Cohn M J
Division of Zoology, School of Animal and Microbial Sciences, University of Reading, Whiteknights, Reading RG6 6AJ, UK.
Novartis Found Symp. 2001;232:47-57; discussion 57-62. doi: 10.1002/0470846658.ch5.
Over the past few years, our understanding of the evolution of limbs has been improved by important new discoveries in the fossil record. Additionally, rapid progress has been made in identifying the molecular basis of vertebrate limb development. It is now possible to integrate these two areas of research in order to identify the molecular developmental mechanisms underlying the evolution of paired appendages in vertebrates. After the origin of paired appendages, several vertebrate lineages reduced or eliminated fins and limbs and returned to the limbless condition. Examples include eels, caecilians, snakes, slow worms and several marine mammals. Analyses of fossil and extant vertebrates show that evolution of limblessness frequently occurred together with elongation of the trunk and loss of clear morphological boundaries in the vertebral column. This may be suggestive of a common developmental mechanism linking these two processes. We have addressed this question by analysing python embryonic development at tissue, cellular and molecular levels, and we have identified a developmental mechanism which may account for evolution of limb loss in these animals.
在过去几年中，化石记录中的重要新发现增进了我们对肢体进化的理解。此外，在确定脊椎动物肢体发育的分子基础方面也取得了迅速进展。现在有可能将这两个研究领域结合起来，以确定脊椎动物成对附肢进化背后的分子发育机制。在成对附肢起源之后，几个脊椎动物谱系减少或消除了鳍和肢体，恢复到无肢状态。例子包括鳗鱼、蚓螈、蛇、慢缺肢蜥和几种海洋哺乳动物。对化石和现存脊椎动物的分析表明，无肢进化常常与躯干伸长以及脊柱中明显形态边界的丧失同时发生。这可能暗示了连接这两个过程的共同发育机制。我们通过在组织、细胞和分子水平上分析蟒蛇胚胎发育来解决这个问题，并且我们已经确定了一种可能解释这些动物肢体丧失进化的发育机制。
