Toxic Effects of Arsenic in Commercially Important Fish Rohu Carp, Labeo rohita of Bangladesh

Abstract

This study was designed to elucidate the effects of arsenic (As) on the morpho-behavior, growth development and molecular mechanisms of a commercially important fish, rohu carp, Labeo rohita, in Bangladesh. Fish fry with an average weight of 387.5 ± 169.25 mg and an average length of 3.35 ± 0.37 cm were collected from a local hatchery in Mymensingh, Bangladesh and acclimatized for a week in the Department of Fisheries, University of Dhaka before starting the exposure with arsenic. Fishes were exposed for a period of 14 days with three treatments of NaAsO2, namely treatment 1(T1)—2.5 mg/L; treatment 2 (T2)—15 mg/L; and treatment 3 (T3)—30 mg/L, along with a control (C)—0.0 mg/L, with three replicates. These concentrations were determined based on the LC50 value for 96 h measured for this experiment. This study revealed remarkable morphological abnormalities and deformities in arsenic-exposed rohu carp. In fish exposed to 30 mg/L, caudal fin erosion was a frequent deformity. There was no significant difference in RNA:DNA ratio among the treatments. The overall weight of fish was decreased as the concentration of arsenic was increased. The T3 fish had a statistically significant negative weight gain (−0.05 ± 0.07 g), but the other treatments (T1 and T2) and control fish had no significant weight gain. Different types of histopathological changes were observed in the gills and intestines of arsenic-treated fish. Necrosis and severe damages were found in the secondary lamellae of gills at the highest arsenic concentration (30 mg/L). Epithelial lifting, irregular shape and damages in the gill raker were also observed in the primary lamellae of the gills for the same treatment. In this study, the expression of heat shock protein (HSP 60) and metallothionein (MT) genes was assessed by qPCR, and these genes were upregulated in different treatments compared to controls. The findings of the present study suggest that arsenic pollution significantly changes the morphology, behavior, growth, development, histopathology and molecular mechanisms of this economically important fish, rohu carp, in Bangladesh.