Journal
CHEMOSPHERE
Volume 100, Issue -, Pages 50-56Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.chemosphere.2013.12.078
Keywords
Amphibian embryo-larval development; Differential toxicity; Teratogenesis; Neurotoxicity; Uptake; Diazinon
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Funding
- Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Argentina
- Universidad Nacional de San Martin (UNSAM), Argentina
- Agencia de Promocion Cientifica y Tecnologica, Argentina [PICT-2010-0891]
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Diazinon, an anti-cholinesterase organophosphate, is an extensively used pesticide. The main objective of this work was to assess the lethal and sublethal effects of Diazinon and its comparison with the uptake by embryos and larvae of the common South American toad Rhinella arenarum by means of standardized bioassays during acute (96 h), short-term chronic (168 h) and chronic (504 h) exposures. Toxicity resulted time- and stage-dependent, thus the lethal concentration 50 for 96 h, 168 h and 504 h were 27.2; 20.1 and 6.8 mg Diazinon L-1 for embryos and 8, 6.7 and 1.9 mg Diazinon L-1 for larvae. It is noteworthy the remarkable differences found in the concentration which caused lethality with those causing adverse effects on development such as malformations (teratogenic effects). Therefore, the teratogenic index from 144 h was greater than two; the main adverse effects were axial flexures, irregular borders, wavy tail, microcephaly, malformed mouth and adhesive structures, gut miscoiling, underdeveloped gills, cloaca( edema, desquamation and severe hydropsy. Moreover, the characteristic sublethal effect of Diazion on larvae was abnormal behavior related to neurotoxicity with a NOEC-168 h of 4.5 mg Diazion L-1. Diazinon contents in R. arenarum were time-dependent and significantly related to exposure concentration for both embryos and larvae. Diazinon contents were also stage-dependent, as it was up to 27 times higher for organisms exposed from blastula stage onwards than early larvae. These facts and the Hazard Quotients, a numerical expression of ecological risk, of 2.73, which is above USEPA's Level of Concern, showed the threat that Diazinon represents for R. arenarum populations. (C) 2014 Elsevier Ltd. All rights reserved.
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