The toxicity of cadmium (Cd2+) towards embryos and pro-larva of soldatov's catfish (Silurus soldatovi)

A six-day static-renewal toxicity test was performed to determine the influences of cadmium on the development of embryos of soldatov's catfish (Silurus soldatovi). The median lethal concentration (LC50) value and median effective concentration (EC50, i.e., the total adverse effects, including developmental defects and mortality) were calculated to be 2740 and 133 μg/L, respectively, when cadmium was prepared in dilution water. The LC50 decreased to 266 μg/L in a subsequent test one month later, thereby suggesting that the sensitivity of this fish to cadmium in the early life stage1 was largely influenced by the quality of fertilized eggs, which is known to be dependent on the season. The mortality and total adverse effects showed a concentration-dependent relationship at dosages greater than 1000 or 10 μg/L (p<0.05), respectively, at pro-larva stage (i.e., 144 hpf) with dilution water. To compare the toxic effects of cadmium under field and experimental conditions, filtered river water was adopted as a solvent simultaneously compared with dilution water. No significant differences were observed in mortality rate, hatching rate and adverse effect prevalence between the two solvents. In comparison to previously published toxicity data for other fish, the pro-larva of soldatov's catfish were less sensitive than established test fish in the early life stage. Therefore, the environmental risks would be overestimated when considering only existing toxicity data for other test fish.

► Embryo toxicity test for the freshwater fish Silurus soldatovi.
► Large difference in LC50 in two consecutive tests, minimal in EC50.
► No significant differences in adverse effects between river water & dilution water.
► Helps in the development of area-specific environment regulations.