Guan Rui, Wang Wen-Xiong
Atmospheric Marine Coastal Environment Program and Department of Biology, The Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon.
Aquat Toxicol. 2006 Mar 10;76(3-4):217-29. doi: 10.1016/j.aquatox.2005.10.003. Epub 2005 Nov 9.
We investigated the effects of genotype (two different clones) and multigenerational Cd-exposure history on Cd toxicity, individual fitness, and biokinetics in populations of a freshwater cladoceran Daphnia magna. The adults of the tolerant (T) clone had longer mean-survival-time than the sensitive (S) clone in both control groups (without Cd-exposure) and continuous Cd-exposure groups, but the two clones showed comparable resistances to acute Cd stress in the recovery groups. The body concentration of metallothionein (MT) played a critical role in handling Cd stress, which mainly accounted for the significant difference between the two clones in terms of survival distribution. High comparability of these two clones in individual fitness parameters and biokinetics suggested that these parameters are unlikely driven by genetic variation. For each specific clone, continuous Cd-exposure inhibited the animal growth, elevated the MT induction, and increased the Cd uptake rate (ingestion rate, assimilation efficiency from dietary phase, and uptake rate from dissolved phase), all of which enhanced the weight-specific Cd accumulation in daphnids' bodies. The strong dependence of biokinetic parameters on environmental factors (e.g., food concentrations, pH, dissolved or dietary metal concentration, and metal exposure histories) rather than on genotypes implied the great potential of using biokinetics in inter-lab comparisons and environmental risk assessments.
我们研究了基因型（两个不同克隆）和多代镉暴露史对淡水枝角类大型溞种群中镉毒性、个体适合度和生物动力学的影响。在对照组（无镉暴露）和持续镉暴露组中，耐受（T）克隆的成年个体平均存活时间均长于敏感（S）克隆，但在恢复组中，两个克隆对急性镉胁迫的抗性相当。金属硫蛋白（MT）的体内浓度在应对镉胁迫中起关键作用，这主要解释了两个克隆在存活分布方面的显著差异。这两个克隆在个体适合度参数和生物动力学方面具有高度可比性，表明这些参数不太可能由遗传变异驱动。对于每个特定克隆，持续镉暴露会抑制动物生长、提高MT诱导水平并增加镉摄取率（摄食率、饮食阶段的同化效率以及溶解相的摄取率），所有这些都会增强大型溞体内单位体重的镉积累。生物动力学参数对环境因素（如食物浓度、pH值、溶解或饮食中的金属浓度以及金属暴露史）而非基因型的强烈依赖性，意味着在实验室间比较和环境风险评估中使用生物动力学具有巨大潜力。
