World Congress of Malacology Antwerp ... - Unitas Malacologica

Amino acids in calcite: a tiny time-capsule for the Quaternary
Penkman, K.E.H. 1 ; Maddy, D. 2 ; Keen, D.H. 3 ; Preece, R.C. 4 ; Collins, M.J. 1
1. BioArch, Biology S Block, University of York, PO Box 373, York, YO10 5YW, UK,
Email: kp9@york.ac.uk
2. Department of Geography, University of Newcastle, Newcastle-upon-Tyne, NE1 7RU, UK,
Email: darrel.maddy@ncl.ac.uk
3. Birmingham Archaeology, University of Birmingham, Birmingham, B15 2TT, UK,
4. Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK,
Email: rcp1001@cam.ac.uk
Whilst amino acid racemization (AAR) in mollusc shells was once applied widely as a dating
technique for the Quaternary, recently other geochronological tools have become more routinely
used, at the expense of AAR. However, successful results have been achieved using AAR of proteins
in ratite eggshell, proposed to act as a closed-system with respect to the entrapped protein. At those
sites not lucky enough to have an abundance of large flightless birds, a commonly occurring
biomineral with similar closed-system properties would extend the potential of AAR to provide a
simple dating tool. In an attempt to isolate a closed system in gastropod shells, we: (i) use multiple
amino acid DL ratios, (ii) cross-check the Free amino acids (released from degraded proteins) against
the Total amino acid compositions in the biomineral, (iii) bleach to remove contaminants and the
degradable organic matrix. This approach both ensures the analysis of only the original amino acids,
and allows the identification of bacterial contamination and post-depositional recrystallization.
Despite these innovations, beyond MIS 9 the level of resolution in gastropod shells becomes limited.
However, this work has been recently eclipsed by results obtained from the analysis of the tiny
Bithynia opercula, common fossils in Quaternary freshwater deposits. The shells are aragonite, but
the humble operculum which closes the gastropod aperture is calcite. Preliminary results with
opercula are spectacular and as a consequence, the extent of protein degradation in opercula can be
used to resolve not only stages but sub-stages within the Quaternary. The analyses of over 600 single
opercula from 100 northern European sites are reported, with this coherent calcite intra-crystalline
system allowing the development of an AAR chronology to at least 2.5 Ma.
Populations of baikalian endemic mollusks Baicalia carinata (Mollusca: Caenogastropoda) and
evolution relation with close related species.
Peretolchina, Tatiana E.; Sherbakov, Dmitry Yu; Sitnikova, Tatiana Ya
Limnological Institute SB RAS, Ulan-Batorskaya 3, Irkutsk 664033, Russia,
Email: info@lin.irk.ru
Baicalia carinata (Dybowski, 1875) belongs to endemic family Baicaliidae of Lake Baikal. High
intra-specific shell polymorphism is peculiar to this family and makes species identification based on
morphological traits a very difficult task.
Here we use molecular phylogeny of mitochondrial cytochrome oxidase 1 (mtCO1) gene (588 bp)
and nuclear internal transcribed spacer (ITS1) (360 bp) nucleotide sequences in order to study
evolution relation with close related species and population genetic structure of B. carinata in Lake
Baikal. In total, 130 sequences of mtCO1 and 105 sequences of ITS1 were obtained.
The phylogeny based on mtCO1 sequences shows that B. carinata forms two clades named North-
West and East population but close related species aren't separated from B. carinata. In contrast, on
ITS1 tree B. carinata doesn't form geographically defined clades but B. rugosa, B. dybowskiana and
other close related species are situated separately from B. carinata.
In spite of the fact that nuclear genome evolves on the whole slower than the mitochondrial one, there
are some exceptions. That is, observed level of polymorphism for nuclear DNA in some cases may be
higher than in mitochondria. This fact may be explained by "sweeping effect", which may occur
when an advantageous mutation appears in mitochondrial genome In this case the advantageous
haplotype may "weep" other haplotypes. As a result, the level of genetic polymorphism in mtDNA
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