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A. E. Lindsey, B. C. Politylo, A. J. Rivera; Psychophysical Measurement of Color Vision in Neotenic Tiger Salamander. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2734.
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Molecular and cellular techniques have been used to study spectral sensitivity in the tiger salamander (Ambystoma tigrinum) retina, but color vision in these animals has not been fully assessed. The purpose of this work was to apply psychophysical techniques to determine if neotenic tiger salamanders respond to color stimuli of differing wavelengths.
The stimulus was a drifting (5 Hz) square-wave grating of alternating red/green stripes that was generated by a computer program and displayed on a 17" LCD monitor. The optomotor response, swimming in the direction of a moving stimulus, was used to determine whether salamanders could visually detect moving red/green square-wave gratings. Animals (n = 8; 23-27 cm body length) were individually placed in an aquarium where they faced the monitor at a viewing distance of 29.0 cm. One cycle of the grating subtended 0.40 cycles/degree visual angle. An experimenter determined whether or not the animal’s swimming movements were oriented in the direction of the moving grating.
No animals responded to a stationary uniform green field (0.25 V video signal). Five animals responded to the red/green drifting grating when the intensity of the red/green stripes was equal. When the intensity of the green stripe was held constant (0.46 V signal) and the intensity of the red stripe varied in 10 step increments to produce 10-100% grating contrasts, three of the five salamanders responded throughout the range, one animal responded to contrasts between 10 and 40%, and one animal responded to contrasts between 40 and 100%. The remaining three animals did not respond to any contrast of the drifting red/green gratings.
(1) Behavioral methods can be used to assess color vision in neotenic tiger salamanders. (2) The capacity to detect moving color stimuli varies among these animals. (3) Once conditions that result in consistently positive responses are identified through further research, the tiger salamander can become a useful model to study the relationship between cone photoreceptor physiology and morphology and color vision.
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