Radula

The radula (US: /ˈrædʒʊlə/; pl.: radulae or radulas) is an anatomical structure found in most mollusks, serving as their primary feeding tool. Often compared to a tongue, this minutely toothed, chitinous ribbon typically functions by scraping or cutting food before it enters the esophagus. Mollusks in every class possess a radula, except for bivalves, which instead employ waving cilia to draw in minute organisms for feeding.

The radula typically functions as a rasping organ to scrape food particles. However, its form and use have diversified significantly; it is modified for drilling holes in prey shells (e.g., in Muricidae), transformed into venomous harpoons (e.g., in Conidae using conotoxins), or reduced/lost in fluid feeders (such as in the Pyramidellidae where the highly specialized, needle-like radula is called a stylet).

Within the gastropods, the radula is used in feeding by both herbivorous and carnivorous snails and slugs. The arrangement of teeth (denticles) on the radular ribbon varies considerably from one group to another.

In most of the more ancient lineages of gastropods, the radula is used to graze, by scraping diatoms and other microscopic algae off rock surfaces and other substrates.

Predatory marine snails such as the Naticidae use the radula plus an acidic secretion to bore through the shell of other mollusks. Other predatory marine snails, such as the Conidae, use a specialized radular tooth as a poisoned harpoon. Predatory pulmonate land slugs, such as the ghost slug, use elongated razor-sharp teeth on the radula to seize and devour earthworms. Predatory cephalopods, such as squid, use the radula for cutting prey.

The introduction of the term "radula" (Latin, "little scraper") is usually attributed to the Russian zoologist Alexander von Middendorff in 1847.