【作者】 黄伟；

【导师】 窦硕增；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋生态学， 2010， 博士

【摘要】 本论文选取我国近海典型重金属污染物汞、锌、铅,在实验室条件下(温度18±1°C;盐度33‰)分别研究它们对褐牙鲆Paralichthys olivaceus早期生活(胚胎、仔稚鱼)阶段的毒理效应,揭示重金属污染对褐牙鲆早期生活阶段的致毒机制,为研究近海污染条件下鱼类资源衰退机理及利用其监测海洋重金属污染提供科学依据。胚胎、仔鱼急性毒理实验表明,Hg2+对褐牙鲆胚胎的24-h和48-h LC50值(半致死浓度)分别为75.8(70.1-81.5,95%置信区间)和48.1(32.8-63.6)μg L-1;对仔鱼的24-h,48-h和96-h LC50值分别为99.4(72.9-147.0),51.2(39.1-65.8)和46.6(33.3-64.8)μg L-1。Zn2+对褐牙鲆胚胎的24-h和48-h LC50值分别为22.3(16.1-26.7)和7.1(6.2-8.3)mg L-1;对仔鱼的48-h和96-h LC50值分别为10.06(7.89-12.88)和6.77(5.25-8.02)mg L-1。结果表明褐牙鲆胚胎比仔鱼对汞、锌暴露更为敏感。胚胎-仔鱼亚急性毒理实验分别将褐牙鲆胚胎置于0-60μg Hg2+ L-1和0-4 mg Zn2+ L-1的溶液中连续暴露6天,研究汞、锌对胚胎、仔鱼阶段生长和存活的影响。结果表明Hg2+浓度≥20μg L-1时会引起胚胎和仔鱼孵化率降低,延迟孵化,死亡率、畸形率增加,抑制生长和卵黄囊吸收率。另一方面,当Zn2+浓度≥1 mg L-1时会引起胚胎和仔鱼孵化率降低,延迟孵化,死亡率、畸形率增加,抑制生长。胚胎慢性毒理实验中,将褐牙鲆从胚胎期分别在0-10μg Hg2+ L-1和0-400μg Pb2+ L-1溶液中连续暴露80天。实验第20,35和80天分别取变态期仔鱼(18 dph),着底期仔鱼(33 dph)和稚鱼(78 dph)研究暴露对其组织中抗氧化防御系统和脂质过氧化作用的影响。实验结束时,取稚鱼测定其体内汞、铅的蓄积及生长情况。结果表明,汞暴露使变态期仔鱼的GSH(谷胱甘肽)含量增加,却使稚鱼的GSH含量减少。汞暴露对变态期仔鱼、着底期仔鱼和稚鱼三个阶段的GST(谷胱甘肽硫转移酶)活性无影响,却显著诱导了变态期仔鱼、着底期仔鱼和稚鱼的SOD(超氧化物岐化酶)、CAT(过氧化氢酶)活性,而且使稚鱼的MDA(丙二醛)含量显著增加。铅暴露减少了着底期仔鱼的GSH含量,却增加了变态期仔鱼和稚鱼的GSH含量。铅暴露显著诱导了稚鱼的GST活性,变态期仔鱼的SOD活性以及变态期仔鱼、稚鱼的CAT活性,并且使着底期仔鱼的MDA含量显著增加。另一方面,经80天的低浓度暴露,汞、铅在稚鱼组织中的蓄积量显著增加,同时它们对褐牙鲆的生长有显著抑制作用。上述结果表明重金属暴露下褐牙鲆(仔稚鱼)的抗氧化反应受其发育阶段,污染物种类、浓度及暴露时间等因素的影响。此外,褐牙鲆在变态期体内剧烈的生理变化,很可能也会影响其在这一阶段的氧化还原作用。幼鱼亚慢性毒理实验将褐牙鲆幼鱼在0-160μg Hg2+ L-1的溶液中连续暴露28天,研究汞暴露对幼鱼各组织中抗氧化防御系统和脂质过氧化作用的影响以及汞在不同组织中的蓄积情况。结果表明,暴露7天时,幼鱼鳃中SOD活性被诱导,GPx(谷胱甘肽过氧化物酶)活性却被抑制;肝脏中GSH含量显著增加,GST活性被抑制;肾脏中SOD、GPx活性同时被诱导。此外,汞暴露并未影响各组织中MDA含量。暴露28天时,幼鱼鳃中SOD、CAT活性都被诱导,而GST活性被抑制GSH含量则降低。肝脏中SOD、CAT活性都被诱导,GSH含量也显著增加。肾脏中SOD活性被诱导,GSH含量显著增加。此时幼鱼鳃和肾脏中MDA含量显著增加。另一方面,28天的汞暴露对褐牙鲆幼鱼的体长、体重和SGR(特定生长率)产生了显著抑制作用,却未影响幼鱼的CF(肥满度)。幼鱼肌肉、肝脏、肾脏、鳃和骨组织中汞的蓄积量随暴露溶液中Hg2+浓度的升高而显著增加,汞在各组织中蓄积量呈肾脏≈肝脏>鳃>骨骼>肌肉的趋势。结果表明汞暴露下褐牙鲆(幼鱼)的抗氧化反应在不同组织中表现各异,此外,暴露浓度和时间也会影响实验结果。更多还原

【Abstract】 Mercury, zinc and lead represent typical heavy metal pollutants in the Chinese coastal waters. In the present study, the toxic effects of mercury, zinc and lead to early life stages (ELS) of flounder (Paralichthys olivaceus) was investigated under laboratory conditions (18±1°C; 33±1‰in salinity), respectively. The aim of the present study is to explore the mechanism underlying metals toxicity to early life stages of flounder, and provide data for using flounder at ELS in monitoring metal pollution of marine environments.The acute toxicity tests indicated that the 24-h and 48-h LC50 values (median lethal concentration) of Hg2+ to embryos were 75.8 (70.1-81.5, with 95% confidence interval) and 48.1 (32.8-63.6)μg L-1; while the 24-h, 48-h and 96-h LC50 values to larvae were 99.4 (72.9-147.0), 51.2 (39.1-65.8) and 46.6 (33.3-64.8)μg L-1. The 24-h and 48-h LC50 values of Zn2+ to embryos were 22.3 (16.1-26.7) and 7.1 (6.2-8.3) mg L-1; the 48-h and 96-h LC50 values to larvae were 10.06 (7.89-12.88) and 6.77 (5.25-8.02) mg L-1. This result indicated that embryos were more sensitive than larvae to mercury and zinc exposure. In the embryonic-larval toxicity tests, embryos were exposed to 0-60μg Hg2+ L-1 and 0-4 mg Zn2+ l-1 solutions for 6 days, respectively. The results indicated that mercury exposure at concentrations≥20μg Hg2+ L-1 would lead to low hatching rate, delay in time-to-hatch, high mortality and morphological abnormality, reduced growth and inhibited yolk absorption in embryos or/and larvae. Zinc exposure at concentrations≥1 mg Zn2+ L-1 would also induce low hatching rate, delay in time-to-hatch, high mortality and morphological abnormality, reduced growth to embryos or/and larvae. In the chronic toxicity tests, fish were exposed to 0-10μg Hg2+ L-1 and 0-300μg Pb2+ L-1 solutions from embryonic to the juvenile stages for 80 days, respectively. Responses of antioxidant defense system and lipid peroxidation to mercury exposure were studied in metamorphosing larvae (20th day; 18 days post hatching, dph), settling larvae (35th day; 33 dph) and juveniles (80th day; 78 dph). The results indicated that elevated mercury or lead concentration led to increased metal bioaccumulation and reduced growth after 80 days of low concentration exposures. On the other hand, mercury exposure elevated glutathione (GSH) level in metamorphosing larvae, but decreased that in juveniles. Glutathione-S-transferase (GST) activity did not significantly vary with mercury concentration in either larvae or juveniles. However, superoxide dismutase (SOD) and catalase (CAT) activities at the three developmental stages were increased with elevated mercury concentration. Moreover, malondialdehyde (MDA) content in juveniles was significantly increased. Lead exposure significantly decreased GSH level in settling larvae, increased those of the metamorphosing larvae and juveniles. GST activity in juveniles, SOD activity in metamorphosing larvae, CAT activity in metamorphosing larvae and juvenile were increased with increasing lead concentration. Meanwhile, MDA content in settling larvae was significantly increased in lead solutions. The results indicated that these antioxidative responses varied with the types of chemical, exposure concentration and duration. On the other hand, since flounder undergo drastic physiological transitions during their early life stages, this may cause differences in the antioxidative responses to metal exposures of the flounder at differental life phases.In toxicity test on juveniles, fish were exposed to 0-160μg Hg2+ L-1 solutions for 28 days. After 7 days of exposure, SOD activity was increased, but glutathione peroxidase (GPx) activity was decreased in the gill; GSH level was elevated, while GST activity was decreased in the liver; SOD and GPx activities were increased in the kidney. MDA content in all the three tissues did not significantly vary with mercury concentration. After 28 days of exposure, SOD and CAT activities were increased, GST activity and GSH level were decreased in the gill; SOD and CAT activities GSH level were significantly increased in the liver; SOD activity and GSH level were significantly increased in the kidney. MDA content in the gill and kidney were significantly increased. On the other hand, total length, body weight and specific growth rate (SGR) of juveniles were significantly reduced while condition factor (CF) was not affected by 28 days of mercury exposure. Moreover, mercury bioaccumulation in muscle, liver, kidney, gill and bone of juveniles significantly increased with elevating exposure Hg2+ concentration. The metal accumulation efficiency in these organs was in an order of kidney≈liver > gill > bone > muscle. The results indicated that the antioxidative responses of juveniles to mercury exposure varied with different tissue types. Moreover, exposure concentration and duration could also affect the responses of antioxidants and lipid peroxidation.更多还原