Effects of four protease inhibitors on the survival of worker bumblebees, Bombus terrestris L.

Abstract

To assess risks posed by transgenic pest-resistant plants, a bumblebee bioassay system was developed. Small and large adults of Bombus terrestris were held individually or in groups of 5, 10 or 20 in cages and survival and rates of pollen, sugar and water consumption determined. Effects on bee survival of Kunitz soybean trypsin inhibitor (SBTI), bovine pancreatic trypsin inhibitor (BPTI) and two potato protease inhibitors, POT-1 and POT-2 were determined. SBTI (10 mg·g-1) and POT-1 (10 and 5 mg.g-1) reduced survival significantly. Bees fed POT-2 (10 mg·g-1) had poorer survival than those fed 0.1 or 0.01 mg·g-1 POT-2. BPTI had no effect. Untreated bee midguts had elastase-like (283.0 ± 16.9 nmol·min-1·g-1 gut), chymotrypsin (148.5 ± 8.4), trypsin (27.2 ± 2.8) and leucine aminopeptidase (258.6 ± 9.6) activities. Elastase-like and chymotrypsin activities were inhibited by SBTI, POT-1 and POT-2, but not BPTI. Trypsin activity was reduced by each inhibitor. Leucine aminopeptidase activity was unaffected.