Meanders of systematics of Microsporidia. Taxonomical questions of Microsporidia, its systematic position and evolutionary relationship with other Eukaryota are discussed. Utilizations of modern methods of investigations of microsporidians cause new taxonomical troubles. At the present time it is difficult to create a clear hypothesis concerning the phylogeny and evolution of Microsporidia. Most likely they are representatives of a new kingdom of Eukaryota. Existing problems will not be dissolved until new detailed data concerning the new and common species are obtained.
Ultrastructural data of the sporulation stages of the microsporidium Gurleya orchestiae, infecting the muscles of talitrid amphipods Orchestia sp. (Crustacea, Amphipoda), are presented. The developmental stages of the parasite have isolated nuclei. Sporogonial reproduction is by rosette-like budding. Sporophorous vesicles contain 4, seldom 8 spores. The episporontal space contains granules and tubules. Spores are of oval shape, monokaryotic with lamellate bipartite polaroplast, double-layered exospore and isofilar polar filament, turned into 8-9 coils.