Are Daphnia Adequate Model Organisms for Chemical Testing?

Erica Lynn Geerdes


Model organisms provide a simplified method for determining relative chemical toxicities. It is necessary that the model organism chosen to represent a group of taxa accurately portrays the sensitivity of the taxa being analyzed. The Environmental Protection Agency widely uses Daphnia as model organisms for aquatic chemical testing. In order to decipher the relative sensitivity of Daphnia to different chemical categories, species sensitivity distributions (SSD’s) were built using acute toxicity data present in the EPA’s AQUIRE database. HC50 values of a total of 21 aquatic taxa were compared across 29 chemical categories. The results for 19 of the 29 chemical categories revealed one or multiple taxa more highly sensitive than Daphnia, suggesting the use of alternative or secondary model organisms may be necessary.