Multiple rod-cone and cone-rod photoreceptor transmutations in snakes: evidence from visual opsin gene expression.
Proc Biol Sci
; 283(1823)2016 Jan 27.
Article
en En
| MEDLINE
| ID: mdl-26817768
ABSTRACT
In 1934, Gordon Walls forwarded his radical theory of retinal photoreceptor 'transmutation'. This proposed that rods and cones used for scotopic and photopic vision, respectively, were not fixed but could evolve into each other via a series of morphologically distinguishable intermediates. Walls' prime evidence came from series of diurnal and nocturnal geckos and snakes that appeared to have pure-cone or pure-rod retinas (in forms that Walls believed evolved from ancestors with the reverse complement) or which possessed intermediate photoreceptor cells. Walls was limited in testing his theory because the precise identity of visual pigments present in photoreceptors was then unknown. Subsequent molecular research has hitherto neglected this topic but presents new opportunities. We identify three visual opsin genes, rh1, sws1 and lws, in retinal mRNA of an ecologically and taxonomically diverse sample of snakes central to Walls' theory. We conclude that photoreceptors with superficially rod- or cone-like morphology are not limited to containing scotopic or photopic opsins, respectively. Walls' theory is essentially correct, and more research is needed to identify the patterns, processes and functional implications of transmutation. Future research will help to clarify the fundamental properties and physiology of photoreceptors adapted to function in different light levels.
Palabras clave
Texto completo:
1
Banco de datos:
MEDLINE
Asunto principal:
Serpientes
/
Regulación de la Expresión Génica
/
Opsinas de Bastones
/
Células Fotorreceptoras Retinianas Bastones
/
Células Fotorreceptoras Retinianas Conos
/
Opsinas de los Conos
Límite:
Animals
Idioma:
En
Año:
2016
Tipo del documento:
Article