the Epistylis sp. and temperature was found at the Morón farm, a finding that is consistent with the results of Hüsey and Selcuk (2005).In our study, the DO showed a significant inverse correlation with the Zoothamnium sp. and Epistylis sp., indicating that the prevalence of
both ciliates decreases as the DO increases. Only a few previous reports have addressed the statistical relationship of ciliates with the DO levels. Because higher DO concentrations are expected in ponds with less organic matter and other nutrients, fewer bacteria and epi-
bionts will occur in these ponds. In the present study, the Epistylis sp. was also negatively correlated with the pH. Although Jayasree et al. (2001) reported that the prevalence and mean intensity of infection of ciliates were negatively correlated with the salinity (r=−0.74 and −0.56), these authors did not find any correlation between ciliate abundance and any of the parameters tested in the present study.