The developmental origin of zygodactyl feet and its possible loss in the evolution of Passeriformes
The developmental origin of zygodactyl feet and its possible loss in the evolution of Passeriformes
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DOI：
10.1098/rspb.2014.0765
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发表时间：
2014-08-07
影响因子：
4.7
通讯作者：
Vargas, Alexander O.
中科院分区：
文献类型：
--
作者：
Francisco Botelho, Joao;Smith-Paredes, Daniel;Vargas, Alexander O.
脚趾的对趾方向（第二和第三指向前，第一和第四指向后）在不同的现存鸟类类群中独立进化。为了了解这一特点在现代鸟类的起源，我们调查了发展的zygodactyl脚的虎皮鹦鹉（鹦鹉形目）。我们比较了它的肌肉发育与异趾鹌鹑（Galliformes），并表明，而展趾肌IV（ABDIV）成为强烈发展在HH 36在这两个物种，伸趾短肌IV（EBDIV）退化，几乎消失，只有在虎皮鹦鹉。在虎皮鹦鹉足发育早期，这些肌肉的不对称动作会导致第四趾（dIV）倒转。麻痹的虎皮鹦鹉胚胎不会恢复dIV，并且是异趾的。分子系统发育分析和古生物学资料都表明雀形目的祖先可能是对趾类。我们跟踪了斑胸草雀（雀形目）足肌的发育，发现在这个物种中，ABDIV和EBDIV的原基都没有发育。这些数据表明，由于缺乏ABDIV而导致的施加在dIV上的肌肉活动的不对称力的丧失，可能导致雀形目中继发性指/趾不等畸形。
The zygodactyl orientation of toes (digits II and III pointing forwards, digits I and IV pointing backwards) evolved independently in different extant bird taxa. To understand the origin of this trait in modern birds, we investigated the development of the zygodactyl foot of the budgerigar (Psittaciformes). We compared its muscular development with that of the anisodactyl quail (Galliformes) and show that while the musculus abductor digiti IV (ABDIV) becomes strongly developed at HH36 in both species, the musculus extensor brevis digiti IV (EBDIV) degenerates and almost disappears only in the budgerigar. The asymmetric action of those muscles early in the development of the budgerigar foot causes retroversion of digit IV (dIV). Paralysed budgerigar embryos do not revert dIV and are anisodactyl. Both molecular phylogenetic analysis and palaeontological information suggest that the ancestor of passerines could have been zygodactyl. We followed the development of the zebra finch (Passeriformes) foot muscles and found that in this species, both the primordia of the ABDIV and of the EBDIV fail to develop. These data suggest that loss of asymmetric forces of muscular activity exerted on dIV, caused by the absence of the ABDIV, could have resulted in secondary anisodactyly in Passeriformes.