The ecological risks of BT crops in amphibians: possible effects of insect-resistant intacta RR2 PRO® soybean diets on Leptodactylus Gracilis tadpoles

Abstract

The toxic or nutritionally deleterious effects resulting from theconsumption of genetically modified (GM) foods are still a matter ofdebate worldwide. In amphibians, the environmental impact of theBacillus thuringiensis (Bt) toxin (e.g., Cry proteins) engineered into GMBt crops is barely known. Thus, the aim of the present study was toevaluate the possible effects of a diet based on GM Bt-soybean in contrastwith a common vegetable diet (lettuce) on Leptodactylus gracilistadpoles. We evaluated their growth performance, histological changes inthe intestine, and some hematological parameters as indicators ofphysiological stress. In the laboratory, tadpoles were either fed with greenBt-soybean leaves for 15 days or with lettuce leaves (controls). Bothtreatments resulted in a low mortality rate (less than 3%) during theexperimental period. No external anomalies were detected anddevelopment Gosner stages were similar (36-37). However, larvae fed onlettuce grew faster and reached a larger size and greater weight than Btsoybean-fed tadpoles. Thus, the Bt-soybean diet may have inducedhistopathological changes in the tadpole intestine (greater thickness of theintestinal wall) and some cytotoxic effects on erythrocytes (lower mitoticindex and anisocytosis). Our preliminary results highlight the potentialeffects of a diet based on Bt-soybean leaves on L. gracilis tadpoles.Further research is needed to evaluate the ecotoxicological risk oftransgenic insecticidal proteins on non-target herbivores due to themassive use of Bt crops.