Investigating the potential of African land snail shells (Gastropoda: Achatininae) for amino acid geochronology

Abstract

Aragonitic calcium carbonate (CaCO3) terrestrial mollusc shells with complex shell microstructures, such as those in the African subfamily Achatininae, have the potential to be used to build amino acid geochronologies across the African continent. However, as different microstructural shell layers are likely to have different protein compositions, sampling strategies need to be developed to identify the most appropriate shell portion to target. To test possible variability in protein degradation rates between microstructural layers, sampling of a single microstructural shell layer (the ‘nacreous’ layer) was compared to sampling all three aragonitic layers ('3AL') in modern and fossil shells. Reliable isolation of the nacreous layer in all samples proved impractical, and additional complications arose due to mineral diagenesis induced by sampling with a drill. Pleistocene fossils of Lissachatina sp. and modern specimens of Achatina tavaresiana Morelet, 1866 were shown to have an intra-crystalline protein fraction. The 3AL shell portion adhered more closely to closed-system behaviour in heated modern, and fossil, samples. The intra-crystalline protein degradation (IcPD) patterns of Achatininae fossil samples were not consistent with IcPD under forced degradation experiments at high temperatures in the laboratory. However, reliable degradation trends were observed in the 3AL shell portion, demonstrating the potential of fossil achatinids for building relative amino acid geochronologies across Africa.

Metadata

Item Type:	Article
Authors/Creators:	Baldreki, Chloë Burnham, Andrew Conti, Martina (mc1029@york.ac.uk) Wheeler, Lucy Simms, Michael J. Barham, Lawrence White, Tom S. Penkman, Kirsty https://orcid.org/0000-0002-6226-9799
Copyright, Publisher and Additional Information:	Funding Information: This work was supported by the Natural Environment Research Council [ NE/S00713X/1 ], European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No 856488 ) and the fieldwork in Zambia was funded by the National Geographic Society [ GEFNE38-12 ]. We would like to thank Constance Mulenga and Clare Mateke at the Livingstone Museum, Zambia for providing registration numbers and curatorial assistance. Photographs included in Fig. 1 were taken by Kevin Webb, Natural History Museum Publishing and Image Resources, © Trustees of the Natural History Museum, London. We also acknowledge Sheila Taylor and Samantha Presslee for technical support, and Marc Dickinson for helpful comments on an earlier version of this manuscript. Funding Information: This work was supported by the Natural Environment Research Council [NE/S00713X/1], European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No 856488) and the fieldwork in Zambia was funded by the National Geographic Society [GEFNE38-12]. We would like to thank Constance Mulenga and Clare Mateke at the Livingstone Museum, Zambia for providing registration numbers and curatorial assistance. Photographs included in Fig. 1 were taken by Kevin Webb, Natural History Museum Publishing and Image Resources, © Trustees of the Natural History Museum, London. We also acknowledge Sheila Taylor and Samantha Presslee for technical support, and Marc Dickinson for helpful comments on an earlier version of this manuscript. Publisher Copyright: © 2023 The Authors
Keywords:	AAR,Africa,Dating,Gastropod shell,Quaternary,Racemisation
Dates:	Published: 1 January 2024 Published (online): 9 October 2023 Accepted: 25 September 2023
Institution:	The University of York
Academic Units:	The University of York > Faculty of Sciences (York) > Chemistry (York)
Funding Information:	Funder Grant number EUROPEAN COMMISSION 856488
Depositing User:	Pure (York)
Date Deposited:	13 Oct 2023 13:10
Last Modified:	01 Jan 2025 00:14
Published Version:	https://doi.org/10.1016/j.quageo.2023.101473
Status:	Published
Refereed:	Yes
Identification Number:	10.1016/j.quageo.2023.101473
Related URLs:	http://www.scopus.com/inward/record.url?...
Open Archives Initiative ID (OAI ID):	oai:eprints.whiterose.ac.uk:204225