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Ecological impact of selenium and mercury on two insect food chains.

机译：硒和汞对两条昆虫食物链的生态影响。

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Despite the important roles played by insects in most ecosystems, surprisingly little is known about how anthropogenic pollutants or their mixtures interact to affect insect populations. In this dissertation I focused on the toxicological effects of the metalloid selenium on several insect species.; Selenium can be present in the environment in many forms simultaneously producing very different toxicological responses. I assessed the relative chronic toxicities of selenate, selenite, seleno-L-methionine, and selenocysteine to Megaselia scalaris larvae in artificial diet bioassays. I found significant differences in the relative toxicities of each selenium species, decreases in larval survival, increases in developmental time, differences between male and female eclosion times, but no female ovipositional preference for selenium versus control treatments.; Selenium can interact with many other pollutants causing unpredictable toxicity in contaminated environments. I used the relative chronic toxicity results and bioassay protocols from the previous study to examine the effects of selenate and methylmercury mixtures on M. scalaris. I found significant decreases in larval survival and female fecundity, increases in larval development time, no female ovipositional preference, and strong evidence for twenty-fold potentiation and synergism between selenium and methylmercury versus control treatments.; I developed new protocols to investigate the chronic toxicity of selenate and methylmercury on the aquatic larvae of a mosquito, Culex quinquefasciatus . Methylmercury was much more toxic than selenate and I found evidence again for synergism. Larval survival and rate of growth were significantly decreased in laboratory bioassays, but no evidence for female ovipositional preference was found in field trials using artificial ponds.; To measure the effects of methylmercury on selenium speciation, biotransfer, and bioaccumulation M. scalaris and C. quinquefasciatus were exposed to selenate and methylmercury and fed to Podisus maculiventris and Sympetrum corruptum respectively. All insect species were analyzed using X-ray Absorption Spectroscopy. Selenium speciation was unique in each test insect species and was further altered by methylmercury. Similarities between insect and vertebrate selenium detoxification were inferred from the observed selenium metabolites. Predators suffered decreased survival and feeding rates when fed treated prey. Selenocysteine was found to be important in the toxicity, biotransfer, and bioaccumulation of selenium in terrestrial insects.
机译：尽管昆虫在大多数生态系统中发挥着重要作用，但令人惊讶的是，关于人为污染物或其混合物如何影响昆虫种群的信息知之甚少。在这篇论文中，我重点研究了准金属硒对几种昆虫的毒理作用。硒可以多种形式存在于环境中，同时产生非常不同的毒理学反应。在人工饮食生物测定中，我评估了硒酸盐，亚硒酸盐，硒代L-蛋氨酸和硒代半胱氨酸对大鳞菜幼虫的相对慢性毒性。我发现每种硒的相对毒性有显着差异，幼虫存活率下降，发育时间增加，雄性和雌性抽发时间之间存在差异，但是雌性对硒的产卵相对于对照治疗没有偏爱。硒可与许多其他污染物相互作用，在受污染的环境中造成不可预测的毒性。我使用先前研究的相对慢性毒性结果和生物测定规程，研究了硒酸盐和甲基汞混合物对标尺分枝杆菌的影响。我发现幼虫的存活率和雌性繁殖力显着下降，幼虫的发育时间增加，没有雌性产卵偏爱，并且有力的证据表明硒和甲基汞相对于对照处理具有二十倍的增强作用和协同作用。我开发了新的方案，以研究硒酸和甲基汞对蚊子库克斯库克斯库图斯水生幼虫的慢性毒性。甲基汞的毒性比硒酸盐大得多，我再次发现了协同作用的证据。在实验室生物测定中，幼虫的存活率和生长速度显着降低，但在使用人工池塘进行的田间试验中，没有发现雌性产卵偏爱的证据。为了测量甲基汞对硒形态，生物转移和生物富集的影响，将斯卡里霉和西洋参纤毛虫暴露于硒酸盐和甲基汞中，并分别喂食Macdisventris和腐败的Sympetrum。使用X射线吸收光谱法分析所有昆虫种类。硒的形态在每种受试昆虫中都是独特的，并且会被甲基汞进一步改变。从观察到的硒代谢物可以推断出昆虫与脊椎动物硒的解毒之间的相似性。捕食被捕食者时，捕食者的存活率和摄食率降低。发现硒代半胱氨酸对陆生昆虫中硒的毒性，生物转移和生物蓄积具有重要作用。

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