The present investigation aimed to evaluate the long-term effects of malathion (Elathion®) at two sub-lethal concentrations (0.36 and 1.84 mgL⁻¹) for 45 days after the determination of 96 h-LC₅₀ value (18.35 mgL⁻¹) in a commercially important aquaculture species, Labeo rohita by assaying multiple biomarker approaches. Total erythrocyte count (TEC), and haemoglobulin count (Hb) were found to be decreased while total leucocyte counts (TLC) were increased (p < 0.05) in malathion-intoxicated fish. Malathion exposure significantly reduced (p < 0.05) serum protein levels while significantly increased (p < 0.05) blood glucose levels. RNA activity in muscle was reduced (p < 0.05) while DNA activity increased (p < 0.05) in malathion-intoxicated fish. Acid phosphatase (ACP) activities in the brain; lacate dehydrogenase (LDH) activities in brain and liver were increased (p < 0.05), while alkaline phosphatase (ALP) activities in the brain; succinate dehydrogenase (SDH) activities in the brain, liver and kidney; acetylcholine esterase (AChE) activity in the brain; and ATPase activities in the brain, liver and kidney were reduced (p < 0.05) in comparison to control. Thus, the alteration in studied biomarkers was in a concentation-time dependent manner; however, it was more pronounced at the higher concentration at 45 days of exposure. The alteration in biomarker activity is probably a defensive mechanism/ adaptive response of fish to overcome the stress induced by malathion, which is a novel insight and possible impact on L. rohita. Our findings suggest malathion-induced stress, therefore, the use of malathion needs to be regulated to safeguard aquatic animals including fish and human health.

^{本研究旨在评估马拉硫磷 (Elathion®) 在两种亚致死浓度（0.36 和 1.84 mgL -1}）测定 96 h-LC ₅₀值（18.35 mgL ^-1）后 45 天的长期影响通过检测多种生物标志物方法，在商业上重要的水产养殖物种Labeo rohita中进行了检测。 发现马拉硫磷中毒的鱼的总红细胞计数 (TEC) 和血球蛋白计数 (Hb) 减少，而总白细胞计数 (TLC) 增加 ( p < 0.05)。马拉硫磷暴露显着降低（p  <0.05）血清蛋白水平，同时显着增加（p  <0.05）血糖水平。马拉硫磷中毒的鱼肌肉中的RNA活性降低（p < 0.05），而 DNA活性增加（p < 0.05）。大脑中的酸性磷酸酶（ACP）活动；大脑和肝脏中的乳酸脱氢酶（LDH）活性增加（p  <0.05），而大脑中的碱性磷酸酶（ALP）活性增加；大脑、肝脏和肾脏中的琥珀酸脱氢酶 (SDH) 活性；大脑中乙酰胆碱酯酶（AChE）的活性； 与对照组相比，大脑、肝脏和肾脏中的 ATP 酶活性降低 ( p < 0.05)。因此，所研究的生物标志物的变化呈浓度-时间依赖性方式。然而，在暴露 45 天时浓度较高时，这种现象更为明显。生物标志物活性的改变可能是鱼类克服马拉硫磷引起的应激的一种防御机制/适应性反应，这是一种新颖的见解，也可能对L. rohita产生影响。我们的研究结果表明，马拉硫磷会引起应激，因此，需要规范马拉硫磷的使用，以保护包括鱼类在内的水生动物和人类健康。