Block-by-block and layer-by-layer growth modes in coral skeletons
Block-by-block and layer-by-layer growth modes in coral skeletons
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DOI：
10.2138/am-2015-4990
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发表时间：
2015-04-01
影响因子：
3.1
通讯作者：
Floquet, Nicole
中科院分区：
文献类型：
--
作者：
Perrin, Jonathan;Vielzeuf, Daniel;Floquet, Nicole
了解生物矿物生长的动力学是生物矿物学的一个具有挑战性的目标，部分可以通过破译生物矿物结构和化学来实现。用X射线微电子计算机断层扫描、偏光显微镜、扫描电子显微镜和电子探针研究了地中海、大西洋和太平洋六种珊瑚和副珊瑚(C.rubrum、C.elatius、C.johnsoni、C.Niobe、P.Japan和P horinax)的形态、结构和化学组成。所有物种都有两种类型的生物矿物结构：内部骨架和片岩，片岩是在骨架周围的活组织中发现的镁方解石小颗粒。所有骨架都显示一个中心核心，周围环绕着一个环状域。在电子探针研究的物种中，中心核区和环状域的化学成分不同，核心区比环状域更富镁，硫更贫化。在结构方面，特别强调了缺乏数据的中央核心。中心岩芯由片岩和片岩集合体组成，水泥中含有细小的镁方解石。另一方面，环形部分由同心细小的方解石微晶组成，只有稀有的片晶。这些不同的特征暗示了两种不同的生长模式：(1)发生在树枝顶端的“块和水泥”模式，与较快的轴向生长速度(类似于2 mm/年)有关；(2)发生在树枝顶端下方的逐层模式，与缓慢的径向生长(类似于0.2 mm/年)有关。从一种生长模式到另一种生长模式的转变在解剖学上是由根尖下骨骼周围存在的连续的胃真皮管网络控制的，这在很大程度上阻止了骨痂的聚集。人们普遍认为珊瑚科表现出不同类型的骨骼发育。与此相反，我们观察到所有研究的珊瑚物种在骨骼发生方面都表现出显著的相似性，并提出了珊瑚属的统一生长模式。讨论了与已有模型的异同。本研究表明，最初用于建立珊瑚科副冠藻属的形态标准是不充分的。
Understanding the dynamics of biomineral growth is a challenging goal of biomineralogy that can be achieved in part by deciphering biomineral structures and chemistries. The morphology, structure, and chemistry of six skeletons of Corallium and Paracorallium species (C. rubrum, C. elatius, C. johnsoni, C. niobe, P. japonicum, and P thrinax) from the Mediterranean, the Atlantic, and the Pacific oceans have been studied by X-ray micro-computed tomography, polarized light microscope, scanning electron microscope, and electron microprobe. All species have two types of biomineral structures: an inner skeleton and sclerites that are small grains of Mg-calcite found in the living tissues surrounding the skeleton. All skeletons display a central core surrounded by an annular domain. In the species studied by electron microprobe (C. rubrum, C. elatius, and P japonicum), the central core and the annular domains display different chemical compositions with the core richer in magnesium and poorer in sulfur than the annular domain. In terms of structure, special emphasis has been put on central cores for which little data are available. The central cores are made of sclerites and sclerite aggregates within a cement consisting of fine layers of Mg-calcite. On the other hand, the annular parts are made of fine concentric layers of calcite crystallites with only rare sclerites. These contrasting features imply two different growth modes: (1) a "block and cement" mode taking place at the apex of a branch and associated with a fast axial growth rate (similar to 2 mm/yr); and (2) a layer-by-layer mode occurring below the apex and associated with a slow radial growth (similar to 0.2 mm/yr). The change from a growth mode to another is anatomically controlled by the presence of a continuous network of gastrodermal canals around the sub-apical skeleton, preventing to a large extent the aggregation of sclerites. It is generally accepted that the Coralliidae family exhibits different types of skeletogeneses. In contrast with this idea, we observe that all studied Corallium species display remarkable similarities in terms of skeletogenesis and a unifying growth model for the Corallium genus is proposed. Similarities and differences with previous models are discussed. The present study shows that the morphological criterion initially used to establish the genus Paracorallium in the Coralliidae family is inadequate.