title: How parrots see their colours: novelty in the visual pigments of Platycercus elegans.
abstract: Intraspecific differences in retinal physiology have been demonstrated in several vertebrate taxa and are often subject to adaptive evolution. Nonetheless, such differences are currently unknown in birds, despite variations in habitat, behaviour and visual stimuli that might influence spectral sensitivity. The parrot Platycercus elegans is a species complex with extreme plumage colour differences between (and sometimes within) subspecies, making it an ideal candidate for intraspecific differences in spectral sensitivity. Here, the visual pigments of P. elegans were fully characterised through molecular sequencing of five visual opsin genes and measurement of their absorbance spectra using microspectrophotometry. Three of the genes, LWS, SW1 and SWS2, encode for proteins similar to those found in other birds; however, both the RH1 and RH2 pigments had polypeptides with carboxyl termini of different lengths and unusual properties that are unknown previously for any vertebrate visual pigment. Specifically, multiple RH2 transcripts and protein variants (short, medium and long) were identified for the first time that are generated by alternative splicing of downstream coding and non-coding exons. Our work provides the first complete characterisation of the visual pigments of a parrot, perhaps the most colourful order of birds, and moreover suggests more variability in avian eyes than hitherto considered.
authors.affiliation: Centre for Behavioural Biology, School of Biological Sciences, University of Bristol, Bristol BS8 1UG, UK.
authors.forename: Ben
authors.initials: B
authors.lastname: Knott
authors.forename: Wayne I L
authors.initials: WI
authors.lastname: Davies
authors.forename: Livia S
authors.initials: LS
authors.lastname: Carvalho
authors.forename: Mathew L
authors.initials: ML
authors.lastname: Berg
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Buchanan
authors.forename: James K
authors.initials: JK
authors.lastname: Bowmaker
authors.forename: Andrew T D
authors.initials: AT
authors.lastname: Bennett
authors.forename: David M
authors.initials: DM
authors.lastname: Hunt
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D030161:Avian Proteins / Q000737:chemistry / Q000502:physiology; D003116:Color; D055253:Color Vision; D008969:Molecular Sequence Data; D055355:Opsins / Q000737:chemistry / Q000235:genetics; D010311:Parrots / Q000502:physiology*; D010802:Phylogeny; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein
chemical_list: D030161:Avian Proteins; D055355:Opsins
keywords: Platycercus elegans; alternative splicing; microspectrophotometry; opsin; parrot; visual pigment