Question

How do jellyfish breathe underwater?

Answer 1

The medusa-phase of certain gelatinous members of the subphylum Medusozoa, a key portion of the phylum Cnidaria, is referred to as jellyfish or sea jellies. The majority of jellyfish are free-swimming marine animals with umbrella-shaped bells and trailing tentacles, while a few are stalk-anchored to the seafloor. The bell has the ability to pulsate in order to create propulsion for extremely efficient mobility.

Complete answer :
Jellyfish, also known as Scyphozoans, lack breathing and circulatory mechanisms. They do, however, require oxygen, just like any other mammal. Jellyfish have a number of physiological adaptations that enable them to absorb and retain oxygen, allowing them to survive in low-oxygen situations.
The term respiration can be used to describe two distinct processes. To begin, respiration can refer to the process through which an organism obtains oxygen. Breathing or pushing water over gills are examples of this. The process of utilising oxygen at the cellular level is also considered respiration, and is frequently referred to as “cellular respiration” to avoid confusion. Since jellyfish have such thin tissue, the majority of the oxygen they require may be obtained through diffusion rather than respiration.
Oxygen can easily diffuse into tissues of jellyfish because they have thin tissue,. Their bodies are made up of two layers of tissue: an epidermis on the outside and a gastrodermis on the inside, which lines their blind guts. The mesoglea is an elastic, jellylike substance sandwiched between two layers of tissue. The mesoglea is made up of non living substances secreted by living tissues and does not require oxygen to function. As a result, jellyfish tissue only requires a little amount of oxygen.

Note :
Jellyfish, unlike humans, have a two-way gut. This means they ingest, digest, and excrete food through the same opening. The coelenteron is the name for the gut's interior region. The coelenteron's form boosts the gastrodermis surface area-to-volume ratio. This enhances oxygen diffusion and guarantees that the tissue's inner layer receives enough oxygen.