Protection of dietary selenium-enriched seaweed Gracilaria lemaneiformis against cadmium toxicity to abalone Haliotis discus hannai.

Seaweed Gracilaria lemaneiformis is the main dietary source of the abalone mariculture industry in China. In this study, we examined the protection of selenium (Se)-enriched G. lemaneiformis against cadmium (Cd) toxicity in the abalone, Haliotis discus hannai, using various indices including metal concentration (Se and Cd), growth rate, GPx enzymatic antioxidants, and metallothionein (MT) concentration over a period of 28 days of exposure. The growth rates and Se contents increased significantly in abalones fed with Se-enriched G. lemaneiformis, while the toxicity of Cd was reduced. Seven to 12 days Cd exposure to the Se-enriched G. lemaneiformis not only affected GPx activity but the MT levels fluctuated irregularly. MT concentrations increased after 3 days exposure and then gradually decreased to the control level after Day 7. There were statistically significant positive correlations between MT levels, GPx activity and Se concentrations, and negative relationships between MT levels, GPx activity and Cd levels in abalones. These findings suggest that Se-enriched Gracilaria protects abalone against Cd toxicity. The possible mechanism is the induction of MT with a concomitant increased capacity of GPx enzymatic antioxidants.