Eye Fashion—Not Just for Looks
Eye fashion among animals is nothing less than fantastic. Yet they are designed not just for looks but for sight. Each animal has its particular needs and each meets them beautifully.
Look at the eyes illustrated on the left. Can you tell whose eyes they are?
If you say the one at the top belongs to the cat you are absolutely right. The characteristic pupil gives it away. Its ability to contract and expand in response to brightness has been used by the Chinese as a device to tell the time of day. But the wide-open pupil is only one means the cat uses to see in dim light. Have you ever noticed a cat’s eyes shine at night? A layer of cells at the rear of the eye acts as a mirror to reflect traces of light back into the eye so that the nerves can pick it up a second time. The feline eye is also much admired for its delicate hues—blue, hazel, brown, green, orange. Some cats even have a different color in each eye. Some competition for the ladies!
For the second picture, if you think you see the eyes of some creature from outer space, you are on the wrong track. Actually, the two stalks that seem to be growing out on top of the head are the eyes of a crab. By means of thousands of light-sensitive facets on each eyestalk, the crab can see all around—360 degrees. It can detect the altitude and slightest movement of the sun and the moon, and can sense changes in brightness as small as 2 percent. Some crabs have such keen vision that they can detect a six-foot-tall person 60 feet (18 m) away and run for cover. Even when hiding in the sand, the crab can send an eyestalk up as a periscope.
What about the angry-looking eye in the third picture? That is one that has become proverbial—the hawk eye. Why does the hawk or eagle always look so fierce, or bold? Actually, the raised “eyebrow,” which we interpret as a sign of boldness, is a bony protrusion above the eye socket that serves as a protection for the eye. It has nothing to do with attitude, and the eagle cannot change its looks even if it wants to. Notice the narrow crescent at the left of the eye? It is the eagle’s third eyelid. Most birds close their upper and lower lids only to sleep. Blinking is done by sweeping the eye with a semitransparent membrane (its third eyelid)—so it won’t lose sight of its prey in the process.
If you have trouble identifying the fourth eye, don’t be discouraged. It is surely one of the strangest of all. It belongs to the Anableps, the four-eyed fish of Central and South America. It has two pupils in each eye. When the fish swims along the surface of the water to hunt for food, it keeps its eyeballs halfway above the water, using one pupil to scan the world above and the other to see below the surface—doubling the chances for a meal, or an escape. The four-eyed fish not only has dual vision but can also see two things at the same time. Try topping that with your bifocals.
The eye is said to be the window of the body, and “window dressing” among animals is far more sophisticated than anything man can devise. Each one, in its own special way of seeing, praises its Maker, “the One doing great things unsearchable, wonderful things without number.”—Job 5:9.