Covi Joseph A, Hutchison Evan R, Neumeyer Courtney H, Gunderson Matthew D
Department of Biology and Marine Biology, University of North Carolina at Wilmington, Wilmington, North Carolina, United States of America.
Department of Biology, University of Wisconsin-Stevens Point, Stevens Point, Wisconsin, United States of America.
PLoS One. 2016 Sep 21;11(9):e0163231. doi: 10.1371/journal.pone.0163231. eCollection 2016.
While many zooplankton species recover quickly after the treatment of water resources with the piscicide, rotenone, some fail to reach pretreatment population density or, in rare cases, do not reappear at all. The variable impact of rotenone on zooplankton populations could stem from differences in the capacity of species to switch entirely to anaerobic catabolic pathways in the presence of rotenone, which blocks mitochondrial electron transport. Alternatively, variable responses among species could originate from differences in permeability of dormant life-stages to lipophilic chemicals like rotenone. The purpose of the present study was to determine the effects of rotenone on development, emergence and hatching of zooplankton embryos that lack both the anaerobic capacity to develop in the presence of rotenone and a permeability barrier to prevent the entry of rotenone during dormancy. Post-diapause embryos of the brine shrimp, Artemia franciscana, were employed as a model system, because they are permeable to lipophilic compounds when dechorionated and require aerobic conditions to support development. Early development in this species is also well characterized in the literature. Brine shrimp embryos were exposed to rotenone while development was either slowed by chilling or suspended by anoxia. Development, emergence and hatching were then observed in rotenone-free artificial seawater. The data presented demonstrate that rotenone freely diffuses across the embryonic cuticle in a matter of hours, and prevents development and emergence after brief exposures to ecologically relevant concentrations (0.025-0.5 mg L-1) of the piscicide. Neither the removal of rotenone from the environment, nor the removal of embryonic water with a hypertonic solution, are sufficient to reverse this block on development and emergence. These data indicate that rotenone could impair recruitment from egg banks for species of zooplankton that lack both an embryonic barrier to the entry of lipophilic compounds and the anaerobic capacity to develop when NADH:ubiquinone oxidoreductase activity is inhibited by rotenone.
虽然许多浮游动物物种在用鱼藤酮处理水资源后能迅速恢复，但有些物种未能达到处理前的种群密度，或者在极少数情况下根本不再出现。鱼藤酮对浮游动物种群的影响各异，这可能源于物种在鱼藤酮存在时完全转向无氧分解代谢途径的能力差异，鱼藤酮会阻断线粒体电子传递。或者，物种间的不同反应可能源于休眠生命阶段对鱼藤酮等亲脂性化学物质的通透性差异。本研究的目的是确定鱼藤酮对缺乏在鱼藤酮存在时进行无氧发育能力以及缺乏阻止鱼藤酮在休眠期间进入的通透性屏障的浮游动物胚胎发育、孵化和出膜的影响。卤虫（Artemia franciscana）的滞育后胚胎被用作模型系统，因为它们去壳后对亲脂性化合物具有通透性，并且需要有氧条件来支持发育。该物种的早期发育在文献中也有很好的描述。卤虫胚胎在发育因低温而减缓或因缺氧而暂停时接触鱼藤酮。然后在不含鱼藤酮的人工海水中观察发育、孵化和出膜情况。所呈现的数据表明，鱼藤酮在数小时内就能自由扩散穿过胚胎表皮，并且在短暂暴露于生态相关浓度（0.025 - 0.5 mg L-1）的鱼藤酮后会阻止发育和出膜。无论是从环境中去除鱼藤酮，还是用高渗溶液去除胚胎水分，都不足以逆转这种对发育和出膜的阻滞。这些数据表明，对于既缺乏亲脂性化合物进入胚胎的屏障又缺乏在鱼藤酮抑制NADH：泛醌氧化还原酶活性时进行无氧发育能力的浮游动物物种，鱼藤酮可能会损害其从卵库中的补充。
