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Published on: February 2, 2016
Segmental mode of neural patterning in sipuncula.
Alen Kristof1, Tim Wollesen, Andreas Wanninger
1Department of Biology, Research Group for Comparative Zoology, University of Copenhagen, Copenhagen DK-2100, Denmark.
Current Biology : CB
|July 29, 2008
Summary
The nervous system of peanut worms (Sipuncula) initially forms in segments, like their relatives, the annelids. This segmental pattern is lost during larval development, resulting in the adult worm
Area of Science:
- Developmental Biology
- Evolutionary Biology
- Neuroscience
Background:
- Phylogenetic studies suggest Sipuncula (peanut worms) are closely related to Annelida.
- Annelids possess a segmented nervous system, while Sipuncula have a single ventral nerve cord without segmentation.
- Understanding Sipuncula neurogenesis can illuminate the evolution of segmented body plans.
Purpose of the Study:
- To investigate the early development of the central nervous system (CNS) in the sipunculan Phascolosoma agassizii.
- To compare neurogenesis in Sipuncula with that of Annelida to understand evolutionary relationships.
- To test the Haeckelian hypothesis of recapitulation in Sipuncula development.
Main Methods:
- Utilized serotonin and FMRFamide labeling in Phascolosoma agassizii.
- Observed neurogenesis and neural remodeling during larval development.
- Analyzed the formation and subsequent loss of segmental neural structures.
Main Results:
- Neurogenesis in P. agassizii initially exhibits a segmental pattern, with paired axons and ganglia.
- Segmental structures like commissures disappear during later larval stages.
- The developing nervous system remodels into the non-segmented ventral nerve cord of the adult.
Conclusions:
- Sipuncula neurodevelopment supports a segmented ancestry, aligning with phylogenetic data.
- The findings provide a model for ontogenetic recapitulation of evolutionary history.
- This study clarifies the relationship between Sipuncula and Annelida through comparative neurodevelopment.
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