title: Limitations in dose-response and surrogate species methodologies for risk assessment of Cry toxins on arthropod natural enemies.
abstract: Dose-response assays and surrogate species are standard methods for risk analysis for environmental chemicals. These assume that individuals within a species have unimodal responses and that a surrogate species can predict responses of other related taxa. We exposed immature individuals of closely related aphidophagous coccinellid predators, Cycloneda sanguinea and Harmonia axyridis, to Cry1Ac and Cry1F toxins through uniform and constant artificial tritrophic exposure through Myzus persicae aphids. Both toxins were detected in coccinellid pupae, with individual and interspecific variation. Uptake was significantly higher in H. axyridis than in C. sanguinea, both in the proportion of individuals and the concentrations per individual. We also observed bimodal uptake of the Cry toxins by H. axyridis, which indicated that some individuals had low bioaccumulation and some had high bioaccumulation. This suggests that standard dose-response assays need to be interpreted with caution and future assays should examine the modality of the responses. In addition, the similarity in the biological effects of the Cry toxins in the two predators was due to different biological exposure mechanisms. The majority of H. axyridis were exposed both internally and in the gut, while C. sanguinea was exposed primarily in the gut. Thus, despite their close phylogenetic relatedness, these species would not be good surrogates for each other and the surrogate species methodology should be tested more rigorously.
authors: Embrapa Genetic Resources and Biotechnology, Parque Estação Biológica, W5 Norte, P.O. Box 02372, Brasília, DF, 70770-917, Brazil. debora.pires@embrapa.br.
authors: Débora P
authors: DP
authors: Paula
authors: Department of Entomology, University of Minnesota, 219 Hodson Hall, 1980 Folwell Ave., St. Paul, MN, 55108, USA.
authors: David A
authors: DA
authors: Andow
authors: Embrapa Genetic Resources and Biotechnology, Parque Estação Biológica, W5 Norte, P.O. Box 02372, Brasília, DF, 70770-917, Brazil.|University of Brasília, Campus Universitário Darcy Ribeiro, Brasília, DF, Brazil.
authors: André
authors: A
authors: Bellinati
authors: Embrapa Genetic Resources and Biotechnology, Parque Estação Biológica, W5 Norte, P.O. Box 02372, Brasília, DF, 70770-917, Brazil.|University of Brasília, Campus Universitário Darcy Ribeiro, Brasília, DF, Brazil.
authors: Renata Velozo
authors: RV
authors: Timbó
authors: Embrapa Genetic Resources and Biotechnology, Parque Estação Biológica, W5 Norte, P.O. Box 02372, Brasília, DF, 70770-917, Brazil.
authors: Lucas M
authors: LM
authors: Souza
authors: Embrapa Genetic Resources and Biotechnology, Parque Estação Biológica, W5 Norte, P.O. Box 02372, Brasília, DF, 70770-917, Brazil.
authors: Carmen S S
authors: CS
authors: Pires
authors: Embrapa Genetic Resources and Biotechnology, Parque Estação Biológica, W5 Norte, P.O. Box 02372, Brasília, DF, 70770-917, Brazil.
authors: Edison R
authors: ER
authors: Sujii
mesh_terms: D000818:Animals; D001042:Aphids / Q000502:physiology*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000633:toxicity*; D001517:Coleoptera / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004731:Endotoxins / Q000633:toxicity*; D006460:Hemolysin Proteins / Q000633:toxicity*; D007814:Larva; D010572:Pest Control, Biological / Q000379:methods*; D018570:Risk Assessment
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis
keywords: Coccinellid; GM crops; Predator; Surrogacy