Gastropod Radula

Radula

Radula Details

Snails

 Radula specific to snails  (from Latin radere - to scrape)

Most Mollusks (with the exception of bivalves) have a specialized feeding organ within the mouth called the radula.

The mouth opens into a pocket-like buccal cavity. Inside this cavity is  the radula sac which protects the mouth when the radula is not in use.

Supporting the radula is a structure of cartilage called the odontophore. Controlled by muscles, it is capable of being thrust forward and retracted in a rhythmic motion for feeding and retracted when finished.

As for the radula itself. it is a ribbon-like structure covered with many denticles (tiny teeth). It is movable over the odontophore and is also controlled by muscles.

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As the snail feeds, these actions continually wear down the frontal teeth. New teeth are continuously formed at the posterior end of the buccal cavity in the radula sac. They are slowly brought forward to the tip by a slow forward movement of the ribbon, to be replaced in their turn when they are worn out

Fun Fact - The teeth (denticles) of the radula consist of the same material as the exoskeleton  

The feeding behavior of marine snails include some that are herbivores, detritus (debris) feeders, scavengers and  predatory carnivores.

Herbivores use radula is used in two main ways:

- as a "rake" to comb up microscopic algae from a surface such as a rock (or side of a fish tank)

- as a "rasp" to break away small pieces when feeding on a plant

The array of horny teeth shown to the right belong to the radula of the Oyster Drill, a member of the Murex family noted for boring drill holes into heavy shells of mussels and other mollusks.

 The left and right ranks of teeth are hooked, and the middle tooth shows three cusps. Like all gastropods, the radular teeth are continually renewed from top to bottom, as they are worn away. In the case of the oyster drill, rather than depending on silicon- or iron-hardened radular cusps, drilling is facilitated by secretions of an accessory salivary gland used to soften shell materials.   <click on image to enlarge>