Tissue distribution of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the adult Eastern oyster (Crassostrea virginica, Gmelin) and its effect on egg and larval survival

Laboratory distribution studies examining accumulation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the Eastern oyster (Crassostrea virginica), following a bolus injection into the mantle cavity, revealed that by day 28 of TCDD elimination the highest dioxin concentration was reached in the digestive gland followed by the mantle, gonad, hemolymph, gill, adductor muscle, and the kidney/heart, on a mass weight basis. However, the gonad, having a lower lipid content (1.58% wet wt. lipid content), was able to accumulate a dioxin concentration higher than that of other tissues on a lipid basis. This observation suggested that dioxin distribution was not being driven by the lipid content in the gonad but possibly by a binding receptor. In a separate set of studies TCDD exposure resulted in a poor fertilization rate (52.2–99.0% unfertilized eggs). Eggs that were fertilized had 3.2–0.0% survival, and did not develop beyond the zygote stage. In contrast, the control eggs had 80.3% survival to the straight hinge stage. TCDD concentrations in the gonadal tissue from day 28 of the distribution study (9.69 pg+5.28), corresponded with the range of TCDD detected in the gametes on day 28 of the larval study (1.58 pg+0.038). These studies support the hypothesis that dioxin is incorporated into the developing eggs and/or sperm of the Eastern oyster during gametogenesis.