Patterns & Phenotypes
Sinistral equal-size spiral cleavage of the indirectly developing polychaete Hydroides elegans
Article first published online: 30 APR 2007
Copyright © 2007 Wiley-Liss, Inc.
Special Issue: Special Focus on Segmentation
Volume 236, Issue 6, pages 1611–1622, June 2007
How to Cite
Arenas-Mena, C. (2007), Sinistral equal-size spiral cleavage of the indirectly developing polychaete Hydroides elegans. Dev. Dyn., 236: 1611–1622. doi: 10.1002/dvdy.21164
- Issue published online: 16 MAY 2007
- Article first published online: 30 APR 2007
- Manuscript Accepted: 26 MAR 2007
- spinal cleavage;
- equal cleavage;
- asymmetric cleavage;
- sinistral cleavage;
Two major variants of the stereotypic spiral cleavage correlate with distinct developmental modes in polychaetes. Indirect development through a feeding trochophore larva correlates with development from four equal-sized blastomeres, whereas direct development correlates with unequal cleavage characterized by a large dorsal blastomere precursor maternally predetermined. The equal-size spiral cleavage of the indirectly developing serpulid Hydroides elegans has been reconstructed from serial sections of nuclei-stained embryos. The order of cell divisions has been determined from the 2-cell stage to the 80-cell stage, when gastrulation cell movements start to overlap with late spiral-cleavage divisions. In contrast to related species, the third cleavage in Hydroides elegans is invariably sinistral. The four quadrants remain indistinct until the 60-cell stage, when the small 2d22 and large 2d21 cells are generated. The developmental significance of the invariant spiral cleavage relates to the spatial distribution of gene functions that it partitions and their relation to blastomere fate commitments. The conservation and divergence of the cleavage pattern among spiralians is well suited to study the developmental control of the cell-cleavage machinery and its evolution. Developmental Dynamics 236:1611–1622, 2007. © 2007 Wiley-Liss, Inc.