Molecular, micro- and ultrastructural investigations of labile tissues in deep time

Research output: ThesisDoctoral Thesis (compilation)

Abstract

This thesis comprises investigations of microstructures and molecular remains, preserved in a variety of fossil specimens. The results are presented in six papers, collectively aiming to thoroughly examine fossil traces of such remains by employing a combination of both established and relatively new analytical methods. The main questions asked are: What can we learn about the biology, ecology and behaviour of ancient organisms by studying these fossilised remnants, and what methods are best suited to accomplish this?
The work presented herein has been conducted through a series of case studies performed on fossils representing an array of taxa, collected from different geological ages and settings. Methods applied include light and electron microscopy, computed tomography, and molecular analyses, such as time-of-flight secondary ion mass spectrometry, IR microspectroscopy and X-ray absorption spectroscopy.
Microscopic analysis and histology of teeth from Mesozoic marine reptiles allowed calculations of dentine formation and tooth replacement rates. My findings include evidence that while teeth of larger mosasaur taxa took longer time to develop, their dentine formation rates were more rapid, relative to that of smaller species.
In other fossils, microscopic investigations of eye, skin and feather remnants revealed aggregations of micrometre-sized, sub-rounded to elongate structures. Because similar microbodies have previously been described alternatively as relict melanosomes (i.e. pigment-containing, eukaryotic cellular organelles) and lithified bacteria, my co-authors and I performed chemical and molecular analyses in order to explore the affinity of these structures. To ascertain the chemical identity of our fossil samples, corresponding analyses were carried out also on molecularly similar compounds, including modern eumelanin, as controls. My studies show chemical evidence of animal eumelanin in close association with the microbodies, advocating the melanosome interpretation for the analysed specimens.
Beyond the results reported in the included papers, this thesis provides a short review of melanin formation in vertebrate eyes and integument, as well as in fungi and bacteria which also produce this type of pigment. An overview of the various methods applied is presented and followed by a discussion about possible outcomes and pitfalls when studying fossil microstructures and molecular palaeontology. Whereas remnant melanosomes could potentially provide new insight into a multitude of biological and ecological aspects of ancient life, there is still no straight-forward approach to determine the affinity of ‘melanosome-like’ microstructures found in fossils. Therefore, a thorough investigation of such remains, including chemical analyses, should be applied in each study – at least until a consensus has been reached regarding the minimum amount of criteria to be used for a confident recognition.

Details

Authors
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Geology

Keywords

  • eumelanin, fossils, histology, integument, IR microspectroscopy, melanin, melanosomes, molecular palaeontology, ToF-SIMS, XAS
Original languageEnglish
QualificationDoctor
Awarding Institution
Supervisors/Assistant supervisor
Award date2018 Jan 19
Place of PublicationLund
Publisher
  • Lund University, Faculty of Science, Department of Geology, Lithosphere and Biosphere Science
Print ISBNs978-91-87847-34-9
Electronic ISBNs978-91-87847-35-6
Publication statusPublished - 2017 Dec
Publication categoryResearch

Bibliographic note

Defence details Date: 2018-01-19 Time: 13:15 Place: Lecture hall “Pangea”, Geocentrum II, Sölvegatan 12, Lund External reviewer(s) Name: McNamara, Maria Title: Dr. Affiliation: School of Biological, Earth and Environmental Sciences, University College Cork, Ireland ---

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Related research output

Johan Gren, Sjövall, P., Mats Eriksson, Sylvestersen, R., Marone, F., Kajsa Sigfridsson Clauss, Taylor, G., Stefan Carlson, Per Uvdal & Johan Lindgren, 2017 Jan 1, In : Palaeontology. 60, 1, p. 73-90 18 p.

Research output: Contribution to journalArticle

Johan Lindgren, Moyer, A., Mary Higby Schweitzer, Sjövall, P., Per Uvdal, Dan-E Nilsson, Heimdal, J., Engdahl, A., Johan Gren, Schultz, B. P. & Kear, B. P., 2015, In : Royal Society of London. Proceedings B. Biological Sciences. 282, 1813, 20150614.

Research output: Contribution to journalReview article

Johan Lindgren, Sjövall, P., Carney, R. M., Cincotta, A., Per Uvdal, Hutcheson, S. W., Gustafsson, O., Lefèvre, U., Escuillié, F., Heimdal, J., Anders Engdahl, Johan Gren, Kear, B. P., Wakamatsu, K., Yans, J. & Godefroit, P., 2015, In : Scientific Reports. 5, 13520.

Research output: Contribution to journalArticle

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