Publications
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Author:
Boisvert, Catherine Anne (Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology)
Title:
The Origin of Tetrapod Limbs and Girdles: Fossil and Developmental Evidence
Department:
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology
Publication type:
Doctoral thesis, comprehensive summary (Other academic)
Language:
English
Place of publ.: Uppsala Publisher: Acta Universitatis Upsaliensis
Pages:
53
Series:
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214; 613
Year of publ.:
2009
URI:
urn:nbn:se:uu:diva-98911
Permanent link:
http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-98911
ISBN:
978-91-554-7448-5
Subject category:
Microbiology
SVEP category:
Organism biology
Abstract(en) :

Around 375 million years ago, the first tetrapods appeared, marking one of the most important events in vertebrate evolutionary history. The fin to limb transition saw the appearance of fingers and a weight bearing pelvic girdle. While very little research has been done on the evolution of the tetrapod pelvic girdle, a fair amount has been done on the origins of fingers but some aspects remained controversial. A combination of palaeontology, developmental biology and comparative morphology was therefore used in this thesis to better understand the fin to limb transition. The pectoral fin of Panderichthys, a sarcopterygian fish closely related to tetrapods was CT-scanned and modeled in three dimensions and its pelvic girdle and fin were examined with traditional techniques. This information from the fossil record was integrated with comparisons of the development of the Australian lungfish, Neoceratodus forsteri, our closest living fish relative and the axolotl (Ambystoma mexicanum), a salamander representing well the condition of early tetrapods. Development of bone and cartilage was studied through clearing and staining and development of skeletal muscles through immunostaining. In situ hybridizations were performed on the lungfish to study the expression of Hoxd13, associated with the formation of digits in tetrapods.

This work shows that the late expression phase of Hoxd13 is present in Neoceratodus and is associated with the formation of radials. Redescription of the pectoral fin of Panderichthys reveals that distal radials are present, which, in addition to other information, lead us to conclude that digits are not novelties in tetrapods but rather have evolved from the distal radials present in the fins of all sarcopterygian fish. The earliest tetrapods lack a full set of wrist + carpals/ankle + tarsal bones. Here, we propose that this region of the limbs evolved after fingers and toes through an expansion of the region between the proximal limb bones and the digits. As for the pelvic girdle, it is very primitive in Panderichthys but comparison of its development in Neoceratodus and Ambystoma suggest that the ischium evolved through the posterior expansion of the pubis and the ilium, through an elongation of the iliac process already present in sarcopterygian fishes.

The results of this thesis help to better understand the fin to limb transition and show that it is more gradual than previously believed.

 

Public defence:
2009-04-09, Lindhalsalen, EBC, Norbyvägen 14, Uppsala, 13:00 (English)
Degree:
degree of Doctor of Philosophy
Supervisor:
Ahlberg, Per Erik, Prof. (Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology)
Ohlsson, Rolf, Prof (Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Animal Development and Genetics)
Ledin, Johan, Dr (Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Evolutionary Organism Biology)
Opponent:
Olsson, Lennart, Prof. (Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum Friedrich-Schiller-Universität Jena)
Available from:
2009-03-13
Created:
2009-03-04
Last updated:
2009-04-03
Statistics:
634 hits
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