EFFECTS OF DIFFERENT MALACHITE GREEN DERIVATIVES AND METABOLITES ON THE FISH ECTOPARASITE, ICHTHYOPHTHIRIUS-MULTIFILIIS, FOUQUET 1876 (HYMENOSTOMATIDA, CILIOPHORA)

For the control of fish ectoparasites malachite green is one of the mo st important fishtherapeutics. This triphenylmethane dye exists in dif ferent derivatives, in the acid pH-range as the coloured salt, in the basic range as the carbinolbase and as the reduced leuco-compound. In microorganisms p-dimethylaminobenzophenone and N,N-dimethylaniline wer e found as some possible primary metabolites. In the present investiga tion the efficacy of these different derivatives and metabolites again st the skin-inhabiting stage of Ichthyophthirius multifiliis were test ed. It was demonstrated that only the coloured form and the carbinolba se were effective against the parasite. In addition, it was shown that there were no differences between fish species with a stomach, which have a low pH-value inside the stomach, and fish species without a sto mach, which have a high pH-value due to the digestive tract. In electr on microscopy investigations also only the coloured form and the carbi nolbase had any deleterious effects on the parasites' structure, causi ng the same kind of damages.