Rakotondravelo Mamy L, Anderson Troy D, Charlton Ralph E, Zhu Kun Yan
Department of Entomology, Kansas State University, 123 Waters Hall, Manhattan, Kansas 66506, USA.
Arch Environ Contam Toxicol. 2006 Oct;51(3):352-9. doi: 10.1007/s00244-005-0219-0. Epub 2006 Jul 21.
Effects of long-term exposure to each of three pesticides including atrazine, DDT, and chlorpyrifos on larval survivorship, growth, and macromolecule (total body protein and RNA) production were evaluated in the aquatic midge, Chironomus tentans, under laboratory conditions. Newly hatched larvae were exposed to atrazine at 30 and 150 microg/L, DDT at 0.01 and 0.05 microg/L, or chlorpyrifos at 0.02 and 0.10 microg/L throughout one life cycle. Larval survivorship was evaluated at 20 d and the end of the test, and larval growth at 20 d. Chlorpyrifos at 0.1 microg/L reduced the midge survivorship by 67% after 20-d exposure. However, neither atrazine nor DDT affected larval survivorship. The ash-free dry weight of midge larvae exposed to chlorpyrifos at 0.1 microg/L was 1.5-fold greater than that of the control whereas neither atrazine nor DDT showed a significant effect on the ash-free dry weight. In addition, exposures of midges to chlorpyrifos at 0.1 microg/L increased the adult emergence rate by 81% as compared to the control although the actual number of adults that emerged from chlorpyrifos-treated larvae was significantly decreased. Both the increased ash-free dry weight of larvae and increased adult emergence rate were likely caused by reduced competition for both food and space among the survivors due to increased larval mortality. Although neither total protein nor total RNA production was significantly affected in larvae exposed to each pesticide for 20 d, a significantly higher number of males over females (ratio = 4) emerged from midges exposed to DDT at 0.05 microg/L. Our study indicates that chronic exposure to low concentrations of chlorpyrifos and DDT results in significant mortality of midge larvae and alteration of the sex ratio of adult emergence, respectively. Because midges are important components of the food web, our results suggest that effects elicited directly or indirectly by long-term pesticide exposures may potentially disrupt both food chains and community structure in aquatic environments.
在实验室条件下，评估了长期暴露于三种农药（阿特拉津、滴滴涕和毒死蜱）中的每一种对水生摇蚊（Chironomus tentans）幼虫存活率、生长以及大分子（全身蛋白质和RNA）产生的影响。刚孵化的幼虫在整个生命周期内分别暴露于浓度为30和150微克/升的阿特拉津、0.01和0.05微克/升的滴滴涕或0.02和0.10微克/升的毒死蜱。在20天及试验结束时评估幼虫存活率，在20天时评估幼虫生长情况。暴露于0.1微克/升毒死蜱20天后，摇蚊存活率降低了67%。然而，阿特拉津和滴滴涕均未影响幼虫存活率。暴露于0.1微克/升毒死蜱的摇蚊幼虫无灰干重比对照组高1.5倍，而阿特拉津和滴滴涕对无灰干重均无显著影响。此外，与对照组相比，暴露于0.1微克/升毒死蜱的摇蚊成虫羽化率提高了81%，尽管从经毒死蜱处理的幼虫中羽化出的成虫实际数量显著减少。幼虫无灰干重增加和成虫羽化率提高可能是由于幼虫死亡率增加导致幸存者之间对食物和空间的竞争减少所致。虽然暴露于每种农药20天的幼虫中总蛋白质和总RNA的产生均未受到显著影响，但暴露于0.05微克/升滴滴涕的摇蚊中羽化出的雄性比雌性数量显著更多（比例为4）。我们的研究表明，长期暴露于低浓度的毒死蜱和滴滴涕分别导致摇蚊幼虫显著死亡和成虫羽化性别比例改变。由于摇蚊是食物网的重要组成部分，我们的结果表明，长期农药暴露直接或间接引发的影响可能会破坏水生环境中的食物链和群落结构。
