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Shifting mirrors: adaptive changes in retinal reflections to winter darkness in Arctic reindeer.

Stokkan, KA; Folkow, L; Dukes, J; Neveu, M; Hogg, C; Siefken, S; Dakin, SC; (2013) Shifting mirrors: adaptive changes in retinal reflections to winter darkness in Arctic reindeer. Proc Biol Sci B , 280 (1773) , Article 20132451. 10.1098/rspb.2013.2451. Green open access

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Abstract

Arctic reindeer experience extreme changes in environmental light from continuous summer daylight to continuous winter darkness. Here, we show that they may have a unique mechanism to cope with winter darkness by changing the wavelength reflection from their tapetum lucidum (TL). In summer, it is golden with most light reflected back directly through the retina, whereas in winter it is deep blue with less light reflected out of the eye. The blue reflection in winter is associated with significantly increased retinal sensitivity compared with summer animals. The wavelength of reflection depends on TL collagen spacing, with reduced spacing resulting in shorter wavelengths, which we confirmed in summer and winter animals. Winter animals have significantly increased intra-ocular pressure, probably produced by permanent pupil dilation blocking ocular drainage. This may explain the collagen compression. The resulting shift to a blue reflection may scatter light through photoreceptors rather than directly reflecting it, resulting in elevated retinal sensitivity via increased photon capture. This is, to our knowledge, the first description of a retinal structural adaptation to seasonal changes in environmental light. Increased sensitivity occurs at the cost of reduced acuity, but may be an important adaptation in reindeer to detect moving predators in the dark Arctic winter.

Type: Article
Title: Shifting mirrors: adaptive changes in retinal reflections to winter darkness in Arctic reindeer.
Location: England
Open access status: An open access version is available from UCL Discovery
DOI: 10.1098/rspb.2013.2451
Publisher version: http://dx.doi.org/10.1098/rspb.2013.2451
Language: English
Additional information: © 2013 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0/, which permits unrestricted use, provided the original author and source are credited.
Keywords: retina, scotopic vision, seasonal adaptation
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Institute of Ophthalmology
URI: https://discovery.ucl.ac.uk/id/eprint/1424253
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