SPECTRAL SENSITIVITY AND PHOTOPIGMENTS OF A NOCTURNAL PROSIMIAN, THE BUSH-BABY (OTOLEMUR CRASSICAUDATUS)

Earlier studies yielded conflicting conclusions on the types of photor eceptors and photopigments found in the eyes of nocturnal prosimians. In this investigation a noninvasive electrophysiological procedure, el ectroretinogram flicker photometry, was employed to measure scotopic a nd photopic spectral sensitivity in the thick-tailed bushbaby (Otolemu r crassicaudatus). The scotopic spectral sensitivity function of the b ushbaby has a peak of about 507 nm. Under photopic test conditions, sp ectral sensitivity shifts toward the longer wavelengths. The results f rom a series of adaptation experiments indicate that the cones of the bushbaby retina contain only a single type of cone photopigment (peak sensitivity at about 545 nn). One implication from this result is that these animals do not have color vision. The photopigment arrangement of the bushbaby is different from that earlier found in diurnal and cr epuscular prosimians but is similar to that of the owl monkey, the onl y nocturnal simian. (C) 1996 Wiley-Liss, Inc.