ULTRASTRUCTURAL-STUDY OF THE DEVELOPMENT OF VAIRIMORPHA NECATRIX (KRAMER, 1965) (PROTOZOA, MICROSPORIDA) IN LARVAE OF THE CORN-EARWORM, HELIOTHIS-ZEA (BODDIE) (LEPIDOPTERA, NOCTUIDAE) WITH EMPHASIS ON SPOROGONY

The ultrastructure of the life cycle of Vairimorpha necatrix (Kramer) was studied in Heliothis (Helicoverpa) tea larvae raised at temperatures ranging from 15 degrees C to 30 degrees C. In contrast to the description of the type species, both patterns of development (Nosema-like and Thelohania-like) that characterize the genus Vairimorpha were present at all temperatures examined. No temperature-related differences in the ultrastructure of Vairimorpha necatrix were observed; however, the effects of temperature variation were apparent in 1) the time between inoculation with V. necatrix and the initiation of the parasite life cycle and 2) the duration (or length) of the parasite life cycle. An additional form of the parasite, that of a diplokaryon in a sporophorous vesicle, was present during early sporogony. The nuclei of the diplokaryon separated followed by cytokinesis, forming two monokaryotic parasites, and eventually two plasmodia, within the sporophorous vesicle. This pattern of development is characteristic neither of Nosema nor Thelohania, nor has it been described for Vairimorpha.