Waterborne cadmium impacts immunocytotoxic and cytogenotoxic endpoints in green-lipped mussel, Perna canaliculus

Abstract

Mussels are sentinel species that can be used to monitor coastal metal pollution through the application of biomarkers. Among the several important metal toxicants in coastal settings, cadmium (Cd) is of particular concern, being a non-essential metal that is known to cause harmful impacts in aquatic organisms at low concentrations. The aim of the present study was to examine the immunocytotoxic and cytogenotoxic effects of Cd on the green-lipped mussel, Perna canaliculus, under laboratory conditions. The acute (96 h; 0, 2000 and 4000 μg Cd L(-1)) and subchronic (28 d; 0, 200 and 2000 μg Cd L(-1)) toxic effects of waterborne Cd were measured in haemocytes and gill cells using differential haemocyte cell count, the micronucleus test and the comet assay. During subchronic exposure to Cd the relative counts of eosinophils and hyalinocytes increased significantly in Cd-exposed mussels while the proportion of basophils decreased. All of these effects were time- and concentration-dependent. Conversely, the relative numbers of basophils and eosinophils increased significantly during acute Cd exposure. Nuclear aberrations such as the formation of micronuclei, nuclear buds, fragmented-apoptotic cells and binuclei were observed in gill cells of Cd-exposed mussels. All of these parameters increased significantly at 2000 μg Cd L(-1) during subchronic exposure to Cd, and all showed a strong and significant correlation to gill Cd accumulation. Comet assay results demonstrated a significant increase in DNA damage in the haemocytes of mussels exposed to subchronic Cd concentrations. The results indicate that Cd has the capacity to induce immune system and genotoxic damage in green-lipped mussels, an impact that may have implications such as reduced disease resistance and compromised survival. These data also suggest that immunocytotoxic and cytogenotoxic biomarkers would be a valuable addition to environmental monitoring programmes using green-lipped mussels.

Keywords: Comet assay; Genotoxic; Gill; Haemocytes; Immune system; Micronucleus test.