The ultrastructural cytology and taxonomy of Duboscqia sidaeJírovec, 1942 (Microspora, Duboscqiidae), with establishment of the new genus Agglomerata gen. nov.

Abstract

Summary The cytology of the microsporidium Duboscqia sidae (Microspora, Duboscqiidae), a parasite of Holopedium gibberum in a Canadian Shield Lake, was investigated using light and electron microscopical methods. Persistent aggregates of spores, generally 16 in number, were produced in polysporous sporophorous vesicles. The integrity of aggregates was maintained by a dense reticulum of tubules which were modified from characteristic inclusions observed in vesicles with sporoblasts and immature spores. The ultrastructure of mature spores was unique, characterized by a five-layered exospore, a slightly anisofilar polar filament and a polaroplast with three structurally distinct regions. The species is compared with other microsporidia reported from Cladocera and its systematic position is examined. As the ultrastructural cytology is specialised and the developmental attributes of the species differ from those of the type species of Duboscqia and all other genera with polysporoblastic sporogony in sporophorous vesicles, a new genus, Agglomerata, is created for D. sidae.