MICROSPECTROPHOTOMETRIC AND IMMUNOCYTOCHEMICAL IDENTIFICATION OF ULTRAVIOLET PHOTORECEPTORS IN GECKOS

Retinas of the nocturnal geckos, Hemidactylus turcicus, Hemidactylus g arnotii, and Teratoscincus scincus, were studied with microspectrophot ometry and immunocytochemistry against various visual pigment epitopes to reveal UV-sensitive photoreceptors. From 6-20% of the thinner memb ers of type C double photoreceptors, earlier believed to be blue-sensi tive, were found to contain a UV absorbing visual pigment with lambda( max) at 363-366 nm. The pigment had bleaching and dichroic properties typical of other photoreceptor cell types of the retina. Presumptive U V-sensitive cells in retinal sections were ''negatively'' labeled as t hey did not react with either the cone-specific monoclonal antibody CO S-1 or with the anti-rhodopsin polyclonal serum AO, which together lab eled all of the remaining photoreceptor types (green-sensitive A singl es, B doubles, and thicker members of C doubles, as well as the blue-s ensitive majority of thinner members of C doubles). UV cells were mode rately stained with the mAb K42-41 produced against the 5-6 loop of bo vine rhodopsin, which also moderately labeled blue-sensitive cells. mA b OS-2 strongly stained all outer segments, including the UV-sensitive ones. Similarities between gecko UV visual pigments, and UV visual pi gments of other vertebrates, as well as possible functional significan ce of these cells are discussed.