Pigment migration in fish erythrophores is controlled by alpha 2-adrenoceptors.

1. The aggregation of erythrosomes within erythrophores of the squirrel fish (Myripristis occidentalis; belonging to the family Holocentridae) was, on pharmacological grounds, shown to be mediated by alpha 2-adrenoceptors. 2. The erythrophores were shown to be controlled by adrenergic nerves activating the alpha 2-adrenoceptors. 3. The erythrophores themselves were found to possess a K+-sensitive mechanism of aggregation. 4. Some similarities and differences of the alpha 2-adrenoceptor-mediated chromatosome aggregation in melanophores and erythrophores are also discussed.