Demographic responses of Daphnia magna fed transgenic Bt-maize

02.11.2009

By Thomas Bøhn, Terje Traavik and Raul Primicerio

Abstract

The food/feed quality of a variety of genetically
modified (GM) maize expressing Cry1Ab Bt-toxin was
tested over the life-cycle of Daphnia magna, an arthropod
commonly used as model organism in ecotoxicological
studies. Demographic responses were compared between
animals fed GM or unmodified (UM) near isogenic maize,
with and without the addition of predator smell. Agespecific
data on survival and birth rates were integrated and
analysed using life tables and Leslie matrices. Survival,
fecundity and population growth rate (PGR) data generally
disfavoured transgenic Bt-maize as feed for D. magna
compared to animals fed the unmodified (UM) near isogenic
line of maize. Decomposition of age-specific effects
revealed that the most important contributions to a reduced
PGR in the GM-fed group came from both fecundity and
survival differences early in life. We conclude that juvenile
and young adult stages are the most sensitive experimental
units and should be prioritized in future research. These
stages are often omitted in toxicological/ecotoxicological
studies and in feeding trials.

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