An early sporulation event in the host midgut tissues has been reported for several species of microsporidia infecting Diptera, Hymenoptera, and Lepidoptera. The role of these primary spores, formed between 35 and 96 h postinfectionper os,has been suggested to be the cell to cell spread of infection within the host, but the sequence of events during the early sporulation stages has been reported for only a few species of microsporidia. We investigated these early life cycle events for two species of microsporidia,Vairimorpha necatrixandVairimorphasp. fromLymantria dispar,tested in the laboratory hostsSpodoptera exiguaandL. dispar,respectively. We injected hemolymph drawn from orally infected host larvae into uninfected larvae at time periods from 2 to 96 h postinfection to determine the timing of infection of the hemolymph and target tissues. Our studies demonstrated that, for bothVairimorphaspecies, the early sporulation in the midgut tissues is a discrete first stage of infection. Invasion of the hemolymph and infection of the target tissues follows maturation of "primary spores" in the midgut and coincides with the germination of these spores beginning approximately 30 h postinfection for hosts held at a constant 24°C. The developmental stages of the microsporidia observed in the target tissues at specific time periods postinfection corresponded to the stages observed in the hemocytes, suggesting that sporoplasms from the germinating primary spores are directly injected into the target tissues and the hemolymph.
- Lymantria dispar
- Spodoptera exigua;microsporidia; infection by injection; primary spores; early life cycle stages; spore germination
- Vairimorpha necatrix
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics