Acoel development supports a simple planula-like urbilaterian
- 11 January 2008
- journal article
- review article
- Published by The Royal Society in Philosophical Transactions B
- Vol. 363 (1496), 1493-1501
- https://doi.org/10.1098/rstb.2007.2239
Abstract
Molecular approaches to the study of development and evolution have had profound effects on our understanding of the nature of the evolutionary process. Developmental biologists became intoxicated with fanciful notions of reconstructing genetic pathways of morphogenesis while evolutionary biologists were sobered by the fallacy of reconstructing organismal relationships along increasing grades of morphological complexity. Increased taxon sampling and improvements in analytical techniques are providing a new approach and are forcing biologists to move past historical biases to allow more accurate mapping of morphological and developmental characters through evolutionary time. Here, we discuss the possible developmental and morphological features of the ‘urbilaterian’, the triploblastic animal with anterior-posterior and dorsoventral axes and predecessor of the protostome–deuterostome ancestor. We argue that this animal, with features resembling acoelomorph flatworms, was far simpler morphologically than the protostome–deuterostome ancestor despite possessing a nearly complete eubilaterian genome. We show that the deployment of some genes expected to pattern the protostome–deuterostome ancestor is not deployed in acoels in the predicted manner and thus might have been co-opted after the evolution of the urbilaterian. We also identify the developmental changes related to gastrulation that gave rise to the urbilaterian from a simpler cnidarian-like ancestor.Keywords
This publication has 78 references indexed in Scilit:
- Assembling the lophotrochozoan (=spiralian) tree of lifePhilosophical Transactions B, 2008
- Polychaete trunk neuroectoderm converges and extends by mediolateral cell intercalationProceedings of the National Academy of Sciences of the United States of America, 2007
- Deuterostome phylogeny reveals monophyletic chordates and the new phylum XenoturbellidaNature, 2006
- Molecular evidence for deep evolutionary roots of bilaterality in animal developmentProceedings of the National Academy of Sciences of the United States of America, 2006
- The phylogenetic distribution of metazoan microRNAs: insights into evolutionary complexity and constraintJournal of Experimental Zoology Part B: Molecular and Developmental Evolution, 2006
- The dawn of bilaterian animals: the case of acoelomorph flatwormsBioEssays, 2004
- Xenoturbella is a deuterostome that eats molluscsNature, 2003
- The Nemertodermatida are basal bilaterians and not members of the PlatyhelminthesZoologica Scripta, 2002
- Phylogenetic Perspectives in Innate ImmunityScience, 1999
- The zootype and the phylotypic stageNature, 1993