Eye to Eye With a Fly

The eye is an organ of extreme perfection. I have a strong interest in evolution, and eyes have developed stunning adaptations over time. This mayfly (above) is a male with what are called turban eyes—greatly enlarged eyes at the top of the head in the shape of a turban. The male uses his eyes to scout for the silhouette of a female in the dim light of dusk. He doesn’t even have a working mouth. If you live for only one day, as adult males usually do, you don’t need to eat. But you do need tremendous eyes to find a female before you die.

I am a cancer researcher, but I also work as a science photographer under the name “Micronaut.” The “micro” is because I specialize in shooting very small things using a scanning electron microscope at the School of Life Sciences in Muttenz, Switzerland. “Naut” is because I feel like an astronaut with the scanner, flying along and making discoveries. The scanner creates black-and-white images that can take a week for me to enhance with color. Research like this is not just scientifically important—it is extremely beautiful.

The fruit fly has a compound eye, a tightly packed collection of single lenses that gives the fly a gridlike view of the world. Scientists suspect the bristles may help protect the lenses, which have no eyelids, from dirt and debris.

Moths have huge eyes covering almost their entire, relatively small, head. For better vision in the dark, moths’ brains store up images over time, giving their photoreceptors more chances to see in dim light. (In contrast, our photoreceptors “stream” images in a constant flow, which means old images are almost immediately lost.)

Shrimps have compound eyes with square-shaped lenses. Scientists once believed that shrimps were blind. They now understand that although square lenses can’t bend light to create an image, as insect eyes do, mirrors in the box-shaped lenses do the trick.

The book scorpion, so called because it likes to live in old books, has a primitive set of eyes equipped with only a few receptors. Some species lack external eyes altogether and use receptors just below the skin to detect light.

Spider mites have a pair of eyes on each side of their bodies that can detect color and ultraviolet light waves. They rely on their vision to locate the undersides of host plant leaves in order to avoid UV radiation, which can be lethal to mites.

source: nationalgeographic.com

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