Relative Toxicity of PCB Congeners to Sea Urchin Embryos

The toxicity of three PCB congeners having different structural characteristics was studied using water exposures and the embryos of two sea urchin species, Strongylocentrotus purpuratus (purple sea urchin) and Lytechinus pictus (white sea urchin). Biological effects were assessed using two endpoints: percentage of normal embryo development and mitotic rate. Differential toxicity of the congeners was observed, with Congener 47 producing much stronger effects than Congeners 77 and 153 at comparable body burdens. The effects of PCBs on embryo development were similar in both species investigated. It was found that mitotic rate measurement was a more sensitive indicator of effects than was embryo development. The results of this study illustrate that different PCB congener structure activity relationships exist for various animal groups and/or endpoints. Widely used estimates of congener relative toxicity derived from mammalian research are not accurate for estimating effects on marine organisms due to the physiological differences of these two groups.