Abstract:

Histolopathological effects of heavy metals (Cu and Pb) and their bioaccumulation in the giant land snails, Archachatina marginata were assessed by feeding experiments. On the basis of 168h LC50, CuSO4 with 168h LC50 value of 2.35mM was found to be significantly (no overlaps in 95% confidence limit) more toxic than Pb(NO3)2 (5.79mM). The exposure of the snails to sublethal concentrations of the metals resulted in a prevalence of hepatocellular foci of cellular alterations (FCA) in the hepatopancreas of snails. Hepatocytes of test animals exposed to sublethal concentration of Cu were also observed to be clogged together with peripheral thickening while exposure to lead caused inflammation of hepatic tubules. Basophilic adenoma and ovotesticular fibrillar inclusions were also observed in the ovotestes of snails exposed to the test metals. Post treatment analysis of A. marginata tissues revealed that exposure to sublethal Cu concentrations resulted in a five-fold and three-fold accumulation of the metal, respectively, in the hepatopancreas and muscular foot of exposed animals compared to the control animal. The bioaccumulation studies also indicate the ability of the snail to regulate and excrete excess level of copper from its body. The accumulation of Pb in the hepatopancreas were found to be up to 375 folds while accumulation of over 1000 folds compared to the concentrations detected in control animals was observed in the edible muscular foot. The array of toxicopathic organ or tissue alterations observed in this study represents biological end-points of contaminant exposure and therefore reinforces the application of histopathology as a powerful tool for monitoring anthropogenic contamination of terrestrial environments. The combination of these pathological end points with the monitoring of metal levels in body tissues of edible animals provides important tools for early detection of impending environmental problems and prevention of potential public health issues.