Department of Biology & CESAM, University of Aveiro, 3810-193, Portugal.
NEPEA, Campus do Litoral Paulista, Universidade Estadual Paulista Júlio de Mesquita Filho, Praça Infante Dom Henrique, s/n, CP 11330-900 São Vicente, SP, Brazil.
Ecotoxicol Environ Saf. 2019 May 30;173:77-85. doi: 10.1016/j.ecoenv.2019.02.001. Epub 2019 Feb 12.
To better evaluate chemical damage in chronically contaminated habitats, a nine-generational exposure to Lead (Pb) was done with two monophyletic Daphnia species, from temperate (Daphnia magna) and tropical (Daphnia similis) environments. The multi-generational test consisted generally of a continuous Pb exposed set of organisms, plus an extra control set running simultaneously. To assess daphnids recovery after Pb exposure, some organisms from the sixth generation were transferred to clean media for three extra generations (recovery period; F6 to F9), while others were keep Pb exposed. All setups (control, Pb exposure and recovery period) were submitted to two different dietary regimes, the standard (3 × 10 cells/mL) and restricted food (1.5 × 10 cells/mL) regimes. To evaluate the effects of generational Pb exposure and food regimes, individual, functional and population related endpoints were assessed (number of offspring, body length and rate of population increase (r) and feeding rate (FR)). The tests were conducted on the first (F0) and last generations (F9). No differences were shown on number of offspring and feeding among F9 control and continuous Pb exposed D. magna, although a higher r was shown for F9 Pb exposed organisms. F9 Pb exposed D. similis also presented a higher r than F9 control, however, lethality was induced at high Pb exposure levels. At food restriction the patterns were opposite and D. magna died at high Pb exposure while Pb exposed D. similis was the only setup (compared to control and recovery period) to survive at high Pb exposure levels. Regarding the recovery period, D. magna (standard food) did not cope well with the Pb re-exposure and lethality was induced, while D. similis indicate a decreased Pb sensitivity (only setup that survived high Pb exposure levels). Under food restriction, both species presented a decreased Pb sensitivity and consequent failed recovery (possibly due to epigenetic changes). Both species presented similar patterns regarding generations. Organisms from F0 presented enhanced reproductive outputs in comparison to F9 and the contrary occurred to the FR (even in control organisms). Data show an acclimation under a generational Pb exposure, which could increase the population of adapted organisms in natural habitats. And, since there was not a full recovery after three generations in clean media, an indication of epigenetic changes for both species may also be considered.
为了更好地评估慢性污染栖息地中的化学损伤，我们用两种单系的水蚤（来自温带的大型水蚤和热带的近似水蚤）进行了为期九代的铅（Pb）暴露实验。多代实验通常包括一组连续暴露于 Pb 的生物体，以及一组同时运行的额外对照。为了评估 Pb 暴露后水蚤的恢复情况，第六代的一些生物体被转移到清洁的培养基中进行三代额外的培养（恢复期；F6 至 F9），而其他生物体则继续暴露于 Pb 下。所有设置（对照、Pb 暴露和恢复期）都接受了两种不同的饮食方案，标准（3×10 个细胞/mL）和限制食物（1.5×10 个细胞/mL）方案。为了评估代际 Pb 暴露和食物方案的影响，评估了个体、功能和种群相关的终点（后代数量、体长和种群增长率（r）和摄食率（FR））。测试在第一代（F0）和最后一代（F9）进行。在最后一代，连续 Pb 暴露的大型水蚤和对照组的 F9 之间在后代数量和摄食方面没有差异，尽管 Pb 暴露的 F9 生物体显示出更高的 r。Pb 暴露的 F9 近似水蚤也显示出比 F9 对照组更高的 r，但在高 Pb 暴露水平下诱导了致死性。在食物限制下，模式相反，高 Pb 暴露下大型水蚤死亡，而 Pb 暴露的近似水蚤是唯一在高 Pb 暴露水平下存活的设置（与对照和恢复期相比）。关于恢复期，大型水蚤（标准食物）在重新暴露于 Pb 时无法很好地应对，导致死亡，而近似水蚤则显示出较低的 Pb 敏感性（唯一在高 Pb 暴露水平下存活的设置）。在食物限制下，两种水蚤都表现出较低的 Pb 敏感性和随后的恢复失败（可能是由于表观遗传变化）。两种水蚤在代际方面都表现出相似的模式。与 F9 相比，F0 的生物体表现出更高的繁殖产出，而 FR 则相反（即使在对照生物体中也是如此）。数据显示，在代际 Pb 暴露下存在一种适应，这可能会增加自然栖息地中适应生物体的数量。并且，由于在清洁培养基中三代后没有完全恢复，这两种水蚤也可能存在表观遗传变化的迹象。
