Establishing a system with Drosophila melanogaster (Diptera: Drosophilidae) to assess the non-target effects of gut-active insecticidal compounds

Abstract

Potentially adverse effects on ecosystem functioning by the planting of insect-resistant, genetically engineered plants or by the direct application of insecticidal compounds are carefully evaluated in pre-market risk assessments. To date, few studies have assessed the potential risks of genetically engineered crops or insecticidal compounds on the survival and fitness of dipteran species, despite their important contribution to ecosystem services such as decomposition in agricultural systems. Therefore, we propose that Drosophila melanogaster Meigen (Drosophilidae) be used as a surrogate species for the order Diptera and for the functional guild of soil arthropod decomposers in pre-market risk assessments. We developed two assays to assess the toxicity of gut-active insecticidal compounds to D. melanogaster. One assay uses groups of fly larvae, and the other uses individuals. Cryolite, a mineral pesticide, proved to be an adequate positive control. The effects of cryolite on D. melanogaster larvae were comparable between the two assays. Statistical power analyses were used to define the number of replications required to identify different effect sizes between control and treatment groups. Finally, avidin, E-64, GNA, and SBTI were used as test compounds to validate the individual-based assay; only avidin adversely affected D. melanogaster. These results indicate that both D. melanogaster assays will be useful for early tier risk assessment concerning the effects of orally active compounds on non-target dipterans.

Effects of purified or plant-produced Cry proteins on Drosophila melanogaster (Diptera: Drosophilidae) larvae

“…Feeding experiments were conducted with a strain of D. melanogaster that had been used in earlier studies in our laboratory 16 . The flies were initially provided by W. J. Gehring (University of Basel, Switzerland) and cultured at Agroscope for several generations on an artificial diet according to Haller et al .…”

“…The flies were initially provided by W. J. Gehring (University of Basel, Switzerland) and cultured at Agroscope for several generations on an artificial diet according to Haller et al . 16 . Freshly laid eggs (<4 h old) of D. melanogaster were used in the feeding experiments.…”

“…The bioassays followed the “single-fly” protocol by Haller et al . 16 with the following modification: the standard D. melanogaster diet was prepared with the amount of solid ingredients reduced by one third. Once the diet cooled down below 55 °C, it was poured into plastic boxes and the milled plant material was added immediately with steady stirring.…”

“…After one freshly laid egg (<4 h old) of D. melanogaster was added to each test well, the plates were sealed, stored in the climate chamber (25 ± 1 °C, 70 ± 10% humidity, photoperiod 16 hours), and checked every day until all adults had emerged. The following parameters were recorded: survival (emergence of an adult fly), developmental time, adult dry weight, and wing size 16 .…”

“…One of the trials, however, had to be discarded because the control mortality exceeded 30%; a quality criterion established in Haller et al . 16 . Additionally, wells in which the diet dried out or which were contaminated with fungi, were excluded from analyses, resulting in a total of 51 to 61 replications per treatment and 110 replications for the negative control treatment that could be used for analyses.…”