title: Variable light environments induce plastic spectral tuning by regional opsin coexpression in the African cichlid fish, Metriaclima zebra.
abstract: Critical behaviours such as predation and mate choice often depend on vision. Visual systems are sensitive to the spectrum of light in their environment, which can vary extensively both within and among habitats. Evolutionary changes in spectral sensitivity contribute to divergence and speciation. Spectral sensitivity of the retina is primarily determined by visual pigments, which are opsin proteins bound to a chromophore. We recently discovered that photoreceptors in different regions of the retina, which view objects against distinct environmental backgrounds, coexpress different pairs of opsins in an African cichlid fish, Metriaclima zebra. This coexpression tunes the sensitivity of the retinal regions to the corresponding backgrounds and may aid in detection of dark objects, such as predators. Although intraretinal regionalization of spectral sensitivity in many animals correlates with their light environments, it is unknown whether variation in the light environment induces developmentally plastic alterations of intraretinal sensitivity regions. Here, we demonstrate with fluorescent in situ hybridization and qPCR that the spectrum and angle of environmental light both influence the development of spectral sensitivity regions by altering the distribution and level of opsins across the retina. Normally, M. zebra coexpresses LWS opsin with RH2Aα opsin in double cones of the ventral but not the dorsal retina. However, when illuminated from below throughout development, adult M. zebra coexpressed LWS and RH2Aα in double cones both dorsally and ventrally. Thus, environmental background spectra alter the spectral sensitivity pattern that develops across the retina, potentially influencing behaviours and related evolutionary processes such as courtship and speciation.
authors.affiliation: Department of Biology, University of Maryland, Baltimore County, MD, 21250, USA.|Department of Biology, University of Maryland, College Park, MD, 20742, USA.
authors.forename: Brian E
authors.initials: BE
authors.lastname: Dalton
authors.affiliation: Department of Biology, University of Maryland, College Park, MD, 20742, USA.
authors.forename: Jessica
authors.initials: J
authors.lastname: Lu
authors.affiliation: Department of Biology, University of Maryland, Baltimore County, MD, 21250, USA.
authors.forename: Jeff
authors.initials: J
authors.lastname: Leips
authors.affiliation: Department of Biology, University of Maryland, Baltimore County, MD, 21250, USA.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Cronin
authors.affiliation: Department of Biology, University of Maryland, College Park, MD, 20742, USA.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Carleton
mesh_terms: D000818:Animals; D023681:Cichlids / Q000235:genetics / Q000502:physiology*; D055358:Cone Opsins / Q000235:genetics / Q000502:physiology*; D004777:Environment; D005838:Genotype; D017404:In Situ Hybridization, Fluorescence; D008027:Light; D016133:Polymerase Chain Reaction; D012160:Retina / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*
chemical_list: D055358:Cone Opsins
keywords: cichlid; gene expression; opsin; plasticity; spectral tuning; visual sensitivity