Evo-Devo of the Fin-to-Limb Transition

Abstract

Tetrapod limbs evolved from paired fins. Although the limbs and fins share similar sets of tissue components, structure, and developmental processes, some characteristics of the skeletal morphology of fins are distinct from those of limbs. Fin rays, the distal-most components of the fin, consist of several types of tissues not seen in tetrapods. The fin ray skeletons of teleosts have the same developmental origin (lateral plate mesoderm, LPM) as that of the basal endoskeleton that also develops in the fin bud. The ectodermal jacket of the fin bud has a ridge along the dorsoventral border called the apical ectodermal ridge (AER), which elongates into the apical fold (AF) during development. Tetrapod limb buds never Yoshitaka Tanaka, Hidehiro Kudoh and Gembu Abe contributed equally with all other contributors.