Mammalian mandible and cranium are well-established model systems for studying canalization and developmental stability (DS) as two elements of developmental homeostasis. Nematode infections are usually acquired in early life and increase in intensity with age, while canalization and DS of rodent skulls could vary through late postnatal ontogeny. We aimed to estimate magnitudes and describe patterns of mandibular and cranial canalization and DS related to age and parasite intensity (diversity) in adult yellow-necked mice (Apodemus flavicollis). We found the absence of age-related changes in the levels of canalization for mandibular and cranial size and DS for mandibular size. However, individual measures of mandibular and cranial shape variance increased, while individual measures of mandibular shape fluctuating asymmetry (FA) decreased with age. We detected mandibular and cranial shape changes during postnatal ontogeny, but revealed no age-related dynamics of their covariance structure among and within individuals. Categories regarding parasitism differed in the level of canalization for cranial size and the level of DS for cranial shape. We observed differences in age-related dynamics of the level of canalization between non-parasitized and parasitized animals, as well as between yellow-necked mice parasitized by different number of nematode species. Likewise, individual measures of mandibular and cranial shape FA decreased with age for the mandible in the less parasitized category and increased for the cranium in the most parasitized category. Our age-related results partly agree with previous findings. However, no rodent study so far has explored age-related changes in the magnitude of FA for mandibular size or mandibular and cranial FA covariance structure. This is the first study dealing with the nematode parasitism-related canalization and DS in rodents. We showed that nematode parasitism does not affect mandibular and cranial shape variation and covariance structure among and within individuals. However, parasite intensity (diversity) is related to ontogenetic dynamics of the levels of canalization and DS. Overall, additional studies on animals from natural populations are required before drawing some general conclusions.

中文翻译：

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与年龄和线虫寄生相关的黄颈小鼠（Apodemus flavicollis）下颌骨和颅骨的管道化和发育稳定性

哺乳动物的下颌骨和颅骨是用于研究管道化和发育稳定性 (DS) 作为发育稳态的两个要素的完善模型系统。线虫感染通常在生命早期获得，并且随着年龄的增长而增加，而啮齿动物头骨的管道化和 DS 可能因出生后个体发育晚期而异。我们的目的是估计成年黄颈小鼠（Apodemus flavicollis）的大小并描述与年龄和寄生虫强度（多样性）相关的下颌骨和颅骨运河和 DS 的模式。我们发现下颌骨和颅骨大小的管化水平和下颌骨大小的 DS 没有与年龄相关的变化。然而，下颌骨和颅骨形状变异的个体测量值增加，而下颌骨形状波动不对称 (FA) 的个体测量值随着年龄的增长而下降。我们在出生后个体发育过程中检测到下颌和颅骨形状的变化，但没有发现个体之间和个体内部协方差结构的年龄相关动态。关于寄生的类别在颅骨大小的管道化水平和颅骨形状的 DS 水平上有所不同。我们观察到非寄生动物和寄生动物之间以及被不同数量的线虫物种寄生的黄颈小鼠之间运河化水平的年龄相关动态差异。同样，下颌骨和颅骨形状 FA 的个体测量值随着年龄的增长而减少，寄生虫较少的下颌骨，而寄生虫最严重的颅骨则增加。我们与年龄相关的结果部分同意先前的发现。然而，迄今为止，还没有啮齿类动物研究探讨了下颌骨大小或下颌骨和颅骨 FA 协方差结构的 FA 大小与年龄相关的变化。这是第一项研究啮齿类动物线虫寄生相关的运河和 DS。我们表明线虫寄生不影响个体之间和个体内部的下颌和颅骨形状变化和协方差结构。然而，寄生虫强度（多样性）与运河化和 DS 水平的个体发生动力学有关。总的来说，在得出一些一般性结论之前，需要对来自自然种群的动物进行额外的研究。我们表明线虫寄生不影响个体之间和个体内部的下颌和颅骨形状变化和协方差结构。然而，寄生虫强度（多样性）与运河化和 DS 水平的个体发生动力学有关。总的来说，在得出一些一般性结论之前，需要对来自自然种群的动物进行额外的研究。我们表明线虫寄生不影响个体之间和个体内部的下颌和颅骨形状变化和协方差结构。然而，寄生虫强度（多样性）与运河化和 DS 水平的个体发生动力学有关。总的来说，在得出一些一般性结论之前，需要对来自自然种群的动物进行额外的研究。