Reduced fitness of Daphnia magna fed a Bt-transgenic maize variety

Abstract

Genetically modified (GM) maize expressing the Bt-toxin Cry1Ab (Bt-maize) was tested for effects on survival, growth, and reproduction of the water flea <i>Daphnia magna</i>, a crustacean arthropod commonly used as a model organism in ecotoxicological studies. In three repeated experiments, <i>D. magna</i> were fed 100% ground maize in suspension, using either GM or isogenic unmodified (UM) maize. <i>D. magna</i> fed GM-maize showed a significantly reduced fitness performance: The mortality was higher, a lower proportion of females reached sexual maturation, and the overall egg production was lower compared to <i>D. magna</i> fed UM isogenic maize. We conclude that the tested variety of Bt-maize and its UM counterpart do not have the same quality as food sources for this widely used model organism. The combination of a reduced fitness performance combined with earlier onset of reproduction of <i>D. magna</i> fed Bt-maize indicates a toxic effect rather than a lower nutritional value of the GM-maize.