What is an Atlantic horseshoe crab? Atlantic horseshoe crabs may appear alien, but their history as earthlings is pretty impressive. They’ve been around for 450 million years, predating the ...

and red hairy legs mottled with white. Atlantic Blue crab - this crab has a blue-brown shell and can grow to 20cm/8in, but is usually sold smaller. When newly 'moulted' (crabs regularly shed their ...