Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, USA.
Commun Biol. 2024 Aug 6;7(1):951. doi: 10.1038/s42003-024-06635-2.
Intense environmental pressures can yield both regressive and constructive traits through complex evolutionary mechanisms. Although regression is well-studied, the biological bases of constructive features are less well understood. Cave-dwelling Astyanax fish harbor prolific extraoral taste buds on their heads, which are absent in conspecific surface-dwellers. Here, we present novel ontogenetic data demonstrating extraoral taste buds appear gradually and late in life history. This appearance is similar but non-identical in different cavefish populations, where patterning has evolved to permit taste bud re-specification across the endoderm-ectoderm germ layer boundary. Quantitative genetic analyses revealed that spatially distinct taste buds on the head are primarily mediated by two different cave-dominant loci. While the precise function of this late expansion on to the head is unknown, the appearance of extraoral taste buds coincides with a dietary shift from live-foods to bat guano, suggesting an adaptive mechanism to detect nutrition in food-starved caves. This work provides fundamental insight to a constructive evolutionary feature, arising late in life history, promising a new window into unresolved features of vertebrate sensory organ development.
强烈的环境压力可以通过复杂的进化机制产生退行性和建设性特征。虽然退行性特征已经得到了很好的研究，但建设性特征的生物学基础还不太清楚。洞穴栖息的 Astyanax 鱼的头部有大量的额外的口腔味觉感受器，而在同种的水面栖息者中则没有。在这里，我们提出了新的个体发育数据，证明额外的口腔味觉感受器在生命史后期逐渐出现。这种出现与不同洞穴鱼类种群中的情况相似但不相同，在这些种群中，模式已经进化到允许味觉感受器在内外胚层之间重新指定。定量遗传分析表明，头部不同位置的味觉感受器主要由两个不同的洞穴主导基因座介导。虽然这种向头部的后期扩展的确切功能尚不清楚，但额外的口腔味觉感受器的出现与从活食到蝙蝠粪便的饮食转变相吻合，表明这是一种在食物匮乏的洞穴中探测营养的适应机制。这项工作为生命史后期出现的建设性进化特征提供了基本的见解，有望为尚未解决的脊椎动物感觉器官发育特征提供一个新的视角。
