Plasma Lysozyme Levels and Secondary Stress Response in Rainbow Trout, Oncorhynchus mykiss (Walbaum) after Exposure to Leteux-Meyer Mixture


Abstract: Leteux-Meyer mixture (LMM) contains formalin and malachite green and can be externally applied to fish as an antimicrobial agent. To determine the effects of prophylactic treatment with LMM on plasma lysozyme levels and the secondary stress indices, alterations in plasma glucose, chloride, sodium, potassium and hematocrit were monitored in healthy rainbow trout, Oncorhynchus mykiss W. Fish were i) exposed to 25 ppm Leteux-Meyer mixture for 60 min and ii) the same treatment followed by 60 min recovery in clean freshwater. Treatment with LMM resulted in a decrease in plasma lysozyme values. After a recovery period of 60 min plasma lysozyme levels were not restored to control values. Treatment of fish with LMM elicited marked elevations in plasma glucose and plasma potassium values. Plasma chloride and sodium values dropped after LMM treatment. Recovery for 60 min was not sufficient to restore the electrolyte levels. Hematocrit values were not affected by LMM treatment.

Keywords: Oncorhynchus mykiss, rainbow trout, Leteux-Meyer mixture, secondary stress, plasma lysozyme

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