Evo-Devo of scales, feathers and hairs (Evolutionary Developmental Biology - A reference guide

Integument forms the interface between the organism and its environment. Because of the need for adaptation, it has evolved a robust ability to regenerate under physiological conditions (age, sex, and season) and sometimes in different forms which we call organ-level metamorphosis. Here we identify the organization principles of skin appendage organs: periodic patterning, stem cell renewal, temporo-regional specification, the ability to undergo regenerative healing, and the robust ability to evolve. We identify “core-morphoregulatory modules” for basic appendage formation, and “morphoregulatory modules” which sense environmental changes and mediate the signals to modify core morphogenesis processes. Here, we highlight key knowledge and recent development in the evolution and development of feather, scales, and hairs.