Evolution, Ecology & Genetics, Research School of Biology, Australian National University, Canberra, ACT 0200, Australia.
J Insect Physiol. 2010 Dec;56(12):1958-65. doi: 10.1016/j.jinsphys.2010.08.016. Epub 2010 Sep 8.
Larvae of Manduca sexta are parasitised by the braconid wasp, Cotesia congregata. In this study we examined whether contraction activity of the semi-isolated foregut was affected by parasitism. Parasitised larvae fed significantly less compared with unparasitised control larvae, therefore starved unparasitised animals were used as controls. Rate and force of foregut contraction in control caterpillars significantly increased with days of starvation. However, only contraction force in foreguts of parasitised larvae increased over time following infection. The presence of food in the foregut of caterpillars starved 7 days suggested that food moved anteriorly from the midgut and that contraction became antiperistaltic, but only normal peristalsis occurred in parasitised caterpillars. Rate and force of gut contractions may be controlled independently and starvation did not truly mimic the effects of the parasitoids. Dissection of caterpillars with emerged wasps indicated that 47% had a single wasp larva wedged between the brain and foregut. Removal of this wasp caused an increased rate of foregut contraction of the caterpillar. Brain removal resulted in an increased rate of foregut contraction only for unparasitised insects. Sectioning of the recurrent nerve temporarily eliminated foregut contraction, but the contraction began again in 250 s in parasitised caterpillars prior to wasp emergence, compared with over 500 s for unparasitised controls and parasitised caterpillars following wasp emergence.
烟青虫的幼虫被长尾小蜂寄生。在这项研究中，我们研究了半分离前肠的收缩活动是否受到寄生的影响。与未被寄生的对照幼虫相比，被寄生的幼虫进食量明显减少，因此饥饿的未被寄生的动物被用作对照。对照幼虫的前肠收缩率和收缩力随着饥饿天数的增加而显著增加。然而，只有感染后被寄生的幼虫的前肠收缩力随着时间的推移而增加。饥饿 7 天后，前肠中存在食物表明食物从前肠向后移动，收缩变为反蠕动，但寄生幼虫只发生正常蠕动。肠道收缩的速度和力可能是独立控制的，饥饿并不能真正模拟寄生蜂的影响。对有已羽化的寄生蜂的幼虫进行解剖表明，47%的幼虫在前脑和前肠之间有一个单一的寄生蜂幼虫。取出这个寄生蜂会导致幼虫前肠收缩速度增加。去除大脑只会导致未被寄生的昆虫前肠收缩速度增加。切断返回神经会暂时消除前肠收缩，但在寄生幼虫中，前肠收缩在寄生蜂羽化前 250 秒再次开始，而未被寄生的对照幼虫和寄生幼虫在寄生蜂羽化后则需要超过 500 秒。
