At puberty they produce juvenal feathers, and during the reproductive stage they form sexually dimorphic feather types. ( b) A bird exhibits different plumage at various ages for different physiological needs. There also can be size and pigmentation gradients. In distinct tracts, feathers have unique, region-specific shapes. Different body regions produce feathers with specific characteristics. ( a) Different types of feathers from different body regions of a finch. On the basis of these seminal works, we overview the progress in development, regeneration, and evolution of feathers during the past three decades.įeather diversity: regional specificity and temporal difference. Experimental work on feathers, starting from the beginning of the twentieth century, was summarized in a chapter on skin morphogenesis by Sengel ( 3). Major genetic variants were covered in Poultry Breeding and Genetics, edited by Crawford ( 2). The basic facts of feathers have been comprehensively described in the two volumes of Avian Anatomy Integuments ( 1), which are still highly useful. How feather diversity from a single follicle is regulated at the molecular level is a wonderful biological question. Single follicles can produce feathers with different shapes, sizes, and color patterns for distinct functions at the various life stages of a bird ( Figure 1 b). One single bird, such as the zebra finch, has feathers with diverse colors and shapes on different parts of the body ( Figure 1 a). There are numerous feathers (usually >20,000) on one bird, and their morphological forms are diverse. Inspiration from biomaterials and flight research further fuels biomimetic potential of feathers as a multidisciplinary research focal point. The discovery of feathered dinosaurs redefines the relationship between feathers and birds. We cover the development of feather buds in chicken embryos, regenerative cycling of feather follicle stem cells, formation of barb branching patterns, emergence of intrafeather pigmentation patterns, interplay of hormones and feather growth, and the genetic identification of several feather variants. Here we review the progress in aspects of development, regeneration, and evolution during the past three decades. In addition, feathers are an excellent model for morphogenesis studies because of their accessibility, and their distinct patterns can be used to assay the roles of specific molecular pathways. Studies of feather growth, cycling, and health are of fundamental importance to avian biology and poultry science. It provides functions in endothermy, communication, and flight. The feather is a complex ectodermal organ with hierarchical branching patterns.
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