Introduction | 1 | 2 | 3

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Following the discovery of another isolate of Helicosporidium parasiticum in a larva of Hepialis pallens (Hepialidae, Lepidoptera), another taxonomic position was proposed for the group Helicosporidia. Based on observation of this new isolate as well as the original specimen described by Keilin, Weiser (1970) claimed that the Helicosporidia are best placed among the lower Fungi. He argued that the spore characteristics are too much different from what is found in Protozoa, but are similar in some aspects to primitive Fungi, such as insect pathogens of the genus Monosporella, classified as Nematosporoideae inside the Saccharomycetaceae (primitive Ascomycetes).

In the ealy 1970s Helicosporidium parasiticum was isolated from larvae and adults of the beetle Carpophilus mutilatus Erichson (Nitidulidae, Coleoptera). This isolate was infectious per os to 18 species of arthropods, including three orders of insects (Lepidoptera, Coleoptera, Diptera) and one family of mites (Kellen and Lindegren 1973). Contrarily, species of Orthoptera, Hymenoptera and Diptera were not susceptible to this isolates. The spores (cysts), present in the host artificial diet, were ingested and released the three round cells and the filamentous cells in the host midgut. After 24 h, helicosporidial cells appeared in the host hemolymph and grew vegetatively. The vegetative growth is characterized by cell division that occurs within a pellicle. After division, the pellicle ruptures and releases the daughter cells (4 or 8). Empty pellicles and daughter cells eventually fill the entire host hemocoel. Daughter cells then develop into spores, in which the filamentous cell differentiates and encircles the three round cells. Additional studies reported the presence of Helicosporidium sp. in new host species, such as crustaceans, mites and collembola, and trematodes.

Introduction | 1 | 2 | 3