Evens Roel, De Schamphelaere Karel A C, Janssen Colin R
Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University, J. Plateaustraat 22, B-9000 Ghent, Belgium.
Aquat Toxicol. 2009 Aug 31;94(2):138-44. doi: 10.1016/j.aquatox.2009.06.011. Epub 2009 Jun 26.
Although there is growing evidence that dietborne metals can be toxic to various aquatic species, there is still insufficient knowledge to integrate this information in environmental risk assessment procedures. In this study, we investigated the effects of a 21-day exposure of Daphnia magna to a control diet (i.e. the green alga Pseudokirchneriella subcapitata containing <4.0microgNi/g dry wt) and five diets with elevated Ni concentrations (i.e. the same alga contaminated with Ni burdens between 33.7 and 837microgNi/g dry wt). A significant accumulation of dietborne Ni in D. magna, i.e. between 49.6 and 72.5microgNi/g dry wt, was observed when they were fed with diets containing between 85.6 and 837microgNi/g dry wt. This was paralleled by a significant reduction of reproduction (by 33.1%), measured as the total number of juvenile offspring per female and growth (by 9.1%), measured as the carapax length of 21-day-old females. Life-history analysis showed that the time to first brood of Ni exposed organisms was between 7.8 and 8.2 days, and occurred 0.7-1.1 days earlier than for the control organisms (time to first brood=8.9 days). The number of offspring in the first brood was significantly reduced (by 21-33% compared to the control) in all dietary treatments. Longer exposure (> or =8.9 days, i.e. from the second brood onwards) led to a reduction of brood size only when given diets containing 85.6 and 837microgNi/g dry wt. The results suggest that a variety of mechanisms may be involved in the effects of dietary Ni exposure, including altered resource allocation or targeted reproductive inhibition. While Ni exposure clearly altered the quality of the diet (measured as essential omega3 polyunsaturated fatty acid content and C:P ratio), we found no conclusive evidence that these diet quality shifts could have affected growth or total reproductive output. More research is required to fully understand the mechanisms of Ni toxicity associated with the dietary exposure route.
尽管越来越多的证据表明，饮食中的金属可能对各种水生物种有毒，但在环境风险评估程序中整合这些信息的知识仍然不足。在本研究中，我们调查了大型溞暴露于对照饮食（即每克干重含镍量低于4.0微克的绿藻小形伪菱形藻）和五种镍浓度升高的饮食（即被镍污染的同一种藻类，镍含量在33.7至837微克/克干重之间）21天的影响。当大型溞喂食镍含量在85.6至837微克/克干重之间的饮食时，观察到饮食中的镍在大型溞体内显著积累，即每克干重49.6至72.5微克。这伴随着繁殖能力显著下降（下降33.1%，以每只雌性后代总数衡量）和生长显著下降（下降9.1%，以21日龄雌性的背甲长度衡量）。生活史分析表明，暴露于镍的生物首次产卵的时间在7.8至8.2天之间，比对照生物（首次产卵时间=8.9天）提前0.7 - 1.1天。在所有饮食处理中，首次产卵的后代数量显著减少（与对照相比减少21 - 33%）。只有当喂食镍含量为85.6和837微克/克干重的饮食时，更长时间的暴露（≥8.9天，即从第二次产卵开始）才导致产卵量减少。结果表明，饮食中镍暴露的影响可能涉及多种机制，包括资源分配改变或靶向生殖抑制。虽然镍暴露明显改变了饮食质量（以必需的ω - 3多不饱和脂肪酸含量和碳磷比衡量），但我们没有确凿证据表明这些饮食质量变化会影响生长或总生殖产出。需要更多研究来充分了解与饮食暴露途径相关的镍毒性机制。
