Beschreibung:
<jats:title>Abstract</jats:title><jats:p>Representatives of the genus <jats:italic>Anncaliia</jats:italic> are known as natural parasites of dipteran and coleopteran insects, amphipod crustaceans, but also humans, primarily with immunodeficiency. <jats:italic>Anncaliia algerae</jats:italic>‐caused fatal myositis is considered as an emergent infectious disease in humans. <jats:italic>A. (=Nosema, Brachiola) algerae</jats:italic>, the best studied species of the genus, demonstrates the broadest among microsporidia range of natural and experimental hosts, but it has never been propagated in <jats:italic>Drosophila</jats:italic>. We present ultrastructural analysis of development of <jats:italic>A. algerae</jats:italic> in visceral muscles and adipocytes of <jats:italic>Drosophila melanogaster</jats:italic> 2 wk after per oral experimental infection. We observed typical to <jats:italic>Anncaliia</jats:italic> spp. features of ultrastructure and cell pathology including spore morphology, characteristic extensions of the plasma membrane, and presence of “ridges” and appendages of tubular material at proliferative stages. <jats:italic>Anncaliia algerae</jats:italic> development in <jats:italic>D. melanogaster</jats:italic> was particularly similar to one of <jats:italic>A. algerae</jats:italic> and <jats:italic>A.(Brachiola) vesicularum</jats:italic> in humans with acute myositis. Given <jats:italic>D. melanogaster</jats:italic> is currently the most established genetic model, with a fully sequenced genome and easily available transgenic forms and genomic markers, a novel host–parasite system might provide new genetic tools to investigate host–pathogen interactions of <jats:italic>A. algerae</jats:italic>, as well to test antimicrosporidia drugs.</jats:p>