Polymorphus
Polymorphus is a genus of parasitic worms from the phylum Acanthocephala. This group uses amphipod crustaceans as intermediate hosts and various birds as final hosts.
The genus used to be a larger group, but species that were formerly placed in the genus have now been placed in the genus Profilicollis based on morphological characteristics and the use of decapod crustaceans as intermediate hosts.