Journal
AQUATIC TOXICOLOGY
Volume 96, Issue 2, Pages 130-134Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.aquatox.2009.10.009
Keywords
Adaptation; Dictyosphaerium chlorelloides; Diquat; Mutation; Scenedesmus intermedius; Simazine
Categories
Funding
- [S-OSOS/AMB/0374]
- [MAM 093/2002]
- [CGL 2005- 01938/BOS]
- [CGL 2004-02701-HID]
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Aquatic ecosystems located close to agricultural areas are increasingly polluted by herbicides. We evaluated the capacity for adaptation of green microalgae to lethal concentrations of the herbicide simazine in one strain of Dictyosphaerium chlorelloides and two strains of Scenedesmus intermedius, as well as adaptation to the herbicide cliquat in one of the strains of S. intermedius. A Luria-Delbrilck fluctuation analysis was carried out in order to distinguish between resistant cells arising from physiological adaptation (acclimatization) or post-adaptive mutation (both events occurring after the exposure to the herbicides), and adaptation due to mutations before the exposure to the herbicides. Simazine-resistant cells arose by rare spontaneous mutations before the exposure to simazine, with a rate of 3.0 x 10(-6) mutants per cell per generation in both strains of S. intermedius, and of 9.2 x 10(-6) mutants per cell per generation in D. chlorelloides. Diquat-resistant cells in S. intermedius arose by pre-selective mutations with a rate of 17.9 x 10(-6) per cell per generation. Rare, pre-selective mutations may allow the survival of green microalgae in simazine- or diquat-polluted waters, via herbicide-resistant selection. Therefore, human-synthesized pollutants, such as the herbicides simazine and cliquat, could cause the emergence of evolutionary novelties in aquatic environments. (C) 2009 Elsevier B.V. All rights reserved.
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