Free University of Bolzano-Bozen, Faculty of Computer Science, Bolzano, Italy.
CNRS-Sorbonne Université, Laboratoire d'Ecogéochimie des Environnements Benthiques, Observatoire Océanologique de Banyuls sur Mer, Banyuls sur Mer, France; University of Cagliari, Department of Life and Environmental Sciences, Cagliari, Italy.
J Theor Biol. 2022 Nov 21;553:111247. doi: 10.1016/j.jtbi.2022.111247. Epub 2022 Aug 28.
The colony formation in Mediterranean coral Corallium rubrum is initiated by a larva that metamorphoses into the first polyp of the emerging colony approximately two weeks after settlement. The primary polyp then sets up a slow process that eventually, at least after a few years, gives rise to a tree-like rigid colony structure on which other polyps flourish. For a mature colony, this axial skeleton provides support for new polyps. However, the first emergence of the characteristic axial skeleton can take two years or more from the larva stage. The early colony morphology, instead, is shaped exclusively by the polyps' abundant deposition of sclerites, a magnesian calcite biomineral that has a different granularity from the distinctive red-coloured skeleton. With the appearance of the first polyp, a growing sclerite heap in a mesoglea layer provides a base for the emerging colony. In this paper, to elucidate the mechanical processes of early skeleton development in C. rubrum colonies, we present a computational model whereby the mesoglea layer provides a diffusion medium for the sclerites that the polyps deposit. We show that our stochastic model with three parameters captures the dynamic variability observed in measurements on living colonies. Our simulation results provide evidence for a diffusion process whereby the interplay between polyp budding and sclerite deposition are the main determinants of structure in early colony formation. Our model demonstrates that the frequency of budding events in an early colony can be described as a function of the available mesoglea surface whereas the number of polyps on the colony plays a secondary role in determining this frequency. We show that these model predictions are confirmed by direct observations on the colonies in our sample. Moreover, our results indicate that diffusion is a prevalent mechanism of colony development also at later stages of a colony's life span.
地中海珊瑚 Corallium rubrum 的群体形成是由幼虫启动的，幼虫大约在定居后两周内变态为新群体的第一个水螅体。然后，第一个水螅体开始一个缓慢的过程，最终（至少在几年后）在一个刚性的树状群体结构上产生其他水螅体。对于一个成熟的群体，这个轴状骨骼为新的水螅体提供支撑。然而，从幼虫阶段到特征性轴状骨骼的首次出现可能需要两年或更长时间。相反，早期的群体形态完全由水螅体大量沉积的小刺所塑造，小刺是一种富含镁的方解石生物矿化物质，其粒度与独特的红色骨骼不同。随着第一个水螅体的出现，在中胶层中生长的小刺堆为新的群体提供了一个基础。在本文中，为了阐明 C. rubrum 群体早期骨骼发育的力学过程，我们提出了一个计算模型，其中中胶层为水螅体沉积的小刺提供了一个扩散介质。我们表明，我们的具有三个参数的随机模型可以捕捉到对活体群体进行测量所观察到的动态可变性。我们的模拟结果提供了证据，证明了扩散过程，其中水螅体出芽和小刺沉积之间的相互作用是早期群体形成中结构的主要决定因素。我们的模型表明，早期群体中出芽事件的频率可以描述为可用中胶层表面的函数，而群体中的水螅体数量在决定该频率方面起次要作用。我们表明，这些模型预测通过对我们样本中群体的直接观察得到了证实。此外，我们的结果表明，扩散是群体发育的一种普遍机制，即使在群体寿命的后期阶段也是如此。
