Europ. J. Protisto!' 32,251-261 (1996) May 31, 1996 European Journal of PROTISTOLOGY Redescription of Pleistophora intestinalis Chatton, 1907, a Microsporidian Parasite of Daphnia magna and Daphnia pulex, With Establishment of the New Genus Glugoides (Microspora, Glugeidae) J. I. Ronny Larsson 1, Dieter Ebert 2 , 3, Jifi Vavra", and Vladimir N. Voronln- 1 Department of Zoology, University of Lund, Sweden 2Zoology Department, Oxford University, UK "Currem address: Centre for Population Biology, Imperial College at Silwood Park, Ascot, Berks, UK 4Department of Parasitology, Charles University, Prague, Czech Republic 5State Research Institute of Lake and River Fisheries, Sankt Petersburg, Russian Republic SUMMARY The cytology of a microsporidium identified as Pleistophora intestinalis Chatton, 1907, is described with emphasis on the ultrastructure. The spores are somewhat asymmetrical, ovoid to lightly kidney-shaped, measuring 1.1-1.7 x 2.4-2.7 urn in fresh preparations. The spore wall is three-layered with an approximately 15 nm thick exospore, which is electron-dense with a more dense surface coat. The polar filament is isofilar with 5 -8, mostly 6, coils in a single layer, and the polaroplast has two regions with lamellae, the anterior ones more densely packed. All life cycle stages have isolated nuclei and the spores are uninucleate. Merozoites and sporoblasts are produced by plasmotomy, and the sporogony is polysporoblastic. Merogonial stages are enclosed in parasitophorous va- cuoles, sporogonial stages in double envelopes: the parasitophorous vacuole and a spor- ophorous vesicle, formed by duplication of the plasma membrane of the sporont. There is some doubt that Pleistophora intestinalis of Daphnia magna and of D. pulex is the same microsporidian species, but that was not proven by the cytological analysis. The identi- fication has been verified by study of material originating from Chatton and of the micro- sporidium Otto jirovec, the first reviser,identified as P. intestinalis. The microsporidium is not a Pleistophora species. The new genus Glugoides is established, and placed in the family Glugeidae. Abbreviations A = anchoring disc C = centriolar plaque E = exospore EN = endospore EX = exospore F = polar filament HN = host nucleus M = host mitochondrion MP = merogonial plasmodium © 1996 by Gustav Fischer Verlag, Stuttgart N = nucleus P = parasitophorous vacuole PA = anterior part of the polaroplast PM = plasma membrane PP = posterior part of the polaroplast PS = polar sac PV = polar vesicle SB = sporoblast SV = sporophorous vesicle V = posterior vacuole 0932-4739-96-0032-0251$3.50-0