The Evolution and Development of Cephalopod Chambers and Their Shape.
The Evolution and Development of Cephalopod Chambers and Their Shape.
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DOI：
10.1371/journal.pone.0151404
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Hoffmann R
中科院分区：
文献类型：
--
作者：
Lemanis R;Korn D;Zachow S;Rybacki E;Hoffmann R
Ammonoidea是一组灭绝的头足类动物，是研究进化的理想对象。在菊石的planispiral壳和复杂折叠隔膜的演变已被认为增加了功能表面积的室，允许增强代谢功能，如：室排空，矿化率和整个个体发育的增长率增加。使用纳米计算机断层扫描和同步辐射的显微计算机断层扫描，我们提出了第一个研究的个体发育变化的表面积与体积比的phragmocone室的几个同源遥远的菊石和现存的头足类动物。与最初的假设相反，菊石不具有持续高的相对室表面积。相反，与螺旋藻相比，在最早的个体发育中，腔室的功能表面积更高。功能表面积越大，腔室的潜在排空速率越快;腔室排空速率越快，理论上允许生长越快。这是由我们收集的菊石Amauroceras sp.与S.螺旋体或鹦鹉螺。我们表明，腔室的表面曲率增加，更大的间隔复杂性增加潜在的再充盈率。我们进一步显示了一个独特的关系，菊石室的形状和大小，不存在于S。螺旋体或鹦鹉螺。这一观点的商会功能也有影响的内部壳的coleoids的演变，这一事件的脱钩软体生长和壳生长。
The Ammonoidea is a group of extinct cephalopods ideal to study evolution through deep time. The evolution of the planispiral shell and complexly folded septa in ammonoids has been thought to have increased the functional surface area of the chambers permitting enhanced metabolic functions such as: chamber emptying, rate of mineralization and increased growth rates throughout ontogeny. Using nano-computed tomography and synchrotron radiation based micro-computed tomography, we present the first study of ontogenetic changes in surface area to volume ratios in the phragmocone chambers of several phylogenetically distant ammonoids and extant cephalopods. Contrary to the initial hypothesis, ammonoids do not possess a persistently high relative chamber surface area. Instead, the functional surface area of the chambers is higher in earliest ontogeny when compared to Spirula spirula. The higher the functional surface area the quicker the potential emptying rate of the chamber; quicker chamber emptying rates would theoretically permit faster growth. This is supported by the persistently higher siphuncular surface area to chamber volume ratio we collected for the ammonite Amauroceras sp. compared to either S. spirula or nautilids. We demonstrate that the curvature of the surface of the chamber increases with greater septal complexity increasing the potential refilling rates. We further show a unique relationship between ammonoid chamber shape and size that does not exist in S. spirula or nautilids. This view of chamber function also has implications for the evolution of the internal shell of coleoids, relating this event to the decoupling of soft-body growth and shell growth.