What are Chitons?
Chitons have a shell on their back made up of eight separate shell plates or valves. On different species, the plates have different colours, patterns, and textures. These plates are made from calcium carbonate and overlap a little at the front and back edges. 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 30cm. All chitons are marine, living, in both 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 6,000m.
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 an opening close to the anus.
Structure of a Chiton
Chitons have a heart with three chambers, two collect blood from the gills and the third pumps blood around the body. The mouth is on the underside of the animal, and a radula which has many rows of teeth.
What do Chitons eat?
Chitons eat algae, bryozoans, diatoms, barnacles. Sometimes they eat bacteria by scraping the rocky substrate with their well-developed radulae. Some chitons exhibit homing behaviour, returning to the same spot for the daylight hours and moving during the night to feed.
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 behaviour, returning to the same spot for the daylight hours and moving during the night to feed.
Chitons are excellent cleaners of tanks. Their various colourings and patterns’ will make an excellent addition to your clean up crew. These charming and interesting critters are currently culturing in our tanks and will be ready in the coming weeks.