The dual rod system of amphibians supports colour discrimination at the absolute visual threshold.
Philos Trans R Soc Lond B Biol Sci
; 372(1717)2017 Apr 05.
Article
em En
| MEDLINE
| ID: mdl-28193811
ABSTRACT
The presence of two spectrally different kinds of rod photoreceptors in amphibians has been hypothesized to enable purely rod-based colour vision at very low light levels. The hypothesis has never been properly tested, so we performed three behavioural experiments at different light intensities with toads (Bufo) and frogs (Rana) to determine the thresholds for colour discrimination. The thresholds of toads were different in mate choice and prey-catching tasks, suggesting that the differential sensitivities of different spectral cone types as well as task-specific factors set limits for the use of colour in these behavioural contexts. In neither task was there any indication of rod-based colour discrimination. By contrast, frogs performing phototactic jumping were able to distinguish blue from green light down to the absolute visual threshold, where vision relies only on rod signals. The remarkable sensitivity of this mechanism comparing signals from the two spectrally different rod types approaches theoretical limits set by photon fluctuations and intrinsic noise. Together, the results indicate that different pathways are involved in processing colour cues depending on the ecological relevance of this information for each task.This article is part of the themed issue 'Vision in dim light'.
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Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Ranidae
/
Bufonidae
/
Percepção de Cores
/
Células Fotorreceptoras Retinianas Cones
/
Visão de Cores
Tipo de estudo:
Prognostic_studies
Limite:
Animals
Idioma:
En
Revista:
Philos Trans R Soc Lond B Biol Sci
Ano de publicação:
2017
Tipo de documento:
Article
País de afiliação:
Suécia