UCLA

A goal of this project was to demonstrate how sea urchins could be utilized as an animal

model to assess aspects of developmental toxicity relevant to humans as well as other organisms.

Haber’s Law states that the toxic effect of a substance depends on the concentration and exposure time (C x t = k (constant)). Theoretically, if the product of concentration and exposure time are equivalent, there should be a constant toxic response. To test this theory, Strongylocentrotus purpuratus (purple sea urchins) embryos were exposed to nickel chloride (NiCl2), zinc sulfate (ZnSO4), and trichostatin A (TSA) with differing combinations of concentrations and exposure times having equivalent Haber’s Law products. The toxic endpoint observed was oral radialization for nickel chloride, animalization for zinc sulfate and aboral radialization for trichostatin A. Phenotypes were scored approximately 96 hours post fertilization (hpf). The results revealed the sensitive period was around 16-24 hours post-fertilization (hpf) for oral radialization and approximately 8-16 hpf for aboral radialization. Additionally, the importance of seemingly nontoxic periods of time was revealed to contribute to the overall toxicity when the exposure period is extended. Since exposure time impacts toxic effects, it’s important to study chemicals at “safe concentrations” to better understand the risks associated with these chemicals.