淡足侧沟茧蜂寄生对斜纹夜蛾幼虫血淋巴游离氨基酸的影响

为探讨寄生蜂调控寄主的生理学机制,测定了淡足侧沟茧蜂Microplitis pallidipes Szepligeti寄生斜纹夜蛾Spodoptera litura(Fabricius)后寄主幼虫血淋巴中17种游离氨基酸含量。结果发现,寄生后连续5d的时间内,与对照相比,寄生后1~4d,被寄生幼虫血淋巴中游离氨基酸总量明显增加,而寄生后第5天则有所下降。寄生能导致寄主血淋巴中各种游离氨基酸含量发生变化,与对照相比,谷氨酸、脯胺酸和酪氨酸含量总体上均升高,寄生后第1天和第3天,胱氨酸和丙氨酸含量分别显著上升,寄生后第4天,亮氨酸、异亮氨酸、赖氨酸和精氨酸含量也表现相同的趋势。推测寄生蜂在寄主体内生长发育消耗了虫体内的养分,引起寄主幼虫体内游离氨基酸含量发生变化,且这种变化有利于寄生蜂生长发育。

Changes in content of free amino acid in hemolymph of host larval Spodoptera litura parasitized by Microplitis pallidipes

The beet armyworm (Spodoptera litura) is a global insect pest that feeds on various agricultural crops including vegetables,cotton,and ornamentals.To investigate the physiological mechanism that Microplitis pallidipes parasitizes larval S.litura,we collected the hemolymph of host larvae (parasitizated and unparasitized),and measured the content of free amino acid using an amino acid analyzer.The results indicated that the content of total free amino acid in the hemolymphs of larval S.litura were consistently higher from 1 to 4 d,but lower on 5 d after parasitization in the parasitized group than in the control.The content of 17 free amino acids in the hemolymph of the S.litura larvae changed after parasitization with significant differences in some free amino acids.The content of Glu,Pro and Tyr in the larval hemolymph were consistently higher after parasitization than that in the control.The content of Cys and Ala significantly increased on 1 and 3 d after parasitization and the content of Leu,Ile,Lys and Arg showed similar trend on 4 d after parasitization.Our results reveal that the content of free amino acid varies in host larvae at different developmental stages of the parasitoids and that this variation benefits the growth of parasitoids.