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

cleus of the valvogenic cell is sometimes still discernible. Between the tubercles and the suture pectiniform structures can be seen on the spore surface, indicating the presence of fine ribs. The polar capsules are spherical and 4.4 (4.0-4.8) in size. The polar filament takes 5, less often 6, turns in the polar capsules. Anterio-laterally 4 bright granules can be observed between the capsules and the wall of the spores. No membraneous envelope can be seen on the spore surface. Two blood smears made from striped ruffe contained one blood stage each. The blood stages were spherical or short ellipsoidal primary cells measuring 13-14 /urn and containing mostly 4 and 3 secondary cells, respectively (Fig. 6). Enlargement of the kidney was rarely found in the infected fish. Histological findings included widening of the infected tubules and deformation of the otherwise low columnar epithelial cells which had become cuboidal (Fig. 7). Of parasite stages situated in the tubules, the granular pseudoplasmodia were mostly attached to the wall of the tubules and loosely connected with the microvilli. Most of the mature spores were floating freely in the lumen of the tubules. DISCUSSION So far only one Sphaerospora species, S. markewitschi, has been reported from ruffe and Don ruffe. The spores of S. danubialis described here differ from those of the above species in their less rounded shape, the pectiniform projections seen on their caudal surface, and the spherical shape of the polar capsule. These differences are striking even if we consider that, according to Dyková and Lorn (1982), lateral tubercles (ear-like projections) are typical of young spores only and can be regarded as remnants of valvogenic nuclei. The possible identity of S. danubialis with S. pectinacea is a much more controversial question. Namely, both species are characterized by the presence of ribs on the spore surface and characteristic pectiniform projections on the caudal part of the spore. However, as is evidenced by the original drawings of Bocharova and Donets (1974) and the photographs taken by Lorn et al. (1989), the triangular spores of S. pectinacea strikingly differ in shape from the rounded spores of S. danubialis. In this respect, the studies of Pronin and Pronina (1985) are remarkable. Although they identified the spores found in Perca fluviatilis with the species S. pectinacea, morphologically their spores were more similar to those of S. cristata, a parasite of Gasterosteus aculeatus. In spore morphology S. danubialis indeed resembles this Sphaerospora parasitizing a taxonomically distant host. The host specificity of Sphaerospora species is insufficiently known. Therefore, the validity of a given species is primarily based on spore morphology. The only thing which has been confirmed experimentally is that Sphaerospora blood stages can be transmitted from goldfish to common carp (Körting et al. 1989). It is very likely that a given Sphaerospora species can infect several taxonomically related hosts. Based upon this assumption, the species described here as S. danubialis from G. schraetzer as typical host is, in all likelihood, identical with those found in G. cernua and S. lucioperca. Further studies are needed to elucidate why the perch (Perca