Adverse effects of (surface water pollutants) Cd, Cr and Pb on the embryogenesis of the mallard

The effects of chromium, lead and cadmium were studied on the embryogenesis, hatching success and viability of the mallard. Eggs were exposed to relatively low environmental concentrations that are characteristic to the level in polluted Hungarian surface waters. Eggs were treated by injection or immersion--prior to incubation. In study I, effects on early embryogenesis (first 10 days of incubation) were examined. Eggs were opened daily, mortality was determined and permanent slides of the embryos were made to help further external examinations. Each metal proved to be toxic to the developing mallard embryo, causing an increase in mortality and developmental anomalies. Chromium was the most teratogenic of the three heavy metals increasing the rate of malformations by 30% (P<0.001) after immersion, and 17% (P<0.01) after injection of the eggs. Cadmium proved to cause the highest rate of mortality. Embryonic death was increased by 27% (P<0.01) and 40% (P<0.001) after Cd immersion and injection, respectively. In study II, effects on hatching and viability of the ducklings were studied. The eggs were hatched, hatching and mortality rates were established, the liver of animals was histopathologically examined. However each heavy metal decreased hatching success, cadmium was found the most toxic compound, causing a 21% (P<0.01) and 47% (P<0.001) reduction in hatching success after immersion and injection, respectively. The liver of hatched ducklings showed significant lesions, dystrophy in the form of hepatic necrosis was detected in each treated animal. Each heavy metal (Cr, Pb, Cd) proved to have adverse effects on the embryonic development, hatching and viability of the mallard.