The effect of long-term therapeutic bath of Malachite green on common carp (Cyprinus carpio L.)

Abstract

The aim of this paper was to determine acute toxicity of malachite green of the Vert Malachite J3E SA Crystaux type for common carp and to evaluate the effect of a 6-day therapeutic bath in 0.5 mg.l-1 concentration of this pharmaceutical on values of selected haematological indicators including micronuclei test, as well as on histological composition of tissues of one- to two-year-old carp. The 48hLC50 value of the malachite green tested was 0.84 mg.l-1. After the 6-day bath, changes in red blood picture [decrease in haematocrit value - PCV (P<0.001), decrease in mean corpuscular volume - MCV (P<0.05) and increase in mean corpuscular haemoglobin concentration - MCHC (P<0.01)] as well as in white blood picture/decrease in both relative and absolute monocyte count (P<0.05 and P<0.01), respectively/ were recorded in treated fish (n=30) compared to the control group (n=29). Other indices of red and white blood picture in these fish did not differ from the control group. A decrease in total protein concentration (TP, P<0.01) in blood plasma was found in fish treated with malachite green. By means of a micronuclei test, no effect of long-term bath in malachite green on increase of their frequency in erythrocytes was proved. Histological examination revealed mild regressive changes on gills, mild dystrophic changes in parenchymatous tissues and an increased macrophage activity in treated fish. These changes indicate an increased sensitivity of the fish treated with malachite green to hypoxia and impaired proteosynthesis.