If jellyfish do not have a heart true stomach brain or any other major organ As result what else also lack?

If jellyfish do not have a heart, true stomach, brain, or any other major organs, it follows that they also lack a circulatory system, a respiratory system, and a digestive system. These systems are essential for the basic functions of life and are found in most animals. Without these systems, jellyfish would be unable to circulate blood, breathe, or digest food, and would not be able to survive.