Early life-stage toxicity is a sensitive response of fishes to coplanar PCBs, PCDD/Fs and PAHs. In controlled laboratory experiments, environmentally-relevant profiles and concentrations of coplanar PCBs and TCDD were tested for their abilities to induce early life-stage toxic responses in F1 and F2 tomcod of HR and MR ancestry (R. C. Chambers and I. Wirgin, unpublished data). Toxic effects were evaluated by means of lethal (hatcha-bility, yolk-sac larval lifespan) and sublethal (morphometry, behavior, growth) responses of tomcod offspring from the two source populations. HR embryos had a high percentage of embryos hatching at all doses whereas survival of MR young life stages decreased with increasing dose. A multivariate set of fourteen morphometric characters were unresponsive in HR tomcod to PCBs or TCDD dose, whereas twelve of these characters were modified by dose among the MR treatment groups. In all responses, young life stages of MR descent displayed effects at doses equivalent to burdens of
PCBs and TCDD found in livers of environmentally exposed HR tomcod. These results show that early life stages oftomcodfromunimpactedpopulations are sensitive to PCBs/TCDD, that these two populations differ dramatically in their sensitivities to these chemicals, and are consistent with HR population having undergone significant evolutionary change perhaps due to chronic exposure to these pollutants.
In summary, tomcod from the HR exhibit biomarker alterations at a variety of mechanistically linked hierarchical steps of biological organization from exposure through the community levels (Fig. 30.4). This is suggestive of a chemical etiology to cancer and perhaps reduced size of the HR population.
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