Comparisons of the effects of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin on chemically impacted and nonimpacted subpopulations of Fundulus heteroclitus: I. TCDD toxicity

A subpopulation of Fundulus heteroclitus inhabiting the chemically impacted estuary of Newark Bay, New Jersey, was found to be resistant to the toxicity of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) as compared to a chemically non‐impacted subpopulation of F. heteroclitus in Tuckerton, New Jersey. The Newark/Raritan Bay estuary is a major site of TCDD contamination. The Newark F. heteroclitus embryos, when exposed to 12 to 100 parts per trillion (pptr) [³H]TCDD/acetone (nominal water concentrations) did not exhibit TCDD‐dependent lesions or death. In contrast, the Tuckerton embryos exhibited both TCDD concentration‐related lesions and death that was associated with the lesions. The Newark embryonic resistance to TCDD toxicity could not be attributed to a lesser absorption of [³H]TCDD as compared to the Tuckerton embryos. The Newark F. heteroclitus adult fish, when dermally treated with 0.30 to 60 ng/g [³H]TCDD/DMSO, did not exhibit TCDD treatment‐related increases in death, lesions, or liver‐to‐body‐weight ratios, whereas the Tuckerton adult fish did. The Newark fish did exhibit greater parasitic infestations of the liver, greater hepatic neoplasias, and greater liver‐to‐body‐weight ratios, all of which were independent of laboratory TCDD treatment, as compared to the Tuckerton fish. These hepatic effects in the Newark fish may be indicative of the chronic chemical exposure of this F. heteroclitus subpopulation.