Ultraviolet vision in a bat

Abstract

Most mammals, with the exception of primates, have dichromatic vision and correspondingly limited colour perception¹. Ultraviolet vision was discovered in mammals only a decade ago², and in the few rodents and marsupials where it has been found, ultraviolet light is detected by an independent photoreceptor^2,3. Bats orient primarily by echolocation, but they also use vision. Here we show that a phyllostomid flower bat, Glossophaga soricina, is colour-blind but sensitive to ultraviolet light down to a wavelength of 310 nm. Behavioural experiments revealed a spectral-sensitivity function with maxima at 510 nm (green) and above 365 nm (ultraviolet). A test for colour vision was negative. Chromatic adaptation had the same threshold-elevating effects on ultraviolet and visible test lights, indicating that the same photoreceptor is responsible for both response peaks (ultraviolet and green). Thus, excitation of the β-band of the visual pigment is the most likely cause of ultraviolet sensitivity. This is a mechanism for ultraviolet vision that has not previously been demonstrated in intact mammalian visual systems.