Metal accumulation by Ceratitis capitata (Diptera) and transfer to the parasitic wasp Coptera occidentalis (Hymenoptera)

Abstract

AbstractAccumulation of lead (Pb), cadmium (Cd), and copper (Cu) (from food) by the fruit fly (Ceratitis capitata Wiedemann; Diptera, Tephritidae) and the transfer of the metals to the internal solitary pupal parasitoid Coptera occidentalis Muesebeck (Hymenoptera, Proctotrupoidea, Diapriidae) were investigated experimentally by exposing host larvae to contaminated diets. Each metal was added to the diet at two concentrations: Cd, 50 and 100 μg/g; Pb and Cu, 400 and 800 μg/g diet dry weight. Whole‐body concentrations of the applied metals and of zinc (Zn) in the host and parasitoid were determined by atomic absorption photospectrometry. Concentration factors (CFs) for all metals (based on initial dietary concentrations) were lower at the higher food contamination level. Cadmium (CF = 3.2–7.05) and Zn (CF = 2.79–7.05) were accumulated by fruit fly larvae more efficiently than were Pb (CF = 0.95–1.02) and Cu (CF = 0.35–0.78, except control: 37.2). Considerable quantities of the metals taken up by host larvae and retained in their pupae were eliminated via the meconium after eclosion of flies (Cd, 33%; Pb, 33–51%; Cu 24–39% of pupal metal burdens). Low proportions of the host metal content were transferred to the parasitoid (0.4–5.6% and 0.3–1.4% to pupae and adults, respectively, depending on the applied metal). The remaining amounts of the metals were detected in the host puparia that remained after wasp eclosion. Vitality and fecundity of the parasitoid were not impaired by host metal contamination. Thus, the parasitic wasp probably possesses an efficient regulatory mechanism that mediates excretion of toxic metals before pupation and that diminishes the potential hazard of high metal loads in the host.