|
They look like bubbles on the surface of the water. Looking closer, you see they are actually eyes which float just above the surface of the water. They belong to the anableps, a minnow-sized fish often referred to as “four eyes.” Isn’t that awesome! I’m a minnow—you don’t get much more ordinary than that! But wait until I tell you about myself, and especially about my marvelous Creator. I think you will be surprised. We are native to the tropical waters of the Americas, either brackish or fresh. We aren’t fussy about what we eat either. We like worms, insects, crustaceans—just about anything that comes along. And we aren’t very large. Most of us average three- to four-inches in length, though a few of our kind reach as long as a foot. Being so small, we have one very big problem: surviving. You see, we’re lunch for lots of the bigger fish. So we have to be—you guessed it—all eyes! It’s the only way we can survive. |
|
|
But if I may brag a little, I think our eyes are wonderful. I had nothing to do about their design—I have to give all credit to our marvelous Creator for knowing what we needed. Maybe we don’t look spectacular, but we can really see. You think you can catch me off guard? I’ll always be a hop ahead of you! Yes, I had an eye on you (one of my “four”) long before you saw me! Actually, “four eyes” is a slight exaggeration. We have two divided eyes that work like four distinct eyes. How our eyes work Your eyes are designed to see objects in the air (out of water). Each of your eyes has a pupil, and in front of it a large front window (the cornea). Light entering your eye is focused by a combination of the front window (cornea) and a flat-type lens. If you try to look at objects under water, everything is out of focus. Animals that live under water, like fish, have spherical lenses, which produce a perfect image of the underwater world but would not work in the air. |
|
Now we anableps have a special problem, because most eyes are designed to see objects either in the air (out of water) or under water. Because we live at the surface of the water, we need to see both through the air and through the water. If we had eyes like yours, we could see very well in the air, but underwater images would be out of focus. If we had eyes like other fish, we would be able to see very well in the water, but objects in the air would be out of focus. And in either case, I can assure you, I would be so hungry, I wouldn’t be able to swim anymore. Or else I’d be eaten so quickly by some predator, I would never need to eat anything! Well, what do you suppose my Designer did? He designed my eyes with four parts—I can actually see above the water and under the water with each eye at the same time! Really! How? Each of my eyes has two corneas (front windows), one that looks out into the air, and one that looks down through the water. The same eye looks two directions. Light entering through both of these corneas passes through a lens in my eye. But the lens is neither round nor flat; it is elliptical. (Who thought up that one?!) And it is perfectly aligned so that light coming from above the water passes through the shorter axis of the lens and strikes a special retina in the bottom of my eye, producing a sharp clear image. And light coming through the other window from underneath the water passes through the long axis of the lens and strikes the upper retina of my eye, also creating a sharp clear image. So I am able to see two images with each eye at the same time. Isn’t that pretty wonderful? That is why it looks like I have four eyes. Really I have only two, but each eye has two pupils and two corneas, one above water and one below the water, separated by a line of pigment at the water level. Do you see why our eyes are so important? Little minnows are delicious food for many larger animals, so we have to be constantly looking out for predators. Using my “four eyes” and floating right at the water’s surface, I’m able to see both up and down simultaneously. Yes, I can focus on an airborne predator and a tasty underwater snack at the same time. How about that!
Some of your scientists think I have achieved this remarkable feat on my own. They talk about all the years I was developing these eyes. Isn’t that fantastic? Fancy little “me” figuring out how to stay out of the sharks’ mouths while my eyes were under construction! And how would I find anything to eat in the blur under the water? I can’t imagine what I would do. But then, I’m only a little minnow. |
