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Somitomeres: mesodermal segments of vertebrate embryos.
1Department of Zoology, Center for Developmental Biology, University of Texas, Austin 78712.
Development (Cambridge, England)
|January 1, 1988
Summary
Vertebrate embryos possess somitomeres, precursors to somites, which are segmented structures in the paraxial mesoderm. These early embryonic units are crucial for understanding head and trunk development across diverse species.
Area of Science:
- Developmental Biology
- Embryology
- Comparative Anatomy
Background:
- Paraxial mesoderm segmentation precedes somite formation in vertebrate embryos.
- Somitomeres are early, patterned mesenchymal cell arrays appearing before somites.
- Their presence challenges and refines models of vertebrate segmentation.
Purpose of the Study:
- To investigate the early segmentation of paraxial mesoderm into somitomeres.
- To determine the role and distribution of somitomeres in vertebrate head and trunk development.
- To update models of vertebrate segmentation incorporating somitomere data.
Main Methods:
- Stereo scanning electron microscopy for initial discovery in chick embryos.
- Comparative embryological studies across various vertebrate species (chick, quail, mouse, turtle, newt, Xenopus, medaka).
- Analysis of somitomere arrangement relative to nervous system development.
Main Results:
- Somitomeres are identified as early segmented units in the paraxial mesoderm of diverse vertebrates.
- Cranial somitomeres contribute to head structures, unlike trunk somitomeres which form somites.
- A consistent cranial-to-caudal order and relationship to neural structures are observed.
Conclusions:
- Somitomere discovery settles the question of head segmentation in craniates at the paraxial mesoderm level.
- Somitomere patterns show variations but fundamental presence across studied vertebrates.
- Current vertebrate segmentation models must integrate somitomeres as fundamental early units.