EFFECTS OF 3,3',4,4',5-PENTACHLOROBIPHENYL (PCB-126), 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN (TCDD), OR AN EXTRACT DERIVED FROM FIELD-COLLECTED CORMORANT EGGS INJECTED INTO DOUBLE-CRESTED CORMORANT (PHALACROCORAX-AURITUS) EGGS

Double-crested cormorant (Phalacrocorax auritus) eggs were injected wi th either 3,3',4,4',5-pentachlorobiphenyl (PCB 126), 2,3,7,8-tetrachlo rodibenzo-p-dioxin (TCDD), or an extract derived from field-collected double-crested cormorant eggs. These compounds were injected into the yolks of cormorant eggs from an isolated colony on Lake Winnipegosis, Manitoba, Canada. Upon hatching, chicks were necropsied. The brain, bu rsa, heart, liver, and spleen were removed and weighed. An approximate median lethal dose (LD50) of 158 mu g/kg egg was determined for PCB 1 26, which is 69 times greater than the LD50 determined for the chicken (Gallus domesticus) in a previous study. A significantly greater mort ality occurred at the highest dose of TCDD (4.0 mu g/kg egg) when comp ared to the vehicle control. However, the mortality data did not provi de sufficient information for the determination of an LD50. The cormor ant egg extract did not adversely affect hatchability. No significant increases were observed in the incidence of developmental abnormalitie s, including pronounced edema, in any of the treatment groups, nor wer e there any relevant effects on body and organ weights. Based on the r esults from this study, the cormorant appears to be considerably less sensitive to polyhalogenated diaromatic hydrocarbons than the chicken, which has been the typical species used for egg injection studies.