The Herpetological Journal

pp. 307-317

Authors: Zahra Mossadeghi, Zeinab Parvaresh, Nazihe Seddighi, Fatemeh Roushenas, Samira Rahimi,
Elmira Hasani, Zahra Derakhshan & Mohsen Nokhbatolfoghahai

Abstract: Butachlor is the most commonly used herbicide on rice paddy fields in Asian countries. Paddy fields are habitats commonly
used for reproduction by many species of amphibians. We examined the effects of butachlor on Bufotes viridis development.
Amplectant pairs of B. viridis were kept in the laboratory in an aquarium overnight, and their spawn collected the next morning.
Eggs were exposed to butachlor at different concentrations (0.1, 0.2, 0.8, 1, 2, 3.5, 7, 14μg/l), all lower than the concentration
used in the area (rice paddy fields) by farmers. Eggs were allowed to develop to Gosner stage 24 and their developmental
patterns compared with those reared in normal conditions (control). In order to examine whether jelly coats have a significant
role in the protection of developing eggs from the toxin, another group of eggs were de-jellied and treated in the same
procedure. The LC50 value of butachlor was calculated as 14μg/l and 7μg/l after 96h for jellied eggs and de-jellied eggs
respectively. Butachlor lead to a range of external and internal body malformations. Butachlor concentrations of 2μg/l, 7μg/l
and 14μg/l reduced embryonic growth and development. A high mortality rate and both internal and external abnormalities
were observed at lower concentrations than used in fields, suggesting that butachlor can have significant negative effects on
amphibians where this herbicide is used.

Keywords: amphibian; Bufotes viridis; butachlor; embryo; embryonic development; de-jellied egg