Uptake of Bt-toxin in herbivores feeding on transgenic maize and consequences for the predator Chrysoperla carnea
Authors: Dutton, A., Klein, H., Romeis, J., Bigler, F.
Journal, Volume, Year: Ecological Entomology, volume 27:441-447, 2002
Three herbivores (Rhopalosiphum padi, Tetranychus urticae, and Spodoptera littoralis) were fed transgenic (Cry1Ab) or isogenic corn material. The amount of Bt toxin in each was determined using ELISA and their performance was assayed using the intrinsic rate of increase. Only performance of S. littoralis was significantly affected. T. urticae had 2.5 microgram toxin/g, S. littoralis had 0.72 microgram/g, and only trace amounts were found in R. padi. The three herbivores were also used in tests as a food source for Chrysoperla carnea, assessing survival, development, and weight. Instar-specific survival and development were affected only in C. carnea fed S. littoralis (Bt fed vs non-Bt fed). The prey (T. urticae) with the highest concentration of Bt had no significant effect compared with non-Bt fed T. urticae.
Authors suggest that only S. littoralis changes the protein so that it is more toxic to C. carnea or that the T. urticae deactivate or degrade the toxin and that this accounts for the discrepancy between effects on C. carnea and the amount of toxin in prey. However, it is more likely that the S. littoralis, which are already a sub-optimum food source, were of reduced quality to C. carnea. The T. urticae were not susceptible to the toxin, despite having more. It is unlikely that T. urticae degraded or changed the toxin, as it would have been harder to detect with the ELISA.