Morphogenesis of the turtle shell: the development of a novel structure in tetrapod evolution
Morphogenesis of the turtle shell: the development of a novel structure in tetrapod evolution
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DOI：
10.1046/j.1525-142x.2001.003002047.x
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发表时间：
2001-03-01
影响因子：
2.9
通讯作者：
Burke, AC
中科院分区：
文献类型：
--
作者：
Gilbert, SF;Loredo, GA;Burke, AC
龟壳是一种进化上的新事物，是龟类动物的突触形态。甲壳由背外胚层和真皮中胚层的外侧凸起的甲壳脊（CR）包围肋骨而形成。CR发生的机制、肋骨夹持和背侧真皮骨化的机制尚不清楚。同样，板层的形成仍然无法解释。在此，我们对红耳滑龟（Trachemys scripta）和鳄龟（Chelydra serpentina）的板壳形成进行了一系列解剖学研究。我们记录了CR对肋骨的夹持以及膜内骨化形成的板骨和甲骨。我们注意到每根肋骨周围骨化中心的形成，这表明肋骨通过分泌旁分泌因子来组织皮肤骨化。颈骨化中心很复杂，似乎涉及多个骨形成区域。甲壳周围的单个骨化中心形成外周骨和耻骨。板的膜内骨化从九个不同的骨化中心开始，当它们彼此靠近时，相对中心的针状体之间似乎存在相互作用。
The turtle shell is an evolutionary novelty that is synapomorphic for chelonians. The carapace is initiated by the entrapment of the ribs by the carapacial ridge (CR), a lateral bulge of the dorsal ectoderm and dermal mesoderm. The mechanisms by which the CR is initiated, the ribs entrapped and the dorsal dermis ossified, remains unknown. Similarly, the formation of the plastron remains unexplained. Here, we present a series of anatomical investigations into plastron and carapace formation in the red-eared slider, Trachemys scripta, and the snapping turtle, Chelydra serpentina. We document the entrapment of the ribs by the CR and the formation of the plastron and carapacial bones by intramembranous ossification. We note the formation of the ossification centers around each rib, which suggest that the rib is organizing dermal ossification by secreting paracrine factors. The nuchal ossification center is complex and appears to involve multiple bone-forming regions. Individual ossification centers at the periphery of the carapace form the peripheral and pygial bones. The intramembranous ossification of the plastron proceeds from nine distinct ossification centers, and there appear to be interactions between the spicules of apposing centers as they draw near each other.