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

Thanh-Luu Pham; Kazuya Shimizu; Thanh-Son Dao; Lan-Chi Hong-Do; Motoo Utsumi

doi:10.1016/j.toxrep.2015.01.012

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

Toxicol Rep. 2015 Feb 7:2:88-98. doi: 10.1016/j.toxrep.2015.01.012. eCollection 2015.

Authors

Thanh-Luu Pham^{1

2}, Kazuya Shimizu³, Thanh-Son Dao⁴, Lan-Chi Hong-Do⁵, Motoo Utsumi¹

Affiliations

¹ Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan.
² Institute of Tropical Biology, 85 Tran Quoc Toan Street, District 3, Ho Chi Minh City, Viet Nam.
³ Faculty of Life Sciences, Toyo University, Ora-gun, Gunma 374-0193, Japan.
⁴ Ho Chi Minh City University of Technology, 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Viet Nam.
⁵ Vietnam National University-Ho Chi Minh City, 6 Quarter, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Viet Nam.

Abstract

We investigated the accumulation and adverse effects of toxic and non-toxic Microcystis in the edible clam Corbicula leana. Treated clams were exposed to toxic Microcystis at 100 μg of MC (microcystin)-LR_eq L^-1 for 10 days. The experimental organism was then placed in toxin-free water and fed on non-toxic Microcystis for the following 10 days for depuration. Filtering rates (FRs) by C. leana of toxic and non-toxic Microcystis and of the green alga Chlorella vulgaris 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^-1 dry weight (DW) of free MC and 4.2 ± 0.6 μg g^-1 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 C. leana was far beyond the World Health Organization's (WHO) provisional tolerable daily intake (0.04 μg kg^-1 day^-1), suggesting that consuming clams harvested during cyanobacterial blooms carries a high health risk.

Keywords: 2,2-Dimethoxypropane (PubChem CID: 6495); 4-Phenylbutanoic acid (PubChem CID: 4775); Bioaccumulation; Biochemical response; Boron trifluoride-methanol-complex solution (PubChem CID: 11062313); Corbicula leana; Dithioerythritol (PubChem CID: 439352); Microcystin LR (PubChem CID: 445434); Microcystins; Toxic and non-toxic.