Strange Thai stone shells

The creator of the video shows stone like animals called Hin Hoi, meaning rock shell fossil. He got them from a temple near Udon Thani and was told they are to be found at a specific location along the Mekong River. They react by moving when you put them on a thin layer of lemon juice. According to a French website, where you can order them, these stone-like shells are really alive, but will eventually die. Then they will not move anymore I guess, so the words rock or stone and fossil are a bit misleading. Small Hin Hoi cost €19/$26 and bigger ones €25/$37.