Ultrastructure and tissue specificity of Nosema costelytrae and Nosema takapauensis, microsporidian pathogens of grass grubs, Costelytra zealandica, (Coleoptera: Scarabaeidae) in New Zealand

Abstract

Nosema costelytrae and Nosema takapauensis, microsporidian pathogens of grass grub beetle larvae of the scarabaeid pasture pest species, Costelytra zealandica, are redescribed. N. costelytrae has spherical meronts (6.34 µm) and elongate-ovoid or fusiform sporonts (6.81 × 3.27 µm). Stages have one, two, or four nuclei, usually in diplokaryotic arrangement. Spores are ovoid (4.37 × 2.50 µm, fresh), with a distinct point at one end. Spores develop in the fat body, tracheole cells, nerve ganglia, and muscle. There is no evidence of dimorph-ism when Planotortrix excessana (Lepidoptera) are experimentally infected with N. costelytrae at 15 or 22°C. N. takapauensis has spherical meronts (7.74 µm), with one, two, or four nuclei and spherical sporonts (3.70 µm), with one or two nuclei. Spores are ovoid to cylindrical (6.37 × 2.82 µm, fresh), with some macrospores. Fat body, tracheole cells, and ocnocytes support growth of this parasite. Both species have a fine structure that is usual for Nosema species.

Keywords:

• microsporidia
• protozoa
• Nosema costelytrae
• Nosema takapauensis
• grass grubs
• Costelytra zealandica
• Coleoptera
• Scarabaeidae;
• pathogens
• ultrastructure
• tissue specificity
• lifecycle