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posted 12. December 2006 15:14
Origin of insect metamorphosis based on design-by-contract: larval stages as an atavism
by Albert D.G. de Roos
Abstract: The steps leading to the insertion of a larval stage during the evolution of holometabolous insects remain largely unknown and appear to be irreducibly complex. The main problem is that an introduction of a new body plan would disrupt existing developmental processes and would require many sequential steps that have to be implemented simultaneously in order to be functional. In the evolution of insect metamorphosis, this would have required the parallel evolution of set aside cells, of a new functional larva and of the induction of metamorphosis. In this article, the engineering paradigm design-by-contract is used to unravel the potential evolutionary steps for metamorphosis. In modelling on design-by-contract, evolution is seen as a continuously expanding system of functional modules which are separated by conserved interfaces. A scenario in which the larval stages were developed before the adult body plan, is relatively simple since it will keep existing developmental interfaces intact. It is therefore proposed that the larval stage of holometabolous insects reflect the reintroduction of an ancient, existing body plan and therefore represents an atavism. This scenario can be based on a developmental switch by a differential expression of Hox genes that can be induced by changes in hormonal timing. Thus, design-by-contract as a predictive evolutionary framework may provide an alternative explanation for the origin of insect metamorphosis.
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[ 12. December 2006, 15:14: Message edited by: Moderator ]