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CW Hawryshyn, H Moyer, WT Allison, TJ Haimberger, WN McFarland; Polarization Vision in Coral Reef Fishes: Multichannel Detection Capabilities in Damselfishes . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4548.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Various coral reef fishes are known to possess ultraviolet (UV) visual sensitivity. In other teleost fishes, such as salmonids, UV-sensitive cones mediate polarization vision. Coral reefs host complex photic conditions and fishes on the reef rely heavily on visual communication. Thus we hypothesize polarization vision may facilitate visual behavior. In this study, we examined three species of Pomacentrid fishes (damselfishes) and determined their spectral and polarization sensitivity and the geometry of the cone mosaic. Methods: We examined spectral and polarization sensitivity using ERG recording techniques in three species of juvenile damselfishes: Dascyllus trimaculatus, D. melanurus and Chromis viridis. Glass micropipettes (10-30 µm) filled with seawater were placed in contact with the cornea in the region of the pupil. A tungsten reference electrode was located over the cranium. Images of retinal wholemounts were digitally captured using Nomarski microscopy, where the tissue was treated or untreated with antibodies against the UV opsin employing standard immunohistochemical methodology. Results: All three species had similar spectral sensitivity based on the possession of four spectrally distinct cone types (UV, S, M, L). Absorbance spectra were determined using CCD-based microspectrophotometry for the four cone types in the three species of damselfish. UV sensitivity directly related to the UV-sensitive cones was further demonstrated using UV chromatic adaptation and examining resultant difference spectra. Immunhistochemical labeling also supports the prescence of a UV-sensitive cones. Measurement of polarization sensitivity (PS) was made using a 360 nm plane-polarized stimulus, on a broad-spectrum background. D. trimaculatus and D. melanurus exhibited trimodal polarization sensitivity while C. viridis exhibited tetramodal PS. Conclusion: Damselfishes exhibit the most complex pattern of PS observed in any vertebrate species examined to date. Much of the current evidence for PS in teleost fishes is based on research with salmonid fishes, which possess bimodal PS. In contrast, damselfishes with added dimensionality in PS, suggest unambiguous and highly sensitive e-vector discrimination capabilities. Three and four channel PS eliminates e-vector discrimination confusion points over a spectrum of e-vectors and brightness differences. This research was supported by an Alzheimer Society Fellowship to WTA, NSERC to HM, and a NSERC grant to CWH.
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