New Species of Spartiella and Legeriosimilis from Mayflies and Other Arthropod-Associated Trichomycetes from Nova Scotia, Canada

The digestive tracts of non-predaceous, aquatic insects and other arthropods living in moist habitats harbour a group of fungal and protistan microorganisms known as trichomycetes or “gut fungi”. A former class of Zygomycota, “trichomycetes” now refers to an ecological group of gut microbes. This report adds to the growing inventory of gut fungi that have been described from Atlantic Canada, with two new fungal trichomycetes, Legeriosimilis hiemalis sp. nov. Strongman and M.M. White and Spartiella aurensis sp. nov. Strongman and M.M. White, both from Ephemeroptera (mayfly) nymphs. Legeriosimilis hiemalis is now the fourth of seven known species of the genus to be recorded only from Canadian sites. Spartiella aurensis displays an unusual feature, with thalli apparently able to grow from the hindgut back into the midgut of its host, a growth pattern not typically observed in other gut fungi. The potential significance of this development is discussed. Despite the focus on immature freshwater insects and their habitats, we also record a species of Orchesellaria from Collembola (springtails) and Astreptonema corophii from the amphipod crustacean Corophium volutator .