title: Daphnia magna negatively affected by chronic exposure to purified Cry-toxins.
abstract: Cry-toxin genes originating from Bacillus thuringiensis are inserted into genetically modified (GM) plants, often called Bt-plants, to provide insect resistance to pests. Significant amounts of Bt-plant residues, and thus Cry-toxins, will be shed to soil and aquatic environments. We exposed Daphnia magna to purified Cry1Ab and Cry2Aa toxins for the full life-span of the animals. We used single toxins in different doses and combinations of toxins and Roundup(®), another potential stressor on the rise in agricultural ecosystems. Animals exposed to 4.5 mg/L (ppm) of Cry1Ab, Cry2Aa and the combination of both showed markedly higher mortality, smaller body size and very low juvenile production compared to controls. Animals exposed to 0.75 mg/L also showed a tendency towards increased mortality but with increased early fecundity compared to the controls. Roundup(®) stimulated animals to strong early reproductive output at the cost of later rapid mortality. We conclude that i) purified Cry-toxins in high concentrations are toxic to D. magna, indicating alternative modes-of-action for these Cry-toxins; ii) Cry-toxins act in combination, indicating that 'stacked events' may have stronger effects on non-target organisms; iii) further studies need to be done on combinatorial effects of multiple Cry-toxins and herbicides that co-occur in the environment.
authors.affiliation: GenØk - Centre for Biosafety, The Science Park, P.O. Box 6418, 9294 Tromsø, Norway. Electronic address: thomas@genok.org.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bøhn
authors.affiliation: GenØk - Centre for Biosafety, The Science Park, P.O. Box 6418, 9294 Tromsø, Norway; Laboratory of Plant Developmental Physiology and Genetics, Federal University of Santa Catarina (UFSC), Rodovia Admar Gonzaga 1346, Florianópolis, 88034-001, Brazil.
authors.forename: Carina Macagnan
authors.initials: CM
authors.lastname: Rover
authors.affiliation: GenØk - Centre for Biosafety, The Science Park, P.O. Box 6418, 9294 Tromsø, Norway; Climate Impact Research Center CIRC, Department of Ecology and Environmental Sciences, Umeå University, SE-98107 Abisko, Sweden.
authors.forename: Philipp Robert
authors.initials: PR
authors.lastname: Semenchuk
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000378:metabolism*; D003621:Daphnia / Q000378:metabolism*; D014118:Toxins, Biological / Q000494:pharmacology*
chemical_list: D014118:Toxins, Biological
keywords: Bt-transgenic plants; Cry-toxins; Daphnia magna; Non-target organisms; Roundup; Toxicity