Revising the Freshwater to gen. et comb. nov., and Description of Two New Species.

Crayfish are common hosts of microsporidian parasites, prominently from the genus . is a polyphyletic genus, with multiple genetically distinct lineages found from freshwater and marine environments. Researchers have been calling for a revision of this group for over a decade. We provide evidence that crayfish-infecting freshwater are genetically and phylogenetically distinct from the marine (Clade V/Glugeida), whilst also describing two new species that give further support to the taxonomic revision. We propose that the freshwater should be transferred to their own genus, gen. et comb. nov., in a new family (Astathelohaniidae n. fam.). This results in the revision of (), (), and (). We also describe two novel muscle-infecting species, n. sp. and n. sp., from North American crayfishes ( sp.). We used histological, molecular, and ultrastructural data to formally describe the novel isolates. Our data suggest that the are genetically distinct from other known microsporidian genera, outside any described family, and that their SSU rRNA gene sequence diversity follows their host species and native geographic location. The range of this genus currently includes North America, Europe, and Australia.