A census of the Arctic shellfish

Проведена перепись арктических моллюсков

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The laboratory staff of macroecology and biogeography of invertebrates, SPbSU on the basis of previously published data and our own research assessed the species diversity of freshwater mollusks of the Arctic region. All scientists have counted 104 of these invertebrates in ponds located North of the Arctic circle. To survive in the far North shellfish helped hermaphroditism, the ability to marginalise in the ice and “friendship” with the birds. The study is published in the journal Hydrobiologia.

The list of species compiled by scientists, reflects all the available information on this issue, including first obtained by the group of authors. The last time a similar list was published in Sweden in 1887 and has now seriously outdated.

According to the study, on the territory of the Arctic was able to penetrate less than 2% of the global fauna of freshwater mollusks. Due to specific natural conditions of the Northern polar region species diversity of snails and bivalves are small here. Analyzing the biology and ecology of Arctic species of mollusks, scientists have suggested which the biological characteristics have helped these invertebrates get into the Arctic and survive there.

“First of all, this hermaphroditism, whereby an individual in a limited number of individuals of the same species can mate with any member of the population (besides many species of Arctic mollusks are capable pregnant). Another useful feature is the ability to settling on the air, such as birds. In addition, the short life cycle of shellfish helps to quickly reproduce and form viable populations in the Northern waters. We should also highlight the ability of these invertebrates to survive being frozen in the ice. The combination of these biological characteristics, apparently, is the “entry ticket” to the Arctic for shellfish, allowing them to seep through an invisible filter that is created by the environment”, — said the head of the laboratory of macroecology and biogeography of invertebrates SPSU Vinarskaya, Maxim.

Genetic and biogeographical analysis showed that in the circumpolar Arctic zone no endemic — a species that would have lived only in the Arctic. As it turned out, all live in the area of freshwater shellfish newcomers from lower latitudes. In 2017, St. Petersburg state University Professor Vinarskaya, Maxim and senior researcher of Department of applied ecology Ivan Nekhaev got these results for Greenland, and now this conclusion has been extended to the entire Arctic region. Scientists believe that the lack of endemic molluscs in the Arctic is due to the geological youth of this territory, recently freed from the covering of the glacier.

The biologists also compared the species richness of individual subregions of the Arctic: European Arctic, the far North of Siberia, Beringia, and North America. It turned out that the greatest species diversity is observed in Siberia — here is home to 57 of the 104 species described. All poorer fauna of mollusks in North America, where it was found only 39 species of freshwater mussels. This difference cannot be attributed to insufficient study of the mollusks of North America, which examines more than 200 years.

Separately, scientists have considered the geothermal ecosystem of the Arctic and subarctic, which, in their opinion, could serve as a potential refuge for molluscs in glacial periods. Unlike most water bodies in the Arctic region, the thermal mode of which is largely determined by seasonal changes in temperature, in geothermal sources is maintained year-round high (more than 20 degrees Celsius) water temperature. Most freshwater snails and bivalves do not survive in such extreme conditions, however, biologists at the University found that at least five types of detachment Pulmonata (lung snails gastropods) was able to overcome the thermal shock of introduction to geothermal sources and mold them into stable populations.

Despite the fact that the Arctic biota as a whole is highly vulnerable to global changes and human intervention, only three mollusks from the number listed to date have gained international conservation status: Margaritifera margaritifera (freshwater pearl), Euglesa hinzi and Valvata mergella. Most Arctic species are among the widespread and massive forms. However, according to biologists, SPbSU, this does not mean that these types don’t need protecting. The negative impact of intensive economic development of the Arctic, leading to degradation of freshwater ecosystems, are added and global climate change.

“Because of warming in the Arctic region, penetrate the species, which formerly lived in less harsh conditions. Now we can conclude that at least three kinds of snails and bivalves extend their habitats far to the North under conditions of global climate change. This can have unpredictable until the impact on native ecosystems — for example, to cause the displacement of local species of mollusks. Perhaps northward foci of parasitic diseases, intermediate hosts which are a species of freshwater molluscs. While the impact of alien species on freshwater molluscs communities of the Arctic is minimal, but in the coming decades this situation may change,” — said Maxim Vinarsko.

The study was supported by a grant from the Russian science Foundation (project No. 19-14-00066).

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