Nosema adaliae sp. nov., a new microsporidian pathogen from the two-spotted lady beetle, Adalia bipunctata L. (Coleoptera: Coccinellidae) and its relationship to microsporidia that infect other coccinellids.

The two-spotted lady beetle, Adalia bipunctata L., is a tree-dwelling lady beetle endemic to parts of Europe, Central Asia and North America that is commercially available for aphid control in Europe and North America. Lady beetles host a wide variety of symbionts including parasitoids, viruses, eugregarines, fungi, bacteria, nematodes and microsporidia. Four species of microsporidia have been described from lady beetles, and an undescribed microsporidium was recently isolated from local populations of A. bipunctata in Nova Scotia, Canada. In a previous study, this pathogen prolonged the development of A. bipunctata larvae but had no effect on adult fecundity, longevity or sex ratios. The objective of this study was to formally describe the microsporidium by means of its ultrastructure, tissue pathology and molecular characterization. All stages of the microsporidium were diplokaryotic and developed in direct contact with the host cell cytoplasm. Mature spores measured 4.25±0.09×1.82±0.03μm (SE, n=49, from micrographs) and fresh spores measured 6.10±0.06×3.01±0.05μm (±SE, n=60; range: 5.0-6.9×2.18-3.86μm). The polar filament was isofilar with 10-18 coils that were frequently arranged in a single row. The lamellar polaroplast was not typically visible and spores contained a relatively small posterior vacuole. Both the flight muscles and fat body were heavily infected and a large number of spores were observed within and between the cells of these tissues. The ovaries, developing oocytes, spermatocytes and accessory glands within the testes, midgut epithelium, Malpighian tubules, ileum, colon, and ventral nerve cord were also infected but not as heavily. Connective tissue near the cuticle and surrounding the trachea were lightly infected. The presence of spores in both the alimentary canal and ovaries (particularly within developing oocytes) suggests that the microsporidium can be transmitted per os (horizontally) and transovarially (vertically). Molecular analysis of the genome of the microsporidium described in this study was 97% similar to Nosema bombi and 96% similar to Nosema thomsoni, Nosema vespula and Nosema oulemae. Based on information gained during this study, we propose that the microsporidium in A. bipunctata be given the name Nosema adaliae sp. nov.