title: Eye spectral sensitivity in fresh- and brackish-water populations of three glacial-relict Mysis species (Crustacea): physiology and genetics of differential tuning.
abstract: Absorbance spectra of single rhabdoms were studied by microspectrophotometry (MSP) and spectral sensitivities of whole eyes by electroretinography (ERG) in three glacial-relict species of opossum shrimps (Mysis). Among eight populations from Fennoscandian fresh-water lakes (L) and seven populations from the brackish-water Baltic Sea (S), L spectra were systematically red-shifted by 20-30 nm compared with S spectra, save for one L and one S population. The difference holds across species and bears no consistent adaptive relation to the current light environments. In the most extensively studied L-S pair, two populations of M. relicta (L(p) and S(p)) separated for less than 10,000 years, no differences translating into amino acid substitutions have been found in the opsin genes, and the chromophore of the visual pigments as analyzed by HPLC is pure A1. However, MSP experiments with spectrally selective bleaching show the presence of two rhodopsins (λ(max) ≈ 525-530 nm, MWS, and 565-570 nm, LWS) expressed in different proportions. ERG recordings of responses to "red" and "blue" light linearly polarized at orthogonal angles indicate segregation of the pigments into different cells differing in polarization sensitivity. We propose that the pattern of development of LWS and MWS photoreceptors is governed by an ontogenetic switch responsive to some environmental signal(s) other than light that generally differ(s) between lakes and sea, and that this reaction norm is conserved from a common ancestor of all three species.
authors.affiliation: Department of Biosciences, University of Helsinki, P.O.Box 65 (Viikinkaari 1), 00014, Helsinki, Finland. kristian.donner@helsinki.fi.
authors.forename: Kristian
authors.initials: K
authors.lastname: Donner
authors.affiliation: Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Pavel
authors.initials: P
authors.lastname: Zak
authors.affiliation: Department of Biosciences, University of Helsinki, P.O.Box 65 (Viikinkaari 1), 00014, Helsinki, Finland.
authors.forename: Martta
authors.initials: M
authors.lastname: Viljanen
authors.affiliation: Tvärminne Zoological Station, University of Helsinki, Hanko, Finland.
authors.forename: Magnus
authors.initials: M
authors.lastname: Lindström
authors.affiliation: Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia.|Department of Molecular Physiology, Biological Faculty, Lomonosov Moscow State University, Moscow, Russia.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Feldman
authors.affiliation: Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia.|Department of Molecular Physiology, Biological Faculty, Lomonosov Moscow State University, Moscow, Russia.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Ostrovsky
mesh_terms: D000818:Animals; D003445:Crustacea / Q000145:classification / Q000502:physiology*; D004596:Electroretinography; D004777:Environment; D005123:Eye; D015591:Microspectrophotometry; D009799:Ocular Physiological Phenomena; D010775:Photic Stimulation; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology; D025603:Sensory Rhodopsins / Q000378:metabolism*; D013045:Species Specificity; D013057:Spectrum Analysis
chemical_list: D025603:Sensory Rhodopsins
keywords: Compound eye; Evolutionary adaptation; Phenotypic plasticity; Polarization sensitivity; Rhodopsin; Vision