Description of Ordospora
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The type species is O. colligata (Larsson, Ebert & V1/2vra, 1997) in gut epithelial cells of Daphnia magna (Crustacea, Cladocera). Monomorphic, monokaryotic throughout life cycle. Meiosis unknown. Transmission unknown. All stages lie in a parasitophorous vacuole bounded by a membrane of presumed host origin. Immature stages are situated at the periphery, mature stages in the centre. Merogony: uninucleate meronts become rounded tetranucleate plasmodia, which elongate before separating into 4 uninucleate progeny. Sporogony: binucleate cells with membranes thickened by deposition of surface coat become tetranucleate and divide into a chain of 4 uninculeate sporoblasts. The binucleate cells are often associated in pairs so that the resultant chains consist of 8 sporoblasts. Spores: 1.3-2.3 x 2.3-3.7 µm (fresh) are pyriform with pointed anterior end and are sometimes slightly curved. Fresh spores show a distinct posterior vacuole. Polaroplast is composed of uniformly spaced lamellae arranged as folds around each other. Polar tube is isofilar with 5-6 coils in one rank. Single nucleus is located within the coil. Spores, as well as sporoblasts, frequently remain connected in chains.
