|London Aquarium Moon jellyfish|
The moon jellyfish otherwise know as Aurelia aurita is one of the most common jellyfish. Its other names include; the saucer jelly, the moon jelly and the common sea jelly. Its bell can be anywhere from 5-40 cm wide. You can recognize them because of their unique spots and streaks. The behavior of the jellyfish can depend on the type of conditions that it may be in, for instance, where the jellyfish's food supply is located. The Moon Jellyfish swims using the bell-shaped covering of the animal. Swimming for the jellyfish is used to help stay at the top of the water instead of moving through it. The jellyfish swims sideways in order to keep the bell near the surface of the water when possible. Doing this allows the tentacles to cover a larger area in order to have a better chance at catching food. The coronal muscle it the main muscle that enables the jelly to move its tentacles. You can find this Jellyfish almost anywhere in the world. 
The Moon jellyfish’s body consists of a round flat shaped disk known as the bell because of its bell shaped structure, it is also known as the umbrella. Recently some scientists have done some research on the jellyfish and how temperature can effect its growth. At the temperature of about 21 celsius showed the greatest growth change in the jellyfish where as the temperature of 8 degrees celsius slowly decreased the size of the bell. [] Located below the bell are the jellyfish’s mouthparts and the sub umbrella. On the opposite side is the exumbrella. The oral-aboral axis reaches out from the middle of the aboral surface to the middle of the oral surface which then shows its central line of symmetry. The outside of the bell is slightly indented in eight different spots so it may appear to some as a scallop. Within the indentations are sensory complices or the rhopalia.
The stomach, otherwise known as the coelenteron consists of many chambers and a channel coated by ciliated gastrodermis and goes through the mesoglea and then opens the exterior by using the mouth. It is separated into two parts and is used to transport fluids as well as the digestive system.
The sensory system of the Moon Jellyfish consists of the eight rhopalia that are positioned evenly around the bell. Every rhopalium has a statocyst which is used for the detection of gravity. There are two smaller, triangular; side by side rhopalial lappets and they are located on the side of the rhopalium. The whole thing is supplied by a small branch-like structure of the ring canal. 
Aurelia aurita or the Moon Jellyfish’s life history is very interesting. There are both male and females and the sperm cells enter the female through the mouth and fertilization of the eggs occurs internally. Coverings in the eight arms act as temporary chambers for the eggs until they become free-swimming larvae. Following the brief swimming period the planulae then attach themselves to hard substratum and develop into small sessile (not moving) animals otherwise known as scyphistomae. These then reproduce asexually by budding and make free-swimming tiny jellyfish or ephyrae. The ephyrae then feed on plankton and other small animals and will reach the age of maturity at about 3 months. But some ephyrae might up to two or more years to grow into sexually-reproducing adult medusae. 
Moon jellyfish feed on plankton as well as other things such as, mollusks, crustaceans, tunicate larvae, copepods, rotifers, nematodes, young polychaetes, protozoans, diatoms and eggs. []They will sometimes show up in massive swarms of plankton which may be so densely populated and it may seem like the sea is red and may slow down the passageway of small boats. In one aquarium they feed the jellyfish millions of one or sometimes two day old shrimp. On the bell of the jellyfish are stinging cells and mucus secretions which enable the jellyfish to trap prey. Once the food is trapped it is moved to the perimeter of the jellyfish so that the four central feeding arms can grab a hold of the food and bring it to the mouth. The food is moved slowly into the four stomach pouches where it is digested and then the nutrients are dispersed throughout the body. 
The moon jellyfish is Great Britain's most commonly known and inhabited jellyfish. It is not always recognized with its appearance; sometimes they will form massive populations or colonies in some areas but will be totally absent in others for many years. The Moon Jellyfish is an open-sea species but can also be found sometimes washed up on the shore. It is known to happen up estuaries and also into some harbors and is really common in some of the Scottish sea lochs. 
The different places that you may find the Moon jellyfish are in the Atlantic Ocean, Pacific Ocean, and Indian Ocean. The Moon jellyfish can be found by the coastlines, but usually only in the warm and tropical areas of the water. They can be found in both inshore seas and most oceans. The habitat in which they live includes the coastal waters of all the oceans and they usually will appear in big numbers. They have been known to inhabit brackish waters with a low salt content of 0.6%. With not as much salt in the water the bells curvature can diminish. The perfect temperature for the Moon jellyfish is about 9-19°C but the temperature may vary depending uopn the area. 
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