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Molluscs of Australia



Chitons have a shell on their back made upof eight separate shell plates or valves. On different species the plates have different colours, patterns and testures. These plates (made from calcium carbonate) overlap a little at the front and back edges but the plates can still move separately. This means that the plates provide protection from above but still allow them to curl up into a ball if they are lifted.

There are between 900 to 1,000 species of Chiton worldwide, Australia has about 150 species and 90% of these are native to Australia. Most species are quite small (between 2 and 5 cm long). The largest rarely exceed 30 cm.

All chitons are marine, living, in cold water and in the tropics, mostly in intertidal or subtidal zones.

They live on hard surfaces, such as on or under rocks, or hidden in rock crevices. Some species live quite high in the intertidal zone and are exposed to air and sunlight for many hours each day. A few species live in deep water, as deep as 6,000 m.

Chitons (41 secs)

Anatomy of a chiton (underside)

Most of the body is a snail-like foot, but no head or other soft-parts beyond the girdle can be seen from above. Water flows into the mantle cavity through openings either side of the mouth, passes through the gills then leaves through anopening close to the anus.

Chitons have a heart with three chambers, two collect blood from the gills and the third pumps blood round the body.

The mouth ison the underside of the animal, and a radulawhich has many rows of teeth.

Chiton found at Point Danger, Torquay, Victoria, Australia. Image from aje152000, Flickr

Nearly all chitons are grazing herbivores. The radula is used to scrape microscopic algae and even bacteria off the rocks they are grazing. A few species of chitons are predators eating other small invertebrates, such as shrimp and possibly even small fish. Some chitons exhibit homing behavior, returning to the same spot for the daylight hours and moving during the night to feed.

Sea stars, c rabs, fish, sea anemones and even seagulls eat chitons. Sea stars lift chitons from rocks, then use their tube feet to keep the chiton from curling up.



Chiton pelliserpentis (Snake-skin Chiton). A common chiton species around Clydes Island, Eaglehawk Neck, Tasmania.
Image: Nuytsia@Tas Flickr

Next: Introduction to Gastropods ...   


Anatomy of Molluscs
The Aplacophora
Tusk Shells
Mollusc Gallery


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