Strelkovimermis papillosus n. sp. (Nematoda: Mermithidae), a parasite of chironomid (Insecta: Diptera) adults from the headwaters of the Mississippi River in northern Minnesota

On 18 August 2002, chironomid imagoes of Rheotanytarsus sp. emerged from the upper Mississippi River in Minnesota and yielded distinctive mermithid nematodes of a new mermithid species. Strelkovimermis papillosus n. sp. is distinguished from the other 14 species of the genus by the presence of unusually large cephalic papillae encircling the mouth and forming a rosette with the mouth in the center and by the absence of a fixator muscle in the males. Additionally, both sexes have very acute posterior ends, long amphids, and a long stoma. Strelkovimermis is revised by eliminating nondiscriminating parameters and accommodating the 15 known species. Intrageneric characteristics useful in separating species of Strelkovimermis are listed. Intensity of infection and intensity of infection versus sex were determined from 41 hosts. Where known, the hosts and geographical distribution are given for all 15 Strelkovimermis species.