Tissue Distributions and Toxic Effects of Hexavalent Chromium in Laboratory-Exposed Periwinkle (Littorina littorea...

The increased use of hexavalent chromium (Cr⁶⁺) in various industrial applications has contributed to its elevated levels in the environment, especially the aquatic environment. Thus, there is the potential for accumulation of Cr⁶⁺ in the tissues of aquatic organisms and consequent toxic effects. The toxic effects of Cr⁶⁺ in aquatic organisms have been widely reported; however, little is known about the patterns of tissue accumulation of Cr⁶⁺ and its toxicity in aquatic mollusks. Thus, the present study investigated the effects of Cr⁶⁺ exposure on the tissue distribution, proximate composition, and histopathology of an aquatic mollusk, periwinkle (Littorina littorea). The animals were exposed to sublethal concentrations of Cr⁶⁺ (0.42, 0.84, and 4.2 mg/L) for 30 days, after which the condition index, tissue accumulation, proximate composition, and histopathological effects were determined. The control animals were maintained in a medium that did not contain Cr⁶⁺ (0 mg/L). The condition index did not differ significantly among the groups. The levels of Cr⁶⁺ in the tissues differed significantly among the different tissue types while there was no significant effect of the exposure concentration, except in the foot tissue. The proximate parameters (protein, carbohydrates, lipid, crude fiber, and moisture contents) differed significantly among the groups. The protein contents of the exposed animals were significantly lower than those of the control animals and the histological architecture of the major organs was altered in the chromium-exposed animals. The findings from this study indicate a low potential of L. littorea to bioaccumulate Cr⁶⁺ in its tissues at the low exposure concentrations tested in this study; as such, its consumption may not pose any serious health risks to humans. However, changes in the proximate composition and histological architecture of the exposed L. littorea show that Cr⁶⁺ is potentially toxic to periwinkles.