Non-consumptive effects of the zigzag ladybird beetle, Cheilomenes sexmaculata (Fab.) on its prey, the cotton aphid, Aphis gossypii Glover

Abstract

ABSTRACT Non-consumptive effects (NCEs) of predators include non-lethal changes in prey altering their behaviour and physiology with increased oxidative stress under predation-risk. Although prey species may exhibit a complex of antioxidant mechanisms, these may be inadequate to result in a reduction of adverse biological consequences in the prey. Reduced prey fitness may result and could contribute to enhancing biological control. Cotton aphid, Aphis gossypii is an important polyphagous pest predated by a variety of coccinellids and very much preferred by zigzag ladybird beetle, Cheilomenes sexmaculata (F.). Possible NCEs of C. sexmaculata on cotton aphid were studied to understand the underlying anti-oxidative mechanisms. We found that the non-consumptive effect is induced by olfactory cues, and even short-duration exposure could raise antioxidant enzyme levels in the cotton aphid. Aphids antioxidant mechanism uses upregulation of superoxide dismutase (SOD) and catalase (CAT) but not sufficiently to offset the oxidative damage that led to increased Malondialdehyde (MDA) content. Affected aphid biology with reduced reproductive performance as recorded 30.0 ± 4.40 nymphs/female under predation-risk compared to no-predation (41.6 ± 5.60). Further, the induction of winged morphs increased with active predation (21.53 ± 1.05%) and increased risk of predation (18.28 ± 4.86%) compared to aphids not exposed to predators (6.00 ± 2.99%). Antioxidant production costs were compensated by the exposed aphids directly through reduced reproduction and also triggered winged morphs in progeny. Non-consumptive effect might directly contribute to declines in aphid populations through reduced reproduction and may also stimulate dispersal of winged morphs.