Effects of a microsporidium from the convergent lady beetle, Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae), on three non-target coccinellids.
A microsporidium from Hippodamia convergens was transmitted horizontally to three non-target coccinellid hosts (Adalia bipunctata L., Coccinella septempunctata L. and Harmonia axyridis Pallas) under laboratory conditions. For all species examined, microsporidia-infected larvae took significantly longer to develop than did uninfected larvae but the microsporidium had no effect on larval mortality. Adult sex ratios of uninfected and microsporidia-infected adults were about 1:1 (female symbol:male symbol) and did not differ significantly. At the end of a 90-day trial, microsporidia-infected H. convergens produced significantly fewer eggs and did not live as long as uninfected individuals. Differences in fecundity and longevity were not observed for the three non-target coccinellids that were examined. Mean spore counts from smear preparations of microsporidia-infected A. bipunctata did not differ significantly from H. convergens, suggesting that A. bipunctata (a native coccinellid) is a suitable host for the microsporidium but infection was lighter in C. septempunctata and H. axyridis (introduced species). Vertical transmission of the pathogen was observed during the 90-day trial by examining eggs and larvae that were produced by microsporidia-infected adults. For all species examined, 100% vertical transmission of the pathogen was eventually observed. Three eugregarines were found in two adult A. bipunctata: Gregarine A trophozoites are similar in size to those of Gregarina katherina Watson (described earlier from Coccinella spp.), Gregarine B trophozoites are similar in size to those of Gregarine A but are morphology distinct, and Gregarine C trophozoites are similar in size to G. barbarara Watson (described earlier from A. bipunctata).
Saito
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Department of Biology, Saint Mary's University, 923 Robie Street, Halifax, Nova Scotia, Canada B3H 3C3.
Bjørnson
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D000818:Animals; D001517:Coleoptera / Q000382:microbiology*; D018562:Disease Transmission, Infectious; D005260:Female; D054884:Host-Pathogen Interactions; D007814:Larva / Q000382:microbiology; D008136:Longevity; D008297:Male; D016814:Microsporidia / Q000472:pathogenicity / Q000502:physiology*; D016881:Microsporidiosis / Q000503:physiopathology / Q000635:transmission / Q000662:veterinary*; D010063:Ovum / Q000382:microbiology; D010572:Pest Control, Biological / Q000379:methods*; D012744:Sex Ratio; D053058:Trophozoites / Q000382:microbiology