Life Cycle of Goussia pannonica (Molnar, 1989) (Apicomplexa, Eimeriorina), an Extracytoplasmic Coccidium from the White Bream Blicca bjoerkna

Life cycle stages of Goussia pannonica from naturally‐infected white bream Blicca bjoerkna were studied by light and electron microscopy. Fourteen of the sixteen fish examined were infected, with developmental stages found in all parts of the intestine. Merogonial, gamogonial, and sporogonial stages were localized intracellularly and extracytoplasmically in the microvillous region of enterocytes. They were separated from the gut lumen by closely apposed enterocyte and parasitophorous vacuole membranes. There were two types of extracytoplasmic attachment: 1) monopodial, with a single zone of attachment, and 2) spider‐like, with several isolated zones of attachment to the host cell. First‐generation merozoites were formed by ectomerogony. Second‐ or third‐generation merozoites were formed by endodyogeny and endopolygeny. Thirty to 50 biflagellated microgametes developed at the periphery of a microgamont. Macrogamonts contained lipid inclusions, amylopectin and dense granules; however, granules comparable to wall‐forming bodies type I and II were absent. At the beginning of sporogony, the sporont cytoplasm detached from two layers which subsequently became constituents of the oocyst wall. After the rupture of enterocyte and parasitophorous vacuole membranes, the sporont was released into the water where exogenous sporulation was completed within 48 h. The thin sporocyst wall contained a small longitudinal suture. Sporocyst and oocyts walls were of similar structure.