This molted shell was blue while damp, but turned pink as it dried. Crayfish grow by shedding ("molting") their shells. They must hide while their new shell hardens to protect their soft bodies.
Shoreline of Lake Lewisville.
There have been recorded fossils found of crayfish that are 30 million years. Fossil records of crayfish older than 30 million years are rare, but fossilised burrows have been found from strata as old as the late Palaeozoic or early Mesozoic.The oldest records of the Parastacidae are in Australia, and are 115 million years old.