Proteocephalus

Proteocephalus is a genus of parasitic flatworms in the family Proteocephalidae, within the order Proteocephalidea, class Cestoda. Members are endoparasites of freshwater fishes. Adults inhabit the intestinal tract of various fish hosts, where they attach with a scolex and feed on ingested nutrients. The genus comprises numerous species described from continents worldwide.

Life cycle: Like other proteocephalids, Proteocephalus species typically have a three-host life cycle. Eggs hatch in water to release oncospheres that are ingested by a crustacean first intermediate host, usually a copepod. Within the crustacean, a larval stage called a procercoid develops. The crustacean is then eaten by a second intermediate host, typically a small fish, where the larva develops into a plerocercoid. The definitive host is a larger predatory fish that consumes the second intermediate host; the tapeworm reaches sexual maturity in the intestine and releases eggs via the host’s feces.

Pathology and significance: Infections are often asymptomatic but can cause enteritis, reduced growth, or intestinal obstruction in heavily infected fish. They are of particular interest in freshwater fish biology and aquaculture because heavy infections can affect growth rates and feed efficiency. Host range varies by species, with some Proteocephalus spp. showing a broad range of fish hosts and others showing higher specificity.