Developmental Toxicity of Lead and Copper in Chick Embryos: Morphometric and Histological Assessment of In Ovo...

Heavy metals are widely recognized as potent teratogenic agents capable of inducing congenital malformations by disrupting normal embryonic development. The present study investigated the teratogenic potential of lead (Pb) and copper (Cu) on chick embryos using two exposure methods: immersion and in Ovo injection. A total of 100 fertile eggs were randomly allocated into five experimental groups: control (CT), lead immersion (Pb-IM), lead injection (Pb-INJ), copper immersion (Cu-IM), and copper injection (Cu-INJ). Eggs were incubated under conventional conditions and treatments were given on the first day. On day 19, embryos were examined for morphological, morphometric, and histological alterations. Control embryos developed normally whereas treated groups exhibited significant abnormalities including reduced body weight, decreased crown rump length, shortened biparietal distance and craniofacial and limb deformities. Multivariate analysis revealed a highly significant overall effect of treatment on developmental parameters (Pillai's Trace = 0.988, p < 0.001). Subsequent univariate ANOVA showed significant differences (p < 0.05) across all measured variables. Post hoc comparisons confirmed that lead injected embryos exhibited the most severe reductions. Histological examination revealed normal hepatic and cardiac architecture in the control group. In contrast, treated embryos showed marked pathological changes. Liver sections demonstrated hepatocellular degeneration, disrupted architecture, and elongated sinusoidal spaces while heart tissues exhibited myofibrillar degeneration and formation of swollen vacuoles. Overall, both Pb and Cu demonstrated significant teratogenic effects with lead showing comparatively greater toxicity. Injection exposure resulted in more pronounced structural and histological abnormalities than immersion indicating that direct embryonic exposure poses a higher developmental risk.