Tapeworms: Cestoda

Physical characteristics: The body of Proteocephalus longicollis worms is about 9 inches (22 centimeters) long and 0.08 inch (2 millimeters) wide. The scolex has small suckers and a small suckerlike organ at the tip. There are reproductive openings on the sides of the proglottids.

Geographic range: Proteocephalus longicollis (abbreviated to P. longicollis) worms live in Europe, Asia, and North America.

Habitat: P. longicollis worms live in freshwater fishes, mainly trouts, salmons, whitefishes, and smelts, that live in lakes and rivers in the northern hemisphere.

Diet: P. longicollis worms absorb nutrients from their hosts.

Behavior and reproduction: Scientists do not know how P. longicollis worms behave. The worms make both eggs and sperm. Eggs released in Proteocephalus longicollis worms live in freshwater fishes, mainly trouts, salmons, whitefishes, and smelts. (Illustration by Brian Cressman. Reproduced by permission.) water are eaten by tiny crustaceans, which are the intermediate hosts. The larvae develop in the body cavity of the crustacean. Fishes become infected by eating crustaceans containing the P. longicollis larvae.

Proteocephalus longicollis and people: P. longicollis worms infect fishes raised in fish farms.

Conservation status: P. longicollis worms are not considered threatened or endangered. ∎