Developmental basis of evolutionary digit loss in the Australian lizard Hemiergis
Article first published online: 28 MAY 2003
© 2003 Wiley-Liss, Inc.
Journal of Experimental Zoology Part B: Molecular and Developmental Evolution
Volume 297B, Issue 1, pages 48–56, 15 June 2003
How to Cite
Shapiro, M. D., Hanken, J. and Rosenthal, N. (2003), Developmental basis of evolutionary digit loss in the Australian lizard Hemiergis. J. Exp. Zool., 297B: 48–56. doi: 10.1002/jez.b.19
- Issue published online: 28 MAY 2003
- Article first published online: 28 MAY 2003
- Manuscript Accepted: 7 APR 2003
- Manuscript Received: 24 FEB 2003
- Putnam Expeditionary Fund, NSF, Society for Integrative and Comparative Biology, and Sigma Xi (MDS); NIH; NASA (NR)
Loss of limb skeletal elements is a recurring theme in tetrapod evolution, but the developmental mechanisms underlying this phenomenon remain largely unknown. The Australian lizard genus Hemiergis offers an excellent model system to study limb reduction among closely related, naturally occurring populations with different numbers of digits. Evolutionary digit loss in Hemiergis does not result from simple truncation of a pentadactyl skeletal developmental program. Rather, the duration of embryonic expression of the patterning molecule Sonic hedgehog (SHH) is shortened in limbs with reduced numbers of digits, and is correlated with decreased cell proliferation in the posterior aspect of the limb. Moreover, this comparative analysis suggests an early role for SHH in specification of digit identity and later importance in maintaining cell proliferation and survival. Subtle changes in spatial or temporal regulation of SHH may alter proliferation and patterning of the developing limb, thereby effecting divergence in adult limb morphology among closely related species. In contrast, expression of MSX and Distal-less proteins were similar among embryos from different populations. J. Exp. Zool. (Mol. Dev. Evol.) 297B:48–56, 2003. © 2003 Wiley-Liss, Inc.