Researchers from St Petersburg University create a new classification of freshwater lymnaeid snails
Zoologists from St Petersburg University and the Laverov Federal Centre for Integrated Arctic Research of the Ural Branch of the Russian Academy of Sciences have proposed a new classification of molluscs of the Lymnaeidae family, which are of great importance in public health science and veterinary medicine as intermediate hosts of parasitic worms (helminths). It has been published as part of a collaborative monograph, involving experts from Cuba, Argentina, France, Germany and the Netherlands.
Freshwater molluscs of the Lymnaeidae family, known as pond snails, are a species-rich and widespread group of invertebrates found on all continents except Antarctica. Today, they are widely used in science as model animals — for example, the great pond snail (Lymnaea stagnalis) is used to study the neurophysiology of behaviour. Many members of this family are of great practical importance as intermediate hosts for parasitic worms, such as the liver fluke.
The findings of the research supported by grants from the Russian Science Foundation are presented in the monograph The Lymnaeidae: A Handbook on Their Natural History and Parasitological Significance published by the international scientific publishing house Springer-Nature.
Today, scientists know more than 150 different species of pond snails. However, with the advent and development of molecular genetic methods, it became clear that the entire previous system of classifying this group of animals, which was based on morphological characteristics, needed to be revised. Maxim Vinarski is Head of the Laboratory of Macroecology and Biogeography of Invertebrates at St Petersburg University, the editor-in-chief of the monograph and co-author of several of its chapters. He pointed out that scientists originally described and classified pond snails using the characteristics of the shells rather than the soft body of the animals. This approach makes true classification difficult because the shells of these molluscs are very plastic and can easily change in size and shape under influence of their environment. It is this variability that creates fallacies in the development of a workable classification. However, soft body characters have not proved to be a very reliable basis either.
‘Deciphering the nucleotide sequences of individual genes (and, in recent years, entire genomes) has shown that all the family systems constructed in the 19th and 20th centuries on the basis of shell analysis, and even those constructed on the basis of anatomical data, contain many inaccuracies. Very often, different species of molluscs that are well distinguished genetically are completely indistinguishable in morphology, and vice versa,’ explained Maxim Vinarski.
Currently, an integrative approach to taxonomy is being used, in which scientists first carry out genetic analyses and then compare the results with previously described species and their morphological characteristics. This approach makes it possible to build up a system at a higher level, from genus to subfamily.
The scientists from St Petersburg University and the Laverov Centre have compiled the largest library of decoded sequences of different species of Lymnaeidae from all continents of the world. This made it possible to develop and propose a new global system of extant representatives of this family, based on the combined use of genetical and morphological characteristics of molluscs.
‘The result of the research presented in the monograph is a new system of the family, which clarifies and completes the previously known variants. The global biogeographic zoning of pond snails, their distribution across continents and zoogeographic regions was carried out using this system. Thanks to this large and sophisticated research, Russian zoology will occupy a leading position in one of the particular but important aspects of biodiversity research for decades to come,’ said Maxim Vinarski, a biologist from St Petersburg University.
As the University scientist noted, the research revealed that the great pond snail (Lymnaea stagnalis), often used as a model animal, turned out to be a complex of at least 15 independent species, 14 of which inhabit Eurasia and only one species inhabits North America. Europe is inhabited by several members of the great pond snail species complex that do not differ in the structure of their shells or in the morphology of their reproductive systems. This suggests that the results of previous laboratory experiments using this model species may need to be corrected.
St Petersburg University, the oldest university in Russia was founded on 28 January (8 February) 1724. This is the day when Peter the Great issued a decree establishing the University and the Russian Academy of Sciences. Today, St Petersburg University is an internationally recognised centre for education, research and culture. In 2024, St Petersburg University will celebrate its 300th anniversary.
The plan of events during the celebration of the anniversary of the University was approved at the meeting of the Organising Committee for the celebration of St Petersburg University’s 300th anniversary. The meeting was chaired by Dmitry Chernyshenko, Deputy Prime Minister of the Russian Federation. Among the events are: the naming of a minor planet in honour of St Petersburg University; the issuance of bank cards with a special design; the creation of postage stamps dedicated to the history of the oldest university in Russia; and the branding of the aircraft of the Rossiya Airlines to name just a few. Additionally, the University has launched a website dedicated to the upcoming holiday. The website contains information about outstanding University staff, students, and alumni; scientific achievements; and details of preparations for the anniversary.