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Blood flow dynamics in the snake spectacle
Kevin van Doorn1, Jacob G Sivak
1University of Waterloo School of Optometry, 200 University Avenue West, Waterloo, ON, Canada, N2L 3G1.
The Journal of Experimental Biology
|November 1, 2013
Summary
Snake spectacles, the transparent eye scales, have blood vessels that constrict during rest and threat to maintain clear vision. During shedding, vessels dilate, ensuring continuous blood flow for eye health.
Area of Science:
- Ophthalmology
- Herpetology
- Comparative Physiology
Background:
- Snakes' eyes are covered by a transparent spectacle, a modified scale.
- Spectacle vascularity can impair vision, necessitating adaptations.
- Previous studies noted reduced vessel density in some species' foveal/binocular fields.
Purpose of the Study:
- To investigate spectacle blood flow dynamics in snakes.
- To identify mechanisms mitigating the visual impact of spectacle blood vessels.
Main Methods:
- Observational study of spectacle blood flow.
- Monitoring vessel diameter and blood flow changes under different conditions (rest, threat, shedding).
Main Results:
- At rest, spectacle vessels cyclically constrict and dilate, with vessels mostly constricted.
- During perceived threats, vessels constrict and remain constricted longer, enhancing visual clarity.
- During stratum corneum renewal (shedding), resting constriction cycles cease, and vessels remain dilated.
Conclusions:
- Snakes actively regulate spectacle blood flow to optimize vision.
- Vessel constriction enhances visual acuity during rest and critical threat situations.
- Continuous dilation during shedding supports spectacle health and renewal processes.
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