Jellyfish is an important plankton in aquatic environment. It is the floorboard of echinoderms and invertebrates. There are many kinds and shapes, which are common in the oceans everywhere. Most marine products are produced in fresh water, and only a few species are abundant in the shallow waters of tropical and subtropical oceans.

Jellyfish are carnivores, feeding on plankton, crustaceans, polychaetes and even small fish. Although it looks beautiful and docile, it is actually fierce. Once it encounters prey, it never lets go easily, but it has no respiratory organs and circulatory system, only primitive digestive organs, so the captured food is immediately digested and absorbed in the lumen, and the digested nutrients swing through the cilia on the wall of the circulatory tube, pushing the nutrients from the radial tube to the annular tube from the gastric cavity, and then the undigested food residues are discharged from the body through the positive radial tube, the indirect radial tube, the gastric cavity and the oral cavity.