Thaumamermis zealandica n sp (Mermithidae: Nematoda) parasitising the intertidal marine amphipod Talorchestia quoyana (Talitridae: Amphipoda) in New Zealand, with a summary of mermithids infecting amphipods.

A new nematode, Thaumamermis zealandica n. sp. (Mermithidae; Nematoda), is described parasitising the intertidal marine amphipod Talorchestia quoyana Milne-Edwards (Talitridae) from the coast of South Island, New Zealand. The new species is characterised by the degree of dimorphism of the spicules, the arrangement of the genital papillae, the shape and length of the vagina and the anteriorly-placed amphids. This is the first known marine host of a member of the family Mermithidae. Published records of mermithid nematodes from amphipods are presented.