The escalating expense and time required to evaluate ecological hazards, whether they be complex environmental mixtures or pure chemical products, warrants the wide-spread use of less expensive alternative toxicity test systems. The Frog Embryo Teratogenesis Assay – Xenopus (FETAX) is one such alternative bioassay that can be effectively used to fill this niche. FETAX is a 4-day, whole embryo-larval developmental toxicity screening assay which uses young embryos of the South African clawed frog, Xenopus laevis. The FETAX system is capable of monitoring acute, chronic, developmental, and behavioral toxicity for ecological and human health hazard assessment. After fifteen years of developing, validating, and standardizing FETAX and over 100 scientific publications, the utility and versatility of this assay is well established for ecological and human health hazard assessment.

With over 300 validation test compounds, the predictive accuracy of the FETAX model with conventional mammalian test systems is approximately 85%. To increase the predictive accuracy of FETAX for human health hazard assessment, we developed an exogenous metabolic activation system that has resulted in an increased predictability of nearly 95%. An American society for Testing and Materials (ASTM) Standard Guide for conducting FETAX assays and a complementary Atlas of Abnormalities have been developed to assist in the standardized conduct of FETAX. (LINK to Publications) The Atlas of Abnormalities provides a thorough description of the types of defects commonly observed in Xenopus embryos to facilitate a standardized objective evaluation


Advantages of the FETAX Model:

  • Increased interest in amphibian populations due to world-wide declines and deformities
  • Non-mammalian developmental toxicity test species
  • Successfully Validation
  • Speed
  • Low Cost
  • Extensive literature available
  • Useful for both ecological and human health hazard assessment
  • Use of alternative species

Ecotoxicological Hazard/Risk Assessment:pic_fetaxeggs_215x300

  • General ecosystem monitoring
  • Hazardous waste site assessment (clean-up prioritization and effectiveness)
  • Water quality criteria establishment
  • Toxic interactions of complex mixtures
  • Routine biomonitoring
  • Stage-specific responsiveness
  • Longer-term effects (limb development and metamorphosis)

Information Generated:

  • Acute amphibian toxicity
  • Chronic amphibian toxicity
  • development toxicity
    • Embryolethality
    • Embryonic malformation
    • Embryonic growth reduction
    • Embryonic developmnet delay
  • Behavioral toxicity

Appropriate Sample Types:pic_fetaxfrog_300x98

  • Pure chemical products (EPA and FDA assessments)
  • Complex aqueous mixtures (effluents, groundwaters, and surface waters)
  • Soils
  • Sediments
  • Sludges
  • Drilling muds
  • Biological agents (i.e., parasites, disease vectors)

Assay Performance Sites:

  • Laboratory
  • In situ
  • Biomonitoring trailer