Restructuring; skin granular gland formation; keratinization and hardening; apoptosis
Induction of collagen, 63 kDa (adult) keratin and magainin; induction of collagenase
Limb bud, lung
Do novo formation of bone, skin, muscle, nerves, and so forth.
Cell proliferation and differentiation; chondrogenesis
Tail, gills
Complete regression
Programmed cell death induction and activation of lytic enzymes (collagenase, nucleases, phosphatases, and matrix metalloproteinases); lysosome proliferation
Pancreas, Intestine
Major tissue restructuring
Reprogramming of phenotype, induction of proteases, fatty acid binding protein, and stromelysin-3
Immune system
Redistribution of cell populations
Altered immune system and appearance of new immunocompetent components