Boots staff were shell-shocked to find a large crab dumped in an alley outside the pharmacy in York city centre.
The crab was found outside the shop in Coney Street on Monday lunchtime and staff alerted the RSPCA.
Shop CCTV showed the crab being abandoned by two young men the previous afternoon.
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It is not known where it came from before it was dumped by the boys.
A RSPCA animal collection officer took the crab to SeaLife Centre in Scarborough where it is now being taken care of
There is currently no law in place protecting crustaceans and cephalopods such as crabs, lobsters or octopuses from mistreatment.
The RSPCA are calling for a bill to give the creatures the same rights as other animals.
RSPCA inspector Thomas Hutton said: “This poor thing must have been feeling crabby after being dumped in an alley in the middle of York - a long way from his natural habitat.
“They managed to catch him before confining him in a bowl with some water.
"It’s extremely irresponsible to leave this crab in this way. It’s an extremely dangerous setting for an animal that is used to living his life on the beaches and rocks and in the sea.
"He could have easily been seriously injured or killed.
“Crustaceans are sentient beings and the RSPCA - along with other animal welfare charities and many members of the public - are calling for a bill enshrining animal sentience law to include decapod crustaceans such as crabs, lobsters and cephalopods like octopuses, cuttlefish and squid.”