Clione is known as ‘sea angel’. Their wing-like flapping foot enable them to swim. They are shellfish but they have lost their shells over the course of evolution. This adaptation explains the scientific name ‘gymnosomata’ derived from Greek gymnos ‘naked’ and soma ‘body’.
These sea angels were on display in a fish tank in Ishya Chocolate Factory in Sapporo, Hokkaido. I was on holiday with my wife and visited the factory on 4 August 2016. This was the first time I saw such shellfishes, hence I took a video of them.