Effects of Maternal Cadmium Exposure on Female Reproductive Functions, Gamete Quality, and Offspring Development in Zebrafish (Danio rerio)

Impacts of maternal Cd2+ exposure on female zebrafish (Danio rerio) were observed in females as well as their offspring. In females, Cd disturbed fecundity and other reproductive functions. In their offspring, it retarded gamete development and growth and influenced gene expression. There was a positive relationship between Cd2+ contents in ovaries of females and treatment doses of 0-8.9 mu M of Cd2+. The mating rate decreased by 60 % when females were exposed to 8.9-35.6 mu M of Cd2+ for 72 h compared with the control group. It was observed that growth is delayed by one somite stage in maternal-Cd2+ embryos compared with control embryos, which grew at the sixth-somite stage. The ceratohyal angles of larvae of Cd-exposed adults (maternal Cd2+) at 72 h postfertilization (hpf) appeared to have a positive response after doses of maternal Cd. In addition, approximately 30 % of 96-hpf larvae that were treated with a dose of 35.6 mu M of maternal Cd2+ appeared to have pericardial edema. At the 5-hpf stage of maternal Cd2+ exposure, embryos showed 33 and 37 target genes, respectively, that were significantly downregulated and upregulated as shown by cDNA microarray analysis. A major effect of maternal Cd2+ exposure on zebrafish embryo genes is that 18.9 % of transcription functions were upregulated. In addition, 33.3 % of transcripts relative to the function of protein biosynthesis were downregulated. These results showed that maternal Cd2+ exposure influenced the reproduction ability of females and also caused their embryos to develop with abnormal gene expression.