Eyes in Their Stars

Almost everyone knows what a starfish is. If we have not seen live starfish ourselves, we have at least seen specimens in curio shops and advertisements on television. The starfish is an echinoderm--a group of animals related to sea urchins and crinoids. One of the stranger versions of starfish is an animal called a brittle star. These starfish can actually move quite rapidly using their star arms in a wiggly kind of motion that is quite different from the starfish most of us ar familiar with.

Brittle Star In Physics Today (October, 2001, page 20) is an article announcing that some species of brittle stars actually have eyes. They can detect shadows and dart into crevices when a predator approaches. Studies done of these eyes which are found on the dorsal arms of the star are actually an array of microlenses that work together. Calcite is the lens material, and the calcite crystals are arranged in such a way that no double images are produced--something that usually happens when calcite is used.

The final design feature of this system is that a bundle of nerves is placed at the focal point of each microlens. This is a group of cells that regulate how much light gets to the nerve bundle. At night, more light is allowed in than during the day, and when the cells close in the day to reduce the amount of light coming in, they change the color of the stars to the darker color of the ocean floor, making them harder for predators to see. How the brittle star processes the information coming from the nerve bundles is still being studied, but there is no question that this is a very different kind of optical system present in a group of animals not believed to have eyes. We suggest it is another design feature God has built into living things to allow them to function uniquely and individually in their own environment.

--John N. Clayton

Back to Contents Does God Exist?, MayJun03.