Department of Zoology, S.B.S. Government College, Hili, Dakshin Dinajpur, 733126 West Bengal, India.
Department of Zoology, Sundarban Hazi Desarat College, South 24 Parganas, 743 611 West Bengal, India.
Sci Total Environ. 2022 Aug 25;836:155716. doi: 10.1016/j.scitotenv.2022.155716. Epub 2022 May 5.
The hydrophilic nature and resultant persistence of neonicotinoids in aquatic systems increase the exposure duration for non-target organisms. The sublethal toxicity of the neonicotinoid Thiamethoxam® spanning sub-chronic and chronic durations was investigated in Clarias batrachus, a non-target freshwater fish species. 96 h LC value of Thiamethoxam® on Clarias batrachus was 138.60 mg L. Pre-determined exposure concentrations of Thiamethoxam® (6.93 and 13.86 mg L) were used and effects were assessed at days 15, 30, and 45 exposure intervals. Biomarker effects were evaluated using antioxidant enzyme responses (CAT, SOD) neurotransmission (acetylcholinesterase activity), haematological and serum biochemistry changes (including haemoglobin content, total erythrocyte count, and serum albumin total leukocyte count, total serum protein, serum globulin, triglyceride, cholesterol, high-density lipoprotein, very low-density lipoprotein, low-density lipoprotein, phospholipid, and total serum glucose), histopathological alterations (gill and liver). Thiamethoxam®-exposed fish showed a marked reduction in haemoglobin content, total erythrocyte count, and serum albumin levels compared to control fish. Similarly, gill and liver antioxidant enzyme activity (CAT, SOD) and neurotransmission (acetylcholinesterase) also showed altered responses between sub-chronic exposure on day-15 and chronic responses on day-45. Histopathological observations in gill tissue revealed alterations ranging from vacuolation, hypertrophy, disruption of primary lamellar architecture, haemorrhage, the fusion of secondary lamella, and sloughing of outer epithelia. For liver tissue of exposed fish histopathological observations included increased sinusoidal spaces (ISS), necrosis of hepatocytes (NOH), nuclear degeneration (ND), disruption of architecture (DOA), macrophage infiltration of the central vein, vacuolation (V), hypertrophied hepatocytes, and haemorrhages. The gradients of toxic responses across exposure concentrations and depictions of impaired fish health with increasing thiamethoxam® exposure duration portend lowered physiological capacity for survival in the wild.
新烟碱类杀虫剂具有亲水性，在水生系统中持久存在，这增加了非靶标生物的暴露时间。本研究调查了新烟碱类杀虫剂噻虫嗪对非靶标淡水鱼类物种斑鳢（Clarias batrachus）的亚慢性和慢性暴露期间的亚致死毒性。噻虫嗪对斑鳢的 96 h LC 值为 138.60 mg/L。使用预定量的噻虫嗪暴露浓度（6.93 和 13.86 mg/L），并在 15、30 和 45 天的暴露间隔时间评估效果。使用抗氧化酶反应（CAT、SOD）、神经传递（乙酰胆碱酯酶活性）、血液学和血清生化变化（包括血红蛋白含量、总红细胞计数和血清白蛋白、总白细胞计数、总血清蛋白、血清球蛋白、甘油三酯、胆固醇、高密度脂蛋白、极低密度脂蛋白、低密度脂蛋白、磷脂和总血清葡萄糖）、组织病理学改变（鳃和肝脏）来评估生物标志物的影响。与对照鱼类相比，噻虫嗪暴露的鱼类血红蛋白含量、总红细胞计数和血清白蛋白水平明显降低。同样，鳃和肝脏抗氧化酶活性（CAT、SOD）和神经传递（乙酰胆碱酯酶）在亚慢性暴露第 15 天和慢性暴露第 45 天之间也表现出不同的反应。鳃组织的组织病理学观察显示，从空泡化、肥大、初级鳃片结构破坏、出血、次级鳃片融合、外上皮脱落等变化。暴露鱼类肝脏组织的组织病理学观察包括窦状隙（ISS）增加、肝细胞坏死（NOH）、核变性（ND）、结构破坏（DOA）、中央静脉巨噬细胞浸润、空泡化（V）、肥大的肝细胞和出血。随着暴露浓度的增加，毒性反应的梯度以及随着噻虫嗪暴露时间的增加鱼类健康受损的描述，预示着在野外生存的生理能力降低。
