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one of the larval stages of certain tapeworms (including the broad fish tapeworm). A procercoid is approximately 0.05 mm long and is spindle-shaped. The posterior end is distinct from the rest of the body and is equipped with three pairs of chitinoid hooklets. The procercoid stage is usually passed in the body cavity of copepods, which serve as the first intermediate hosts of many tapeworms. After the second intermediate host—a fish—swallows the parasitized copepod, the procercoid is converted in the fish’s body into the next larval stage—the plerocercoid.