Polymorphidae

The thorny-headed worm family Polymorphidae contains endoparasites which as adults feed mainly in fish and aquatic birds.

When this taxon was erected by Meyer in 1931, a subfamily Polymorphinae was established in it.

As the Polymorphidae as presently understood would then be monotypic, with no basal genera outside the Polymorphinae, the proposed subfamily is redundant for the time being and therefore most modern treatments simply omit it.

Polymorphus minutus is an economically significant parasite in goose and duck farming.

Ibirhynchus García-Valera, Pérez-Ponce de León, Aznar and Nadler, 2011 Neoandracantha Amin & Heckmann, 2017 is a monotypic genus containing only Neoandracantha peruensis Amin & Heckmann, 2017[2] The genus polymorphus Lühe, 1911 uses amphipod crustaceans as intermediate hosts and various birds as final hosts.

Neoandracantha peruensis
Proboscis, neck and trunk spines of a juvenile Bolbosoma turbinella. Bars is 200um. [ 1 ]
A juvenile female Corynosoma australe with a detail of the proboscis. Bar on the left is 1mm and the bar on the right is 0.25mm. [ 1 ]
Male juvenile Corynosoma cetaceum with a detail of the proboscis, neck, and trunk spines. Bar on the left is 1mm and the bar on the right is 0.5mm. [ 1 ]