Single and mixture toxicity of cadmium and copper to swim bladder in early life stages of Japanese medaka (Oryzias latipes)

In this study, the embryos of Japanese medaka (Oryzias latipes) were treated with individual and binary mixture of copper (Cu) and cadmium (Cd) until 12  days post-fertilization (dpf). Hatching, mortality, development, histology and gene expression were assessed. Our results showed that the highest concentration mixture of Cd (10 mg/L) and Cu (1 mg/L) affected survival, hatching time and hatching success. Occurrence of uninflated swim bladder was the highest (value) with exposure to 10 mg/L Cd. Swim bladder was commonly over-inflated in a mixture (0.1 mg/L Cd + 1.0 mg/L Cu) exposure. Individuals exposed to the mixture (0.1 Cd + 1.0 Cu mg/L) showed up to a 7.69% increase in swim bladder area compared to the control group. The mixt ures containing 0.1 or 10 mg/L Cd, each with 1.0 mg/L Cu resulted in significantly increased ofPbx1b expression, higher than any Cd or Cu alone (p <  0.01). In the co-exposure group (0.1/10 Cd + 1.0 Cu mg/L),Pbx1b expression was found at 12  dpf but not 7 dpf in controls. Higher concentrations of Cd may progressively reducePbx1b expression, potentially explaining why 75% of individuals in the 10  mg/L Cd group failed to inflate their swim bladders. Additionally, the swim bladder proved to be a valuable bio-indicator for biological evaluation.
Source: Environmental Geochemistry and Health - Category: Environmental Health Source Type: research