Nosema notabilis (Microsporidia), its ultrastructure and effect on the myxosporean host Ortholinea polymorpha

Abstract

Nosema notabilis Kudo, 1939 produces chain-forming meronts with a dense cell coat in direct contact with the host cell cytoplasm. Cytoplasmic microtubules and membranaceous whorls could be observed in meront cytoplasm. Sporonts differ in that they have a thicker cell wall and more conspicuous endoplasmic reticulum (ER) cisternae. Sporoblasts have an externally ridged cell wall. Spores have an apically located anchoring disc, an isofilar polar tube with 6 to 9 turns and polyribosomal strands in the sporoplasm. Diplokarya occur in all stages. Heavily infected plasmodia of Ortholinea polymorpha (Davis, 1917) reveal marked pathological signs. The most prominent are reduction of surface projections and/or pinocytosis, inflated mitochondria with altered inner structures, affected vegetative nuclei, damage to generative cells and occurrence of various anomalous formations in the plasmodium cytoplasm. The damage may result in complete disintegration of the plasmodium. However, the development of the microsporidian is affected by a remarkably high percentage of teratological stages revealing membranaceous and tubular structures.