Histological sections of haplosporidian in Diporeia collected from Lake Superior (USA). (A) Plasmodia undergoing various stages of shizogeny lining the epicuticle (small arrow) and sporocysts containing developing spores lining host digestive tissue (large arrow). (B) Transmission electron micrograph of sporocysts containing both amorphous, immature spores (small arrows) and mature spores (large arrows). (C) Sporoblast containing two basophilic bodies (large arrows). Note the sporoblast with a well-defined endosporoplasm (small arrow). (D) Mature spore that has been liberated from the sporocyst (large arrow) and thin filaments projecting from the end of multiple developing spores (small arrows). Scale bars: A = 75 μm, B = 10 μm, C = 25 μm, and D = 5 μm.