Dietary silicate minerals relieving cadmium or lead poisoning in juvenile sea cucumber, Apostichopus japonicus

Industrial activities increase Apostichopus japonicus exposure to toxic heavy metals. This study evaluates the efficacy of three dietary silicate minerals (montmorillonite, zeolite, and kaolin) in relieving cadmium and lead toxicity in A. japonicus. Over four weeks, juvenile A. japonicus (7 - 9 g) were fed diets incorporating montmorillonite, zeolite, or kaolin, replacing sea mud at a 1:1 ratio. Experimental groups were: SM (control with sea mud), M (montmorillonite), Z (zeolite), and K (kaolin). Each group was exposed to cadmium (50 mg kg- 1) or lead (100 mg kg- 1) at the minimal toxic dose (MTD). Groups M and K demonstrated excellent growth performance, marked by improvements in weight gain rate (WGR), specific growth rate (SGR), feed conversion ratio (FCR), and survival rate (SR). Their coelomic fluid revealed higher enzymatic activities, such as acid phosphatase (ACP), alkaline phosphatase (AKP), catalase (CAT), and superoxide dismutase (SOD). Additionally, groups M and K showed a reduced accumulation of cadmium and lead in their tissues; group K notably excelled in mitigating intestinal tissue damage. In contrast, Group Z exhibited significantly poorer performance. In other aspects, the trends among the three experimental groups were generally similar: the activity of intestinal digestive enzymes declined, intestinal microbiota diversity decreased, and the stability of community composition increased. In summary, the supplementation of montmorillonite and kaolin effectively reduces cadmium and lead toxicity, diminishes oxidative damage, and promotes intestinal health in A. japonicus. These findings provide valuable insights for enhancing safety in A. japonicus aquaculture.