Enzymatic disturbances of the Egyptian beetle, Blaps polychresta (Forskål, 1775), as environmental indicators of heavy metal pollution of agricultural soils

Abstract

Heavy metals (HMs) pollution is becoming influential severe trouble in the farming ecosystem, where it causes serious health problems for many living organisms. This study was conducted to estimate the HMs accumulation under different sites from agricultural soil and its effects on enzymatic activities in tissues of the beetle, Blaps polychresta, as an indicator of soil contamination. Beetle and soil samples were collected from three agricultural sites; (A) a reference site, (B) fields located near the River Nile, and (C) fields closed to drainage. The atomic absorption results showed a significant increase in iron (Fe), manganese (Mn), arsenic (As), lead (Pb), chromium (Cr), aluminum (Al), and zinc (Zn) for both soil and beetles from site B & C compared to site A. The highest bioaccumulation (BAF) ratio was observed for nickel (Ni), As, and cadmium (Cd) in site C, while Zn, copper (Cu), and Pb in site B. HMs accumulation in beetle's tissues (gut, fat body, and testis) from site B & C induced the malondialdehyde (MDA) activity. Thus, a significant reduction of the antioxidant enzymes and total protein contents (TPc) were observed in beetle tissues from site C. However, no significant differences in some tissues of site B compared to other sites. A principal component analysis (PCA) and correlation were conducted between HMs concentrations in beetle tissues and antioxidant enzymes, TPc, and MDA. The current results of a principal component analysis (PCA) and the correlation test were used to assist the differences in the decline of the antioxidant enzymes: glutathione (GSH), Superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), glutathione peroxidase (GPx), and glutathione reductase (GR) and TPc, while; the elevation in MDA responses in beetle's tissues due to HMs accumulations in response to protect themselves from metals toxicity. The antioxidant defense and oxidative stress were more prominent in the tissues of the beetle's gut and fat bodies comparing to the testis. Accordingly, the HMs accumulation in agricultural soil can be predicted by the enzymatic activities in beetle tissues.