Pathogenicity and some structural features of Myxidium rhodei (Myxozoa: Myxosporea) from the kidney of the roach Rutilus rutilus

Abstract

Two simultaneously occurring types of pathological change were observed in the kidneyof Rutilus rutilus (L.) infected with Myxidium rhodei. Plasmodia in the renal corpuscles causedhypertrophy concurrent with atrophy of the surrounding renal parenchyma. Granulomatous reaction tothese plasmodia occurred only when they were filled with spores. In contrast, plasmodia locahzed inthe interstitium provoked a granulomatous inflammatory reaction at an early stage in their development.In heavy infections, there was severe damage to the hdney, involving a decrease in the numberof glomeruli, atrophy of surrounding tissue, and granulomatous inflammatory changes in the interstitiurn.The ultrastructure of M. rhodei shows a general similarity to that of other polysporic plasmodia,except for 2 features: (1) generative cells often occur in pairs or groups of 3, penetrating one anotherwith digitiform pseudopodia; (2) early pansporoblasts aggregate in groups formed by individualsclustering together across a thin sheet of plasmodial cytoplasm. The significance of these 2 features isnot yet clear.