TY - JOUR

T1 - Sipunculans and segmentation

AU - Wanninger, Andreas

AU - Kristof, Alen

AU - Brinkmann, Nora

N1 - Key words: Sipuncula, evolution, segmentation, seriality, annelid, Echiura, nervous system, development, phylogeny, bodyplan

PY - 2009/1

Y1 - 2009/1

N2 - Comparative molecular, developmental and morphogeneticanalyses show that the three major segmented animal groups-Lophotrochozoa, Ecdysozoa and Vertebrata-use a wide range ofontogenetic pathways to establish metameric body organization.Even in the life history of a single specimen, different mechanismsmay act on the level of gene expression, cell proliferation,tissue differentiation and organ system formation in individualsegments. Accordingly, in some polychaete annelids the first threepairs of segmental peripheral neurons arise synchronously, whilethe metameric commissures of the ventral nervous system form inanterior-posterior progression. Contrary to traditional belief, lossof segmentation may have occurred more often than commonlyassumed, as exemplified in the sipunculans, which show remnantsof segmentation in larval stages but are unsegmented as adults.The developmental plasticity and potential evolutionary lability ofsegmentation nourishes the controversy of a segmented bilaterianancestor versus multiple independent evolution of segmentation inrespective metazoan lineages.

AB - Comparative molecular, developmental and morphogeneticanalyses show that the three major segmented animal groups-Lophotrochozoa, Ecdysozoa and Vertebrata-use a wide range ofontogenetic pathways to establish metameric body organization.Even in the life history of a single specimen, different mechanismsmay act on the level of gene expression, cell proliferation,tissue differentiation and organ system formation in individualsegments. Accordingly, in some polychaete annelids the first threepairs of segmental peripheral neurons arise synchronously, whilethe metameric commissures of the ventral nervous system form inanterior-posterior progression. Contrary to traditional belief, lossof segmentation may have occurred more often than commonlyassumed, as exemplified in the sipunculans, which show remnantsof segmentation in larval stages but are unsegmented as adults.The developmental plasticity and potential evolutionary lability ofsegmentation nourishes the controversy of a segmented bilaterianancestor versus multiple independent evolution of segmentation inrespective metazoan lineages.

KW - Faculty of Science

KW - Sipuncula

KW - Evolution

KW - Neurogenesis

KW - Segmentation

KW - Annelida

KW - Phylogeny

U2 - 10.4161/cib.2.1.7505

DO - 10.4161/cib.2.1.7505

M3 - Review

VL - 2

SP - 56

EP - 59

JO - Communicative & Integrative Biology

JF - Communicative & Integrative Biology

SN - 1942-0889

IS - 1

ER -