Visual pigments and oil droplets from six classes of photoreceptor in the retinas of birds
Publication Type: |
Journal Article |
Year of Publication: |
1996 |
Authors: |
JK, Bowmaker, LA, Heath, SE, Wilkie, DM. Hunt |
Publication/Journal: |
Vision Research |
Keywords: |
absorption, bird, budgerigar, colour vision, cone, double cone, long-wave, long-wave cone class, melopsittacus undulatus, microspectrophotometric, oil droplet, psittaciformes, retinal photoreceptors, shell parakeet, single cone, taeniopygia guttata, visual pigment, visualpigments, zebra finch |
Abstract:
Microspectrophotometric examination of the retinal photoreceptors of the budgerigar (shell parakeet), Melopsittacus undulatus (Psittaciformes) and the zebra finch, Taeniopygia guttata (Passeriformes), demonstrate the presence of four, spectrally distinct classes of single cone that contain visualpigments absorbing maximally at about 565, 507, 430–445 and 360–380 nm. The three longer-wave cone classes contain coloured oildroplets acting as long pass filters with cut-offs at about 570, 500–520 and 445 nm, respectively, whereas the ultraviolet-sensitive cones contain a transparent droplet. The two species possess double cones in which both members contain the long-wave-sensitive visualpigment, but only the principal member contains an oildroplet, with cut-off at about 420 nm. A survey of the cones of the pigeon, Columba livia (Columbiformes), confirms the presence of the three longer-wave classes of single cone, but also reveals the presence of a fourth class containing a visualpigment with maximum absorbance at about 409 nm, combined with a transparent droplet. No evidence was found for a fifth, ultraviolet-sensitive receptor. In the chicken, Gallus gallus (Galliformes), the cone class with a transparent droplet contains “chicken violet” with maximum absorbance at about 418 nm. The rods of all four species contain visualpigments that are spectrally similar, with maximum absorbance between about 506 and 509 nm. Noticeably, in any given species, the maximum absorbance of the rods is spectrally very similar the maximum absorbance of the middle-wavelength-sensitive cone pigments.