Mottled red chiton

Language English

Onglets

Description

Distinguishing features

Chitons are true “living fossils” since they have not changed in 300 million years. It has preserved vestiges of the segmented body of its ancestors. These molluscs are oval in shape, and have a shell composed of eight separate calcareous plates covering their entire dorsal surface. The shell plates are colored light red to dark brick red, with small whitish marbling.

The mouth contains a tongue-like structure called a radula, which has numerous rows of teeth that are used to scrape algae (its food) off rocky substrates. The radula markings left behind on the rocks are visible under a microscope.

The mottled red chiton is very similar to the northern red chiton (Tonicella rubra), which is also found in the Gulf of St. Lawrence.

Reproduction

There are male chitons and female chitons, but they do not mate. The males release sperm into the sea water. The sperm then drift into a chamber inside the female’s body called a mantle cavity, which is where fertilization takes place.

After fertilization, the larvae are released into the water and swim for some time before settling on the seafloor and transforming into juveniles, which look like mini versions of adults.

Diet

Mottled red chitons feed on algae using their radula, as they slowly creep along the rocks. They also eat bryozoans, sponges and hydroids.

Predators

Mottled red chitons are preyed upon by seabirds (such as eider ducks), fish, crabs, lobsters and certain molluscs.

Habitat

While chitons can be seen in muddy, sandy or stony bottoms, the largest population densities are found on rocky substrates. Mottled red chitons are marine species that live along the rocky shores of the estuary and gulf of St. Lawrence. It is also present along the Atlantic coast, from the Arctic to New York and on the northern european coast.

Chitons live in the littoral zone between the low tide mark and a depth of approximately 100 meters, or even 200 meters. They sometimes occur in high densities in seabeds, reaching populations of 40-50 per square meter.

Ecology, behaviour

Some parts of the world, such as Ireland, are witnessing declines in mottled red chiton populations, possibly due to global warming.

Their shell plates provide great flexibility to move across rocky, uneven surfaces. Moreover, like sowbugs, chitons can roll into tight protective balls when handled.

Mottled red chitons have very high desiccation resistance, which explains why they can survive low tides, by staying sheltered beneath rocks and algae.

French name

Chiton rouge maculé, chiton rouge marbré

Scientific name

Tonicella marmorea

Phylum

Mollusca

Class

Polyplacophora

Order

Chitonida

Family

Ischnochitonidae

Size

Length: up to 3.8 cm Width: up to 1.9 cm

Weight

A few grams

Life span

Unknown

Status

Abundant species, but not evaluated

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