The effects of elevated host-plant cadmium and copper on the performance of the aphid Aphis fabae (Homoptera: Aphididae).
Abstract
The uptake patterns of cadmium and copper by Aphis fabae from its food plant, Vicia faba, grown under control and elevated metal treatments, were compared. Initial experiments demonstrated significant Cu and Cd accumulation by treated food plants. Aphids feeding on treated plants accumulated Cd, but no Cu. Concn of Cu were significantly higher in the honeydew of aphids feeding on treated plants compared with controls, whereas those of Cd were not. The aphid thus dealt with Cu and Cd in different ways. Copper was primarily excreted in the honeydew and concn in body tissues did not increase. Cadmium accumulated within the body and little was excreted in honeydew. Nine separate experiments, 4 using Cu and 5 involving Cd treatments, showed little consistent effect of enhanced metal concn on several parameters of aphid growth and reproduction. In one Cu experiment, development period to maturity and reproductive rate were significantly enhanced, but the result was not repeatable in 3 subsequent experiments. Similarly, significant effects of Cd on the same parameters were shown in only one experiment out of 5. The high metal concn used appeared to have few deleterious effects on aphid growth, development or reproduction. Results are discussed in the context of trace metal transfer between trophic levels in polluted ecosystems and the possible main transfer pathways for Cu and Cd are identified.