Complementary shifts in photoreceptor spectral tuning unlock the full adaptive potential of ultraviolet vision in birds
Abstract
Color vision in birds is mediated by four types of cone photoreceptors whose maximal sensitivities (λmax) are evenly spaced across the light spectrum. In the course of avian evolution, the λmax of the most shortwave-sensitive cone, SWS1, has switched between violet (λmax > 400 nm) and ultraviolet (λmax < 380 nm) multiple times. This shift of the SWS1 opsin is accompanied by a corresponding short-wavelength shift in the spectrally adjacent SWS2 cone. Here, we show that SWS2 cone spectral tuning is mediated by modulating the ratio of two apocarotenoids, galloxanthin and 11’,12’-dihydrogalloxanthin, which act as intracellular spectral filters in this cell type. We propose an enzymatic pathway that mediates the differential production of these apocarotenoids in the avian retina, and we use color vision modeling to demonstrate how correlated evolution of spectral tuning is necessary to achieve even sampling of the light spectrum and thereby maintain near-optimal color discrimination.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jul 12, 2016
- Source ID
- 10.7554/elife.15675
Entities
People
- Almut Kelber
- Christopher C. Witt
- David Wilby
- Earl H Harrison
- Joseph C. Corbo
- Ken M Riedl
- Kevin J Mcgraw
- M Carter Cornwall
- Matthew B Toomey
- Misha Vorobyev
- Nicholas Roberts
- Olle Lind
- Rikard Frederiksen
- Robert W Curley Jr
- Steven J. Schwartz
Organizations
- Air Force Office of Scientific Research
- Arizona State University
- Boston University
- Engineering and Physical Sciences Research Council
- Human Frontier Science Program
- Knut and Alice Wallenberg Foundation
- Lund University
- National Institutes of Health
- National Science Foundation
- Ohio State University
- Research to Prevent Blindness
- Swedish Research Council
- University of Auckland
- University of Bristol
- University of New Mexico
- Washington University School of Medicine