PM01 Amphibian Research and Monitoring
Exhibit Hall
8:00 AM - Monday, 10 November 2003
(PM004) Role of the jelly coat in the development of two frog species exposed to Roundup® and Diazinon®, using FETAX.
Griebeling, K1, Rayburn, J1, 1 Jacksonville State University, Jacksonville, Alabama, USA
ABSTRACT- The jelly coat surrounding the vitelline envelope of frog eggs helps eggs adhere to vegetation and provides a physical barrier between the early-stage zygote and its environment. A well-known developmental toxicity test, the Frog Embryo Teratogenesis Assay--Xenopus (FETAX) assay, uses dejellied Xenopus laevis eggs as standard practice. It is unclear whether the jelly coat of Xenopus or native frog species can provide any protection against a direct chemical agent, such as the pesticide Diazinon or the herbicide Roundup. A modified FETAX assay was used to assess the effects of Roundup and Diazinon on mortality, malformation, and effect on tadpole length for two frog species: the African clawed frog (Xenopus laevis) and the American toad (Bufo americanus). Concentrations of commercially-available formulations of each chemical ranged from 0.001% to 0.015% v/v and were tested on eggs with both jelly coat left intact and removed by cysteine. A multivariate risk analysis (assessing a combination of tadpole mortality, malformation, and growth) using ToxTools (Cytel Software Corp.) was used to calculate the risk of adverse effects for Diazinon and Roundup. A two factor ANOVA, using concentration and jelly coat, was used to determine if the jelly coat had any effect on or interaction with the developmental toxicity. Results indicate that the jelly coat significantly decreases sensitivity to the chemicals at their high concentrations, compared to dejellied eggs. Xenopus embryos show a higher incidence of mortality and malformation with exposure to both Roundup and Diazinon than the Bufo embryos. Lastly, this study confirms that Diazinon has a higher toxicity to developing frog embryos of both species than Roundup.
Key words: Bufo americanus, Xenopus laevis, FETAX, jelly coat