Spectral sensitivity of the cichlid fish Haplochromis burtoni was measured under both scotopic and photopic conditions using a two-choice, food reward, operant conditioning paradigm. The highest absolute sensitivity (scotopic) is one quantum for every 5 to 50 rods measured at 475 nm (equivalent to a corneal irradiance of 3.8 x 10(6) Q s-1 cm-2). A P500(1) photopigment apparently mediates spectral sensitivity over most of the visible spectrum; microspectrophotometric studies of rods had previously shown them to contain this photopigment. However, the scotopic behavioral action spectrum shows a sensitivity to short wavelength light higher than is consistent with a P500(1) photopigment alone mediating the scotopic visual process. Determinations made under photopic conditions reveal a behavioral action spectrum broader than that found under scotopic conditions and consistent with mediation by interaction of the three known cone types in an opponent processing manner. The calculated photopic threshold value of approximately 10(4) Q s-1 (receptor)-1 is in agreement with results from other species and corresponds to a corneal irradiance of about 7 x 10(10) Q s-1 cm-2.

The [¹⁴C]2-deoxygIucose (2-DG) technique was used to study patterns of neural activity associated with the species-typical courtship behavior of male red-sided garter snakes (Thamnophis sirtalis parietalis). Males in this species court females intensely during the first month following spring emergence from their prolonged winter hibernation. Autoradiographic methods were used to measure the accumulation of radioactive label in various regions through the brains of male garter snakes that courted females, males that failed to court females, and males not exposed to females. Male garter snakes that actively courted females showed a pronounced increase in 2-DG accumulation, and therefore presumably neural activity, in the region of the anterior hypothalamus/preoptic area, relative to males that did not actively court females. Males exposed to females (regardless of whether they courted or not) showed widespread, non-specific increases in 2-DG uptake relative to males not exposed to females. The results indicate the utility of the 2-DG technique for studying complex, species-typical behaviors in vertebrates.

Unilateral visual stimulation following 2-deoxyglucose injection was used to delineate functional visual pathways in red-sided garter snakes (Thamnophis sirtalis parietalis) and whiptail lizards (Cnemidophorus inornatus and C. uniparens). Stimulation enhanced both overall uptake and particularly uptake in visual pathways contralateral to the side of stimulation. Bilaterally symmetrical uptake was observed in retinae, septum, nucleus sphericus, and brainstem nuclei. Overall uptake and lateralization of uptake were consistently greater in garter snakes than in whiptail lizards.