Meeting Abstract

S2-2.1  Jan. 4  The Origin of Vertebrate Fin Development FREITAS, R; ZHANG, G; COHN, MJ*; Department of Zoology and The University of Florida Genetics Institute, Gainesville, USA; Department of Zoology and The University of Florida Genetics Institute, Gainesville, USA; Department of Zoology and The University of Florida Genetics Institute, Gainesville, USA cohn@zoo.ufl.edu

The origin of paired appendages was a major evolutionary innovation for vertebrates, marking the first step towards fin- (and later limb-) driven locomotion. The earliest vertebrate fossils lack paired fins but have well-developed median fins, suggesting that the mechanisms of fin development were assembled first in the midline. We have found that shark median fin development involves the same genetic programs that operate in paired appendages, although median fins arise predominantly from somitic (paraxial) mesoderm, whereas paired appendages develop from lateral plate mesoderm. Despite their different embryonic origins, paired and median fins utilize a common suite of developmental mechanisms to specify fin position, number and morphological pattern. By extending our analysis to lampreys, we show that the molecular mechanisms for fin development originated in somitic mesoderm of early vertebrates, prior to the origin of paired fins. The origin of paired appendages was associated with re-deployment of these mechanisms to lateral plate mesoderm.