Cone receptor variations and their functional consequences in two species of hamster

Results from earlier experiments indicate that different species of rodent vary both in the number of cone types found in their retinas and in the spe ctral sensitivities of the cone pigments. These features have now been exam ined in two types of hamster commonly used for research purposes: Syrian go lden hamsters (Mesocricetus auratus) and Siberian dwarf hamsters (Phodopus sungorus). Electroretinogram (ERG) flicker photometry, behavioral discrimin ation tasks, and opsin antibody labeling were used to investigate hamster p hotoreceptors and their visual consequences. Results from the three approac hes support the following conclusions: (1) The retinas of both species have an abundant population of rods containing a photopigment with peak sensiti vity of about 498-500 nm; (2) Siberian dwarf hamsters have two classes of c one: one with maximum sensitivity in the ultraviolet (c. 360 nm), the other with peak sensitivity closely similar to that of its rod; and (3) Syrian g olden hamsters have a class of cone with peak sensitivity at about 506 nm, but they lack a second cone type. Implications of these alternative arrange ments are discussed.