Univ Brest, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzane, France.
Univ Brest, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzane, France.
Mar Environ Res. 2021 Jul;169:105401. doi: 10.1016/j.marenvres.2021.105401. Epub 2021 Jun 23.
Dinoflagellates from the globally distributed genus Alexandrium are known to produce both paralytic shellfish toxins (PST) and uncharacterized bioactive extracellular compounds (BEC) with allelopathic, ichthyotoxic, hemolytic and cytotoxic activities. In France, blooms of Alexandrium minutum appear generally during the spawning period of most bivalves. These blooms could therefore alter gametes and/or larval development of bivalves, causing severe issues for ecologically and economically important species, such as the Pacific oyster Crassostrea (=Magallana) gigas. The aim of this work was to test the effects of three strains of A. minutum producing either only PST, only BEC, or both PST and BEC upon oyster gametes, and potential consequences on fertilization success. Oocytes and spermatozoa were exposed in vitro for 2 h to a range of environmentally realistic A. minutum concentrations (10-2.5 × 10 cells mL). Following exposure, gamete viability and reactive oxygen species (ROS) production were assessed by flow cytometry, spermatozoa motility and fertilization capacities of both spermatozoa and oocytes were analysed by microscopy. Viability and fertilization capacity of spermatozoa and oocytes were drastically reduced following exposure to 2.5 × 10 cells mL of A. minutum. The BEC-producing strain was the most potent strain decreasing spermatozoa motility, increasing ROS production of oocytes, and decreasing fertilization, from the concentration of 2.5 × 10 cells mL. This study highlights the significant cellular toxicity of the BEC produced by A. minutum on oyster gametes. Physical contact between gametes and motile thecate A. minutum cells may also contribute to alter oyster gamete integrity. These results suggest that oyster gametes exposure to A. minutum blooms could affect oyster fertility and reproduction success.
具有麻痹性贝类毒素（PST）和特征不明的生物活性细胞外化合物（BEC）的种类广泛分布的菱形藻属，被认为会产生具有化感、鱼毒性、溶血和细胞毒性的化合物。在法国，微小亚历山大藻通常在大多数双壳类动物的繁殖期出现水华。这些水华可能会改变双壳类动物的配子和/或幼虫发育，从而对生态和经济上重要的物种造成严重问题，例如太平洋牡蛎（Crassostrea [=Magallana] gigas）。本工作旨在测试仅产生 PST、仅产生 BEC 或同时产生 PST 和 BEC 的三种微小亚历山大藻菌株对牡蛎配子的影响，以及对受精成功的潜在影响。卵母细胞和精子在体外暴露于一系列环境现实的微小亚历山大藻浓度（10-2.5×10 个细胞 mL）下 2 小时。暴露后，通过流式细胞术评估配子的活力和活性氧（ROS）的产生，通过显微镜分析精子的运动能力以及精子和卵母细胞的受精能力。暴露于 2.5×10 个细胞 mL 的微小亚历山大藻后，精子的活力和受精能力以及卵母细胞的活力和受精能力均明显降低。产生 BEC 的菌株是最有效的菌株，它降低了精子的运动能力，增加了卵母细胞 ROS 的产生，并降低了受精率，其浓度为 2.5×10 个细胞 mL。本研究强调了微小亚历山大藻产生的 BEC 对牡蛎配子的显著细胞毒性。配子与运动的有壳微小亚历山大藻细胞之间的物理接触也可能导致牡蛎配子完整性发生变化。这些结果表明，牡蛎配子暴露于微小亚历山大藻水华可能会影响牡蛎的生育能力和繁殖成功。
