Interesting Facts About Chitons, Sea Cradles, or Coat-of-Mail Shells
The eight dorsal plates that chitons have can be easily identified in this image.
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 “kī'tŏn'”, as: “any of various marine mollusks of the class Polyplacophora that live on rocks and have shells consisting of eight overlapping calcareous plates.”
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.
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.
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.
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.
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.
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