Effects of maternal exposure to estrogen and PCB on different life stages of zebrafish (Danio rerio)

PCBs have been found to impair both reproduction and development in fish. W e have investigated the effects of 3 PCB congeners, 2,3,3',4,4',5,6-HpCB (P CB-190); 2,3,4,4'-TeCB (PCB-60); and 2,2',4,6,6'-PeCB (PCB-104), and the es trogenic hormone 17 beta-estradiol on fecundity, early life-stage mortality , gross morphology and histology of zebrafish (Danio rerio). While none of the studied substances reduced fecundity, they increased embryo and larval mortality. The most severe effects on viability were observed following tre atment with 17 beta-estradiol or the weakly estrogenic PCB-104. Following 1 7 beta-estradiol or PCB-104 exposure, mortality continued through the yolk- sac absorption phase. PCB-60, on the other hand, resulted in mortality betw een the 30% epiboly stage and 75% epiboly stage. At the same time as embryo s started to die, embryo development and hatching were delayed. PCB-190 sho wed only moderate effects on early-life stage mortality. The fish were rear ed until sexual maturation whereafter they were subjected to gross morpholo gical and histological analyses. Changes in morphology were observed follow ing PCB-104 and PCB-190 treatment. Both substances gave rise to craniofacia l malformations while PCB-104 also led to lordosis in females and scoliosis in fish of both sexes. From histological analysis it was found that PCB-10 4 and 17 beta-estradiol resulted in karyorrhexis and karyolysis in the kidn ey. Possible signs of bile stasis were observed following 17 beta-estradiol and PCB-190 treatment. Some effects were observed on the gonads, including areas in the ovary showing atresia and limited failure of testicular sperm atogenesis in 17 beta-estradiol, PCB-104, and PCB-60 treated fish. While al l studied substances resulted in effects on offspring, the observation that estrogenic substances are highly embryotoxic, raises concern that endocrin e disrupting substances may severely reduce fish populations in polluted ar eas.