Effects and tissue pathology of an unidentified microsporidium from the convergent lady beetle, Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae), on three non-target coccinellids

Abstract

A microsporidium from <i>H. convergens</i> was transmitted horizontally to three non-target coccinellids (<i>Adalia bipunctata</i> L., <i>Coccinella septempunctata</i> L. and <i>Harmonia axyridis</i> Pallas) under laboratory conditions. The effects of microsporidiosis on larval development, larval mortality, sex ratio, fecundity and adult longevity were examined. For all beetle species, larval development was prolonged as a result of infection. Fecundity and longevity was adversely affected only for the natural host, <i>H. convergens</i>. Spore counts were similar for <i>A. bipunctata</i> and <i>H. convergens</i> but fewer spores were observed in <i>C. septempunctata</i> and <i>H. axyridis</i>. Vertical transmission of the pathogen was observed in all host species. Three eugregarines were found and described from two adult <i>A. bipunctata</i>. In <i>H. convergens</i>, the microsporidium infected muscles surrounding the midgut and within the fat body, Malpighian tubules, pyloric valve epithelium, colon epithelium, nerves, muscles, connective tissues, and ovaries. Tissue pathology differed for <i>C. septempunctata</i> and <i>H axyridis</i>.