Rohr Jason R, Elskus Adria A, Shepherd Brian S, Crowley Philip H, McCarthy Thomas M, Niedzwiecki John H, Sager Tyler, Sih Andrew, Palmer Brent D
Department of Biology, University of Kentucky, Lexington, Kentucky 40506-0225, USA.
Environ Toxicol Chem. 2003 Oct;22(10):2385-92. doi: 10.1897/02-528.
Agricultural contaminants may be contributing to worldwide amphibian declines, but little is known about which agrichemicals pose the greatest threat to particular species. One reason for this is that tests of multiple contaminants under ecologically relevant conditions are rarely conducted concurrently. In this study, we examined the effects of 37-d exposure to the agrichemicals atrazine (4, 40, and 400 micrograms/L), carbaryl (0.5, 5, and 50 micrograms/L), endosulfan (0.1, 1, and 10 micrograms/L for 31 d and 0.1, 10, and 100 micrograms/L for the last 6 d), and octylphenol (5, 50, and 500 micrograms/L) and to a solvent control on streamside salamanders (Ambystoma barbouri) in the presence and absence of food. We found that none of the agrichemicals significantly affected embryo survival, but that hatching was delayed by the highest concentration of octylphenol. In contrast to embryos, larval survival was reduced by the highest concentrations of carbaryl, endosulfan, and octylphenol. Growth rates were lower in the highest concentrations of endosulfan and octylphenol than in all other treatments, and the highest concentration of endosulfan caused respiratory distress. Significantly more carbaryl, endosulfan, and octylphenol tanks had larvae with limb deformities than did control tanks. Refuge use was independent of chemical exposure, but 10 micrograms/L of endosulfan and 500 micrograms/L of octylphenol decreased larval activity. Systematically tapping tanks caused a greater activity increase in larvae exposed to 400 micrograms/L of atrazine and 10 micrograms/L of endosulfan relative to solvent controls, suggesting underlying nervous system malfunction. Hunger stimulated a decrease in refuge use and an increase in activity, but this response was least pronounced in larvae exposed to the highest concentration of any of the four agrichemicals, possibly because these larvae were the most lethargic. More studies are needed that concurrently examine the effect of multiple contaminants on amphibians so we can better identify effective mitigating measures.
农业污染物可能是全球两栖动物数量减少的原因之一，但对于哪些农用化学品对特定物种构成最大威胁，我们却知之甚少。原因之一在于，很少会在生态相关条件下同时对多种污染物进行测试。在本研究中，我们考察了溪流蝾螈（巴氏钝口螈）在有食物和无食物情况下，暴露于莠去津（4、40和400微克/升）、西维因（0.5、5和50微克/升）、硫丹（前31天为0.1、1和10微克/升，后6天为0.1、10和100微克/升）、辛基酚（5、50和500微克/升）这几种农用化学品37天以及暴露于溶剂对照的影响。我们发现，没有一种农用化学品对胚胎存活率有显著影响，但辛基酚的最高浓度会延迟孵化。与胚胎不同，西维因、硫丹和辛基酚的最高浓度会降低幼体存活率。硫丹和辛基酚的最高浓度下的生长速率低于所有其他处理组，硫丹的最高浓度还会导致呼吸窘迫。与对照水箱相比，含有西维因、硫丹和辛基酚的水箱中有肢体畸形幼体的数量显著更多。躲避行为与化学物质暴露无关，但10微克/升的硫丹和500微克/升的辛基酚会降低幼体活动水平。相对于溶剂对照，有节奏地轻拍水箱会使暴露于400微克/升莠去津和10微克/升硫丹的幼体活动增加幅度更大，这表明存在潜在的神经系统功能障碍。饥饿会促使躲避行为减少、活动增加，但在暴露于四种农用化学品中任何一种最高浓度的幼体中，这种反应最不明显，可能是因为这些幼体最为慵懒。需要开展更多同时考察多种污染物对两栖动物影响的研究，以便我们能更好地确定有效的缓解措施。
