The research work had as its object the analysis of genetic material found in historical shells of land snails of the species Levantina rechingeri, an endemic species of the Carpathians.
One new species of snail was found in Karpathos according to research by the Institute of Molecular Biology and Biotechnology of the Institute of Technology and Research (IMBB-ITE) of Crete, which was published in the scientific journal Molecular Phylogenetics and Evolution in July 2022.
The research work had as its object the analysis of genetic material found in historical shells of land snails of the species Levantina rechingeri, an endemic species of the Carpathians.
The DNA isolation, extraction and analysis process was carried out at the Ancient DNA Laboratory (Palaeogenomics and Evolutionary Genetics group, PEG) of the Institute of Molecular Biology and Biotechnology of the Institute of Technology and Research (IMBB-ITE) of Crete, by the laboratory researcher Dr. Nikolaos Psoni, who had the initial conception of the idea, in collaboration with Dr. Katerina Vardinogianni, Invertebrate Director of the MFIK, and Dr. Nikos Poulakaki, director of the MFIK, professor at the Biology Department of the University of Crete and head of the IMBB-ITE PEG group.
Gastropod shells occur frequently in nature and are abundant in museum collections. However, they remain an unexploited type of biological material for use in DNA studies, despite their obvious advantages, particularly when the study organism is considered endangered. Genetic material isolated from empty snail shells is expected to be damaged, particularly if the animal’s death occurred a long time ago and/or if the shell was found in an area of ​​high ambient temperature. Postmortem DNA damage includes both its fragmentation and changes in the DNA sequence (eg, cytosine becomes uracil). Thanks to new sequencing technologies, DNA damage processes have been extensively studied in mammals.
In land snails, however, there is no precedent.
The species Levantina rechingeri (Fuchs & Käufel, 1936) is known from only a few localities on the island of Karpathos (wider area of ​​Kali Limni) and has never been found alive despite repeated efforts by researchers over the last 40 years. Due to its limited distribution and because only shells have been collected so far (the most recent in 2017), the species is considered Critically Endangered according to the IUCN. In the absence of soft tissue (and thus a reproductive system, on the basis of which land snails are identified and classified), classification of the species at the genus level based on shell characters is unstable. Previous studies have placed it in four different genera: Codringtonia, Isaurica, Assyriella and Levantina.
The study used shells from the collections of the Natural History Museum of Crete (NHIK) of the University of Crete, which were collected between approximately 5 and 30 years ago, but it is unknown when the animals had died (Figure 1). Using modern approaches and protocols for analyzing ancient DNA the researchers were able to recover multiple mitochondrial and nuclear DNA genes. This allowed the phylogenetic comparison of this species with other related species, more specifically with representatives from all genera of the taxonomic rank Helicini (Figure 2).
The results of the study showed that the specific species does not belong to the genus Levantina, since it belongs to a different branch, closer to the genera Maltzanella and Helix, but neither can it belong to any other, already described, related genus. Consequently, a new genus name had to be given to correctly describe its taxonomic status. The new name given was Aristena with the species now renamed Aristena rechingeri. This taxonomic change results in Karpathos acquiring a new endemic genus of snails.
Furthermore, analysis of the postmortem fragmentation and modification patterns of DNA derived from the shells showed that the harsh thermal climate of Greece may accelerate the process of degradation of the quality of the genetic material preserved after death. These measurements are expected to be a reference point for corresponding future studies. DNA analysis from land snail shells is a new, non-invasive way to elucidate the evolutionary history of these organisms, making it ideal for studying species that are difficult to find alive due to rarity, cryptic ecology and narrow-endemism, or for shells derived from old museum collections and are examples of reference.
It is expected that efforts to extract genetic material from other corresponding species of snails in Greece and the wider eastern Mediterranean will continue, in an effort to fill the knowledge gaps, for which conventional DNA analysis approaches are not sufficient.
The article was published in the 14th issue of the Hellenic Ecological Society Newsletter.
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