Seawater carbonate chemistry and sperm-egg collisions, gamete fusion, and generation of Ca2+ oscillations of a broadcast spawning bivalve, Tegillarca granosa

Although the effect of ocean acidification on fertilization success of marine organisms is increasingly well documented, the underlying mechanisms are not completely understood. The fertilization success of broadcast spawning invertebrates depends on successful sperm-egg collisions, gamete fusion, and standard generation of Ca2+oscillations. Therefore, the realistic effects of future ocean pCO2 levels on these specific aspects of fertilization of Tegillarca granosa were investigated in the present study through sperm velocity trials, fertilization kinetics model analysis, and intracellular Ca2+assays, respectively. Results obtained indicated that ocean acidification significantly reduced the fertilization success of T. granosa, which could be accountable by (i) decreased sperm velocity hence reducing the probability for sperm-egg collisions; (ii) lowered probability of gamete fusion for each gamete collision event; and (iii) disrupted intracellular Ca2+ oscillations.

尽管海洋酸化对海洋生物受精成功率的影响已日益得到广泛研究证实，但其背后的核心调控机制尚未完全明晰。体外排卵受精型（Broadcast Spawning）无脊椎动物的受精成功率，取决于精卵碰撞成功、配子融合以及钙离子（Ca²+）振荡的正常产生。因此，本研究分别通过精子运动速度试验、受精动力学模型分析以及细胞内钙离子测定，探究了未来海洋二氧化碳分压（pCO₂）水平对泥蚶（Tegillarca granosa）受精过程上述关键环节的实际影响。研究结果显示，海洋酸化显著降低了泥蚶的受精成功率，其潜在机制可归结为以下三点：其一，精子运动速度下降，进而降低精卵碰撞的概率；其二，单次精卵碰撞事件中的配子融合概率降低；其三，细胞内钙离子振荡过程受到干扰。