The difference between lobster and crayfish lies in the price. Crayfish is cheap, while lobster is very expensive. The growth environment of lobster and crayfish is completely different. Lobster lives in the sea, while crayfish lives in fresh water. What we usually eat is crayfish, which is actually not a real lobster. Its scientific name is Procambarus clarkii, and it belongs to Crustacea, Decapoda, and crayfish. This kind of freshwater shrimp is commonly known as Lagu in the north of China, and lobster, crayfish and freshwater lobster in the south. Crayfish originated in the south-central United States and northeastern Mexico, and was introduced to China through Japan in the 1920s and 1930s. Astaxanthin, chitin and other substances extracted from crayfish shells can be widely used in food, medicine, paper making and other fields. Coupled with its delicious meat and rich nutrition, crayfish quickly became "red" all over the country.