Nosema scripta N. Sp. (Microsporida : Nosematidae), a microsporidian parasite of the cottonwood leaf beetle, Chrysomela scripta (Coleoptera : Chrysomelidae)

Nosema scripta (Microsporida: Nosematidae), a new species of microsporidian parasite, is described from the cottonwood leaf beetle, Chrysomela scripta F. (Coleoptera: Chrysomelidae), in North America. Studies using light and electron microscopy reveal that this species completes its life cycle in direct contact with the cytoplasm of cells within the fat body, midgut, hindgut, muscles, central nerve cord, Malpighian tubules, tracheal end cells, and ovaries. The microsporidium is monomorphic, all life stages are diplokaryotic, and spores develop from disporous sporonts. The mature spores are broadly oval and measure 4.2 plus or minus 0.10 x 3.4 plus or minus 0.04 mu m. Spores contain a tubular polar filament that is arranged peripherally in a single layer of 13-15 coils. Both horizontal transmission and vertical transmission have been demonstrated for this microsporidium in C. scripta in the laboratory. The Colorado potato beetle, Leptinotarsa decemlineata (Say), was susceptible to infection with this pathogen in cross-infectivity studies.