Microcystin uptake and biochemical responses in the freshwater clam P. exposed to toxic and non-toxic : Evidence of tolerance to cyanotoxins.

We investigated the accumulation and adverse effects of toxic and non-toxic in the edible clam . Treated clams were exposed to toxic at 100 μg of MC (microcystin)-LR L for 10 days. The experimental organism was then placed in toxin-free water and fed on non-toxic for the following 10 days for depuration. Filtering rates (FRs) by of toxic and non-toxic and of the green alga as a control were estimated. Adverse effects were evaluated though the activity of catalase (CAT), superoxide dismutase (SOD) and glutathione S-transferase (GST). Clam accumulated MCs (up to 12.7 ± 2.5 μg g dry weight (DW) of free MC and 4.2 ± 0.6 μg g DW of covalently bound MC). Our results suggest that although both toxic and non-toxic cyanobacteria caused adverse effects by inducing the detoxification and antioxidant defense system, the clam was quite resistant to cyanotoxins. The estimated MC concentration in was far beyond the World Health Organization's (WHO) provisional tolerable daily intake (0.04 μg kg day), suggesting that consuming clams harvested during cyanobacterial blooms carries a high health risk.