Dougherty C T, Knapp F W, Bush L P
Department of Agronomy, University of Kentucky, Lexington 40546-0091, USA.
J Med Entomol. 1999 Jan;36(1):73-7. doi: 10.1093/jmedent/36.1.73.
Dung-dwelling larvae of ectoparasites of livestock such as the horn fly, Hematobia irritans (L.), may be exposed to > or = 1 different alkaloid species in dung from animals ingesting herbage of the tall fescue (Festuca arundinacea Schreb.)--endophyte association (Neotyphodium coenophialum (Morgan-Jones & W. Gams) Glenn, Bacon & Hanlin comb. nov.). First-instar horn flies were exposed to bovine dung supplemented with up to 50 microM each of N-formyl loline and ergotamine tartrate in factorial combination. In the absence of ergotamine tartrate, N-formyl loline caused a linear decline in the number of pupae recovered, and probit analysis indicated an LC50 of 36 microM. In the absence of N-formyl loline, significant quadratic responses of larvae to ergotamine tartrate were established, and probit analysis indicated a LC50 of 34 microM. An interaction (P < 0.001) was found between the 2 alkaloids for larval survival. This interaction showed that ergotamine tartrate moderated the toxicity of N-formyl loline and indicates that a membrane-bound receptor may be involved. There was no evidence of carryover of effects of alkaloids on subsequent stages of development or expressed as abnormalities of pupae or adults. Interactions between alkaloids probably are involved in other plant-herbivore relationships of endophyte-infected grasses.
寄生于家畜体表的寄生虫（如角蝇，Hematobia irritans (L.)）的粪生幼虫，可能会接触到采食了高羊茅（Festuca arundinacea Schreb.）-内生真菌共生体（Neotyphodium coenophialum (Morgan-Jones & W. Gams) Glenn, Bacon & Hanlin comb. nov.）的动物粪便中的≥1种不同生物碱。将一龄角蝇暴露于分别添加了高达50微摩尔N-甲酰洛林和酒石酸麦角胺的牛粪中，二者呈析因组合。在没有酒石酸麦角胺的情况下，N-甲酰洛林导致羽化蛹数量呈线性下降，概率分析表明半数致死浓度（LC50）为36微摩尔。在没有N-甲酰洛林的情况下，幼虫对酒石酸麦角胺呈现出显著的二次反应关系，概率分析表明LC50为34微摩尔。发现这两种生物碱对幼虫存活存在交互作用（P < 0.001）。这种交互作用表明酒石酸麦角胺可减轻N-甲酰洛林的毒性，这表明可能涉及一种膜结合受体。没有证据表明生物碱的影响会延续到后续发育阶段，也未表现为蛹或成虫的异常。生物碱之间的相互作用可能也存在于内生真菌感染的禾本科植物与草食动物的其他关系中。
