Mollusc radula. Light micrograph of a mollusc (Sistrum fiscellum) radula. The radula is a toothed chitinous organ in the mouth of gastropods such as snails and slugs, which like a file, have central teeth which rasp off the surface of a plant whilst the outer ones shear off hairs and other extrusions. Many plant surfaces are covered in abrasive cilia which wear the teeth away but these are replaced by new teeth produced at the back of the radula.