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Presenting Author(s) Koji Tamura
Abstract Title The diversity of limb/fin positions in vertebrates.
Full author List Koji Tamura, Hiroyuki Ide, and Sayuri Yonei-Tamura.
Text of abstract

Limbs and fins, locomotor organs that are unique to vertebrates, often serve as model systems in the field of phylogeny and paleontology because their structures are clearly visible and their bony patterns are well preserved in fossil records. The sizes of limbs/fins and their positions along the rostro-caudal axis of the primary body axis are considerably diverged in vertebrates, and their size and position, which often regulate external morphology of each species, are mainly determined during development. The fact that in limb/fin development common mechanisms and cascades mediated by many key molecules such as Shh, Wnt, Tbx and FGF produce their patterns suggests that modern vertebrates inherited the process of limb/fin development from their common ancestor. Therefore, information based on the study of developmental processes in several species of vertebrates will lead to understanding of what the various modern vertebrate groups acquired, altered and lost to make various morpholog ies of limbs/fins during evolution.

We have obtained insights into the mechanisms responsible for the diversity of positions of limbs by comparing limb/fin development in several species, including mice, chicks, frogs, teleost fishes and cartilaginous fishes. Our findings together with results of previous studies suggest that limb/fin-growing competence in all vertebrates is latently provided in both the flank and dorsal region. The interspecies difference in limb/fin positioning may depend on where a species opens a window to grow the limb/fin by choosing specific positions from the regions of AER-forming competence in the lateral and dorsal region.
Which session is your work most relevant to: Limb evolution