Individuals of the acanthocephalan worm Polymorphus minutus can reach a body length of 2.8 mm to 3.9 mm. This species parasitizes the small and large intestines of waterfowl such as ducks, swans, geese, and occasionally domestic chickens. It utilizes water fleas as intermediate hosts and possibly some fish species (Eckert 2008). With its hook-bearing proboscis, which can also be retracted, Polymorphus minutus burrows into the intestinal wall of the host. The eggs are excreted through the feces and subsequently ingested by the intermediate host (Lucius, Loos-Frank et Lane 2018).

Human pathogenicity: There are no known cases of humans being infested with the acanthocephalan worm Polymorphus minutus.