Do Snails Have Teeth? The Radula and Its Thousands of Teeth

What is a radula?

The radula is the feeding tool of almost all mollusks except clams, mussels and other bivalves. Its name is Latin for “little scraper”. It is a flexible ribbon made largely of chitin, the same tough material found in insect skeletons, and it is covered on its upper surface with rows of tiny, hooked teeth.

The ribbon lies on a muscular, tongue-like pad called the odontophore in the floor of the mouth. When a snail feeds, it pushes the odontophore forward through its mouth, presses the radula against the food and pulls it back, so the teeth rake and rasp off small pieces. In the garden snail and its relatives, a hard, curved jaw on the roof of the mouth acts as a cutting edge that the radula works against.

How many teeth does a snail have?

The number depends on the species. Each row across the radula usually has a central tooth flanked by side teeth, and the radula carries many rows one behind the other. Land snails and slugs typically have dozens to more than a hundred fairly similar teeth in each row, which adds up to thousands of teeth overall. Large land snails can have tens of thousands, and across all mollusks, totals of more than 100,000 teeth are known.

The individual teeth are far too small to see without a microscope. Their exact shape and arrangement differ so much from group to group that scientists use the radula to help identify species.

How snails eat with their teeth

Plant-eating land snails use the radula like sandpaper on a block. They rasp at leaves, stems, fruit, fungi and algae, pulling the shredded food back into the mouth, where it is mixed with mucus from the salivary glands and swallowed. A feeding snail makes rhythmic movements of the mouth and head as the radula moves in and out.

You can sometimes see the results. On algae-covered windows, greenhouse glass, tree bark and painted walls, snails leave zigzag feeding tracks where the radula has scraped away the green film. On leaves, snails make ragged holes and chewed edges rather than the neat cuts of caterpillars.

Do snail teeth wear out?

Yes, quickly. Rasping against plants, soil grains and stone wears down the teeth at the front of the radula. To make up for this, the radula works like a slow conveyor belt. New rows of teeth are produced constantly in a pocket at the back, called the radular sac, and are gradually moved forward to the working tip as the old ones break off. In some species, several new rows are made every day, so a snail replaces its teeth again and again throughout its life.

Do slugs have teeth?

Slugs are snails that have lost or shrunk their shells during evolution, and they feed in the same way. The leopard slug uses its radula to scrape fungi and rotting plants and to eat other slugs. The differences between slugs and snails are explained in slug vs snail.

Hunting slugs have teeth shaped for meat. The ghost slug of Wales, described by scientists in 2008, and the shelled slugs of the genus Testacella catch earthworms underground. Instead of rows of small rasping teeth, they have long, curved, blade-like teeth that grip a worm and draw it into the mouth.

Some sea slugs have taken the radula in yet another direction. Many sap-sucking sea slugs have just a single row of teeth, which they use to pierce the cells of seaweed and suck out the contents.

The strongest teeth in the animal world

Mollusks that scrape rock need especially tough teeth. Limpets, cone-shaped sea snails that cling to shores, graze algae off stone and wear the rock away as they feed. Their teeth are less than 1 mm long but are reinforced with fibers of goethite, an iron mineral.

In 2015, scientists at the University of Portsmouth in England measured the tensile strength of teeth from the common limpet. They found values of about 3–6.5 gigapascals, higher than spider silk, and suggested that limpet teeth may be the strongest biological material known. Chitons, flat mollusks with eight shell plates, also have iron-capped teeth: theirs are hardened with magnetite, a magnetic iron mineral.

Can snails bite people?

Garden snails and slugs cannot hurt people with their teeth. The radula is built to scrape soft plants, and at most a snail on your hand might give a faint, harmless rasp. As with any wild animal, wash your hands after handling snails or slugs.

The exception is a group of tropical sea snails called cone snails. Their radula has become a set of hollow, harpoon-like teeth that inject fast-acting venom into fish, worms or other snails. A few large species have caused human deaths, mostly among people who picked up the shells on reefs. Cone snails should never be handled, and anyone stung by one should seek emergency medical help immediately (911 in the US, 112 in the EU, 999 in the UK).