Differential toxicity and uptake of Diazinon on embryo-larval development of Rhinella arenarum.
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, cloacal edema, desquamation and severe hydropsy. Moreover, the characteristic sublethal effect of Diazinon on larvae was abnormal behavior related to neurotoxicity with a NOEC-168 h of 4.5 mg Diazinon 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.
Instituto de Investigación e Ingeniería Ambiental (3iA), Universidad Nacional de San Martín, Campus Miguelete, 25 de Mayo y Francia, C.P. 1650 San Martín, Provincia de Buenos Aires, Argentina.
Carolina Mariel
CM
Aronzon
Centro de Investigaciones del Medio Ambiente, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calle 47 y 115, C.P. 1900 La Plata, Provincia de Buenos Aires, Argentina.
Damián J G
DJ
Marino
Centro de Investigaciones del Medio Ambiente, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calle 47 y 115, C.P. 1900 La Plata, Provincia de Buenos Aires, Argentina.
Alicia E
AE
Ronco
Instituto de Investigación e Ingeniería Ambiental (3iA), Universidad Nacional de San Martín, Campus Miguelete, 25 de Mayo y Francia, C.P. 1650 San Martín, Provincia de Buenos Aires, Argentina. Electronic address: perezcoll@unsam.edu.ar.
Cristina Silvia
CS
Pérez Coll
D000818:Animals; D001692:Biological Transport; D002025:Bufonidae / Q000196:embryology* / Q000254:growth & development*; D003976:Diazinon / Q000378:metabolism* / Q000633:toxicity*; D054750:Ecotoxicology; D004625:Embryo, Nonmammalian / Q000187:drug effects*; D004785:Environmental Pollutants / Q000378:metabolism / Q000633:toxicity; D005260:Female; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D007928:Lethal Dose 50; D010575:Pesticides / Q000378:metabolism / Q000633:toxicity
D004785:Environmental Pollutants; D010575:Pesticides; D003976:Diazinon
Amphibian embryo-larval development; Diazinon; Differential toxicity; Neurotoxicity; Teratogenesis; Uptake