spectacle

Snakes Control Blood Flow to Aid Vision

A new study from the University of Waterloo shows that snakes can optimize their vision by controlling the blood flow in their eyes when they perceive a threat.

Kevin van Doorn, PhD, and Professor Jacob Sivak, from the Faculty of Science, discovered that the coachwhip snake’s visual blood flow patterns change depending on what’s in its environment. The findings appear in the most recent issue of the Journal of Experimental Biology.

Instead of eyelids, snakes have a clear scale called a spectacle. It works like a window, covering and protecting their eyes. When presented with a threat, the fight-or-flight response changes the spectacle’s blood flow pattern, reducing blood flow for longer periods than at rest, up to several minutes. (Credit: Kevin van Doorn)

K. van Doorn, J. G. Sivak. Blood flow dynamics in the snake spectacle. Journal of Experimental Biology, 2013; 216 (22): 4190 DOI: 10.1242/jeb.093658

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