RT Journal Article
SR Electronic
T1 Shedding Light on Serpent Sight: The Visual Pigments of Henophidian Snakes
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 7519
OP 7525
DO 10.1523/JNEUROSCI.0517-09.2009
VO 29
IS 23
A1 Wayne L. Davies
A1 Jill A. Cowing
A1 James K. Bowmaker
A1 Livia S. Carvalho
A1 David J. Gower
A1 David M. Hunt
YR 2009
UL http://www.jneurosci.org/content/29/23/7519.abstract
AB The biologist Gordon Walls proposed his “transmutation” theory through the 1930s and the 1940s to explain cone-like morphology of rods (and vice versa) in the duplex retinas of modern-day reptiles, with snakes regarded as the epitome of his hypothesis. Despite Walls' interest, the visual system of reptiles, and in particular snakes, has been widely neglected in favor of studies of fishes and mammals. By analyzing the visual pigments of two henophidian snakes, Xenopeltis unicolor and Python regius, we show that both species express two cone opsins, an ultraviolet-sensitive short-wavelength-sensitive 1 (SWS1) (λmax = 361 nm) pigment and a long-wavelength-sensitive (LWS) (λmax = 550 nm) pigment, providing the potential for dichromatic color vision. They also possess rod photoreceptors which express the usual rod opsin (Rh1) pigment with a λmax at 497 nm. This is the first molecular study of the visual pigments expressed in the photoreceptors of any snake species. The presence of a duplex retina and the characterization of LWS, SWS1, and Rh1 visual pigments in henophidian snakes implies that “lower” snakes do not provide support for Walls' transmutation theory, unlike some “higher” (caenophidian) snakes and other reptiles, such as geckos. More data from other snake lineages will be required to test this hypothesis further.