Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, 45221, USA.
Department of Genetics, Blavatnik Institute at Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115, USA.
Dev Biol. 2023 Jan;493:13-16. doi: 10.1016/j.ydbio.2022.11.004. Epub 2022 Nov 5.
Charles Breder, a pioneering researcher of blind Mexican cavefish was the first to note extreme variation in the facial skeleton of this intriguing subterranean-dwelling organism. Using a system of polar coordinate plots, he identified substantial dysmorphic changes affecting bones of the orbital skeleton. A complication of his landmark publication from 1944 was an error in the number of orbital bones depicted for this species. Intriguingly, however, he proposed an unknown "organizing force" likely influences final bone position and associated dysmorphia. At the time this was merely hypothetical. Roughly eight decades since its publication, however, insights into sensory influences on facial bone development may explain dysmorphia and variation in bone numbers for Astyanax cavefish. A morphological association between mechano-sensory neuromasts of the lateral line and dermal bones of the facial skeleton had been appreciated in the classical literature, but the polarity of this interaction has long remained unclear. Here, we propose that sensory-skeletal integration between sensory neuromasts and bones explain the incomplete numbers of bones, and dysmorphic features such as fusion between neighboring elements. We propose that in closely-related surface fish (and most teleost fish) this developmental coupling enables the sensory and skeletal systems to become integrated into a functional unit over the course of life history. In this opinion article, we discuss the relevance of this (poorly understood) phenomenon as a potential evolutionary source of variation in the facial bone structures of taxa across deep geologic time. We provide three potential explanations for the error in Breder's drawings, that may be explained by natural developmental variation documented in other related species. Moreover, we argue that the natural variation in this "evolutionary" model system is useful for explaining diverse cranial features by uniting aberrations occurring during embryogenesis with long-term adult dysmorphia.
查尔斯·布雷德（Charles Breder）是研究墨西哥盲眼洞穴鱼的先驱者，他首次注意到这种引人入胜的地下生物的面部骨骼存在极端变异。他使用极坐标图系统，确定了影响眼眶骨骼的大量畸形变化。1944 年他具有里程碑意义的出版物存在一个问题，即该物种的眼眶骨数量有误。然而，有趣的是，他提出了一种未知的“组织力”可能会影响最终的骨骼位置和相关畸形。当时这只是假设。然而，自他发表这篇论文以来的大约 80 年，关于感官对面部骨骼发育的影响的研究进展，可能可以解释 Astyanax 洞穴鱼的畸形和骨骼数量变异。经典文献中已经认识到侧线机械感觉神经丘和面部骨骼的真皮骨之间存在形态学关联，但这种相互作用的极性长期以来一直不清楚。在这里，我们提出，感觉神经丘和骨骼之间的感觉-骨骼整合可以解释骨骼数量不完整和畸形特征，如相邻元素之间的融合。我们提出，在亲缘关系密切的表型鱼类（和大多数硬骨鱼）中，这种发育耦合使感觉和骨骼系统能够在整个生命史中整合为一个功能单元。在这篇观点文章中，我们讨论了这种（理解甚少）现象作为跨深层地质时间的分类单元面部骨骼结构变异的潜在进化来源的相关性。我们提供了三个可能导致布雷德图纸错误的解释，这些错误可能可以用其他相关物种记录的自然发育变异来解释。此外，我们认为，在这个“进化”模型系统中，自然变异可用于通过将胚胎发生过程中发生的异常与长期的成人畸形结合起来，解释各种颅面特征。
