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. We have investigated the effects of 3 PCB congeners, 2,3,3',4,4',5,6-HpCB (PCB-190); 2,3,4,4'-TeCB (PCB-60); and 2,2',4,6,6'-PeCB (PCB-104), and the estrogenic 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 treatment with 17 beta-estradiol or the weakly estrogenic PCB-104. Following 17 beta-estradiol or PCB-104 exposure, mortality continued through the yolk-sac absorption phase. PCB-60, on the other hand, resulted in mortality between the 30% epiboly stage and 75% epiboly stage. At the same time as embryos started to die, embryo development and hatching were delayed. PCB-190 showed only moderate effects on early-life stage mortality. The fish were reared until sexual maturation whereafter they were subjected to gross morphological and histological analyses. Changes in morphology were observed following PCB-104 and PCB-190 treatment. Both substances gave rise to craniofacial 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-104 and 17 beta-estradiol resulted in karyorrhexis and karyolysis in the kidney. 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 spermatogenesis in 17 beta-estradiol, PCB-104, and PCB-60 treated fish. While all studied substances resulted in effects on offspring, the observation that estrogenic substances are highly embryotoxic, raises concern that endocrine disrupting substances may severely reduce fish populations in polluted areas.