Long-term toxic impact of 2,3,7,8-tetrachlorodibenzo-p-dioxin on the reproduction, sexual differentiation, and development of different life stages of Gobiocypris rarus and Daphnia magna

The sexual ratio of Gobiocypris rarus exposed to 2,3,7,8-tetrachlorodibenzo -p-dioxin (TCDD) and 17 beta -estradiol from embryo to sexually mature reve aled feminization and overdevelopment of connective tissue in male fish gon ad in 2-30 pg/L TCDD concentration range. Daphnia magna was not sensitive t o the high dose of TCDD (0.1-1000 ng/ml), but the reproduction of D. magna treated with TCDD decreased after the 8th day. 7-Ethoxyresorufin-O-deethyla se (EROD) activities in newly fertilized eggs of G. rarus exposed to TCDD d osage groups (1000-100,000 pg/L) were significantly induced and increased w ith TCDD concentrations at the early life stage, while no difference was fo und between low TCDD dosage groups (<100 pg/L), but a good relationship bet ween the EROD activity and the TCDD concentration was observed during a lon g-term developmental stage. There was a pericardial edema formed in a 2-wee k yolk-sac at the concentration of 1000 pg/L TCDD. But in the exposure grou p (2 pg/L TCDD for 120 days), the cell nuclei of hepatocytes was far from t he center and packed toward the cell membrane; the cristae of most mitochon dria in the cell dropped and collapsed; the rough endoplasmic reticulum bro ke into fragments; and numerous lipid droplets formed in the cell. (C) 2001 Academic Press.