Reintroduction of Profilicollis Meyer, 1931, as a genus in acanthocephala:Significance of the intermediate host

Polymorphid acanthocephalans with long necks, spheroid proboscides, and egg s without polar swellings of the fertilization membrane constitute a morpho logically distinct group of species. In the past, this taxon was considered a separate genus, Profilicollis. More recently, workers have been unwillin g to accept these features as generic-level characters, and presently the g roup is considered a subgenus of Polymorphus. An analysis prompted by our s tudies of various polymorphid cystacanths in crabs along the coasts of Scot land and the U.S.A. reveals that all records of Polymorphus in decapods ref er to species with 6 cement glands frequently assigned to Hexaglandula, to incidental occurrences of species purported to be Polymorphus minutus, or t o species of the subgenus Profilicollis. Occurrence in decapod crustaceans implies substantial life history differences from the other species of the genus occurring in amphipod crustaceans. We conclude this, together with mo rphological distinctiveness, justifies return of Profilicollis to full gene ric status within Polymorphidae.