Plateau Olivia, Green Todd L, Gignac Paul M, Foth Christian
Department of Geosciences, University of Fribourg, Fribourg, Switzerland.
Department of Earth Sciences, University of Cambridge, Cambridge, UK.
Anat Rec (Hoboken). 2024 Jan;307(1):5-48. doi: 10.1002/ar.25275. Epub 2023 Jun 20.
To date, several studies describe post-hatching ontogenetic variation in birds; however, none of these studies document and compare ontogenetic variation of the entire skull in multiple avian species. Therefore, we studied ontogenetic skull variation of two bird species with very different ecologies, Pica pica, and Struthio camelus, using μCT based 3D reconstructions. For each specimen, we performed bone-by-bone segmentation in order to visualize and describe the morphological variation of each bone during ontogeny and estimated the average sutural closure of the skulls to identify different ontogenetic stages. Although bone fusion of P. pica occurs more rapidly than that of S. camelus the general sequence of bone fusion follows a similar trend from posterior to anterior, but a more detailed analysis reveals some interspecific variation in the fusion patterns. Although growth persists over a longer period in S. camelus than in P. pica and adults of the former species are significantly larger, the skull of the most mature S. camelus is still less fused than that of P. pica. Different growth and fusion patterns of the two species indicate that the interspecific ontogenetic variation could be related to heterochronic developments. Nevertheless, this hypothesis needs to be tested in a broader phylogenetic framework in order to detect the evolutionary direction of the potential heterochronic transformations.
迄今为止，已有多项研究描述了鸟类孵化后的个体发育变异；然而，这些研究均未记录和比较多种鸟类整个头骨的个体发育变异。因此，我们利用基于μCT的三维重建技术，研究了两种生态习性差异很大的鸟类——喜鹊（Pica pica）和鸵鸟（Struthio camelus）的头骨个体发育变异。对于每个标本，我们逐骨进行分割，以便观察和描述个体发育过程中每块骨头的形态变化，并估计头骨的平均缝合线闭合情况，以确定不同的个体发育阶段。尽管喜鹊的骨融合比鸵鸟发生得更快，但骨融合的总体顺序从后向前遵循相似的趋势，但更详细的分析揭示了融合模式中的一些种间差异。尽管鸵鸟的生长持续时间比喜鹊长，且前者的成年个体明显更大，但最成熟的鸵鸟的头骨融合程度仍低于喜鹊。这两个物种不同的生长和融合模式表明，种间个体发育变异可能与异时发育有关。然而，这一假设需要在更广泛的系统发育框架中进行检验，以便检测潜在异时转变的进化方向。
