RRC ID 31787
Author Saka M, Tada N, Kamata Y.
Title Application of an amphibian (Silurana tropicalis) metamorphosis assay to the testing of the chronic toxicity of three rice paddy herbicides: simetryn, mefenacet, and thiobencarb.
Journal Ecotoxicol Environ Saf
Abstract We examined the chronic toxicity of three rice paddy herbicides (simetryn, mefenacet, and thiobencarb) using an amphibian (Silurana tropicalis) metamorphosis assay (a 28-day semistatic test under an individual-separated exposure system). Each herbicide was tested at two concentrations (1/100 and 1/10 of the 96-h LC50 value reported previously) with morphometric, gravimetric, and thyroid-histological endpoints. Simetryn caused significant retardation in growth and development at both test concentrations (0.04 and 0.40mg/L), as indicated by significantly shorter total body lengths and hind limb lengths, smaller wet body masses, and delayed developmental stages compared to those observed in the control tadpoles. However, no clear histopathology was observed in the thyroid glands of the tadpoles exposed to simetryn. These results suggest that simetryn can act as a chemical stressor retarding tadpole growth and development without disrupting thyroid functions, even at 1/100 of the 96-h LC50 value. In addition, scoliosis near the tail base was observed in the tadpoles exposed to 0.40mg/L of simetryn at a significantly high incidence (7/30=23.3%). Therefore, simetryn can also act as a teratogen inducing axial malformations at 1/10 of the 96-h LC50 value. During the 28 days of exposure, neither mefenacet (0.03 and 0.30mg/L) nor thiobencarb (0.008 and 0.080mg/L) induced any abnormalities, although the test concentrations measured immediately before the solution renewals decreased to nearly 50 percent of the nominal concentrations since day 14. Because the concentrations tested for simetryn are likely to occur in paddy water, wild anuran tadpoles in paddy water may therefore be adversely impacted by simetryn.
Volume 92
Pages 135-43
Published 2013-6-1
DOI 10.1016/j.ecoenv.2013.03.023
PII S0147-6513(13)00111-5
PMID 23597675
MeSH Acetanilides / toxicity* Agriculture Animals Benzothiazoles / toxicity* Biological Assay Herbicides / toxicity* Larva / drug effects Larva / growth & development Lethal Dose 50 Metamorphosis, Biological / drug effects* Oryza Risk Assessment Thiocarbamates / toxicity* Toxicity Tests, Chronic Triazines / toxicity* Water Pollutants, Chemical / toxicity Xenopus / physiology
IF 4.872
Times Cited 5
Xenopus tropicalis Golden line