One or more members of four living amphibian clades have independently dispensed with pulmonary respiration and lack lungs, but little is known of the developmental basis of lung loss in any taxon. We use morphological, molecular, and experimental approaches to examine the Plethodontidae, a dominant family of salamanders, all of which are lungless as adults. We confirm an early anecdotal report that plethodontids complete early stages of lung morphogenesis: Transient embryonic lung primordia form but regress by apoptosis before hatching. Initiation of pulmonary development coincides with expression of the lung-specification gene Wnt2b in adjacent mesoderm, and the lung rudiment expresses pulmonary markers Nkx2.1 and Sox9 . Lung developmental-genetic pathways are at least partially conserved despite the absence of functional adult lungs for at least 25 and possibly exceeding 60 million years. Adult lung loss appears associated with altered expression of signaling molecules that mediate later stages of tracheal and pulmonary development.

中文翻译：

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蝾螈进化性肺丧失的发育基础

四个现存的两栖动物进化枝中的一个或多个成员已经独立地放弃了肺呼吸并且缺乏肺，但是对于任何分类单元中肺损失的发育基础知之甚少。我们使用形态学、分子学和实验方法来检查蝾螈科，这是一种主要的蝾螈家族，所有这些蝾螈成年后都是无肺的。我们证实了早期的轶事报道，即 plethodontids 完成了肺形态发生的早期阶段：短暂的胚胎肺原基形成，但在孵化前因细胞凋亡而退化。肺发育的启动与肺特异性基因的表达一致Wnt2b在相邻的中胚层中，肺雏形表达肺标志物NKX2.1和Sox9. 尽管成人肺功能缺失至少 25 年甚至可能超过 6000 万年，但肺发育遗传途径至少部分保守。成人肺损失似乎与介导气管和肺部发育后期的信号分子表达改变有关。