Mollusc radula. Light micrograph of a mollusc (Navicella borbonica) radula. The radula is a toothed chitinous organ in the mouth of gastropods such as snails and slugs, which, like a file, has central teeth to 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 that wear the teeth away but these are replaced by new teeth produced at the back of the radula.