Influence of dietary Cadmium on sexual maturity and reproduction of Red Tilapia

The influence of dietary cadmium on gonads’ maturation, reproduction and development of offspring of red tilapia was evaluated. The study was conducted on four groups of juvenile red tilapia (average length 8.2 ± 2.5 cm and average weight 38.3 ± 2.5 g). Four doses of cadmium were applied in the feed: 0 mg Cd g−1 (control group), 0.25, 0.5 and 1 mg Cd g−1 of feed (wet weight). The highest dose of Cd (1 mg Cd g−1) inhibited spawning of females, impaired ovarian development. Separation of follicular membrane from underlying ooplasm and abnormal vacuolization of ova were observed. Also in males this dose caused degeneration of spermatogenic elements, fibrosis of lobule walls and blood infiltration. A significant decrease in sperm number and sperm motility was also detected. Cadmium doses of 0.25 and 0.50 mg Cd g−1 did not influence gonads’ development of the studied fish. Ovaries and testis showed no differences in the development between the control group and groups receiving these doses of Cd. However, these doses caused decrease in spawned eggs number, hatchability percentages and increased fries abnormalities. Also, the growth of the developing offsprings was affected by these dietary doses.