Based on previously released data and their own investigations, researchers at the St Petersburg University Laboratory of Macroecology and Biogeography of Invertebrates have assessed the diversity of freshwater molluscs in the Circumpolar region of the World. In total, they registered 104 species of these invertebrates living in waters within the Arctic Circle. Their hermaphroditism, their ability to freeze in ice and their 'friendship' with birds have all helped them to enter the Arctic and to survive under its harsh conditions.