The Physiology and Pharmacology of Crustacean Chromatophores

The color change system of crustaceans is being investigatedalong a broad front. The techniques being used include physiological,pharmacological, biochemical, immunocytochemical, and ultrastructuralones. The problems investigators are seeking answers to includethe cellular bases for pigment granule translocation, the numberand specificity of the chromatophorotropic hormones responsiblefor the color changes, and the identity of the neuroregulators(neurotransmitters and neuromodulators) that control the releaseof these hormones. With respect to the cellular bases of pigmentgranule translocation, microtubules and a microtrabecular latticeare prime candidates as organelles that might be responsiblefor the pigment granule movements. Pigment dispersing and pigmentconcentrating neuropeptides have been identified. Some exhibitno specificity with respect to the chromatophore type they activate.Others show high specificity, affecting only one specific typeof chromatophore, such as the melanophore. Several putativeneuroregulator candidates have been identified as possibly havinga role in controlling chromatophorotropic hormone release. Theseinclude 5-hydroxytryptamine, dopamine, norepinephrine, octopamine,and gamma-aminobutyric acid. Some, like the first three, stimulatehormone release, whereas the latter two have inhibitory actions.