What Are Polyplacophora?

Marine Life Known as Chitons

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The term Polyplacophora refers to a class of marine life that are part of the mollusk family. The tongue-twisting word is Latin for "many plates." The animals in this class are commonly known as chitons and they have eight overlapping plates, or valves, on their flat, elongated shells.

About 800 species of chitons have been described. Most of these animals live in the intertidal zone. Chitons may be from 0.3 to 12 inches long.

Under their shell plates, chitons have a mantle, bordered by a girdle or skirt. They may also have spines or hairs. The shell allows the creature to protect itself, but the overlapping design also lets it flex in an upwards motion and move. Chitons can also curl up into a ball. Because of this, the shell provides protection at the same time as permitting the chiton to flex upward when it needs to move.

How Polyplacophora Reproduce

There are male and female chitons, and they reproduce by releasing sperm and eggs into the water. The eggs may be fertilized in the water or the female may retain the eggs, which are then fertilized by sperm that enters along with water as the female respires. Once the eggs are fertilized, they become free-swimming larvae and then turn into a juvenile chiton.

Here are a few more facts that we know about Polyplacophora:

  • The word is pronounced poly-plac-o-for-a.
  • Chitons are also referred to as sea cradles or "coat-of-mail shells." Other names they are recognized by include loricates, polyplacophorans and polyplacophores.
  • These creatures are not commonly seen by beach-goers, as they live in rock crevices or under rocks. They can also live on rocks.
  • Polyplacophora are found in cold waters and in tropical waters. Some live in tidal zones and can hold up to air exposure for periods of time. Others can live as deep as 20,000 feet under the surface of the water.
  • They are only found in salt water. 
  • They like to stay close to home and exhibit homing, which means they travel to feed and then return to the same spot. 
  • People eat these sea creatures. They are commonly served throughout the Caribbean islands in places such as Tobago, Aruba, Barbados, Bermuda, and Trinidad. People in North and South America also eat them, as well as those in the Philippines.
  • Similar to a mussel, they have a muscular foot that allows them to move. Also like a mussel, they have strong adhesion powers and can cling quite powerfully to rocks in the ocean.
  • There are both male and female chitons, and they reproduce externally.
  • They eat everything from algae and diatoms to barnacles and bacteria.


  • Campbell, A. and D. Fautin. 2001. ​Polyplacophora" (Online), Animal Diversity Web. Accessed August 23, 2010.
  • The Polyplacophora (Online). Man and Mollusc. Accessed August 23, 2010.
  • Martinez, Andrew J. 2003. Marine Life of the North Atlantic. Aqua Quest Publications, Inc., New York
  • University of California Museum of Paleontology. The Polyplacophora (Online). Accessed August 23, 2010.
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Kennedy, Jennifer. "What Are Polyplacophora?" ThoughtCo, Jul. 31, 2021, thoughtco.com/polyplacophora-the-chitons-2291645. Kennedy, Jennifer. (2021, July 31). What Are Polyplacophora? Retrieved from https://www.thoughtco.com/polyplacophora-the-chitons-2291645 Kennedy, Jennifer. "What Are Polyplacophora?" ThoughtCo. https://www.thoughtco.com/polyplacophora-the-chitons-2291645 (accessed March 27, 2023).