There are many kinds of sea urchins, and there are more than 900 kinds of sea urchins at present. They can be divided into regular sea urchin subclass and irregular sea urchin subclass. There are 22 orders in these two subclasses, with more than 900 species belonging to 224 genera. There are more than 100 kinds of sea urchins found in China, and there are more than 7,000 fossil species of sea urchins.

Common sea urchin species are horse manure sea urchin, purple sea urchin, Beihai purple sea urchin, red sea urchin, long thorn sea urchin and so on. Horse manure sea urchins are mainly produced in the south of Hokkaido, Japan, and their diameter is generally about 4 cm. Their shell spines are short, but dense, and most of them are yellow-green in color. Purple sea urchin is a common sea urchin species in Japan. They are large in size, with a diameter of 5-7 cm and a lavender color in adulthood. Red sea urchins are reddish brown in color, but they are rare in production and rare in the market.

If you want to choose good sea urchins, you must first choose some sea urchins with full mouths and slightly protruding sea urchins, because this sea urchin is very fresh. If the mouth is sunken and the color is dark, it is not fresh. Secondly, we should choose a fat sea urchin. Generally, the thorns outside the sea urchin are short and thick, while those with slender thorns are thin. Finally, it depends on the color. There are many kinds of sea urchins. Colorful sea urchins are generally inedible, and only common black or brown sea urchins are edible.