Two new eriophyoid mite species of the genus Leipothrix Keifer (Acariformes, Eriophyoidea) from Russian Siberia and eastern USA

Leipothrix is a morphologically distinct genus of eriophyoid mites (Eriophyoidea), primarily associated with angiosperms but also including a small group of fern-inhabiting species. We describe two new species: L. osmundastris n. sp. from a fern (Osmundastrum cinnamomeum) in West Virginia (USA) and L. ulanudensis n. sp. from a sedge (Carex pediformis) in Siberia (Russia). These findings represent the first records of Leipothrix on ferns in North America and monocots in northern Asia. The two new species closely resemble L. pterisfolii Lotfollahi and de Lillo 2017 from Iran, potentially indicating common ancestry, but their occurrence in geographically widely separated regions and on phylogenetically distant hosts complicates this scenario, raising questions about evolutionary pathways and host-shift events in Leipothrix. Because specimens of L. ulanudensis n. sp. were degraded, we used confocal laser scanning microscopy (CLSM) to clarify key diagnostic features and demonstrate its utility for examining old slide-mounted specimens. Furthermore, we document the first evidence of serial spermatophore-like structures within males of L. osmundastris n. sp. This observation potentially reveals a novel mechanism of spermatophore formation, in contrast to the typical single-spermatophore process reported in many Eriophyoidea. Future work should elucidate the spermatophore production mechanisms in Leipothrix, resolve phylogeny of this genus, and clarify its evolutionary patterns across vascular plant lineages.