Nguyen Kieu-Oanh, Al-Rashid Sayma, Clarke Miller M, Tom Diggs J, Lampert Evan C
Department of Biology, University of North Georgia, Oakwood, GA.
Department of Chemistry and Biochemistry, University of North Georgia, Oakwood, GA.
Environ Entomol. 2019 Jun 7;48(3):540-545. doi: 10.1093/ee/nvz029.
Carotenoids are fundamental precursors for hormones and antioxidants, and insects must acquire carotenoids from their diet. Previous research has shown that insects can selectively absorb dietary carotenoids, often modifying them qualitatively or quantitatively, and quantities may be proportional to those found in the diet. Trichoplusia ni Hübner is a generalist herbivore with host plants varying greatly in carotenoid profiles and concentrations. Larvae sequester carotenoids in their hemolymph, and carotenoid sequestration contributes to their cryptic green coloration. Our objectives were to compare the types of carotenoids found in T. ni and their host plants to determine whether qualitative changes occurred, and compare the amounts of sequestered carotenoids in T. ni reared upon different host plants to determine whether quantitative variation influences sequestration. To fulfill these objectives, larvae were fed romaine lettuce (Lactuca sativa L. [Asterales: Asteraceae] var. longifolia) or kale (Brassica oleracea L. [Brassicales: Brassicaceae] var. sabellica) for a period of 5 d, and sequestered carotenoids from the entire insect were resolved with thin-layer chromatography and measured with spectrophotometer. All carotenoids resolved from plants were also resolved from larvae, and although the carotenoids of plants differed quantitatively, the sequestered carotenoids did not differ between host plants. Regardless of host plant species, T. ni sequestered carotenoids at concentrations up to 20 times higher than the concentrations found in the plants. Future research may be able to explicitly identify enzyme systems involved in the transport and modification of carotenoids in T. ni and other animals.
类胡萝卜素是激素和抗氧化剂的基本前体，昆虫必须从食物中获取类胡萝卜素。先前的研究表明，昆虫能够选择性地吸收食物中的类胡萝卜素，常常对其进行定性或定量的改变，并且其吸收量可能与食物中的含量成比例。粉纹夜蛾是一种多食性食草动物，其寄主植物的类胡萝卜素谱和浓度差异很大。幼虫将类胡萝卜素隔离在血淋巴中，而类胡萝卜素的隔离有助于它们呈现隐秘的绿色。我们的目标是比较粉纹夜蛾及其寄主植物中发现的类胡萝卜素类型，以确定是否发生了定性变化，并比较在不同寄主植物上饲养的粉纹夜蛾中隔离的类胡萝卜素含量，以确定定量变化是否影响隔离。为了实现这些目标，用生菜（长叶莴苣，菊目：菊科）或羽衣甘蓝（野甘蓝，十字花目：十字花科）喂养幼虫5天，然后用薄层色谱法分离整个昆虫体内隔离的类胡萝卜素，并用分光光度计进行测量。从植物中分离出的所有类胡萝卜素也能从幼虫中分离出来，尽管植物中的类胡萝卜素在数量上有所不同，但寄主植物之间隔离的类胡萝卜素并无差异。无论寄主植物种类如何，粉纹夜蛾隔离类胡萝卜素的浓度比植物中的浓度高出20倍。未来的研究或许能够明确鉴定参与粉纹夜蛾和其他动物体内类胡萝卜素运输和修饰的酶系统。
