Survival, and biochemical, physiological, and histopathological responses of the giant freshwater prawn, Macrobrachium rosenbergii, to short-term trichlorfon exposure

The toxicity of trichlorfon was determined in Macrobrachium rosenbergii and the 24-, 48-, 72-, and 96-h LC50 values were 0.7739, 0.3513, 0.2697, and 0.2555 mg l− 1, respectively. Prawns were exposed for 24 h to 0, 0.2, and 0.4 mg l− 1 trichlorfon. Then, certain biochemical and physiological parameters, including acetylcholinesterase (AChE) activity, glucose, lactate, and glycogen contents, and the hemolymph osmolality, ions, and acid–base balance were measured. For prawns in the 0.4 mg l− 1 trichlorfon group, decreased AChE activities of the hemolymph and hepatopancreas, decreased glycogen contents of the hepatopancreas and muscle, decreased osmolality, Cl−, Na+, pCO2, HCO3−, and TCO2 levels of the hemolymph, increased glucose contents of the plasma, hepatopancreas, and muscle, increased lactate contents of the plasma, hepatopancreas, and muscle, and increased pH and pO2 levels of the hemolymph were observed. Similar results were also observed for the prawns exposed to 0.2 mg l− 1 trichlorfon except for lactate in the hepatopancreas and the pH of the hemolymph. Gills of prawns exhibited hemocytic infiltration in the hemocoelic space, swelling and fusion of the lamellae, and necrotic, hyperplastic, and clavate–globate lamellae with exposure to 0.4 mg l− 1 trichlorfon. These results suggest that the reduction in AChE activity and alteration of the histopathology of the gills in M. rosenbergii resulted in variations in carbohydrate metabolism, osmotic and ionic regulation, and the base–acid balance in an attempt to resist and adapt to trichlorfon stress.