Translocation of 2,3,7,8-Tetrachlorodibenzo-p-dioxin from Adult Female Lake Trout (Salvelinus namaycush) to Oocytes: Effects on Early Life Stage Development and Sac Fry Survival

There were no signs of overt toxicity in sexually mature female lake trout (Salvelinus namaycush) exposed to either a control or a 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-containing diet for 11 wk prior to spawning. At spawning the maternally derived egg TCDD concentrations were 42 ± 4 and 43 ± 6% of the maternal skeletal muscle TCDD concentration on a lipid and wet weight basis, respectively. Egg TCDD concentrations of 233–387 pg TCDD/g egg (wet weight) resulted in nonviable oocytes, while concentrations of 50–152 pg/g resulted in a dose-related increase in sac fry mortality associated with yolk sac edema, craniofacial alterations, and arrested development, resembling blue-sac disease. The dose–response relationship for sac fry mortality associated with blue-sac disease was essentially identical to that observed when fertilized lake trout eggs were exposed to either waterborne or injected TCDD. The no and lowest observable adverse effect levels for sac fry mortality were 23 and 50 pg/g (maternal egg exposure), 34 and 40 pg/g (waterborne egg exposure), and 44 and 55 pg/g (egg injection). LD50s, based on egg TCDD concentration, were 58 (36–90), 69 (64–75), and 80 (68–91) pg/g (95% fiducial limits) following egg exposure via maternal, waterborne, or injection routes, respectively.