The radula is the toothed chitinous ribbon in the mouth of most molluscs. It can be compared with the tongue of human beings but, unlike our tongue, it is used for cutting and chewing food before it enters the esophagus.
The radula is present in all molluscs except bivalves, and only in molluscs. For example, Gastropods use it to graze and scrape diatoms and other microscopic algae off rock surfaces and other substrata. Squid use it for cutting up their prey.
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