NEUROSECRETION AND CRUSTACEAN RETINAL PIGMENT HORMONE: ASSAY AND PROPERTIES OF THE LIGHT-ADAPTING HORMONE

Abstract

A standard assay for the content of light-adapting distal retinal pigment hormone in crustacean eyestalk extracts is described. Linear regression equations for response to concentration of eyestalk extract from Palaemonetes and from Libinia are respectively: Y = 0.108 + 0.077 log X; Y = 0.200 + 0.107 log X. A Palaemonetes unit of this hormone is defined as that concentration for eyestalk extract, injected into a minimum of 10 dark-adapted P. vulgaris measuring 35-40 mm in rostrum-telson length, which will result in an average distal retinal pigment index of 0.150. For the Palaemonetes and Libinia used in this study 1 Palaemonetes unit is equivalent respectively to concentrations of 3.5 and 0.34 eyestalk per 1.0 ml. Thermostability, small molecular size, complete or partial inactivation by tissue extracts (peptidases?) and by crystalline trypsin and chymotrypsin are properties of the hormone consistent with a possible peptide structure.