Bioaccumulation of heavy metals in mulberry sericulture: Review

Abstract

Heavy metals take route to higher trophic levels by first of all accumulating in harvestable parts of plants like leaves. Higher the trophic level the amount of metal increase and affect every higher trophic level. Silkworm (Bombyx mori) is used as template to assess the biotransformation of heavy metal in a food chain from soil to mulberry plant then insect. The mulberry plants were irrigated with synthetic effluent of Cr, Co, Pb, Zn (100mg/L with pH 4.5) and the treated soil, mulberry plant leaves, silkworm body, and their excreta were sampled to check Cr, Co, Pb, Zn, contents accumulated by using atomic absorption spectrometry (AAS). The concentration of heavy metals in soil and mulberry leaves tend to increase with increase in irrigation times. On the other hand, the contents of Cr, Co, Pb, Zn in B. mori larvae and the excreta were in considerable amount but decrease with the increase in larval instars. The heavy metals found in B. mori body was liable for toxic effects on its life cycle and the body growth and silk production was also inhibited under the effect of Cr, Co, Pb, Zn accumulation. A considerable amount of heavy metals was also found deposited in the silk glands, cuticle and alimentary canal, and concentration of heavy metals in larval body increased B. mori and death rate also by significantly.