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The dual rod system of amphibians supports colour discrimination at the absolute visual threshold

Yovanovich, Carola A M LU ; Koskela, Sanna M.; Nevala, Noora; Kondrashev, Sergei L.; Kelber, Almut LU and Donner, Kristian (2017) In Royal Society of London. Philosophical Transactions B. Biological Sciences 372(1717).
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... (More)

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.

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author
organization
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Contribution to journal
publication status
published
subject
keywords
Behaviour, Bufo, Colour vision, Photoreceptors, Rana, Visual threshold
in
Royal Society of London. Philosophical Transactions B. Biological Sciences
volume
372
issue
1717
publisher
Royal Society
external identifiers
  • scopus:85012247067
  • wos:000394258900005
ISSN
0962-8436
DOI
10.1098/rstb.2016.0066
language
English
LU publication?
yes
id
eb686a6e-5ac8-44cc-b687-cb4ef8cb332f
date added to LUP
2017-02-22 11:55:02
date last changed
2018-04-08 04:54:19
@article{eb686a6e-5ac8-44cc-b687-cb4ef8cb332f,
  abstract     = {<p>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.</p>},
  articleno    = {20160066},
  author       = {Yovanovich, Carola A M and Koskela, Sanna M. and Nevala, Noora and Kondrashev, Sergei L. and Kelber, Almut and Donner, Kristian},
  issn         = {0962-8436},
  keyword      = {Behaviour,Bufo,Colour vision,Photoreceptors,Rana,Visual threshold},
  language     = {eng},
  month        = {04},
  number       = {1717},
  publisher    = {Royal Society},
  series       = {Royal Society of London. Philosophical Transactions B. Biological Sciences},
  title        = {The dual rod system of amphibians supports colour discrimination at the absolute visual threshold},
  url          = {http://dx.doi.org/10.1098/rstb.2016.0066},
  volume       = {372},
  year         = {2017},
}