Morphogenesis and homology in arthropod limbs

Arthropods exhibit highly diverse limb morphologies ranging from unbranched walking legs to multibranched swimming paddles. Understanding morphogenesi s in structurally diverse limbs can be useful for ascertaining homologies b etween limbs. Structurally similar limbs have been produced by different ev olutionary modifications of morphogenesis in certain cases. Whereas it is e asy to support the claim that whole arthropod limbs are homologous structur es, I demonstrate that it is not always possible to draw web-founded homolo gies between parts of different limbs. This result is important with regard to general models of appendage development and evolution in arthropods bec ause it clarifies contradictory explanations based exclusively on gene expr ession data.