Early Development of Nosema apis (Microspora: Nosematidae) in the Midgut Epithelium of the Honeybee (Apis mellifera)

The early infection of the honeybee midgut by the microsporidian parasite Nosema apis was examined with both light and electron microscopy. Newly ingested spores were found closer to the apex of the epithelium as they moved toward the distal end. The initial infection of the epithelial cells was restricted mainly to a very narrow area, at the posterior end of the midgut. Neither released sporoplasms in the midgut lumen, nor were polar tubes penetrating the host cell plasmalemma detected. The differences in the fine structure between the first and second meronts were minor.