Action of biogenic amines on crustacean chromatophores, II. Analysis of the responses of erythrophores in the fildler crab, Uca pugilator, to indolealkylamines and an eyestalk hormone

Abstract

1. 1. The effects of injection of certain indolealkylamines on the erythrophores of the fiddler crab, Uca pugilator, were determined. 2. 2. Among the compounds tested only those which possess a free 5-hydroxy group on the indole nucleus evoked dispersion of the red chromatophoric pigment after injection into eyestalkless Uca pugilator. 3. 3. Serotonin which was very effective in vivo failed to evoke pigment dispersion when assayed in vitro on the erythrophores in legs isolated from Uca. In contrast, red pigment-dispersing hormone from the eyestalks of Uca stimulated the erythrophores in vitro as well as in vivo. 4. 4. UML (1-methyl lysergic acid butanolamide) antagonized the action of serotonin in vivo, but was without effect on hormonally induced dispersion of the red pigment. 5. 5. Injection of serotonin resulted in a marked decrease in the red pigment-dispersing potency of the supra-oesophageal ganglia and the attached circumoesophageal connectives of the recipients. 6. 6. It is concluded that serotonin acts primarily on the central nervous system to stimulate the release of a red pigment-dispersing hormone, whereas the red pigment-dispersing hormone stimulates the erythrophores directly.