Ultrastructure ofNosema marucae sp. n. (Microspora, Nosematidae), a pathogen ofMaruca testulalis (Lepidoptera, Pyralidae)

Abstract

The development ofNosema marucae was followed in its host, the legume pod borerMaruca testulalis. The meronts had an irregular cell body and were binucleated, with the large diplokaryon occupying most of the cell. The sporonts contained many rough endoplastic reticula. The sporoblasts had a granular cytoplasm with a large number of ribosomes, and nuclear division and cellular cleavage were prevalent, particularly from 84 to 120 h after inoculation. Sporoblasts and young spores were evident from 108 to 144 h after inoculation.

In the mature spores, the exocuticle had a rough and sculptured surface and the endocuticle thinned considerably at the apical end. The anchoring disc was thick at the point of attachment. The polar tube had 12–15 loops, and the polaroplast was multilayered with two distinct regions and occupied almost half of the spore. The diplokaryon was centrally located in the cell; the nuclear membranes of the diplokarya were separated by an electron-dense region about 0.6 nm thick.