The blue crab's scientific name translates as "beautiful swimmer that is savoury"
A rare blue swimmer crab has been discovered during the annual oyster beds survey of the Fal estuary.
It's the first time the species has been recorded in Cornish waters and only the second ever specimen discovered in the UK.
The crab is a young female who measures 12 cms across the shell and has a claw missing.
She is now being looked after at the Blue Reef Aquarium in Newquay.
The crab, which is native to America, was found by Karen Vanstaen and Dave Palmer from CEFAS on board oyster bailiff Paul Ferris' boat The Three Castles during the survey.
Curator Matt Slater said: "Although these crabs are originally from the Americas it's thought that individuals have been accidentally transported over to Europe in ships' ballast.
"There are now populations found in the Mediterranean and around the Japanese coast.
"This is the first recorded specimen in the south west but the likelihood is that there will be more individuals out there.
"It's possible that she was carried up from Spain or Portugal as larvae in the currents and therefore she may well not be alone," he added.
The blue swimmer crab is caught extensively for food in the US. It is an extremely strong swimmer and is also noted for its extreme aggression.
This is the first recorded specimen here in the south west
They can deliver an extremely painful pinch and are noted for being difficult to handle safely by novices.
"We've named her Sally as that is the official name for an immature female crab in the US. Males are called 'Jimmies' and mature females as 'sooks'," said Matt.
"Apart from the missing claw, which will eventually grow back, she appears to be in good condition and could reach up to 25 cms when fully grown. In the wild they are omnivores eating plants, animals - including shellfish and small fish and carrion," he added.
In 1989 the species was designated as the state crustacean for Maryland. The blue crab's scientific name translates as "beautiful swimmer that is savoury" and the meat is often compared to the sweetness of lobster meat.