Ultrastructural study of Glugea cladocera pfeiffer, 1895, and transfer to the genus Agglomerata (microspora, duboscqiidae)

Abstract

Summary The microsporidium Glugea cladocera Pfeiffer, 1895, a parasite of the microcrustacean Daphnia magna , is redescribed based on light microscopic and ultrastructural characters. All life cycle stages have isolated nuclei. Merogonial plasmodia are elongated with a small number of nuclei. Sporogonial plasmodia divide by rosette-like division, producing a variable number of sporoblasts, usually 8 (4–16). A sporophorous vesicle, initiated at the beginning of the sporogony, collects all daughter cells of the sporont. Fibril-like projections connect the primordial exospore layer of the sporont with the sporophorous vesicle. The fibrils remain as a surface coat of mature spores. When sporoblast buds are formed, a second type of projections appear in the episporontal space. These are temporary tubules of exospore material, which disappear when the spores mature. The exospore of the mature spore is layered, with an internal layer resembling a double membrane. The polaroplast has three regions: wide lamellae, narrow lamellae and tubules. The polar filament is lightly anisofilar with 1–2 wide anterior, and 4–3 narrow posterior coils, arranged in one layer of coils in the posterior half of the spores. The identification of the species is discussed. Otto Jŕrovec, who redescribed the species in 1936, transferred it to the genus Thelohania. Comparison with slides in the collection of Prof. Otto Jŕrovec, Prague, revealed that the microsporidium studied by us apparently is identical to Jirovec's Thelohania cladocera from Daphnia magna , but it is not identical to his T. cladocera from D. pulex . Based on life cycle characters and the ultrastructure, the species is transferred to the genus Agglomerata .