Blood stages of Sphaerospora spp. (Myxosporea) in cyprinid fishes

A total of 398 specimens of 14 cyprinid species were examined for the presence of renal sphaerospores and Sphaerospora blood stages (C blood protozoa). Sphaerospora infection of the kidney was demonstrated in 122 fish of 12 species, and blood stages were found in the blood of 30 fish of 6 species. Blood stages only occurred in f.ish infected by renal sphaerospores and were primarily demonstrable in fingerlings. Blood forms found in asp Aspius aspius and white bream Bllcca bloerkna differed from those described earlier and contained 16 to 32 secondary cells resembling Sphaerospora swmbladder stages (K protozoa) of common carp. In the blood stages observed in bleak Alburnus alburnus, secondary cells were sit.uated together in an inclusion-like mass within the primary cell, with 1 to 4 nuclei. In bleak and white bream, forms consisting of 1 secondary and 2 tertiary units were also demonstrable. These can be identified as the earliest renal stages of Sphaerospora species. Organisms circulating in the blood so far referred to as 'C blood protozoa' are probably the early developmental stages of renal sphaerospores.