Scyphozoans live in all oceans, they inhabit the deep seas, but most live near the coastal waters. They move by contracting and relaxing muscles of the body wall.  Scyphozoans, like all Cnidarians, are primarily carnivores, while still others are filter-feeders. Many smaller jellies feed on food particles trapped from the water while larger ones prey on fishes or swimming invertebrates. 

             Scyphozoans exhibit an unique phenomenom when it comes to development: they undergo alternation of generation  (See reproduction & development page). Scyphozoans possess a blind gut, which is a one way digestive system. Their stomach (gastrovascular cavity) is unique in that it takes on multiple fuctions: it breaks down food during digestion, transport fluids, serve as a brooding chamber for gametes, act as an hydrostatic skeleton, and serve as the excretory system. 

              Scyphozoans' nervous system is none centralized and consist of a nerve net in which receptors are directly attached to effecters. Scyphozoans has a well-developed sensory system, which contributes to their fitnes by allow for optimal detection of prey, changes in environmental conditions, and location of food:  some have eyespots, chemoreceptor, mechanoreceptors and gravity receptors.

              One of the key characteristics of Scyphozoans is their cnidocytes and nematocysts or stinging cells. Each cnidocytes house nematocysts, the capsule in which the nematocysts are housed contain toxin and a coiled inverted barb. The Scyphozoan can use its cnidocytes to catch food or for defense. Discharging of the nematocyst is osmoticly controlled and often these cells are highly toxic.   In order to trigger the firing of the stinging cells, two stimuli are needed, stimulation of a machanoreceptor and a chemoreceptor by amino acids from a prey/predator. The cnidocytes are independent of the nervous system.