Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, MI, USA.
Departament de Vertebrats, Museu de Ciències Naturals de Barcelona, Barcelona, Spain.
Mech Dev. 2020 Mar;161:103596. doi: 10.1016/j.mod.2020.103596. Epub 2020 Feb 7.
In the amniote embryo, the upper jaw and nasal cavities form through coordinated outgrowth and fusion of craniofacial prominences. Adjacent to the embryonic prominences are the developing eyes, which abut the maxillary and lateral nasal prominences. The embryos of extant sauropsids (birds and nonavian reptiles) develop particularly large eyes in comparison to mammals, leading researchers to propose that the developing eye may facilitate outgrowth of prominences towards the midline in order to aid prominence fusion. To test this hypothesis, we performed unilateral and bilateral ablation of the developing eyes in chicken embryos, with the aim of evaluating subsequent prominence formation and fusion. Our analyses revealed minor interaction between the developing craniofacial prominences and the eyes, inconsequential to the fusion of the upper beak. At later developmental stages, the skull exhibited only localized effects from missing eyes, while geometric morphometrics revealed minimal effect on overall shape of the upper jaw when it develops without eyes. Our results indicate that the substantial size of the developing eyes in the chicken embryo exert little influence over the fusion of the craniofacial prominences, despite their effect on the size and shape of maxillary prominences and components of the skull.
在羊膜动物胚胎中，上颌和鼻腔通过颅面突起的协调生长和融合形成。胚胎突起的相邻处是正在发育的眼睛，眼睛紧贴上颌和侧鼻突起。与哺乳动物相比，现存的蜥形类动物（鸟类和非鸟类爬行动物）的胚胎发育出特别大的眼睛，这促使研究人员提出，发育中的眼睛可能有助于突起向中线生长，以帮助突起融合。为了验证这一假设，我们在鸡胚中进行了单侧和双侧眼球切除术，旨在评估随后的突起形成和融合。我们的分析表明，发育中的颅面突起和眼睛之间存在较小的相互作用，这对上颌的融合没有影响。在发育的后期阶段，头骨仅表现出由缺失的眼睛引起的局部效应，而当没有眼睛时，上颌的整体形状的几何形态测量学显示出最小的影响。我们的结果表明，尽管鸡胚中发育中的眼睛对上颌突起的大小和形状以及头骨的组成部分有影响，但它们对上颌突起融合的影响很小。
