Three amoeba species were isolated from 3 out of 193 farmed tilapias, Oreochromis niloticus (L.), screened for the presence of free-living amoebae in parenchymatous organs. Hartmannella vermiformis Page, 1967 and Rosculus ithacus Hawes, 1963 were isolated from the kidney tissue. The third strain isolated from the liver shared morphological features of Mayorella and Platyamoeha spp. and therefore its taxonomic position has not been determined as yet. Pathogenicity of cloned strain of H. vermiformis was proved in two fish hosts.
Ninety four aquarium fishes were screened for the presence of amoebae in their internal organs. Five specimens of Ca-rassius auratus (L.) and one specimen of Xiphophorus hetleri Heckel were positive. Of the three strains which were isolated from C. auratus, successfully cloned and cultivated, one was identified as Vannella platypodia (Gläser, 1912) Page, 1976 and two strains as Rosculus ithacus Hawes, 1963. Both species are reported for the first time from organs of fish. None of them could be identified with the amoeba-like agent of goldfish granulomas described here.