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United States Department of Agriculture

Agricultural Research Service

Title: The Impact of Mixed Infection of Three Species of Microsporidia Isolated from the Gypsy Moth, Lymantria Dispar L. (Lepidoptera: Lymantriidae

Authors
item Solter, Leellen - IL NATURAL HISTORY SURVEY
item Siegel, Joel
item Pilarska, Daniela - BULGARIAN ACADEMY OF SCIE
item Higgs, M - IL NATURAL HISTORY SURVEY

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 23, 2002
Publication Date: December 20, 2002
Citation: Solter, L.F., Siegel, J.P., Pilarska, D.K., Higgs, M.C. 2002. The impact of mixed infection of three species of microsporidia isolated from the gypsy moth, lymantria dispar l. (lepidoptera: lymantriidae. Journal of Invertebrate Pathology. Volume(81):103-113.

Interpretive Summary: Competition among three pathogenic species of microsporidia belonging to the genera Endoreticulatus, Nosema, and Vairimorpha, isolated from different Bulgarian populations of the Gypsy Moth, Lymantria dispar, was evaluated in the laboratory. All possible combinations of two species were administered either simultaneously or sequentially to larvae, and differences in mortality, duration of development, and larval weight at 20 days post infection (simultaneous infection) or 23 days post infection (sequential infection) were assessed. Larvae were dissected and the presence of each species of microsporidia and the tissues infected were recorded. The effect of infection varied, depending on both host sex and the type of infection. Infected larvae were more likely to die than uninfected larvae, but there were no differences in mortality between single and mixed infections. Addition of Endoreticulatus to infections of Nosema or Vairimorpha significantly increased duration of development to the fourth ecdysis; this effect was additive. Addition of Nosema or Vairimorpha to an existing infection had no such effect. When Nosema was administered simultaneously with Endoreticulatus or Vairimorpha, infected larvae weighed more than larvae that had single infections with either pathogen; we conclude that competition occurred. Nosema was displaced from the silk glands by Vairimorpha, and Nosema suppressed formation of one lifestage of Vairimorpha in fat body tissues. The histological evidence combined with the data on differences in larval weight support the hypothesis that competition occurred in mixed infections.

Technical Abstract: The outcome of mixed infection by three species of microsporidia in the genera Endoreticulatus, Nosema, and Vairimorpha, isolated from different populations of Lymantria dispar in Bulgaria, was evaluated in the laboratory. All possible combinations of two species were administered either simultaneously or sequentially to larvae, and mortality, duration of development, and larval weight at 20 days post infection (simultaneous inoculation) or 23 days post infection (sequential inoculation) were chosen as the outcome variables. Larvae were dissected and the presence of each species of microsporidia and the tissues infected were recorded for each treatment. Effects of infection were dependent on both host, sex and the type of exposure. Infected larvae were more likely to die than uninfected larvae, but mortality was similar in single and mixed infections. Addition of Endoreticulatus to infections of Nosema or Vairimorpha significantly increased duration of development to the fourth ecdysis; this effect was additive. Addition of Nosema or Vairimorpha to an existing infection had no such effect. When Nosema was administered simultaneously with Endoreticulatus or Vairimorpha, infected larvae weighed more than larvae that had single infections with either pathogen; we conclude that competition occurred. Nosema was displaced from the silk glands by Vairimorpha, and Nosema suppressed octospore formation by Vairimorpha in fat body. The histological evidence combined with the data on larval weight support the hypothesis that competition occurred in mixed infections.

Last Modified: 7/25/2014
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