Mammary glands and feathers: comparing two skin appendages which help define novel classes during vertebrate evolution.
It may appear counter-intuitive to compare feathers and mammary glands. However, through this Evo-Devo analysis, we appreciate how species interact with the environment, requiring different ectodermal organs. Novel ectodermal organs help define evolutionary directions, leading to new organism classes as exemplified by feathers for Aves and mammary glands for Mammals. Here, we review their structure, function, morphogenesis and regenerative cycling. Interestingly, both organs undergo extensive branching for different reasons; feather branching is driven by mechanical advantage while mammary glands nourish young. Besides natural selection, both are regulated by sex hormones and acquired a secondary function for attracting mates, contributing to sexual selection.
Widelitz
Randall B
RB
Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. widelitz@usc.edu
Veltmaat
Jacqueline M
JM
Mayer
Julie Ann
JA
Foley
John
J
Chuong
Cheng-Ming
CM
D000818:Animals; D005075:Biological Evolution; D005241:Feathers / Q000196:embryology*; D006801:Humans; D034582:Integumentary System / Q000196:embryology*; D042361:Mammary Glands, Human / Q000196:embryology*; D008954:Models, Biological; D014714:Vertebrates / Q000196:embryology*