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Mandibular Arch Morphogenesis and the Origin of Jaws: What Does "Maxillary" and "Mandibulary" Really Mean
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology, Department of Animal Development and Genetics.
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Manuscript (Other academic)
URN: urn:nbn:se:uu:diva-90470OAI: oai:DiVA.org:uu-90470DiVA: diva2:162834
Available from: 2003-05-15 Created: 2003-05-15 Last updated: 2010-01-13Bibliographically approved
In thesis
1. A Comparative Study of Head Development in Mexican Axolotl and Australian Lungfish: Cell Migration, Cell Fate and Morphogenesis
Open this publication in new window or tab >>A Comparative Study of Head Development in Mexican Axolotl and Australian Lungfish: Cell Migration, Cell Fate and Morphogenesis
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The development of the vertebrate head is a complex process involving interactions between a multitude of cell types and tissues. This thesis describes the development of the cranial neural crest and of the visceral arch muscles in the head of two species. One, the Mexican axolotl (Ambystoma mexicanum), is a basal tetrapod, whereas the other, the Australian lungfish (Neoceratodus forsteri), belongs to the Dipnoi, the extant sister group of the Tetrapoda.

The migration of neural crest cells, which form most of the bones and connective tissues in the head, and the morphogenesis of the jaw, was determined in the Mexican axolotl. It was shown that both the upper and lower jaws form from ventral condensations of neural crest cells in the mandibular arch. The dorsal condensation, earlier considered to give rise to the upper jaw, was shown to form the trabecula cranii.

The normal spatio-temporal development of visceral arch muscles was investigated in both the Mexican axolotl and the Australian lungfish. In axolotl, the muscles tended to start forming almost simultaneously in all visceral arches at their future origins and extend towards their future insertions at the onset of muscle fibre formation. In lungfish, fibres formed simultaneously throughout most of each muscle anlage in the first and second visceral arch, but were delayed in the branchial arches. The anlagen were first observed at their future insertion, from which they developed towards future origins.

To test the ability of neural crest cells to pattern the visceral arch muscles, migrating crest cells were extirpated from axolotl embryos, which resulted in a wide range of muscle malformations. In most cases, the muscles appeared in the right position but were small and extended in abnormal directions. This shows that neural crest cells are responsible not for the position of the muscles but for their correct anatomical pattern. Fate mapping showed that connective tissue surrounding myofibers is, at least partly, neural crest derived.

In conclusion, the work presented in this thesis shows that although early development may map out the patterns of later development, the differences between axolotl and lungfish head development are not seen until during morphogenesis. Further investigation of morphogenesis is needed to explain the great variation of head morphology seen in vertebrates today.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2003. 47 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 848
Developmental biology, Head development, axolotl, lungfish, Utvecklingsbiologi
National Category
Developmental Biology
Research subject
Developmental Biology
urn:nbn:se:uu:diva-3444 (URN)91-554-5654-5 (ISBN)
Public defence
2003-06-06, Lindahlsalen, Evolutionsbiologiskt centrum, Norbyvägen 18 A, Uppsala, 10:00
Available from: 2003-05-15 Created: 2003-05-15Bibliographically approved

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