Evidence for an amphibian sixth digit.
Evidence for an amphibian sixth digit.
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DOI：
10.1186/s40851-015-0019-y
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发表时间：
2015
影响因子：
2.7
通讯作者：
Tamura K
中科院分区：
文献类型：
--
作者：
Hayashi S;Kobayashi T;Yano T;Kamiyama N;Egawa S;Seki R;Takizawa K;Okabe M;Yokoyama H;Tamura K
尽管四足动物趾形态的多样性反映了它们对生活方式的适应，但现存四足动物的趾数保守地稳定在5个或更少，这被称为五足动物约束。我们发现一种无脊椎两栖动物，热带爪蟾（爪蛙），在脚的前腹部有一个爪状突起。为了确定最前面的爪突出物的性质，我们检查了它的形态、组织组成、发育和基因表达。从解剖学特征、发育和分子标记表达来看，我们证明了热带棘猴后肢的突起是第六趾。对热带爪蟾后肢第六趾的鉴定有力地表明，与第六趾形态相似、位置相同的其他爪蟾物种的前趾也是一个退化趾。我们在这里提出，在各种两栖动物中看到的前趾通常代表一个初级的第六指。本文的在线版本（doi:10.1186/s40851-015-0019-y）包含补充材料，仅供授权用户使用。
Despite the great diversity in digit morphology reflecting the adaptation of tetrapods to their lifestyle, the number of digits in extant tetrapod species is conservatively stabilized at five or less, which is known as the pentadactyl constraint. We found that an anuran amphibian species, Xenopus tropicalis (western clawed frog), has a clawed protrusion anteroventral to digit I on the foot. To identify the nature of the anterior-most clawed protrusion, we examined its morphology, tissue composition, development, and gene expression. We demonstrated that the protrusion in the X. tropicalis hindlimb is the sixth digit, as is evident from anatomical features, development, and molecular marker expression. Identification of the sixth digit in the X. tropicalis hindlimb strongly suggests that the prehallux in other Xenopus species with similar morphology and at the same position as the sixth digit is also a vestigial digit. We propose here that the prehallux seen in various species of amphibians generally represents a rudimentary sixth digit. The online version of this article (doi:10.1186/s40851-015-0019-y) contains supplementary material, which is available to authorized users.