Brachymystax tsinlingensis Li is a threatened fish species endemic to China. With the problems of environmental factors and seeding breeding diseases, it is important to further improve the efficiency of seeding breeding and the basis of resource protection. This study investigated the acute toxicity of copper, zinc and methylene blue (MB) on hatching, survival, morphology, heart rate (HR) and stress behaviour of B. tsinlingensis. Eggs (diameter: 3.86 ± 0.07 mm, weight: 0.032 ± 0.004 g) of B. tsinlingensis were selected randomly from artificial propagation and developed from eye-pigmentation-stage embryos to yolk-sac stage larvae (length: 12.40 ± 0.02 mm, weight: 0.03 ± 0.001 g) and exposed to different concentrations of Cu, Zn and MB for 144 h in a series of semi-static toxicity tests. The acute toxicity tests indicated that the 96-h median lethal concentration (LC50 ) values of the embryos and larvae were 1.71 and 0.22 mg l-1 for copper and 2.57 and 2.72 mg l-1 for zinc, respectively, whereas the MB LC50 after 144-h exposure for embryos and larvae were 67.88 and 17.81 mg l-1 , respectively. The safe concentrations of copper, zinc and MB were 0.17, 0.77 and 6.79 mg l-1 for embryos and 0.03, 0.03 and 1.78 mg l-1 for larvae, respectively. Copper, zinc and MB treatments with concentrations greater than 1.60, 2.00 and 60.00 mg l-1 , respectively, led to a significantly low hatching rate and significantly high embryo mortality (P < 0.05), and copper and MB treatments with concentrations greater than 0.2 and 20 mg l-1 led to significantly high larvae mortality (P < 0.05). Exposure to copper, zinc and MB resulted in developmental defects, including spinal curvature, tail deformity, vascular system anomalies and discolouration. Moreover, copper exposure significantly reduced the HR of larvae (P < 0.05). The embryos exhibited an obvious change in behaviour, converting from the normal behaviour of emerging from the membrane head first to emerging tail first, with probabilities of 34.82%, 14.81% and 49.07% under copper, zinc and MB treatments, respectively. The results demonstrated that the sensitivity of yolk-sac larvae to copper and MB was significantly higher than that of embryos (P < 0.05) and that B. tsinlingensis embryos or larvae might be more resistant to copper, zinc and MB than other members of the Salmonidae family, which benefits their resource protection and restoration.
秦岭细鳞鲑 (Brachymystax tsinlingensis Li, 1966)是我国特有濒危陆封型冷水鱼类，随着环境改变和苗种培育疾病等问题突显，为进一步提高其苗种培育效率及资源保护范围，本研究随机挑选经人繁的同批次秦岭细鳞鲑受精卵 (卵径为3.86±0.07 mm，卵质量为0.032±0.004 g)，采用半静态方式对其胚胎眼色素出现期至卵黄囊仔鱼期 (全长为12.40±0.02 mm，体质量为0.03±0.001 g)进行不同浓度的铜离子、锌离子和亚甲基蓝暴露试验，实验周期为144 h。结果显示，铜和锌分别对秦岭细鳞鲑胚胎和仔鱼的96 h LC50值为1.71mg/L和0.22 mg/L，2.57 mg/L和2.80 mg/L；亚甲基蓝对其胚胎和仔鱼的144h LC50值分别是68.86 mg/L和17.81 mg/L。重金属铜、锌，亚甲基蓝对秦岭细鳞鲑胚胎及仔鱼的安全浓度 (safe concentration，SC)分别为0.17mg/L，0.77 mg/L和6.89 mg/L，0.03 mg/L，0.03 mg/L和1.78 mg/L。当重金属铜、锌和亚甲基蓝的浓度分别高于1.60 mg/L，2.00 mg/L和60.00 mg/L时，秦岭细鳞鲑胚胎孵化率显著降低、胚胎死亡率显著升高(P<0.05)，而当铜和亚甲基蓝浓度高于0.20 mg/L和20.00 mg/L导致仔鱼死亡率显著升高(P<0.05)。重金属铜、锌和亚甲基蓝暴露可导致秦岭细鳞鲑胚胎和仔鱼发育缺陷，包括脊柱弯曲、尾巴畸形、血管系统缺陷和异常色素沉着等。此外，铜暴露显著降低秦岭细鳞鲑仔鱼的心率(P<0.05)。秦岭细鳞鲑胚胎暴露于重金属铜、锌，及亚甲基蓝时都表现出明显规避现象，即由正常情况下的头部破膜转变为尾部破膜，其累积概率分别为34.82%，14.81%和49.07%。研究结果表明，秦岭细鳞鲑卵黄囊期仔鱼对铜和亚甲基蓝的敏感度显著高于胚胎期(P<0.05)，且秦岭细鳞鲑胚胎和仔鱼对重金属铜、锌和亚甲基蓝的耐受性高于鲑科其它种鱼类，该研究结果可为秦岭细鳞鲑的疾病治疗和环境耐受性提供基础数据，有利于其资源保护和恢复。.
Keywords: Brachymystax tsinlingensis; biocide; copper; methylene blue; toxicity assessment; zinc.
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