ULTRASTRUCTURAL-STUDY OF ENDORETICULATUS-DURFORTI N-SP, A NEW MICROSPORIDIAN PARASITE OF THE INTESTINAL EPITHELIUM OF ARTEMIA (CRUSTACEA, ANOSTRACA)

A new microsporidian parasite of the Artemia intestinal epithelium has been studied. The microsporidium developed within a membranous parasi tophorous vesicle from the host rough endoplasmic reticulum consisting of two membranes, with the proximal one usually lacking ribosomes. Al l developmental stages had isolated nuclei. Unikaryotic meronts develo ped into merogonial plasmodia. Merogonial division occurred by binary fission and rosette-shaped fragmentation. In young sporonts, an electr on-lucent space, corresponding to the developing endospore, was immedi ately observed between both the plasmalemma and the exospore primordiu m. Sporogonial division occurred also by rosette-shaped fragmentation, resulting in at least eight sporoblasts that developed directly into spores. Fresh spores were 1.7 x 0.9 mum in size and oval-shaped. The 8 -11 coil isofilar polar filament was arranged in two rows. The polarop last was bipartite. The nature of the parasitophorous envelope, host-p arasite interaction, developmental cycle and taxonomy are discussed.