热带西太平洋沉积物浮游有孔虫壳体发育过程的三维重建与壳体形态对生态和古海洋的指示意义

Three-dimensional reconstruction of ontogeny of planktonic foraminifera in tropical West Pacific sediments and its ecological and paleoceanographic implications

浮游有孔虫钙质骨骼的生物学功能及其作用机制尚不完全清楚,之前的研究认为壳体通过提供负浮力在调节浮游有孔虫的受力平衡中起作用。然而,很少有研究对浮游有孔虫的个体发育过程进行重建和定量分析以揭示在其生命过程中壳体的功能。本研究利用同步辐射X射线断层显微术(SRXTM)重建了来自热带西太平洋沉积物岩芯中的6个不同属种的浮游有孔虫壳体的个体发育。通过计算每个腔室形成前后的壳体和细胞质的总质量,能够确定整个个体发育过程中的平均密度变化模式。不同生态位属种的平均密度变化模式差异显著,表明浮力调节可能与生命周期中的垂直迁移有关,尤其是对于无刺浮游有孔虫属种。个体发育过程中的平均密度变化模式揭示了整个个体发育过程中浮力调节的范围,这可能是影响无刺浮游有孔虫属种垂向迁移的因素之一。此外,浮游有孔虫的形态演化可能涉及对生活水体垂直结构变化的适应。

The biological function and mechanism of the calcareous skeletons of planktonic foraminifera are not fully understood.Previous studies have suggested that the shell plays a role in regulating the force balance of planktonic foraminifera by providing negative buoyancy.However,few studies have reconstructed and quantitatively analyzed the individual development process of planktonic foraminifera to reveal the function of the shell throughout their life cycle.We used synchrotron X-ray tomography to reconstruct the individual development of planktonic foraminiferal chambers from six different genera in sediment cores from the tropical western Pacific.By calculating the total mass of the shell and cytoplasm before and after the formation of each chamber,we were able to determine the average density variation pattern during the entire individual development process.We found significant differences in the patterns of average density among different ecological niche genera,suggesting that buoyancy regulation may be related to vertical migration during the life cycle,especially for non-spinose planktonic foraminifera genera.The density patterns also reveal the range of buoyancy regulation throughout the entire individual development process,which may be one of the factors on the vertical migration of non-spinose planktonic foraminiferal genera.Furthermore,the morphological evolution of planktonic foraminifera chambers may involve adaptation to changes in the vertical structure of the living water column.