Martins Nelson, Lopes Isabel, Harper Ruth Maureen, Ross Philippe, Ribeiro Rui
IMAR-Instituto do Mar, Department of Zoology, University of Coimbra, Coimbra, Portugal.
Environ Toxicol Chem. 2007 Sep;26(9):1904-9. doi: 10.1897/06-111R.1.
Differential resistance to metal pollution in Daphnia longispina populations was reported in previous studies. In this work, we tried to determine if variation in polymorphic enzymes, often referred as being under metal selection, were related with differences in resistance to acute single- and mixed-metal exposure. Allozyme genotype of 20 putatively polymorphic enzymes, 48-h median lethal concentration (LC50) for copper, and median lethal time (LT50) for a 3% dilution of acid mine drainage (AMD) were determined for 24 lineages of D. longispina. The copper LC50s ranged from 29.3 to 226 microg/L, and the AMD LT50s ranged from 48 min to 25 h and 29 min, with a strong correlation between both end points. Five distinct multilocus genotypes were identified based on polymorphisms in glucose-6-phosphate isomerase, lactate dehydrogenase, malate dehydrogenase, nicotinamide adenine dinucleotide phosphate (NADP+), phosphoglucomutase, and peroxidase. No differences were found in average genotype sensitivity for both toxicity end points or in genotype frequencies between the resistant- and sensitive-lineage groups. The results obtained indicate that allozyme genotype is not associated with increased resistance to acute metal stress in D. longispina.
先前的研究报道了长刺溞种群对金属污染的差异抗性。在本研究中，我们试图确定通常被认为受金属选择影响的多态酶的变异是否与对急性单一金属和混合金属暴露的抗性差异有关。测定了24个长刺溞谱系中20种假定的多态酶的等位酶基因型、铜的48小时半数致死浓度（LC50）以及3%酸性矿山排水（AMD）稀释液的半数致死时间（LT50）。铜的LC50范围为29.3至226微克/升，AMD的LT50范围为48分钟至25小时29分钟，两个终点之间存在强相关性。基于葡萄糖-6-磷酸异构酶、乳酸脱氢酶、苹果酸脱氢酶、烟酰胺腺嘌呤二核苷酸磷酸（NADP+）、磷酸葡萄糖变位酶和过氧化物酶的多态性，鉴定出了五种不同的多位点基因型。在抗性谱系组和敏感谱系组之间，未发现两种毒性终点的平均基因型敏感性或基因型频率存在差异。所得结果表明，等位酶基因型与长刺溞对急性金属胁迫的抗性增加无关。
