Neurosecretory Control of Pigmentary Effectors in Crustaceans

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Abstract
A general summary of the current status of the control of crustacean pigmentary effectors is followed by a detailed description of recent experiments with the chromatophores of fiddler crabs. Under appropriate experimental conditions eyestalkless fiddler crabs, Uca pugilator, can exhibit an overt daily rhythm of melanin dispersion. Otherwise, the melanin of eyestalkless crabs remains maximally concentrated. Electrophoretic analysis revealed three peaks of melanin-dispersing activity for sinus glands of Uca pugilator, two for the supraesophageal ganglia, one for the circumesophageal connectives, and one for blood. What appeared to be the same electronegative substance was found in every electrophorogram regardless of whether one, two, or three peaks were present. In addition, a melanin-concentrating substance was found after electrophoresis of circumesophageal connectives. The morphology of postcommissural organs from two species of fiddler crabs is described also. Extracts of post-commissural organs from Uca pugilator were chromatophorotropically active. The extracts were most effective in concentrating red pigment but could also disperse the red and black pigments. Post-commissural organs of crabs had not been assayed previously on any system. Finally, the role that post-commissural organs might have in regulating chromatophores of fiddler crabs during different portions of the daily rhythm of color change is discussed.