Bio-architectural principles of flight feathers (1 Viewer)

[albertonykus]

Not strictly about paleontology, but they examine and discuss fossil feathers so may be of interest.

Chang, W.-L., H. Wu, Y.-K. Chiu, S. Wang, T.-X. Jiang, Z.-L. Luo, Y.-C. Lin, A. Li, J.-T. Hsu, H.-L. Huang, H.-J. Gu, T.-Y. Lin, S.-M. Yang, T.-T. Lee, Y.-C. Lai, M. Lei, M.-Y. Shie, C.-T. Yao, Y.-W. Chen, J.C. Tsai, S.-J. Shieh, Y.-K. Hwu, H.-C. Cheng, P.-C. Tang, S.-C. Hung, C.-F. Chen, M. Habib, R.B. Widelitz, P. Wu, W.-T. Juan, and C.-M. Chuong (2019)
The making of a flight feather: bio-architectural principles and adaptation
Cell 179: 1409-1423
doi: 10.1016/j.cell.2019.11.008
https://www.cell.com/cell/fulltext/S0092-8674%2819%2931229-2

The evolution of flight in feathered dinosaurs and early birds over millions of years required flight feathers whose architecture features hierarchical branches. While barb-based feather forms were investigated, feather shafts and vanes are understudied. Here, we take a multi-disciplinary approach to study their molecular control and bio-architectural organizations. In rachidial ridges, epidermal progenitors generate cortex and medullary keratinocytes, guided by Bmp and transforming growth factor β (TGF-β) signaling that convert rachides into adaptable bilayer composite beams. In barb ridges, epidermal progenitors generate cylindrical, plate-, or hooklet-shaped barbule cells that form fluffy branches or pennaceous vanes, mediated by asymmetric cell junction and keratin expression. Transcriptome analyses and functional studies show anterior-posterior Wnt2b signaling within the dermal papilla controls barbule cell fates with spatiotemporal collinearity. Quantitative bio-physical analyses of feathers from birds with different flight characteristics and feathers in Burmese amber reveal how multi-dimensional functionality can be achieved and may inspire future composite material designs.

 

[Fred Ruhe]

Figure 1. The Cellular Mechanism Guiding the Making of a Feather
(A) Chicken feather schematic, with enlargement of the rachis, pennaceous barbule, and plumulaceous barbule (Lucas and Stettenheim, 1972). (B) Growth phase feather follicle structure. Stem cell ring in the collar region (yellow stripe). Blue arrows indicate barb ridge orientation. (C) Chicken flight feather rachis cross-section showing its composition. Cortex is divided into four regions (white dashed lines). Green line surrounds the medulla. Purple line outlines the rachis. Red arrows in (B) and (C) indicate rachis orientation.(D) Rachis organization along the proximal-distal axis in flight, downy, and contour feathers. The rachis is parameterized along the z-axis (z), where z = 0 at SUR (superior umbilical region, junction of the calamus, and rachis) and z = 1.0Z at the distal tip of the rachis. Cortex is depicted in blue. Medulla cell organization is quantified by QMorF measurements.Vertical PS scale is for the main figures, and horizontal PS scale is for the insets. dc, dorsal cortex; lc, lateral cortex; m, medulla; vc, ventral cortex.

Fred