![]() BMP signals are most likely responsible for the interdigit apoptosis as they are expressed in the interdigit tissue and blocking BMP signaling will prevent interdigital apoptosis. All vertebrate limb formation initially has tissue between the digits after which apoptosis occurs to separate the digits. Presence of webbed digits įormation of the bat wing membrane (the patagium) allowed a greater surface area of the wing necessary for flight. Researchers can study the genetic basis of bat wing development by using comparative in situ hybridization to examine gene expression domains and using experimental embryology in mice and bats. Thus, it is likely that this major morphological transition was a consequence of cis- regulatory changes. Surprisingly, the coding regions of many of these genes with different expression domains are highly conserved between mouse and bat. Īlthough many of the molecular mechanisms involved in limb development are conserved between mouse and bat, there are a number of differences primarily seen in gene expression patterns. Since mice are also mammals, it is convenient to compare morphology and development of forelimbs between mice and bats these comparisons may elucidate the genetic basis of adaptive bat wing development. Surprisingly many of the same signaling pathways known to play a role in tetrapod limb development have been found to play a role in bat forelimb development but the timing, intensity, and spatial gene expression of some orthologous genes have changed. The apical ectodermal ridge is a structure found at the distal most tip which becomes a key signaling center for the developing limb. Tetrapod limb development involves many signaling molecules such as FGF, BMP, SHH and WNT. Consequently, the bat wing is a valuable evo-devo model for studying the evolution of vertebrate limb diversity.ĭiagram showing homologous skeletal structures of bat and mouse Comparisons to mouse limb development Recently, there have been comparative studies of mouse and bat forelimb development to understand the genetic basis of morphological evolution. Through adaptive evolution these structures in bats have undergone many morphological changes, such as webbed digits, elongation of the forelimb, and reduction in bone thickness. Because bats are mammals, the skeletal structures in their wings are morphologically homologous to the skeletal components found in other tetrapod forelimbs. Bat wings are modified tetrapod forelimbs. The order Chiroptera, comprising all bats, has evolved the unique mammalian adaptation of flight. ![]()
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