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Int. J. Mol. Sci. 2017, 18(10), 2068;

Circadian Rhythms of Retinomotor Movement in a Marine Megapredator, the Atlantic Tarpon, Megalops atlanticus

College of Science, Florida Institute of Technology, 150 West University Blvd, Melbourne, FL 32901, USA
Author to whom correspondence should be addressed.
Received: 28 August 2017 / Revised: 21 September 2017 / Accepted: 21 September 2017 / Published: 28 September 2017
(This article belongs to the Special Issue Molecular and Cellular Mechanisms of Circadian Rhythms)
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Many ecologically and economically important marine fish species worldwide spend portions of their lives in coastal regions that are increasingly inundated by artificial light at night. However, while extensive research illustrates the harmful effects of inappropriate light exposure on biological timing in humans, rodents and birds, comparable studies on marine fish are virtually nonexistent. This study aimed to assess the effects of light on biological clock function in the marine fish retina using the Atlantic tarpon (Megalops atlanticus) as a model. Using anti-opsin immunofluorescence, we observed robust rhythms of photoreceptor outer segment position (retinomotor movement) over the course of the daily light–dark cycle: cone outer segments were contracted toward the inner retina and rods were elongated during the day; the opposite occurred at night. Phase shifting the daily light–dark cycle caused a corresponding shift of retinomotor movement timing, and cone retinomotor movement persisted in constant darkness, indicating control by a circadian clock. Constant light abolished retinomotor movements of both photoreceptor types. Thus, abnormally-timed light exposure may disrupt normal M. atlanticus clock function and harm vision, which in turn may affect prey capture and predator avoidance. These results should help inform efforts to mitigate the effects of coastal light pollution on organisms in marine ecosystems. View Full-Text
Keywords: retinomotor movement; photoreceptors; circadian rhythm retinomotor movement; photoreceptors; circadian rhythm

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Kopperud, K.L.; Grace, M.S. Circadian Rhythms of Retinomotor Movement in a Marine Megapredator, the Atlantic Tarpon, Megalops atlanticus. Int. J. Mol. Sci. 2017, 18, 2068.

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