Retinal and extraretinal entrainment action spectra for the activity rhythms of the lake chub, Couesius plumbeus

Abstract

The roles of retinal, pineal, and other extraretinal photoreceptors in determining light responses and the entrainment of circadian locomotor activity rhythms were investigated with a cyprinid fish, the lake chub, Couesius plumbeus. Determinations were made of the action spectra for inducing activity responses and entraining circadian activity. In normal, intact fish entrainment occurred over 368 to 742 nm with maximal sensitivity at wavelength bands centered at 538 to 568 nm (10−6−10−4 μw cm−2). In blinded and blinded-pinealectomized fish extraretinal photoreception and entrainment was restricted to approximately 568 to 742 nm. In all cases the energy fluence rates for entraining activity were significantly greater than those required for effecting activity responses.