| Reduced Fitness of Water Fleas Fed GM Corn (27/3/2008) | |
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1.Reduced Fitness of 'Water Fleas' Fed GM Corn - TWN EXTRACT: The authors conclude that the study demonstrated significant and negative long-term effects after feeding a transgenic Bt-maize variety. The combination of life-history traits indicates a toxic response of D. magna to the GM-maize. (item 1) --- 1.Reduced Fitness of Water Fleas Fed GM Corn Dear Friends and Colleagues, RE: Reduced Fitness of Daphnia magna Fed on GM Maize A new study has been published in the Archives of Environmental Contamination and Toxicology which found that the organism Daphnia magna showed reduced fitness performance when fed with a transgenic Bt-maize variety. Daphnia magna is used commonly as a model organism in ecotoxicological studies. The feeding study involved feeding Daphnia magna with either the transgenic maize or the isogenic non-genetically modified variety. The diet consisted of 100% maize. Among the findings are: * Daphnia magna had reduced survival when fed with GM maize compared with non-GM maize. * There was a tendency for those fed with non-GM maize to have a larger body size than those fed on GM maize, however the difference was not significant. * The percentage of females reaching maturation (i.e. producing eggs) was generally lower in the group fed on GM-maize compared to those fed with non-GM maize. * The overall productive output (i.e. total number of eggs produced) was higher in the non-GM maize groups. The results indicate that D. magna, and potentially also other related aquatic zooplankton species, might be vulnerable to transgenic Cry1Ab-maize. The authors conclude that the study demonstrated significant and negative long-term effects after feeding a transgenic Bt-maize variety. The combination of life-history traits indicates a toxic response of D. magna to the GM-maize. The observed effects of transgenic Bt-maize on D. magna call for greater attention, not only on the runoff material from transgenic agricultural fields but also on the sensitivity of aquatic nontarget organisms to transgenic products. The abstract of the study is reproduced below. With best wishes, --- 2.Archives of Environmental Contamination and Toxicology (1) Genøk—Centre for Biosafety, The Science Park, P.O. Box 6418, Tromso, 9294, Norway 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 Daphnia magna, a crustacean arthropod commonly used as a model organism in ecotoxicological studies. In three repeated experiments, D. magna were fed 100% ground maize in suspension, using either GM or isogenic unmodified (UM) maize. D. magna 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 D. magna 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 D. magna fed Bt-maize indicates a toxic effect rather than a lower nutritional value of the GM maize. --- 2.Daphnia - from Wikipedia [extracts only] Daphnia are small, mostly planktonic, crustaceans, between .2 and 5 mm in length. Daphnia are members of the order Cladocera, and are one of the several small aquatic crustaceans commonly called water fleas because of their saltatory swimming style (although fleas are insects and thus only very distantly related). They live in various aquatic environments ranging from acidic swamps to freshwater lakes, ponds, streams and rivers. Uses Sometimes Daphnia may be used in certain environments to test the effects of toxins on an ecosystem. This makes Daphnia an indicator species, particularly useful in that area because of its short lifespan and reproductive capabilities. Ecology The populations of several water flea species are considered threatened. The following are listed as vulnerable by IUCN: Daphnia nivalis, Daphnia coronata, Daphnia occidentalis, and Daphnia jollyi. |
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