Visual pigments, oil droplets, ocular media and cone photoreceptor distribution in two species of passerine bird: The blue tit (Parus caeruleus L.) and the blackbird (Turdus merula L.)

N. S. Hart, J. C. Partridge, I. C. Cuthill, A. T.D. Bennett

Research output: Contribution to journalArticle

317 Citations (Scopus)

Abstract

The spectral absorption characteristics of the retinal photoreceptors of the blue tit (Parus caeruleus) and blackbird (Turdus merula) were investigated using microspectrophotometry. The retinae of both species contained rods, double cones and four spectrally distinct types of single cone. Whilst the visual pigments and cone oil droplets in the other receptor types are very similar in both species, the wavelength of maximum sensitivity (λ(max)) of long-wavelength-sensitive single and double cone visual pigment occurs at a shorter wavelength (557 nm) in the blackbird than in the blue tit (563 nm). Oil droplets located in the long-wavelength-sensitive-single cones of both species cut off wavelengths below 570-573 nm, theoretically shifting cone peak spectral sensitivity some 40 nm towards the long-wavelength end of the spectrum. This raises the possibility that the precise λ(max) of the long-wavelength-sensitive visual pigment is optimised for the visual function of the double cones. The distribution of cone photoreceptors across the retina, determined using conventional light and fluorescence microscopy, also varies between the two species and may reflect differences in their visual ecology.

Original languageEnglish
Pages (from-to)375-387
Number of pages13
JournalJournal of Comparative Physiology - A Sensory, Neural, and Behavioral Physiology
Volume186
Issue number4
DOIs
Publication statusPublished - 1 Jan 2000
Externally publishedYes

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