Toxic effects of carbendazim and n‐butyl isocyanate, metabolites of the fungicide benomyl, on early development in the African clawed frog, Xenopus laevis

Abstract

ABSTRACT:We investigated the toxic effects of carbendazim and n-butyl isocyanate (BIC), metabolites of the fungicide benomyl, on development in the African clawed frog, Xenopus laevis. To test the toxic effects, frog embryo teratogenesis assays using Xenopus were performed. Embryos were exposed to various concentrations of carbendazim (0-7 lM) and BIC (0-0.2 lM). LC 100 for carbendazim and BIC were 7 and 0.2 lM, respectively, and the corresponding LC 50 , determined by probit analysis, were 5.606 and 0.135 lM. Exposure to carbendazim concentrations !3 lM and BIC concentrations !0.1 lM resulted in 10 different types of severe external malformation. Histological examinations revealed dysplasia of the brain, eyes, intestine, and somatic muscle, and swelling of the pronephric ducts. These phenomena were common in both test groups. The tissue-specific toxic effects were investigated with an animal cap assay. Neural tissues are normally induced at a high frequency by activin A, however, the induction of neural tissues was strongly inhibited by the addition of carbendazim. Conversely, the addition of BIC resulted in weak inhibition of neural tissues. Electron micrographs of animal cap explants revealed degeneration of cell junctions in the carbendazim-treated group, but not in the BIC-treated group. Numerous residual yolk platelets and mitochondrial degeneration were commonly observed in both test groups. The gene expression of cultivated animal cap explants was investigated by reverse transcriptase-polymerase chain reaction and revealed that expression of the neural-specific marker neural cell adhesion molecule was more strongly inhibited in the carbendazim-treated group than in the BIC-treated group. # 2008 Wiley Periodicals, Inc. Environ Toxicol 23: 131-144, 2008.

Infrared spectroscopy detects changes in an amphibian cell line induced by fungicides: Comparison of single and mixture effects

“…The generation of ROS by environmental contaminants and subsequent oxidative damage may negatively affect tadpole reproduction and development and is related to amphibian population declines (Costa et al, 2008); therefore, there may be population-level consequences of these low-dose exposures. Carbendazim has previously been associated with lipid peroxidation in milk fish (Palanikumar et al, 2014) and in rats (Rajeswary et al, 2007), although only developmental and genotoxic effects have been measured thus far in amphibians (Yoon et al, 2008;ZollMoreux and Ferrier, 1999), despite the wide usage and detection of carbendazim in surface waters at low concentrations (Palma et al, 2004).…”

“…Such effects include endocrine disruption in adult amphibians (Poulsen et al, 2015), and developmental defects such as craniofacial abnormalities in the case of triazole fungicides (Di Renzo et al, 2011;Groppelli et al, 2005;Papis et al, 2006), or inhibition of the differentiation of neural tissues and organ dysplasia following exposure to benzimidazole fungicides (Yoon et al, 2003;Yoon et al, 2008).…”

Unlikely Remedy: Fungicide Clears Infection from Pathogenic Fungus in Larval Southern Leopard Frogs (Lithobates sphenocephalus)

“…This may be due in part to the relatively short half-life of TM [12] and potential breakdown into inert products. However, a byproduct of TM breakdown, carbendazim, has been linked to adverse effects on amphibian larval growth, development, and survival [13]. Even so, with repeat pesticide exposure, runoff, and spraydrift [9], [14], aquatic organisms with prolonged larval periods are likely exposed to TM multiple times through ontogeny, thus decreasing the probability of breakdown into inert components.…”

Numerical variations and spontaneous malformations in the early embryos of the Korean salamander, Hynobius leechii, in the farmlands of Korea

“…According to reports, diazinon in combination with other pesticides reduces the growth and survival rate of amphibians (Relyea, 2004) and increases the rate of spinal malformations along with a reduction in the hatching rate (Hamm and Hinton, 2000). The fungicide, benomyl, inhibits neural tissue differentiation in X. laevis (Yoon et al, 2003), and its metabolites cause malformations of various organs, including dysplasia of the brain (Yoon et al, 2008).…”