Cells of embryonic and regenerating germinal layers within barb ridges: implication for the development, evolution and diversification of feathers.

The formation of feathers occurs by the transformation of the embryonic epidermis of feather filaments into keratinized barbules and barbs. The present ultrastructural study directly documents this transformation in chick and zebrafinch downfeathers and juvenile feathers. The transformation of the epidermis in the feather filament (downfeathers) or in the follicle (juvenile feathers) is similar. The change in cell shape of subperiderm or...