The isolated iridescent cornea of the sand goby is photoresponsive.

After a 2 h period of dark adaptation the iridescent cornea of the sand goby, Pomatoschistus minutus, responds to illumination by increasing the amplitude of iridescent reflexions and shifting the wavelength of maximum reflexion towards longer wavelengths. This characteristic response is found to occur in both the intact eye and in the isolated cornea, indicating that the light-induced colour changes are mediated by extra-retinal photoreceptors.