Systemic ciliatosis caused by histophagous ciliates constitutes a serious disease of cultured turbot. Six ciliate isolates were obtained from parasitized turbot during six epizootics at four different farms located in Spain, France and Portugal. Axenic cultures of the six isolates were obtained by periodical subculturing in ATCC 1651MA or supplemented L-15 media. In basal media or seawater, the parasites could survive starving for long periods with no apparent proliferation. In adequate media, growth kinetics was found to be very similar for isolates A and B, with a clear influence of temperature. Morphological studies demonstrated that all isolates share common features that allows their assignment to either Philasterides Kahl, 1931 or Miamiensis Thompson et Moewus, 1964. However, statistically significant differences were evident in pairwise comparisons of the isolates from the four farm sites in 16 taxonomically relevant morphometric features. This could allow the discrimination of different species or strains. Virulence of isolates A and B for healthy turbot was tested in several experiments. Differences in the virulence were especially evident after long-term in vitro culturing, isolate A being clearly attenuated after 35-42 passages, whereas isolate B became more virulent after 20-42 passages. The need of further studies to confirm such virulence variability and its implications in pathogenesis and prevention of turbot scuticociliatoses is stressed.
During surveys of parasites of the whitemouth croaker Micropogonias furnieri (Desmarest) and the mullet Mugil platanus Günther from Samborombón Bay, Argentina, Trichodina puytoraci, T. lepsii, T. jadranica, T. murmanica, Diparitella simplex and Trichodina scalensis sp. n. were morphologically studied. Taxonomic and morphometric data for these trichodinids based on dry silver nitrate-impregnated specimens are presented. This study is the first formal report of these trichodinids from the southwest Atlantic Ocean, and the description of a new species from M. platanus.