Radulae

Radulae are ribbon-like feeding organs found in most mollusks, acting as a conveyor of microscopic, chitinous teeth that scrape, cut, or drill food from surfaces. The key structural unit is the radular ribbon, which bears rows of teeth anchored to a muscular odontophore. Teeth are continually formed and replaced, usually at the posterior end of the ribbon, so worn teeth disappear from the anterior edge as new ones are added.

Across mollusks, radulae vary in tooth shape and number. Gastropods such as snails and slugs use their radula primarily for scraping algae, detritus, or plant matter, while many predatory species employ sharper, more robust teeth to capture prey or drill into their shells. Cephalopods retain a radula behind the beak, though their diet is more often torn or punctured by the beak and radula together. Chitons (polyplacophorans) have a highly specialized radula with iron- or magnetite-strengthened teeth that helps gnaw over rock surfaces. Bivalves generally lack radulae, having adapted filter-feeding gills instead.

Radulae are of interest in paleontology and taxonomy because radular morphology is often preserved in fossils and varies with diet and lineage. In many mollusks, the radula and odontophore develop from a shared embryonic apparatus and are renewed throughout life.