LAUSR

The impact of predatory or parasitic natural enemies on their pest prey or hosts arises not only through consumption but also through non-consumptive effects. Multiple studies have investigated the impacts of non-consumptive effects from predators on the behaviour, development and metabolism of invertebrate pests. However, the non-consumptive effects from parasitoids on their insect hosts remain less well understood. Here, we investigated the non-consumptive effects of the parasitoid Encarsia formosa on the fecundity, longevity and metabolism of the whitefly Bemisia tabaci. Results showed that both the fecundity and longevity of whitefly females were significantly reduced when the whiteflies were threatened by Encarsia parasitoids during their nymphal stages. In addition, we tested three costly and potential physiological correlates that may contribute to the fecundity and longevity variation of B. tabaci under the non-consumptive effects: the relative expression level of vitellogenin and its receptor genes (Vg and Vgr), relative expression level of stress proteins (Hsp70 and Hsp90) and the activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). When B. tabaci 4th instar nymphs were threatened for 24 h by E. formosa the relative expression levels of Vg and Vgr were reduced, whereas Hsp70 and Hsp90 were significantly increased. SOD and CAT activities were distinctly up-regulated while POD activity was down-regulated. We propose that, in order to counteract the negative effects of non-consumption, whitefly nymphs need to adjust their performance by changing the expression of related metabolic genes in an energetic cost way, thus reducing the fecundity and longevity of female adults.