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What Is the Tongue-Shaped Structure That Some Mollusks Use for Feeding?

The Mollusca family is diverse and includes common species, such as squid, snails, scallops, chitons, octopuse, clams and oysters. There are more than 50,000 species of mollusks and each species' dietary habits depend on their habitat, hunting and feeding mechanisms. Some species have a specialized tongue-like structure known as radula, which is used for scraping food from rocks and other surfaces in the water.

Structure of a Radula
- A radula is a rough, horny tongue-shaped structure that is commonly found in the mouth of some mollusks species. However, bivalves do not have this tongue-shaped structure. Radula is made of chitin or infused with magnetite which makes them sturdy and hard. The radula is supported by the odontophore, which is a mass that looks like a cartilage. This cartilage-like structure can be protruding and is covered with denticles, or rows of small teeth, that wear out over a period of time. When the front portion of the teeth gets worn out, new rows or sections are formed. The mollusks species are identified based on the arrangement and shape of the radular teeth. Radulas help in drilling holes and injecting a poison into the prey in order to subdue them or make them immobile. They are also useful in scraping particles of food, such as algae, from rocky or coralline surfaces.
Gastropoda
- Gastropods primarily feed on plant matter and have a radula that resembles the structure of a conveyor belt. Slugs and garden snails are examples of gastropod mollusks and have large number of hardened teeth that can break the cell walls of the plants. This helps in digestion of food. The radula of predatory gastropods helps in grinding the shells of bivalve mollusks. In some cases, the radula injects a poisonous substance while holding the shells together, allowing the predator to feed on its prey. In species that feed on fish, the radula is used as a poison dart while catching fish using a slow ambush.
Cephalopoda
- Cephalopods are usually predators that have large eyes and tentacles that help them to find and grasp their prey. Cephalopods feed on invertebrates or vertebrates (crabs, snails, shrimps and fish) depending on where they live. They either kill the prey or subdue them with a poison before feeding on them. Squid, octopuse and cuttlefish belong to this group. The powerful jaws that resemble a beak bite off the tissue pieces of the prey and the radula functions like a tongue that draws these pieces towards the species for feeding.
Polyplacophora
- Members from this group are also known as chitons and resemble pill-bugs (though they are not related to pill-bugs). They are mostly found on rocky surfaces. The radula contains magnetite-hardened teeth that help them to forage and scrap off food, such as algae, from the rocky surfaces. It is believed that the denticles on the radula of a chiton are so hard that they have the ability to etch glass.

Nature