The Physiology and Pharmacology of Crustacean Chromatophores

The color change system of crustaceans is being investigated along a broad front. The techniques being used include physiological, pharmacological, biochemical, immunocytochemical, and ultrastructural ones. The problems investigators are seeking answers to include the cellular bases for pigment granule translocation, the number and specificity of the chromatophorotropic hormones responsible for the color changes, and the identity of the neuroregulators (neurotransmitters and neuromodulators) that control the release of these hormones. With respect to the cellular bases of pigment granule translocation, microtubules and a microtrabecular lattice are prime candidates as organelles that might be responsible for the pigment granule movements. Pigment dispersing and pigment concentrating neuropeptides have been identified. Some exhibit no specificity with respect to the chromatophore type they activate. Others show high specificity, affecting only one specific type of chromatophore, such as the melanophore. Several putative neuroregulator candidates have been identified as possibly having a role in controlling chromatophorotropic hormone release. These include 5-hydroxytryptamine, dopamine, norepinephrine, octopamine, and gamma-aminobutyric acid. Some, like the first three, stimulate hormone release, whereas the latter two have inhibitory actions.