【作者】 王春凤；

【导师】 方展强；

【作者基本信息】 华南师范大学 ， 动物学， 2004， 硕士

【摘要】 本研究中首先调查了广州市河涌沉积物及底栖生物体内重金属含量及分布，并以珠江水产研究所培育的水生实验动物—剑尾鱼为实验材料，利用环境生物技术，电镜观察等技术方法研究了重金属—汞对剑尾鱼组织的毒害及机体必需微量元素硒对其毒害的拮抗性影响。研究内容主要有：广州市河涌沉积物及底栖生物体内重金属含量及评价；汞和硒对剑尾鱼的急性毒性和联合毒性及安全浓度的评价；汞对剑尾鱼鳃和肝脏中抗氧化系统的毒性，包括对总抗氧化能力、超氧化物歧化酶、谷胱甘肽过氧化物酶活力及丙二醛含量的测定及硒对其保护作用；汞对剑尾鱼组织生理毒性即：汞对Na⁺-K⁺／ATPase活力的影响及硒的保护作用和汞和对剑尾鱼组织超微结构的损伤等。 以高氯酸—硝酸消化法和火焰原子吸收分光光度法测定了广州市河涌沉积物和底栖生物中重金属含量。结果显示：沉积物中Cd，Cu，Zn，Pb，Cr，Ni的平均含量分别为：5.61，302.12，727.03，163.37，67.70，84.58μg／g干重。底栖生物中Cd，Cu，Zn，Pb，Cr，Ni的平均含量分别为：0.78，29.20，268.38，10.75，3.89，3.44μg／g干重。表明广州市河涌已受到不同程度的重金属污染，受污染最严重的是赤岗涌、海珠涌和棠下涌，工业活动是造成污染的主要原因。河涌中的水栖寡毛类与沉积物中的重金属含量显著相关（p＜0.01）。 采用静水法生物测试了汞(Hg²⁺)和硒(Se⁴⁺)对剑尾鱼的急性毒性和联合毒性。结果表明：Hg²⁺对剑尾鱼的24、48、96h的LC₅₀分别为1.71、1.35、0.84mg／L；Se⁴⁺对剑尾鱼24、48、96h的Lc₅₀分别为17.91、12.59、6.64mg／L；在浓度和毒性比都为1：1的条件下，24h都表现联合作用，而48h、96h则为拮抗作用，结果还表明，剑尾鱼对汞和硒敏感，是一种较理想的环境污染指示生物。 浸浴法处理剑尾鱼鱼种，检测鳃和肝脏抗氧化系统指标（T-AOC，SOD，GSH-Px和MDA）的毒害及膜损伤的变化等，以研究剑尾鱼在重金属离子Hg²⁺胁迫下微量元素Se⁴⁺的缓解效应。结果显示：各浓度的汞离子均对剑尾鱼鳃和肝脏组织的抗氧化系统、保护酶系统、膜系统等具有明显的毒害作用。抗氧化酶系统在受到低浓度及染毒初期的一定限度内能被诱导而加强，但随着重金属毒害加深而减弱，尤其是肝组织。混合处理后，与单一汞处理相比，se⁴⁺在一定程度上能有效抑制汞胁迫引起的T—AOC，SOD，GSH—Px的降低，降低膜脂质过氧化水平，减轻了对膜的硒对汞致剑尾鱼抗氧化系统的毒害和生理损伤的拮抗作用损伤，表现为随一K+/ATPase活力升高，而MDA含量降低，提高了机体对Hg叶毒害的抗性;但随着染毒时间延长，硒不能最终阻止毒害的加深。单一硒处理时，可使组织T一AOC和ATPase活力显著提高。 利用透射电镜技术观察了HgZ+对剑尾鱼鳃和肝脏组织细胞超微结构的损伤。结果发现，HgZ十暴露对鳃细胞的影响主要表现在鳃丝外表面肿大，基膜部分断裂，上皮细胞间出现非组织空腔，柱细胞异形，氯细胞数量增加，线粒体结构破坏，内峭脱落等。对肝脏的损伤表现为肝细胞坏死或解体，出现细胞空泡化，胞质中线粒肿胀或溶解，微绒毛大量脱落，部分微绒毛出现空泡化，脂滴和糖原颗粒明显减少，表明汞暴露使剑尾鱼呼吸，能量及物质代谢等一系列正常的生理功能受到严重影响。更多还原

【Abstract】 On the basis of the investigation of the content and distribution of heavy metals in sediments and benthic organisms from the sewage stream in Guangzhou city, the antagonistic effect of selenium on the harm of mercury (Hg2+) to the tissues in swordtail fish (Xiphophorus helleri), the 22nd offspring purely cultivated by Pearl River Fishery Research Institute, were measured by physiological and biochemical indexes and observation of electron microscopy. The main study in this paper included as follows: the content and distribution of heavy metals in sediments and benthic organisms from the sewage stream in Guangzhou city; the acute toxicity and joint toxicity of mercury and selenium to swordtail fish (Xiphophorus helleri); the damage of mercury to the indexes of antioxidant system in the gills and livers in swordtail (including the measurement of the activities of total antioxidative capacity[T~AOC], Superoxide dismutase [SOD], Glutathione peroxidase[GSH-Px] and the concentration of malondiald-ehyde [MDA])and the relief effects of selenium on it, as well as the physiological damage of mercury on the tissues, namely: the antagonistic effect of Na+-K+~ATPase activity on the tissues between selenite and mercury, and the ultrastructural damage under the exposure of mercury.Employing the flame atomic absorption spectrophotometer, we measured and evaluated the concentrations and distribution of heavy metals in sediments and benthic organisms collected from the sewage stream in Guangzhou. The average concentrations of Cd, Cu, Zn, Pb, Cr, Ni in sediments were 5. 61, 302.12, 727.03, 163.37, 67.70, 84. 58 g/g dry wt ; 0.78, 29.20, 268.38, 10.75, 3.89, 3. 44 Mg/g dry wt in benthic organisms, respectively. The results indicated that all streams in Guangzhou have been polluted by heavy metals in different degree. Chigang stream, Haizhu stream and Shangxia stream are the most serious. Industry activities are responsible for the pollution mainly. The concentrations of heavy metals in benthos(aquatic oligochaetes) is remarkablely correlated with that in sediments (P<0. 01, P<0. 05), so the former can be used as bioindicator of Ni, Cu and Cr.The acute and joint toxicity to swordtail fish (Xiphophorus helleri) were studied in the present test. The LC50 of divalent mercury to swordtail fish were 0.84, 1.35, 1.71 mg/L in 24, 48 and 96 h respectively. The LC50 of tetravalent selenium to swordtail fish were 6.64, 12.59, 17.91 mg/1, respectively. The joint toxicity of the two toxicants to swordtail fish was synergistic in 24 h and antagonistic in 48h and 96h, both when treated as the ratio 1:1 of toxicity and concentration. The results also showed that since the high sensitivity to mercury and selenium, the swordtail fish could be a relatively ideal environmental biomarker.The swordtails were exposed to Hg2+ and Se4+ for 7 d and by examining the change of the antioxidant T-AOC, SOD, GSH-Px and MDA gills and liver tissues, we researched the protective effect of microelement Se4+ on the heavy metal mercury (Hg2+), the results showed that obvious damages to the antioxidant system and membrane system by all the selected con- centrations of Hg2+. The antioxidant abilities of protective enzymes were enhanced in restricted range by Hg2+ stress in the early period and the lower concentrations, which were weaken because of the further exposure,especially in liver. Compared to the single Hg2+ treated, se4++Hg2+ the mixed exposure could restrain the fall of the activity of T?AOC, SOD and GSH ?Px, reducing the level of lipid peroxidation, and alleviating membrane damage, represented with the heighten Na+-K+-ATPase activity and reduced MDA concentration, resulting in the increased resistance to Hg2+damage. However, Se4+ were incapable of preventing from the damage of Hg2+ ultimately, along with the exposure period, regardless of the fact that the obvious enhancement of T- AOC and ATPase activity.Applying electric microscopic technique, we oberserved theultrastructure of gill and liver in the swordtails treated with更多还原