Interesting Facts About Chitons, Sea Cradles, or Coat-of-Mail Shells

Chiton photo taken in Alaska, USA
Chiton photo taken in Alaska, USA | Source

The eight dorsal plates that chitons have can be easily identified in this image.



Dorsal side of a chiton (Polyplacophora). Light grey: girdle; dark grey: shell plates
Dorsal side of a chiton (Polyplacophora). Light grey: girdle; dark grey: shell plates | Source
Ventral side of a chiton (Polyplacophora). Light pink: mantle; dark pink: foot; red: gills.
Ventral side of a chiton (Polyplacophora). Light pink: mantle; dark pink: foot; red: gills. | Source

The last saltwater/marine aquarium that I set up was a live reef aquarium. This means that I used live rock (rock from the ocean that contained live organisms such as corals, snails, anemones, etc. already on it) to form a living reef in my marine tank. Many hitchhikers found their way into the aquarium, some good and some not so good. One of the hitchhikers that I enjoyed looking for were chitons.

The first time I saw one, I wondered what it was. It reminded me of pill bug or a woodlouse. After some research, I determined it was a chiton. So, I began looking for these tiny creatures. The ones I saw in my aquarium were very small – approximately .3 inches (7.6 mm) and very plain.

Answers.com defines a chiton, pronounced “'tŏn'”, as: “any of various marine mollusks of the class Polyplacophora that live on rocks and have shells consisting of eight overlapping calcareous plates.”

Lined Chiton, photo taken at Telegraph Cove, British Columbia, Canada
Lined Chiton, photo taken at Telegraph Cove, British Columbia, Canada | Source

Chiton is a Marine Mollusk

Chitons are also called sea cradles, or coat-of-mail shells. The chiton is a mollusk of which there are approximately 1000 known species. They range in size from .25 inches (2 cm) to about 14 inches (33 cm), the largest being the Gumboot Chiton, Cryptochiton stelleri.

Chitons have a hard shell, and a hard raspy tongue that they use to scrape food from the surfaces of their underwater habitats. Imagine a cat’s tongue which could also be defined as raspy. The tongue, or rather the "teeth" on the tongue, literally scrapes the food from the rocks and coral.

In fact the Eastern beaded chiton has the hardest teeth known to exist in nature! Although, their teeth are hard, they are not brittle, and research scientists are studying this material to see if they can reproduce it so that it could be used in other applications.

Black Katy chiton (Katharina tunicata), photo taken in waters off of Washington, USA
Black Katy chiton (Katharina tunicata), photo taken in waters off of Washington, USA | Source

A Different Kind of Mollusk

Unlike most mollusks, chitons do not have a calcareous shell (such as the snail). Instead, its back is protected by the sturdy cuticula of the mantle (The fleshy part of this sea creature). And over this are the eight overlapping dorsal plates so visible on most chitons.

A chiton has a very powerful foot, allowing it to grasp what it is crawling on with so much force, that it is very difficult to pry a living chiton up from its habitat. Its foot is composed of a muscle running the full length of its body. If you do happen to remove a chiton’s grip, then it will roll up into a tight ball in order to protect itself, much the same way as a hedgehog or an armadillo.

Chitons crawl very slowly by muscular undulations in their foot.

Tonicella lineata 2
Tonicella lineata 2 | Source

The chiton’s gills run almost all around its body between the mantle and the foot on the underside of the creature.

The chiton has a very sophisticated chemical sensing organ located near its mouth that gives it information about any food that could be located in its vicinity.

Most chitons are herbivores, eating mostly algae. Some however, have become carnivores, consuming small crustaceans. Their typical diet consists of algae, seaweed, dead animals, small worms and crustaceans. They tend to feed at night and hide under rock ledges during the day.

Unusual Chiton
Unusual Chiton | Source

They in turn are eaten by humans, seagulls, seastars, lobsters, crabs, fish and sea anemones. The majority of chitons have separate sexes, unlike the nudibranchs which are hermaphrodites. Chitons have a very interesting developmental stage, passing through a larval state, after which they metamorphosis into a very small young chiton. Chitons may live up to 25 years!

Most chitons inhabit low tidal regions, although some live in deeper waters. They are very abundant along rocky coasts throughout most of the world.

Gumboot Chiton underside (Cryptochiton stellari) - You can see why this is compared to the size of a boot. It is the largest chiton.   Looking at a chiton's ventral side is not easy, a chiton may cling to a rock almost as hard as a limpet.
Gumboot Chiton underside (Cryptochiton stellari) - You can see why this is compared to the size of a boot. It is the largest chiton. Looking at a chiton's ventral side is not easy, a chiton may cling to a rock almost as hard as a limpet. | Source
Gumboot Chiton topside - The shell of the Gumboot is hidden under its fleshy mantle.
Gumboot Chiton topside - The shell of the Gumboot is hidden under its fleshy mantle. | Source
Unidentified Chiton - You can really see in this image why the chiton reminds me of a pill bug, or woodlouse.
Unidentified Chiton - You can really see in this image why the chiton reminds me of a pill bug, or woodlouse. | Source

Interesting Behaviors

It is interesting to note that several species of Chiton exhibit homing behaviors, much the same as the monarch butterfly. It has been known to travel in order to find food and then be able to return to the exact same spot they had once inhabited.

It has been theorized that they leave a chemical trail that they can then use to return to the exact same spot. They also use this same homing behavior daily, returning to the same spot for the daylight hours and roaming around at night to feed.

When a chiton dies, the 8 dorsal plates come apart. You may have seen them on the beach. They are sometimes referred to as “butterfly shells” because of their shape.

Chitons are related to: abalone, nudibranchs, sea hares, octopuses, squid, scallops, mussels, oysters, clams, snails, and limpets.








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Comments: "Facts About Chitons, Sea Cradles, or Coat-of-Mail Shells" 8 comments

Seeker7 profile image

Seeker7 5 years ago from Fife, Scotland

I have never heard of the Chiton before. A fascinating hub and the photographs are stunning!! Voted up + awesome!


homesteadbound profile image

homesteadbound 5 years ago from Texas Author

Seeker7 - It was my pleasure to introduce you to the chiton. I'm pleased that you found the hub both fascinating and stunning. Thank you for stopping by.


Cloverleaf profile image

Cloverleaf 5 years ago from Calgary, AB, Canada

Hi Homesteadbound, I am going to show this to my husband tonight - I wonder if he has ever seen any of these while scuba diving. I'm surprised at how big they are!!

Cloverleaf


homesteadbound profile image

homesteadbound 5 years ago from Texas Author

Most are very small, clover leaf. Let me know if your husband has even seen any of these. I would like to know.


jami l. pereira 5 years ago

I love everything of the sea, ive seen the chiton before , but also very tiny. I thought this hub was wonderfully written , I always wanted to be a marine biologist when i grew up , fascinating in every aspect to me (the sea) anyways , now , im an underpaid poet lol on hub pages no doubt ! lol , (joking) I voted up , all the way across thanks for the read !:)oh ..except funny , of course


homesteadbound profile image

homesteadbound 5 years ago from Texas Author

jami l. pereira - I love the sea also, and the times I been able to make to the ocean, I could have enjoyed it a lot more if I could have learned to swim. But I have snorkeled in an inner tube just to be able to do it. And they even tethered my inner tube to the boat so I couldn't get away! LOL

Thanks for stopping by, from an underpaid writer. LOL


Ahydz profile image

Ahydz 5 years ago from Philippines

I really appreciate people who are fond of sea creatures such as this 'bugs'. I think marine biologist is what they are called by profession? I find their interest so unique and they themselves have a lot of talents like swimming, diving and a scientist at the same time. I think they are brave enough to have explored the ocean deeps. Because even though I love the sea and I dream of diving just like my father yet I can't swim, maybe because I'm not brave enough...hahaha! I'm so grateful there are few brave people such as the marine biologists. They are my channel where I have the chance to see the beauty of the oceans.


homesteadbound profile image

homesteadbound 5 years ago from Texas Author

Ahydz - I think that I would have loved to have been a marine biologist, but I never learned to swim either, and it was not something I ever thought about doing as a career until I was much older.

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