Dick Dubielzig demonstrating at is set-up with several microscope for viewing animals eyes.
On Saturday, February 3, Dick Dubielzig led a field trip, "The Eyes Have It", at the School of Veterinary Medicine. The Comparative Ocular Pathology Laboratory of Wisconsin has a collection of eyes from over 600 different species, used for comparative anatomy and for study of eye diseases in animals. His fascinating talk concentrated on differences between mammalian and avian eyes. These groups evolved from ancestors with very different habits. The ancestors of birds (and most reptiles) were active in the day, while those of mammals were active at night or at least in the dim light of dawn and dusk, when they were a lot less likely to be eaten. As such, bird eyes are far more sophisticated in their form and structures, and mammal eyes are comparatively much simpler. For example, most bird eyes contain bone and cartilage to help shape the eye and for better muscle attachment, allowing much faster changes to the focus. Mammal eyes are more like spheres and are kept rigid just by internal pressure. Birds can also vary the shape of the cornea of the eye as well as the lens, again for better focus – many can focus right down to the end of their beak. Old-world primates (like us) can see in three colors, but birds typically see in four or more. Birds also have a nictitans, an extra eyelid, to keep the tear layer over the eye clean and extremely smooth, another adaptation for sharp vision. It's no wonder that when we go out birding, they always see us before we see them. Thank you for teaching us, Dick. The Friends host was Steve Sentoff who also provided the top photos. All other photos are from Arlene Koziol's Flicker site, with permission.
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