Nautilus is a mollusk. It mainly depends on smell to find food. It is carnivorous and mainly feeds on crabs, shellfish, sea urchins and benthic fish. Because they live in deep water, they have low requirements for water temperature.

Nautilus has experienced hundreds of millions of years of evolution on earth, but the changes in shape and habits are very small. It is called "living fossil in the ocean". It is of high value in the study of biological evolution and paleontology.

Source: @prezhiuz