Effects of various treatments on hatching of eggs and viability of oncomiracidia of the monogenean Pseudodactylogyrus anguillae and Pseudodactylogyrus bini

In this study, effects of potassium permanganate, trichlorfon, methylene blue, sodium chloride or chlorine treatments on elimination of hatched Pseudodactylogyrus oncomiracidia were examined in order to control Pseudodactylogyrus infections and to disinfect equipment used in eel culture. Effects of potassium permanganate, trichlorfon, methylene blue, sodium chloride, chlorine, heat or drying treatments on hatching ability of the Pseudodactylogyrus eggs were also examined. Our results show that 5-h treatment by 2-20 mg l(-1) potassium permanganate and 2.5-3.4% sodium chloride had an antiparasitic effect against the oncomiracidia; these two treatments were more effective than other treatments examined in this study except the chlorine treatments. Hatching rate in the group treated with 10 mg l(-1) methylene blue for 12 h was significantly lower than that of the control. However, these chemical treatments did not kill the oncomiracidia or the eggs completely. It is suggested that several consecutive days of the chemical treatments are needed to prevent Psedodactylogyrus infections. The oncomiracidia were completely killed by exposing to 24 and 60 mg l(-1) chlorine for 3 h. Eggs were partially killed by exposing to 12 and 36 mg l(-1) chlorine and drying for 1 and 24 h. It was shown that several consecutive days of these treatments are needed to disinfect equipment. The results obtained from the present study could be useful for developing effective methods of controlling the parasite. (C) 2005 Elsevier B.V. All rights reserved.