What Is Aristotle's Lantern?

Our seas are filled with popular creatures – as well as those that are lesser known. This includes creatures and their unique body parts. One of them that has a unique body part and name are sea urchins and sand dollars. The term Aristotle's lantern refers to the mouth of sea urchins and sand dollars. Some people say, however, that it does not solely refer to the mouth alone, but the entire animal.

What is Aristotle's Lantern?

This complex structure is composed of five jaws made up of calcium plates. The plates are connected by muscles. Creatures use their Aristotle's lantern, or mouths, to scrape algae off rocks and other surfaces, as well as biting and chewing prey.

The mouth apparatus is capable of retracting into the urchin's body, as well as moving from side to side. During feeding, the five jaws are pushed out so that the mouth opens. When the urchin wants to bite, the jaws come together to grip the prey or algae and then can tear or chew by moving their mouth from side to side.

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The top part of the structure is where new tooth material is formed. In fact, it grows at the rate of 1 to 2 millimeters per week. At the bottom end of the structure, there is a hard point called the distal tooth. Although this point is rigid, it has a weak outer layer that allows it to sharpen itself while it is scraping. According to Encylopedia Britannica, the mouth can be venomous in some cases.

Where Did the Name Aristotle's Lantern Come From?

It's a funky name for a marine creature body part, isn't it? This structure was named for Aristotle, a Greek philosopher, scientist and teacher who described the structure in his book Historia Animalium, or The History of Animals. In this book, he referred to the "mouth-apparatus" of the urchin as looking like a "horn lantern." Horn lanterns at the time were five-sided lanterns made up of panes of thin pieces of horn. The horn was thin enough for light to shine out, but strong enough to protect a candle from the wind. Later, scientists referred to the urchin's mouth structure as Aristotle's lantern, and the name has stuck thousands of years later.

Sources

Denny, M.W. and S. D. Gaines, eds. 2007. Encyclopedia of Tidepools and Rocky Shores. University of California Press. 706 pp.

Marine Life Series: Aristotle's Lantern.2006. Accessed December 31, 2013.

Meinkoth, N. A. 1981. National Audubon Society Field Guide to North American Seashore Creatures. Alfred A. Knopf: New York. p. 667.

Sea Urchins Do Research: Aristotle's Lantern. Accessed December 31, 2013.

Waller, G. (ed.). 1996. SeaLife: A Complete Guide to the Marine Environment. Smithsonian Institution Press: Washington, DC. 504 pp.