Data from: Shape-shift: semicircular canal morphology responds to selective breeding for increased locomotor activity

Variation in semicircular canal morphology correlates with locomotor agility among species of mammals. An experimental evolutionary mouse model was used to test the hypotheses that semicircular canal morphology (1) evolves in response to selective breeding for increased locomotor activity, (2) exhibits phenotypic plasticity in response to early-onset chronic exercise, and (3) is unique in individuals possessing the minimuscle phenotype. We examined responses in canal morphology to prolonged wheel access and selection in laboratory mice from four replicate lines bred for high voluntary wheel-running (HR) and four nonselected control (C) lines. Linear measurements and a suite of 3D landmarks were obtained from 3D reconstructions of μCT-scanned mouse crania (μCT is microcomputed tomography). Body mass was smaller in HR than C mice and was a significant predictor of both radius of curvature and 3D canal shape. Controlling for body mass, radius of curvature did not differ statistically between HR and C mice, but semicircular canal shape did. Neither chronic wheel access nor minimuscle affected radius of curvature or canal shape These findings suggest that semicircular canal morphology is responsive to evolutionary changes in locomotor behavior, but the pattern of response is potentially different in small- versus large-bodied species.哺乳动物不同物种间，半规管（semicircular canal）形态的差异与其运动敏捷性存在相关性。本研究采用实验性进化小鼠模型，验证了三个相关假说：一是半规管形态会响应于针对高运动活性的选择性育种而发生演化；二是半规管形态会表现出针对早期慢性运动的表型可塑性；三是携带迷你肌肉（minimuscle）表型的个体，其半规管形态具有独特性。我们对4个重复选育的高自主转轮运动（high voluntary wheel-running, HR）品系与4个未经过选择的对照（control, C）品系的实验小鼠进行分析，检测其半规管形态对长期转轮活动与选育的响应。通过对小鼠颅骨进行微计算机断层扫描（microcomputed tomography, μCT）并构建三维重建模型，我们获取了线性测量数据与一系列三维地标点（3D landmarks）。HR组小鼠的体质量显著低于对照组小鼠，且体质量是曲率半径与三维半规管形态的重要预测因子。在控制体质量变量后，HR组与对照组小鼠的曲率半径无统计学差异，但半规管形态存在显著区别。无论是长期转轮活动还是迷你肌肉表型，均未对曲率半径或半规管形态产生影响。本研究结果表明，半规管形态可响应运动行为的演化改变，但这种响应模式在体型较小与体型较大的物种间可能存在差异。