[Morphological characteristics and certain biological problems of the representatives of the genus Apiosoma (Infusoria, Peritricha) from the young of predatory fishes].

13 species of Apiosoma were recorded from the young of Esox lucius, Lota lota and Perca fluviatilis. 7 species were reported from Lota lota, 9 species-from Esox lucius and 6 species--from Perca fluviatilis. Apiosomes were found mainly on the body surface and fins of fishes and move seldom on their gills. Under changing conditions the transition of parasites from one organ to another is possible. Great morphological variability of Apiosoma is reflected in variability of shape and size of the body and mutual arrangement of micro--and macronucleus. The solution of the variability problem is necessary for the classification of the genus Apiosoma. A new species, Apiosoma lotae, and subspecies, Apiosoma piscicola percae, are described.