Acanthocephalans (thorny-headed worms)

Spiny-headed worms are named for the multitude of hooks on their proboscis. Adult worms are found in the intestine of the fish host and are characterized by the number and arrangement of hooks. The hooks are made from chitin. The adult worms can cause physical damage to the gut which can allow secondary infections. Acanthocephalans have been associated with epizootics in hatcheries and local fish extinctions. The typical life cycle of an acanthocephalan involves two hosts: a crustacean invertebrate host (often an amphipod) and a fish vertebrate host.