Gill histopathological characteristics of Caspian roach (Rutilus rutilus caspicus) fingerlings treated with potassium permanganate and formalin

Abstract

The aim of this study was to determine the gill histopathological characteristics of Caspian roach (Rutilus rutilus caspicus) fingerlings exposed to different concentrations of potassium permanganate (PM) and formalin (FO). The fish were exposed to different PM and FO concentrations over different periods: 1 ppm PM for 24 h (1-P24), 2 ppm PM for 24 h (2-P24), 5 ppm PM for 0.5 h (5-P0.5), 10 ppm PM for 0.5 h (10-P0.5), 10 ppm FO for 24 h (10-F24), 20 ppm FO for 24 h (20-F24), 40 ppm FO for 0.5 h (40-F0.5) and 80 ppm FO for 0.5 h (80-F0.5). After exposure, gill samples were collected for histological examination. The most frequent gill histopathological symptoms were hyperplasia and epithelial lifting. The order of the gill injury index (Ig.i) among the treatments was as follow: 1-P24, 2-P24 < 5-P0.5, 40-F0.5 < 10-F24 < 10-P0.5, 20-F24, 80-F0.5. Comparing the two agents, it is concluded that there is no significant difference in the gill damages between the agents during the short-bath treatments. However, PM causes less pathological symptoms than FO during the long-bath treatments. Comparing the bath durations, the agents showed different behaviours. PM-treated fish showed significantly lower gill damage during the long-bath compared to the short-bath treatment; whereas, pathological symptoms of FO-treated fish was dose-dependent for each exposure period, separately. Overall, exposure of Caspian roach to PM, at the concentrations recommended for long bath, resulted in milder gill damages compared to FO.