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Evolution and development of the fish jaw skeleton
1Department of Biology and Geology, University of South Carolina Aiken, Aiken, South Carolina.
Wiley Interdisciplinary Reviews. Developmental Biology
|November 1, 2018
Summary
The evolution of vertebrate jaws involved key developmental changes in pharyngeal arches, leading to diversification. Understanding jaw development offers insights into evolutionary novelties and body plan evolution.
Area of Science:
- Comparative Development and Evolution
- Evolutionary Novelties
- Body Plan Evolution
Background:
- The pharyngeal apparatus in chordate ancestors evolved into branchial structures in jawless vertebrates (agnathans).
- Neural crest cells contributed to pharyngeal arch development, forming jaws, jaw support, and gills in jawed vertebrates (gnathostomes).
Purpose of the Study:
- To elucidate major evolutionary events in jaw structure from agnathans to gnathostomes.
- To explore the genetic and developmental mechanisms underlying jaw joint formation and patterning.
- To analyze transitional jaw phenotypes and test evolutionary hypotheses using genetic manipulation.
Main Methods:
- Analysis of fossil transitional jaw phenotypes from a developmental perspective.
- Review of genetic factors (Hox genes, edn1, dlx, hand2, Jag1b-Notch2, Nr2f) specifying pharyngeal arch identity.
- Examination of gene interactions (nkx3.2, hand2, barx1) in jaw joint formation.
Main Results:
- Key events include axial regionalization of pharyngeal elements and jaw joint formation.
- Specific gene networks regulate anterior-posterior and dorsal-ventral patterning of pharyngeal arches.
- Evolutionary changes in jaw elements occurred between fishes, reptiles, and mammals, including middle ear bone transformation.
Conclusions:
- Jaw evolution is a critical innovation driving vertebrate diversification.
- Developmental genetics provides a framework for understanding ancient vertebrate jaw patterning.
- Further research using extant taxa can validate hypotheses on jaw evolution.
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