Department of Anatomy, Faculty of Veterinary Medicine, Istanbul University-Cerrahpaşa, Istanbul, Turkey.
Evolution & Diversity Dynamics Lab, Université de Liège, Liège, Belgium.
Anat Histol Embryol. 2024 May;53(3):e13050. doi: 10.1111/ahe.13050.
Dogs are animals with strong bite force. This strong bite mechanism has led to significant changes in the skeletal system such as fossa masseterica. It can be thought that one side is used more than the other side in chewing and is related to the preference of using the same side's hand, eye and foot. In the study, directional asymmetry and fluctuating asymmetry, which occurs as a result of chewing asymmetry, were examined on the first molar teeth and the fossa masseterica in 85 dog mandibles including a wide diversity of morphotypes. The association of high PC1 values for directional asymmetry with a pronounced cranial index, as evident in breeds like Pekingese, Pomeranian and Bulldog, indicates a potential evolutionary or selective breeding trend favouring brachycephaly. On the contrary, guardian breeds like the German shepherd and Bernese mountain dog, which typically require strong jaws for their roles, showcased reduced PC1 values, which might be related to their functional morphology. Similarly, the PCA results for the first molar teeth shape variations also highlighted the influence of cranial shape, with boxer dogs displaying notably higher PC1 values. The fluctuating asymmetrical distributions provided valuable insights into individualistic variations. Interestingly, no specific breed distribution trend was observed for these asymmetries, indicating a more individual-based variation rather than breed-based. It is essential to note that while these results provide valuable insights, further studies are required to understand the underlying causes better. Factors like genetic variations, developmental processes, dietary habits and external environmental factors could play pivotal roles in these observed morphological differences.
狗是具有强大咬合力的动物。这种强大的咬合机制导致骨骼系统发生了重大变化，例如咀嚼肌窝。可以认为，咀嚼时一侧比另一侧使用得更多，这与使用同手、眼和脚的偏好有关。在研究中，对包括多种形态类型在内的 85 个犬下颌骨的第一磨牙和咀嚼肌窝进行了咀嚼不对称导致的定向不对称和波动不对称的检查。定向不对称的高 PC1 值与明显的颅指数相关，这在京巴犬、博美犬和斗牛犬等品种中很明显，表明存在有利于短头型的进化或选择性繁殖趋势。相反，牧羊犬和伯恩山犬等护卫犬，由于其角色需要强壮的下颚，其 PC1 值降低，这可能与其功能形态有关。同样，第一磨牙形状变化的 PCA 结果也突出了颅形的影响，拳师犬的 PC1 值明显较高。波动不对称的分布为个体差异提供了有价值的见解。有趣的是，这些不对称性没有表现出特定的品种分布趋势，这表明更多的是基于个体的变化，而不是基于品种的变化。需要注意的是，尽管这些结果提供了有价值的见解，但需要进一步的研究来更好地理解其潜在原因。遗传变异、发育过程、饮食习惯和外部环境因素等因素可能在这些观察到的形态差异中发挥关键作用。
