Dr. Murai Éva szerk.: Parasitologia Hungarica 24. (Budapest, 1991)

MATERIALS AND METHODS From 1987 to 1990, 32 striped ruffe (Gymnocephalus schraetzer), 16 ruffe (G. cernua), 4 pikeperch (Stizostedion lucioperca) and 36 perch (Perca ßiviatilis) specimens were collected from reaches of the River Danube south of Budapest. The striped ruffe and ruffe specimens were 4-12 cm long and more than one summer old, and the pikeperch specimens were 14-18 cm long and 2 summers old. The perch specimens measured 2-6 cm in length and included both fry and several summers old fish. With the exception of 4 striped ruffe and ruffe each and 20 perch specimens, the fish were examined and dissected in April and May. When the fish were killed, a blood smear was prepared from each. The kidneys were examined partly under a coverslip as fresh preparations, partly as 4 fim thick histological sections previously fixed in Bouin's solution, embedded in paraffin, sectioned, and stained with haematoxylin and eosin. RESULTS Twenty-four out of the 32 striped ruffe specimens examined were found to have Sphaerospora spores and sporogonic stages (pseudoplasmodia) in the kidney. In two fish blood stages were also detected. Seven out of the 12 ruffe and 1 out of the 4 pikeperch specimens had renal sphaerosporosis. All perches proved negative. All positive cases occurred in April and May. The spores and pseudoplasmodia found in striped ruffe, ruffe and pikeperch did not differ from each other (Figs la, b, c, d, 2, 3, 4 and 5) but were clearly distinguishable from species described from percids until then. On the basis of preparations made and spores collected from striped ruffe, the new species is described as follows. Sphaerospora danubialis sp. n. The spores and pseudoplasmodia occurred in the lumen of the convoluted tubules and, less often, inside the Bowman's capsule. The youngest pseudoplasmodia contained a primary cell and two secondary cells (sporoblast). All pseudoplasmodia proved to be disporoblastic. The sporoblasts had 6 nuclei, each of which formed one spore. While smaller pseudoplasmodia measured 9 to 14 /urn in diameter and were round in shape, the more mature, spore-containing pseudoplasmodia were short ellipsoidal and reached 9-14x 12-19 urn in size. Description of the spores on the basis of 50 spores collected from Gymnocephalus schraetzer is as follows. In suturai view, the spores have a rounded triangular shape due to their flattened caudal surface (Fig. la). The suture perpendicular to the plane of the two polar capsules protrudes over the spore surface, making the spores lemon-shaped in upper view (Fig. lb). Spores are 10.1 (9.5-11) urn long, 9.1 (8.5-9.5) urn wide and 8.7 (8.5-10) um thick. In suturai view, there are protruding tubercles on both sides of the caudal margin of the spore. In these tubercles the nu-