Premium
Frame‐shifts of digit identity in bird evolution and Cyclopamine‐treated wings
Author(s) -
Vargas Alexander O.,
Wagner Günter P.
Publication year - 2009
Publication title -
evolution and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.651
H-Index - 78
eISSN - 1525-142X
pISSN - 1520-541X
DOI - 10.1111/j.1525-142x.2009.00317.x
Subject(s) - numerical digit , biology , wing , homeotic gene , anatomy , evolutionary biology , identity (music) , frame (networking) , arithmetic , genetics , mathematics , computer science , telecommunications , physics , mutant , acoustics , engineering , gene , aerospace engineering
SUMMARY A highly conserved spatio‐temporal pattern of cartilage formation reveals that the digits of the bird wing develop from positions that become digits 2, 3, and 4 in other amniotes. However, the morphology of the digits of early birds like Archaeopteryx corresponds to that of digits 1, 2, and 3 of other archosaurs. A hypothesis is that a homeotic “frame‐shift” occurred, such that in the bird wing, digits 1, 2, and 3 develop from the embryological positions of digits 2, 3, and 4. Experimental homeotic transformations of single digits are well‐documented, but frame‐shifts of more than one digit are not. We investigated the pattern of cartilage formation in the development of Cyclopamine‐treated wings. When Cyclopamine was applied between stages 18 and 21, morphologies that normally develop from positions 2 and 3 developed from positions 3 and 4. The serial shift of digit identity toward posterior confirms a mechanistic possibility that was previously inferred from the evolutionary history of birds.