离子色谱法测定寄生后小菜蛾血淋巴游离氨基酸

Determination of free amino acids in the hemolymph of parasitized Plutella xylostella by ion chromatography

采用离子色谱法测定了小菜蛾末龄幼虫、预蛹及被菜蛾盘绒茧蜂寄生后,血淋巴中游离氨基酸组成和含量.共检测到17种氨基酸,其中组氨酸、脯氨酸和丙氨酸是主要的种类.随着小菜蛾幼虫的生长,血淋巴中氨基酸总量明显增加,发育到预蛹时,总量下降,表明虫体内氨基酸代谢途径因变态的即将发生而产生了变化.被菜蛾盘绒茧蜂寄生后,小菜蛾幼虫血淋巴中游离氨基酸总量显著增加,导致多数氨基酸种类含量增加,表明该蜂有效地调节了寄主的蛋白质和氨基酸代谢,使之朝着有利于自身发育的方向发展.但是,当蜂幼虫完成在寄主体内的发育时,小菜蛾血淋巴中氨基酸总浓度明显下降,说明该蜂有效地获取了寄主中的氨基酸营养.对这些氨基酸种类的识别将可为今后该蜂大规模的的人工化培养提供极有价值的信息.

Changes in free amino acids were analysed in hemolymph of fourth instar larvae, prepupae and parasitized Plutella xylostella larvae by ion chromatography. Seventeen primary amino acids were detected among which histidine, proline and alanine were the predominant free amino acids at all stages. The concentration of total amino acids increased significantly with the development of larvae. However, the amount declined with the larvae entering the prepupal phase. This suggested that changes in amino acid metabolism occurred. After parasitization by Cotesia vestalis, the concentration of total amino acids increased significantly compared with synchronous non-parasitized controls. The parasitism resulted in increased levels of most of the amino acids. This parasitoid strongly redirected host protein and amino acid metabolisms to make the host nutritional environment suitable to its development. At the end of the immature development of this parasitoid, we observed a very significant decline in total amino acid contents. This suggested that C. vestalis used these amino acids effectively to ensure its larval development. The definition of a suitable artificial diet according to our results for in vitro mass production of this parasitoid in the future is necessary and helpful.