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

TY - JOUR

T1 - Investigating the potential of African land snail shells (Gastropoda: Achatininae) for amino acid geochronology

AU - Baldreki, Chloë

AU - Burnham, Andrew

AU - Conti, Martina

AU - Wheeler, Lucy

AU - Simms, Michael J.

AU - Barham, Lawrence

AU - White, Tom S.

AU - Penkman, Kirsty

N1 - 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

PY - 2024/1/1

Y1 - 2024/1/1

N2 - 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.

AB - 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.

KW - AAR

KW - Africa

KW - Dating

KW - Gastropod shell

KW - Quaternary

KW - Racemisation

UR - http://www.scopus.com/inward/record.url?scp=85173250448&partnerID=8YFLogxK

U2 - 10.1016/j.quageo.2023.101473

DO - 10.1016/j.quageo.2023.101473

M3 - Article

AN - SCOPUS:85173250448

SN - 1871-1014

VL - 79

JO - Quaternary Geochronology

JF - Quaternary Geochronology

M1 - 101473

ER -