CYTOLOGICAL STUDY OF NOSEMA-ARTEMIAE (CODREANU, 1957) SPRAGUE 1977 (MICROSPORIDIA, NOSEMATIDAE)

Two natural populations of Artemia sp. (SW and SE coast of Spain) were infected by microsporidia. The cytology and the life cycle of the mos t important species, Nosema artemiae (CODREANU, 1957) SPRAGUE, 1977, i s described here with focus on the ultrastructure. The parasite develo ped in the musculature, haemocytes and hypoderm. All stages had nuclei coupled as diplokarya and the reproduction was by binary fission. Mer ozoites were frequently arranged in chains. The developing sporont wal l, passed through a series of stages, where the electron-dense materia l secreted on the plasma membrane was rearranged: initially seen as tu bulus-like structures, then as parallel stands, and finally as a confl uent uniform layer. Spores were ovoid measuring 2.8-3.5 x 3.9-5.11 mum in living condition. The spore wall had the normal three components: plasma membrane, a structure-less endospore, and an exospore composed of two layers of different electron-density. The polar filament was ei ther isofilar, with 11-13, or lightly anisofilar with 13-16 coils. The polaroplast had two regions with lamellar compartments. The anterior lamellae were more closely packed.