计算流体力学途径揭示寒武纪乌溜期吐卓虫(Tuzoia)种间游动能力分化图景

Differentiation landscape of swimming ability of Tuzoia species from Wuliuan, Cambrian revealed by computational fluid dynamics

吐卓虫(Tuzoia)是寒武纪出现且广泛分布于全球海洋中的一类具双瓣壳节肢动物,其软躯体性状不完备,并不能直观判断吐卓虫是否是一种擅长游泳的生物,因此其生态位长期存在争议。计算流体力学(Computational Fluid Dynamics,CFD)可以基于保存较好的生物骨骼化石,直观、量化地分析深时生物运动模式,为还原古生态提供了依据。本文采用计算流体力学模拟了加拿大布尔吉斯页岩生物群中的两种吐卓虫(T. retifera, T. canadensis)在底栖和远洋环境下的多种运动状态,对比分析了两种吐卓虫运动流体性能、垂向灵活性的差异。流体模拟结果表明,相同速度下T. retifera相比T. canadensis受到更小的阻力和更大的浮力。所以T. retifera具有更高游泳速度的潜力,同时垂向移动能力更好。计算结果暗示T. canadensis营底栖游泳生活,而T. retifera的栖息范围可以更广,营远洋游泳生活。这表明可能早在寒武纪乌溜期吐卓虫属级分类单元内就出现了生态位的分化。

Tuzoia is one of the most common and globally distributed Cambrian bivalved arthropods.However,the morphology of their rarely and incompletely preserved soft-parts can hardly be utilized to evaluate their swimming and migration abilities.Computational fluid dynamics(CFD)offers quantitative data for inferring the movement patterns of fossilized animals based on the morphology of their often well-preserved exoskeletons.In this paper,Tuzoia retifera and T.canadensis from the Burgess shale are simulated using CFD in benthic and pelagic environments.The differences in fluid performance and vertical flexibility of these two species are compared.Fluid simulation results indicate that T.retifera is subject to less drag force and greater lift force than T.canadensis under the same speed. The results indicate that T. retifera potentially has a faster swimming speed and better vertical migration ability than T. canadensis does. Tuzoia canadensis is probably a benthic species, while T. retifera may occupy wider habitat and has a pelagic swimming lifestyle. We suggest that niche partititoning within a genus occurred as early as the Wuliuan, Cambrian.