Morphoregulation of avian beaks: Comparative mapping of growth zone activities and morphological evolution
Article first published online: 3 APR 2006
Copyright © 2006 Wiley-Liss, Inc.
Special Issue: Craniofacial Development Special Issue
Volume 235, Issue 5, pages 1400–1412, May 2006
How to Cite
Wu, P., Jiang, T.-X., Shen, J.-Y., Widelitz, R. B. and Chuong, C.-M. (2006), Morphoregulation of avian beaks: Comparative mapping of growth zone activities and morphological evolution. Dev. Dyn., 235: 1400–1412. doi: 10.1002/dvdy.20825
- Issue published online: 19 APR 2006
- Article first published online: 3 APR 2006
- Manuscript Accepted: 14 FEB 2006
- NIH. Grant Numbers: AR42177, AR47364
- NCI. Grant Number: CA83716
- craniofacial development;
- Darwin's finches;
- Mesozoic birds;
Avian beak diversity is a classic example of morphological evolution. Recently, we showed that localized cell proliferation mediated by bone morphogenetic protein 4 (BMP4) can explain the different shapes of chicken and duck beaks (Wu et al.  Science 305:1465). Here, we compare further growth activities among chicken (conical and slightly curved), duck (straight and long), and cockatiel (highly curved) developing beak primordia. We found differential growth activities among different facial prominences and within one prominence. The duck has a wider frontal nasal mass (FNM), and more sustained fibroblast growth factor 8 activity. The cockatiel has a thicker FNM that grows more vertically and a relatively reduced mandibular prominence. In each prominence the number, size, and position of localized growth zones can vary: it is positioned more rostrally in the duck and more posteriorly in the cockatiel FNM, correlating with beak curvature. BMP4 is enriched in these localized growth zones. When BMP activity is experimentally altered in all prominences, beak size was enlarged or reduced proportionally. When only specific prominences were altered, the prototypic conical shaped chicken beaks were converted into an array of beak shapes mimicking those in nature. These results suggest that the size of beaks can be modulated by the overall activity of the BMP pathway, which mediates the growth. The shape of the beaks can be fine-tuned by localized BMP activity, which mediates the range, level, and duration of locally enhanced growth. Implications of topobiology vs. molecular blueprint concepts in the Evo–Devo of avian beak forms are discussed. Developmental Dynamics 235:1400–1412, 2006. © 2006 Wiley-Liss, Inc.