TY - JOUR

T1 - Cellular and muscular growth patterns during sipunculan development

AU - Kristof, Alen

AU - Wollesen, Tim

AU - Maiorova, Anastassya S

AU - Wanninger, Andreas

PY - 2011

Y1 - 2011

N2 - Sipuncula is a lophotrochozoan taxon with annelid affinities, albeit lacking segmentation of the adult body. Here, we present data on cell proliferation and myogenesis during development of three sipunculan species, Phascolosoma agassizii, Thysanocardia nigra, and Themiste pyroides. The first anlagen of the circular body wall muscles appear simultaneously and not subsequently as in the annelids. At the same time, the rudiments of four longitudinal retractor muscles appear. This supports the notion that four introvert retractors were part of the ancestral sipunculan bodyplan. The longitudinal muscle fibers form a pattern of densely arranged fibers around the retractor muscles, indicating that the latter evolved from modified longitudinal body wall muscles. For a short time interval, the distribution of S-phase mitotic cells shows a metameric pattern in the developing ventral nerve cord during the pelagosphera stage. This pattern disappears close to metamorphic competence. Our findings are congruent with data on sipunculan neurogenesis, as well as with recent molecular analyses that place Sipuncula within Annelida, and thus strongly support a segmental ancestry of Sipuncula.

AB - Sipuncula is a lophotrochozoan taxon with annelid affinities, albeit lacking segmentation of the adult body. Here, we present data on cell proliferation and myogenesis during development of three sipunculan species, Phascolosoma agassizii, Thysanocardia nigra, and Themiste pyroides. The first anlagen of the circular body wall muscles appear simultaneously and not subsequently as in the annelids. At the same time, the rudiments of four longitudinal retractor muscles appear. This supports the notion that four introvert retractors were part of the ancestral sipunculan bodyplan. The longitudinal muscle fibers form a pattern of densely arranged fibers around the retractor muscles, indicating that the latter evolved from modified longitudinal body wall muscles. For a short time interval, the distribution of S-phase mitotic cells shows a metameric pattern in the developing ventral nerve cord during the pelagosphera stage. This pattern disappears close to metamorphic competence. Our findings are congruent with data on sipunculan neurogenesis, as well as with recent molecular analyses that place Sipuncula within Annelida, and thus strongly support a segmental ancestry of Sipuncula.

KW - Faculty of Science

KW - Sipuncula

KW - Evolution

KW - Segmentation

KW - Myogenesis

KW - Proliferating Cells

KW - EdU

KW - Annelida

U2 - 10.1002/jez.b.21394

DO - 10.1002/jez.b.21394

M3 - Journal article

C2 - 21246707

VL - 316B

SP - 227

EP - 240

JO - Journal of Experimental Zoology. Part B: Molecular and Developmental Evolution

JF - Journal of Experimental Zoology. Part B: Molecular and Developmental Evolution

SN - 1552-5007

IS - 3

ER -