And the purple topshells are not alone. A new report looking at 57 marine species has discovered that Scotland has some of the most dramatic shifts in sea life caused by global warming anywhere in the UK.
The MarClim Project looked at more than 400 locations across the UK to see how marine species distribution had changed since the 1950s.
The creep of the purple topshell snail along the north coast of Scotland from the relatively warm west to the colder east was one of the biggest changes. Its territory has expanded more than 50 miles in just 15 years - an average of around 17 yards a day.
But warmer water has sent the cold-loving common tortoiseshell limpet into retreat from the Irish Sea, forcing it to move back along Scotland's northerly coast.
Other species showing major changes include the purple acorn barnacles, the toothed topshell snail and a type of seaweed, known as dabberlocks, which is disappearing from south-west England.
Source: The Scotsman