elucidated, the red pigment concentrating hormone (RPCH), a chromatophorotropin from Pandalus borealis [3] and, from the same species, one form of the distal retinal pigment hormone (light adapting), a neuropeptide regulating light adaptation of the compound eye [4] that also possesses melanophore dispersing activity. It may therefore also be called melanophore dispersing hormone (MDH, reviews [1, 2]). The next best known neuropeptide is the crustacean hyperglycemic hormone (CHH), a peptide of larger molecular size which has thus far been characterized only in terms of amino acid composition [5]. Apart from these achievements, progress has been slow due to (a) lack of convenient and reliable bioassays and (b) the shortcomings of conventional purification methods in the isolation of minute amounts of neuropeptides from small amounts of starting material.