Paläontologisches Institut und Museum der Universität Zürich, Karl-Schmid-Strasse 4, CH-8006 Zürich, Switzerland.
Zoology (Jena). 2013 Feb;116(1):36-63. doi: 10.1016/j.zool.2012.07.003. Epub 2013 Jan 22.
In recent years, developmental anatomy received increasing interest as a potential new source for phylogenetic research. For skeletal development, studies mainly rely on the first appearance of ossification centers. However, informative events occur during the whole course of skeletogenesis; interactions between external and internal development occur and morphometric changes take place - all of which present potential sources for phylogenetic analyses. Therefore, the Standard Event System (SES) was used to traceably describe the external development of the snake species Bothropoides jararaca and external measurements were analyzed. We then applied micro-computed tomography (μCT), clearing and double-staining, and 2D and 3D morphometric methods to describe, illustrate, and analyze the development of the head in great detail. We found a 3D flattening of the skull during ontogeny, a pattern that is not reflected in external development. This may be explained by a different relationship of skeletogenesis and external characters to the developing jaw musculature or simply by the different type of data. Clearing and double-staining and μCT-scanning revealed a broadly similar sequence in the onset of ossification. Minute differences may be due to the treatment of embryos. Bones of the dermatocranium are among the first to ossify and the development of the calcified endolymph may reflect its function as a calcium source during development. The value of phylogenetic observations using the sequence of first ossifications is critically discussed. The related heterochronic changes are interpreted to contribute at least to the very first phase of divagating skull formation among taxa.
近年来，发育解剖学作为系统发育研究的一个新的潜在来源，受到越来越多的关注。对于骨骼发育，研究主要依赖于骨化中心的首次出现。然而，有意义的事件发生在骨骼发生的整个过程中；外部和内部发育之间发生相互作用，形态发生发生变化——所有这些都为系统发育分析提供了潜在的来源。因此，使用标准事件系统（SES）来追踪蛇类 Bothropoides jararaca 的外部发育，并分析外部测量值。然后，我们应用微计算机断层扫描（μCT）、透明和双重染色以及二维和三维形态计量学方法来详细描述、说明和分析头部的发育。我们发现，在个体发生过程中，头骨发生了 3D 扁平化，而这种模式在外在发育中并没有反映出来。这可能是由于骨骼发生和外部特征与发育中的颌肌肉之间的关系不同，或者仅仅是由于数据类型不同。透明和双重染色以及 μCT 扫描揭示了骨化起始的广泛相似序列。微小的差异可能是由于胚胎的处理方式不同。皮肤颅骨的骨头是最早骨化的骨头之一，钙化内淋巴的发育可能反映了它在发育过程中作为钙源的功能。使用首次骨化序列进行系统发育观察的价值受到了批判性的讨论。相关的异时性变化被解释为至少有助于分类群之间颅形成的最初发散阶段。
