小柯机器人

美国菲尔德自然历史博物馆Kenneth D. Angielczyk，英国伦敦自然历史博物馆Romain David和葡萄牙里斯本大学Ricardo Araújo共同合作，近期取得重要工作进展，他们共同研究发现内耳生物力学揭示了哺乳动物恒温的三叠纪晚期起源。该项研究成果2022年7月20日在线出版于《自然》杂志上。

在这里，研究人员表明，可以使用内耳充满内淋巴的半规管的形态来研究这一关键的进化转变，该导管监测头部旋转，对于运动协调、导航和空间意识至关重要。在哺乳动物祖先的变温-恒温过渡期间体温升高会降低内淋巴粘度，对半规管生物力学产生负面影响，同时增加行为活动，这可能需要提高性能。膜导管和围合骨管的形态变化对于在此过渡期间保持最佳功能是必要的。为了追踪56种已灭绝的合弓纲物种的这些形态功能变化，研究人员开发了基于骨管形态的热动力指数。结果表明，哺乳动物在三叠纪晚期突然进化，与体温的急剧升高（5-9°C）以及有氧和无氧能力的扩大有关。与前人的观点相反，所有茎类哺乳动物都极有可能是变温动物。恒温作为一个重要的生理特征，加入了在这段气候不稳定时期出现的其他独特的哺乳动物特征。

据介绍，恒温是哺乳动物和鸟类在不同环境中的生态优势的基础。然而，这一关键特征在哺乳动物进化史上是何时出现的还不清楚，因为大多数化石证据都是模棱两可的。

附：英文原文

Title: Inner ear biomechanics reveals a Late Triassic origin for mammalian endothermy

Author: Arajo, Ricardo, David, Romain, Benoit, Julien, Lungmus, Jacqueline K., Stoessel, Alexander, Barrett, Paul M., Maisano, Jessica A., Ekdale, Eric, Orliac, Mava, Luo, Zhe-Xi, Martinelli, Agustn G., Hoffman, Eva A., Sidor, Christian A., Martins, Rui M. S., Spoor, Fred, Angielczyk, Kenneth D.

Issue&Volume: 2022-07-20

Abstract: Endothermy underpins the ecological dominance of mammals and birds in diverse environmental settings1,2. However, it is unclear when this crucial feature emerged during mammalian evolutionary history, as most of the fossil evidence is ambiguous3,4,5,6,7,8,9,10,11,12,13,14,15,16,17. Here we show that this key evolutionary transition can be investigated using the morphology of the endolymph-filled semicircular ducts of the inner ear, which monitor head rotations and are essential for motor coordination, navigation and spatial awareness18,19,20,21,22. Increased body temperatures during the ectotherm–endotherm transition of mammal ancestors would decrease endolymph viscosity, negatively affecting semicircular duct biomechanics23,24, while simultaneously increasing behavioural activity25,26 probably required improved performance27. Morphological changes to the membranous ducts and enclosing bony canals would have been necessary to maintain optimal functionality during this transition. To track these morphofunctional changes in 56 extinct synapsid species, we developed the thermo-motility index, a proxy based on bony canal morphology. The results suggest that endothermy evolved abruptly during the Late Triassic period in Mammaliamorpha, correlated with a sharp increase in body temperature (5–9°C) and an expansion of aerobic and anaerobic capacities. Contrary to previous suggestions3,4,5,6,7,8,9,10,11,12,13,14, all stem mammaliamorphs were most probably ectotherms. Endothermy, as a crucial physiological characteristic, joins other distinctive mammalian features that arose during this period of climatic instability28.

DOI: 10.1038/s41586-022-04963-z

Source: https://www.nature.com/articles/s41586-022-04963-z

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
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