Catecholamine-induced colour changes in the corneal iridophores of the sand goby, Pomatoschistus minutus

1. The iridescent cornea of the sand goby, Pomatoschistus minutus, responds to light by an increase in the amplitude and alteration of the maximum wavelength of spectral reflexions from the iridophores. 2. Two distinct physiological mechanisms are responsible for the two types of changes, one involving redistribution of material within the iridophore, the other involving a flow of material into the iridophore as a whole. 3. The types of colour change induced by catecholamines were investigated. 4. Alpha-receptor agonists increased the amplitude of reflexions whereas beta-receptor agonists decreased the amplitude of the reflexions. 5. The beta-antagonist propranolol interrupted the normal light response. 6. It is concluded that, in vitro, both light and catecholamines bring about a redistribution of material within the corneal iridophore.