Effects of starvation and parasitism on foregut contraction in larval Manduca sexta

Paul D. Cooper*, Nancy E. Beckage

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    4 Citations (Scopus)


    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.

    Original languageEnglish
    Pages (from-to)1958-1965
    Number of pages8
    JournalJournal of Insect Physiology
    Issue number12
    Publication statusPublished - Dec 2010


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