Keyhole Urchin – Mellita quinquiesperforata

Tags: North America, Ocean, echinoderm, keyhole sand dollar, keyhole urchin, sand dollar

Five-holed Keyhole Urchin

A living five-holed keyhole urchin is exposed on the beach at low tide. Photo by Gerhard H
Image Source

What does a keyhole urchin look like?

A keyhole urchin, also called a sand dollar, has a very simple flat, round, body. On the top of its body, five lines come together in a point to make a star-shaped pattern. Each one also has a few long, narrow holes in its body. The five-holed keyhole urchin, for example, has five holes in its body.

An urchin has no head, arms, legs, or feet. It does have a mouth on the bottom of its body that it uses to eat small plants and other food it finds buried in the sand.

Small fuzzy spines coat the top and bottom of its body. It moves the spines back and forth to bury itself in the sand and move food into its mouth. It usually takes between one and five minutes for a keyhole urchin to bury itself completely in the sand.

Where does the keyhole urchin live?

These urchins live in shallow ocean waters, below the tideline, underneath the sand most of the time. Because of this, it can be hard to find live keyhole urchins. In North America their range is along the east coast of the United States from Virginia south, surrounding the Florida peninsula and west into the Gulf of Mexico to Texas. Their range also extends south to Mexico and down to the coast of Brazil. They are also found along the coasts of Bermuda, Jamaica, and Puerto Rico.

After they die, the hard shells of their bodies wash up on beaches and turn white.

Additional Images:

Five-holed Keyhole Urchin

When it dies a keyhole urchin leaves behind a hard shell that turns white. Photo by Sharon Mooney
Image Source

Additional Links:


Andrew, Campbell C. Seashore Life. New York: Exeter Books, 1983. Pp. 46-47

Kaplan, Eugene H. A Field Guide to Southeastern and Caribbean Seashores. Houghton Mifflin Company: Boston, 1988. Pp. 339-356.









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