The taxonomy of wide distributed parasites across continents has rarely been evaluated using molecular data, and it remains unclear whether their apparent broad distributions reflect true cosmopolitan and monophyletic lineages. There is also the expectation that long-term parasite–host associations shape the evolution of parasitic lineages and should therefore be reflected in parasite taxonomy. Laelaps Koch, 1836 (Mesostigmata: Laelapidae) is an example of a widespread genus, reported from multiple continents, parasitizing Cricetidae and Muridae rodents. The aim of this study is to evaluate whether Laelaps is monophyletic and truly broadly distributed across continents. To this end, we generated new nuclear (18S-ITS1-5.8S-ITS2-28S) and mitochondrial (cytochrome oxidase I) sequences from 8 species of Laelaps, and 4 related laelapid mite species of the genera Androlaelaps Berlese, 1903, Gigantolaelaps Fonseca, 1939 and Mysolaelaps Fonseca, 1936 associated with cricetid rodents from Argentina. Those sequences were analysed together with sequences from laelapids parasitizing native South American cricetids and from South Africa available in GenBank. Phylogenetic analyses revealed that Laelaps is polyphyletic. Within Cricetidae, tribal host association appears to drive phylogenetic structure, with cricetid-associated Laelaps lineages recovered as more closely related to Gigantolaelaps and Mysolaelaps than to each other. Murid-associated Laelaps from South Africa were recovered as lineages separated from cricetid-associated Laelaps, suggesting that the deep divergence between Cricetidae and Muridae may also shape laelapid phylogeny, a pattern that requires broader sampling to be conclusively evaluated. These results challenge the monophyly and broad distributional status of Laelaps and highlight the need for integrative taxonomic revision of this genus.

The genus Ancyrocephalus sensu lato is a large assemblage of species of dactylogyrid monopisthocotyleans without clear taxonomic boundaries. Despite an urgent need for revision, only three representatives of this taxon have been molecularly characterised so far. We found specimens of Ancyrocephalus curtus, a previously non-genotyped species, in gills of Perccottus glenii caught in the River Syumnyur, Amur Basin, Russia. The aim of this study was to assess the phylogenetic position of this parasite using partial sequences of 28S rRNA gene. In the phylogenetic tree, A. curtus appeared as a sister taxon to the dactylogyrine genus Gobioecetes. The new molecular evidence supports the hypothesis about the non-monophyletic status of Ancyrocephalus sensu lato.