Engineering Technology Research Center of Henan Province for Aquatic Animal Cultivation, College of Fisheries, Henan Normal University, Xinxiang, 453007, China.
Environ Sci Pollut Res Int. 2023 Jan;30(5):13560-13570. doi: 10.1007/s11356-022-22833-z. Epub 2022 Sep 22.
As filter-feeders, bivalves naturally come into direct contact with microcystins (MCs) in eutrophic water bodies suffering from cyanobacteria blooms. To date, however, no studies have quantified the dynamics of microcystin accumulation and depuration in the edible freshwater bivalve Corbicula fluminea when exposed to dense bloom concentrations of Microcystis aeruginosa, while considering dynamic changes of biochemical indexes and feeding structure. In the present study, the bioaccumulation and detoxification of microcystin-LR (MC-LR) in C. fluminea were investigated. Our results showed that C. fluminea would graze equally efficiently on green algae and M. aeruginosa, irrespective of whether the M. aeruginosa strains were toxic or non-toxic. MCs could be accumulated and depurated by C. fluminea efficiently. In addition, linear and exposure time-dependent MC-LR accumulation patterns were observed in C. fluminea. Activities of biotransformation (glutathione S-transferase, GST) and antioxidant enzymes (superoxide dismutase, SOD, and catalase, CAT) and malondialdehyde (MDA) contents in various tissues of treated clams were stimulated by MCs in a tissue-specific manner. Our findings indicated that C. fluminea hepatopancreas was the primary target organ for MC-LR detoxification processes, as evidenced by a significant increase in GST activity. Besides, gills and mantle were more sensitive than the other tissues to oxidative stress in the initial microcystin exposure period with a significant increase in SOD activity. The scanning electron microscopy (SEM) observations revealed that the lateral cilia in the gill aperture were well developed during the MCs exposure period, which could perform the filter-feeding function instead of the damaged frontal cilium. This study provides insight into the possible tolerance of C. fluminea exposed to dense bloom concentrations of M. aeruginosa.
作为滤食动物，双壳类动物在富营养化水体中与蓝藻水华直接接触，自然会接触到微囊藻毒素 (MCs)。然而，迄今为止，还没有研究定量描述当暴露于密集的铜绿微囊藻水华时，食用淡水双壳类贻贝褶纹冠蚌对微囊藻毒素的积累和清除的动态，同时考虑到生化指标和摄食结构的动态变化。在本研究中，研究了褶纹冠蚌对微囊藻毒素-LR (MC-LR) 的生物积累和解毒作用。我们的结果表明，褶纹冠蚌可以同样有效地摄食绿藻和铜绿微囊藻，无论铜绿微囊藻菌株是否有毒。MCs 可以被褶纹冠蚌有效地积累和清除。此外，在褶纹冠蚌中观察到 MC-LR 积累的线性和暴露时间依赖性模式。暴露于 MCs 后，处理贻贝各组织中的生物转化（谷胱甘肽 S-转移酶，GST）和抗氧化酶（超氧化物歧化酶，SOD 和过氧化氢酶，CAT）的活性以及丙二醛（MDA）含量以组织特异性的方式被刺激。我们的研究结果表明，褶纹冠蚌肝胰腺是 MC-LR 解毒过程的主要靶器官，这表现在 GST 活性显著增加。此外，在初始微囊藻暴露期间，鳃和套膜比其他组织对氧化应激更敏感，SOD 活性显著增加。扫描电子显微镜（SEM）观察表明，在 MCs 暴露期间，鳃瓣的侧纤毛发育良好，可以代替受损的前纤毛执行滤食功能。这项研究为褶纹冠蚌暴露于密集的铜绿微囊藻水华时可能具有的耐受性提供了深入了解。
