factoids from Paw Prints

What kind of eyes does a starfish have?

[icon: ochre-rayed star]
ochre-rayed star
[icon: bat star]
bat star
[icon: six-rayed star]
six-rayed star

From the look of it, you might think that a starfish has no eyes. But in fact, it has an eye on the end of each arm. Most starfish have five arms, so they also have five eyes, but some starfish have as many as twenty arms (or more), and as many eyes.

The very simple eyes of a starfish are unable to form images. Each eye is a tiny spot of red pigment that is sensitive to light. Nerves run from the pigment spots to the starfish's central nerve ring.

The signals from the eyespots affect the animal's behavior, enabling it to avoid light that is too bright and change its light preferences according to the time of day, water chemistry, and other factors. Since a starfish has no brain, it would not be able to make much use of images, even if its eyes were able to form them.

Source: The Learning Kingdom's Cool Fact of the Day (http://www.tlk-lists.com/join/) for March 10, 2000


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