Infection Prevalence of Microsporidia () spp. in Japanese Bumblebees.

Microsporidia are spore-forming intracellular parasites of various invertebrates and vertebrates. negatively affects the fitness of bumblebees and its prevalence correlates with declining bumblebee populations. The invasive alien species colonized Japan and possibly introduced new parasites. To assess the infection prevalence of in Japanese bumblebees and , we investigated infections using PCR and microscopy. The prevalence of sporulating infections in three s. str. species/subspecies was low, whereas that of non/low-sporulating sp. infections in three species/subspecies was high. Invasive showed low prevalence of non/low-sporulating infections and shared the same haplotype with found in Hokkaido, where is present, and in Honshu, where is absent. Although may have been introduced with colonies imported from Europe, it seems to be originally distributed in Japan. Furthermore, a new sp. was found in Japanese bumblebee species. and sp. showed different organ and host specificities in bumblebees. There are no reports on the specific effects of other spp. on bumblebees; further studies are needed to clarify the individual characteristics of spp.