ACCUMULATION AND EGESTION OF DIETARY COPPER AND CADMIUM BY THE GRASSHOPPER LOCUST A MIGRATORIA R-AND-F (ORTHOPTERA, ACRIDIDAE)

Copper and cadmium budgets were studied for a model insect herbivore/h ost plant system comprising the oligophagous leaf-chewing grasshopper (Locusta migratoria) feeding on Zea mays (Gramineae). Fifth instar lar vae were fed, for between 5 and 20 days, on maize foliage contaminated with either copper, cadmium or on control foliage containing no exces s metal. Male and female locusts fed on copper-treated maize retained 45 and 42% of ingested copper respectively, figures not significantly different from the 41 and 33% retained on untreated maize. Remaining c opper was egested with the faeces. Locusts fed on copper-treated maize showed an increase of 27% in body copper burden compared with those o n the control diet: the increase was independent of time on the diet. Female locusts retained 33% and males 21% of ingested cadmium. Faecal cadmium levels were elevated, and accumulation in both sexes was propo rtional to time on the Cd-enriched diet. For both copper and cadmium, some ingested metal probably passed directly through the locust gut, b ound to undigested food material. Results suggest that grasshoppers ma y effectively regulate excess dietary copper, but are unable efficient ly to regulate cadmium. Copyright (C) 1996 Elsevier Science Ltd