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    Understanding the mechanisms of polyphyodonty: insights gained from tooth replacement in fish

    Collins, Sally Elizabeth (2023) Understanding the mechanisms of polyphyodonty: insights gained from tooth replacement in fish. PhD thesis, Birkbeck, University of London.

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    Abstract

    Most jawed vertebrates replace their teeth throughout life (polyphyodonty) and there is a great drive to understand the developmental basis of this mechanism. The extreme diversity of fish dentitions offers rich opportunities for investigation. Here, surface feature observations and X-ray micro-CT virtual sections are used to identify tooth replacement mechanisms in fossil and modern fish, which are evaluated in light of existing research. A consensus exists that tooth replacement requires a ‘dental lamina’; an epithelial connection between predecessor and replacement tooth, which provides the putative stems cells required for long-term tooth renewal. This single epithelial connection also enables only one tooth to be replaced by one successor, at any one time. The findings herein show this is not the case in the crushing dentitions of an extinct group of fishes, the pycnodonts. Instead, tooth positioning suggests an opportunistic, gap-filling addition, where teeth fill space arising from tooth damage, loss, and the geometry of neighbouring teeth. Contrastingly, in the modern fish specimens, the mechanisms by which teeth are regenerated are recognisable. However, the crushing dentitions of seabream show occasional unusual change in tooth size, shape, and positioning, over one tooth generation. These crushing dentitions, and those of two other modern specimens, exhibit a close-packed, near-tessellating ‘anamestic’ patterning. A range of research is drawn on to propose hypotheses for these observations. In pycnodonts, I propose that gap-filling was enabled by the oral epithelium retaining an odontogenic potential throughout life, possibly facilitated by stem cells that generate taste buds. I propose that tooth positioning and morphology in pycnodont, seabream and other crushing dentitions is an adaptive phenotypic response to mechanical strain at the crushing surface, a known phenomenon in cichlids. I suggest that alternative sources of stem cells to predecessor teeth, and mechanoreception-mediated tooth morphology and patterning, are promising areas for future study.

    Metadata

    Item Type: Thesis
    Additional Information: Unfortunately not all micro-CT scans are available via the online repository Morphosource but all data is stored at the Natural History Museum, London or contact the author of the thesis at sallyec138@gmail.com
    Copyright Holders: The copyright of this thesis rests with the author, who asserts his/her right to be known as such according to the Copyright Designs and Patents Act 1988. No dealing with the thesis contrary to the copyright or moral rights of the author is permitted.
    Depositing User: Acquisitions And Metadata
    Date Deposited: 24 Oct 2023 15:16
    Last Modified: 01 Jul 2024 21:16
    URI: https://eprints.bbk.ac.uk/id/eprint/52277
    DOI: https://doi.org/10.18743/PUB.00052277

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