Abstract
Recently an infection with a ciliate was found at a guppy (Poecilia reticulata) farm in Thailand. The clinical signs were scale loss and skin ulcer. The ciliate obtained from lesions of the diseased fish was identified as Tetrahymena corlissi based on the morphological characteristics. This is the first report of the disease in guppy caused by T. corlissi in Thailand. This paper describes some biological characteristics of T. corlissi isolates for the basis of treatment of the disease. The optimum temperature for the parasite reproduction was in the range of 25 to 35°C, but it multiplied slowly at 10 and 15°C. Multiplication was optimum in the pH range of 5.0-7.0, while, at pH 3.0 and pH 12.0, the parasite died within a few minutes. The guppies experienced high mortality at pH 4.0 and pH 11.0, while they did not die at pHs in the range of 5.0 to 9.0. The parasite survived in the PPYG medium when NaCl concentration was lower than 0.5%, but died in the medium when it was higher than 1.0%. All guppies survived for 12 h when exposed to 1.5% NaCl, for 6 h and 2 h when exposed to 2.0% and 2.5% NaCl, respectively. Whitish lesions appeared several days after the guppies were challenged with the parasite. All dying fish had many parasites in the lesions.
