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Chitone

Chitons are a class of marine molluscs, with more than 940 living species worldwide. 1 2 On their back they have eight overlapping plates, next to a girdle; if detached from the bottom they can roll up into a ball. 3

Chitone

At a glance

Data from the scientific sources listed at the bottom.

Conservation

NEDDLCNTVUENCREWEX

IUCN Red List: not evaluated.

Where it lives

The living species are found all over the world; the sources read do not give a list of seas for the whole class. 2

How to recognise it

Tap a number on the photo: the key explains what to look for.

12
  1. 1Eight plates overlapping, in a row along the back 3
  2. 2Girdle (perinotum) together with the plates it forms the armour when the animal rolls up 3

Life in the wild

Where it is found

They live from the intertidal zone to ocean trenches, but most studies concern shallow-water species. 2 Ranges vary a lot: in the Southern California Bight most were collected between 30 and 305 m. 2 On intertidal rocks they feed by scraping the rock surface. 4

What it eats

Most intertidal species eat algae and other organisms growing on the rocks, which they scrape off with the radula, a ribbon covered in teeth. 4 5 Diet varies with species and place: in Acanthopleura japonica red algae were the most abundant food (37%), with remains of bivalves and mites; other studies cited report diatoms and coralline algae, or mainly nematodes. 4

Behaviour

When detached from the bottom they can roll up into a ball, protecting themselves with their plates and girdle; unlike trilobites and millipedes they have no mechanism to lock the position. 3 When rolled up they can neither feed nor move normally. 3

Reproduction

Chitons mostly have separate sexes. 6 Planktonic larvae that live on their own reserves hatch from the eggs, then settle on the bottom and change into juveniles resembling the adults. 6

In the aquarium

From the experience of the BallingMania community.

Community rating

No rating in the original sheet.

Original sheet

Chitons are small, and in some cases large, marine molluscs of the class Polyplacophora. Identification is simple thanks to the oval dorsal shell, made up of plates (8 in living species), which also give the class its name. These plates are set into the mantle, which extends to the edge of the animal, forming the perinotum, a cuticle-covered flap that surrounds and links them and, being flexible, allows them to articulate. Chitons live and move on rocky surfaces and feed on algae, bryozoans, diatoms and sometimes bacteria, scraping the rocky substrate with their well-developed radula. They are excellent algae eaters and do not harm corals; the only drawback is that they also feed on the coralline algae that some aquarists love.

good or bad?

VERDICT:

Key: Good! An organism beneficial to the system. Reef Safe!

An organism whose benign or harmful nature is not yet known, to be kept an eye on.

Bad! The organism is a threat to the other inhabitants of the aquarium or could become a pest.

A food source for the other inhabitants of the aquarium.

A potentially toxic or venomous organism.

© Javier Ortíz Duarte · © Leon Altoff

Did you know?

The teeth of the radula contain magnetite, an iron mineral: when fully mineralised they are among the hardest and stiffest biological materials known. 5
Worn teeth are replaced by new rows that form continuously: in Cryptochiton stelleri all the stages can be seen in a single radula, from transparent rows to black, magnetic ones. 5
Besides the living species, about 430 fossil species are known. 2

Sources

  1. WoRMS Editorial Board (2026). Polyplacophora Gray, 1821. World Register of Marine Species.
  2. Stebbins, T.D.; Eernisse, D.J. (2009). Chitons (Mollusca: Polyplacophora) known from benthic monitoring programs in the Southern California Bight. The Festivus 41(6): 53-100.
  3. Sigwart, J.D.; Vermeij, G.J.; Hoyer, P. (2019). Why do chitons curl into a ball?. Biology Letters 15(10): 20190429.
  4. Matsumoto, R.; Kon, K. (2023). Food habit of chiton Acanthopleura japonica from Jogashima, Miura peninsula, Kanagawa prefecture, Japan. La mer 61: 13-18.
  5. Nemoto, M.; Ren, D.; Herrera, S.; Pan, S.; Tamura, T.; Inagaki, K.; Kisailus, D. (2019). Integrated transcriptomic and proteomic analyses of a molecular mechanism of radular teeth biomineralization in Cryptochiton stelleri. Scientific Reports 9: 856.
  6. SeaLifeBase (2026). Leptochiton belknapi Dall, 1878 (nota generale sulla classe Polyplacophora). SeaLifeBase.

Sources checked on 5 November 2026. Community texts and ratings are kept separate from the scientific data.

Download the original sheet (Italian)All species