The visual ecology of avian photoreceptors

Nathan S. Hart*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

421 Citations (Scopus)

Abstract

The spectral sensitivities of avian retinal photoreceptors are examined with respect to microspectrophotometric measurements of single cells, spectrophotometric measurements of extracted or in vitro regenerated visual pigments, and molecular genetic analyses of visual pigment opsin protein sequences. Bird species from diverse orders are compared in relation to their evolution, their habitats and the multiplicity of visual tasks they must perform. Birds have five different types of visual pigment and seven different types of photoreceptor - rods, double (uneven twin) cones and four types of single cone. The spectral locations of the wavelengths of maximum absorbance (λmax) of the different visual pigments, and the spectral transmittance characteristics of the intraocular spectral filters (cone oil droplets) that also determine photoreceptor spectral sensitivity, vary according to both habitat and phylogenetic relatedness. The primary influence on avian retinal design appears to be the range of wavelengths available for vision, regardless of whether that range is determined by the spectral distribution of the natural illumination or the spectral transmittance of the ocular media (cornea, aqueous humour, lens, vitreous humour). Nevertheless, other variations in spectral sensitivity exist that reflect the variability and complexity of avian visual ecology.

Original languageEnglish
Pages (from-to)675-703
Number of pages29
JournalProgress in Retinal and Eye Research
Volume20
Issue number5
DOIs
Publication statusPublished - 2001
Externally publishedYes

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