Cytological variation and pathogenicity of the bumble bee parasite Nosema bombi (Microspora, Nosematidae)

In three field seasons, 2003-2005. bumble bees were collected in southern Sweden and eastern Denmark in search of microsporidian parasites. Of file 16 bumble bee species studied, microsporidia were found in Bomhus hortorum, Bomhus hypnorum, Bombas lapidarius, Bomus lucorum, Bombus pascuorum, Bombus pratorum, Bombus ruderarius, and Bombus terrestris. Only one micro-sporidian species, Nosema bombi, was recorded. A microsporidium found in B. pratorum differed cytologically from microsporidia of the other host species. In the most frequently infected host, B. terrestris, the prevalence was 20.6%. Totally 1049 specimens were dissected. The light microscopic and Ultrastructural cytology and pathology of N. bombi is described with focus Oil the variation recorded. Variation was especially prominent in the shape, size and coupling of spores, and in the length and arrangement of the polar filament. In four host species microsporidian infection was restricted to peripheral fat cells. (c) 2006 Elsevier Inc. All rights reserved.