Graduate School of Science and Engineering, Teikyo University of Science, Uenohara, Japan.
Yamashina Institute for Ornithology, Abiko, Japan.
J Anat. 2022 Sep;241(3):776-788. doi: 10.1111/joa.13690. Epub 2022 May 24.
Studies have suggested that the brain morphology and flight ability of Aves are interrelated; however, such a relationship has not been thoroughly investigated. This study aimed to examine whether flight ability, volant or flightless, affects brain morphology (size and shape) in the Rallidae, which has independently evolved to adapt secondary flightlessness multiple times within a single taxonomic group. Brain endocasts were extracted from computed tomography images of the crania, measured by 3D geometric morphometrics, and were analyzed using principal component analysis. The results of phylogenetic ANCOVA showed that flightless rails have brain sizes and shapes that are significantly larger than and different from those of volant rails, even after considering the effects of body mass and brain size respectively. Flightless rails tended to have a wider telencephalon and more inferiorly positioned foramen magnum than volant rails. Although the brain is an organ that requires a large amount of metabolic energy, reduced selective pressure for a lower body weight may have allowed flightless rails to have larger brains. The evolution of flightlessness may have changed the position of the foramen magnum downward, which would have allowed the support of the heavier cranium. The larger brain may have facilitated the acquisition of cognitively advanced behavior, such as tool-using behavior, among rails.
研究表明，鸟类的脑形态和飞行能力是相互关联的；然而，这种关系尚未得到彻底研究。本研究旨在探讨飞行能力（飞行或不飞行）是否会影响 Rallidae 的脑形态（大小和形状），因为 Rallidae 在单一分类群中已经独立进化出多次适应次生不飞行的能力。通过对颅骨的计算机断层扫描图像进行提取，并使用 3D 几何形态测量学进行测量，得出脑内模，然后使用主成分分析进行分析。系统发育协方差分析的结果表明，不飞行的秧鸡的脑大小和形状明显大于并不同于飞行的秧鸡，即使分别考虑了体重和脑大小的影响也是如此。不飞行的秧鸡的端脑往往更宽，枕骨大孔的位置更低。尽管大脑是一个需要大量代谢能量的器官，但对较低体重的选择性压力降低可能使不飞行的秧鸡拥有更大的大脑。不飞行的进化可能使枕骨大孔向下移动，从而可以支撑更重的颅骨。更大的大脑可能有助于秧鸡获得更高级的认知行为，例如使用工具的行为。
