Friday, October 23, 2009

The Eyes Have It

After my fairly casual explanation of Matt's beautiful alligator eyeball photo, Blair sent a more accurate description and this photo of a Cuban tree frog's eye. One of the great things about Blair is his ability to make scientific stuff understandable, as you'll readily see in the following:

Most of what we see in Matt’s astounding photo is the alligator’s iris. Like many animals, alligators have an iris that is reflective (like a mirror) as well as pigmented. When we stare into an alligator’s eyes with the light directly behind us, we get the same effect we see in highway reflector studs illuminated by our car headlights. Some of the pattern is from vessels supplying the iris. Note the vessels and coppery reflectance of the Cuban tree frog’s eye.
This iris reflectance keeps unwanted light (like from the bright sun) from entering the eye. At night, another reflector that alligators have actually enhances the light available for them to see. This reflector is the tapetum lucidum, right behind the retina. It’s what makes alligator eyes shine red at night, a time when their pupils are wide open.

I hope you will remember all this the next time you find yourself staring into an alligator's eyes!

A kind neighbor made sure my little Italian Greyhound princess did not go without food while I was spending long days at the sea-bean symposium, and I gave her Blair and Dawn's book, Florida's Living Beaches: A Guide for the Curious Beachcomber, as a thank-you. She is totally captivated and has started a list of people she plans to buy copies for.

As always, our thanks to Blair for sharing his expertise and his photos.