The Purplestriped jelly is a species of jellyfish known by the scientific name Pelagia noctiluca. Pelagia noctiluca, in Greek means, Pelagia- "of the sea" and nocti- light. This makes it obvious that all the jellyfish in this species is bioluminescent. The purplestriped jelly in Europe is also known as the Mauve stinger. The jellyfish has distinct purple stripes and when developing lacks a polyp stage. This particular jellyfish is known to be bred in captivity and be put on display in aquariums. Other than being put on display, they serve no economic purpose, in fact, these types of jellys are what drive people from the beaches and have caused economic problems in the past.
The full grown adult purplestriped jelly fish has distinct stripes. The bell of the jellyfish can grow to become seventy centimeters in diameter. The purplestriped jellyfish has radial symmetry.  It has four large oral arms and eight tentacles. The tentacles are able to reach up to ten meters in length. The oral arms can grow to be four to five meters in length. The arms are used for moving food into the stomach area. Cnidocytes cover the tentacles, oral arms, exumbrella, and gastric pouches that eject toxin-filled stinging threads. The sting of the tentacles are not fatal but can be very painful. The only difference between thr male and female sexes are the thickness of the follicles.
Stinging is one of two ways of protection. The other form is by living in large groups,  otherwise known as shoals  or aggressions.  The jellyfish has only one body cavity called the gastrovascular cavity. It acts as both the mouth and anus. 
Purplestriped jelly are bioluminescent (able to produce light). The light is a green  or purplish color  that does not last long and fades gradually. The light is formed when the jellyfish is disturbed. Although scientists are not quite sure how the light is formed, it is likely controlled by the nervous system.
The life span of the average purplestriped jellyfish is two to six months. Death is usually caused by the rough waters. 
The Purplestriped jellyfish reproduces sexually year round. Finding a mate is easy for the jellyfish due to living in a group (also known as aggregations). 
The male releases gametes from gonads. Sperm and ova are released from the mouth of the purplestriped jellyfish and are fertilized externally. Since there is no polyp stage, the planulas may be widely spread due to currents. 
The stages of development for the purplestriped jelly goes Planula larva to ephyra stage to medusa. They have no sessile polyp stage.  The jelly stays an egg for three days and then grows into a planula. After seven days the jelly then grows to be a ephyra and after a month the jelly finally develops into a medusa. When the jellyfish is young, the bell is a light pink color and does not have the distinct stripes that the adult does.
Purplestriped jellyfish are usually found in the warm coastal waters of, Bermuda, the Mediterranean Sea, the Adriatic Sea, and the Atlantic Ocean. The jellyfish is usually found in water 0-16,759 feet. Its diet consists of macrozooplankton  copepodes, larval fish, ctenophores, salps, and fish eggs.  The predators of the jellyfish are fish,  turtles, and sharks.  Cancer crabs can be found clinging to the Purplestriped jelly. The crab helps by eating parasitic amphipods that feed on the jelly and injure the jellyfish. The Purplestriped jelly is not endangered. 
The oral arms have stinging cells, which is what they use paralyze and hold small animals. A sticky mucus holds the prey and then they are passed up grooves in the arms and finally into the mouth. 
The Purplestriped jellyfish have no commercial importance  although, they can cause major damages. In Northern Ireland on November 21, 2010, a 10 sq miles  by 35 feet deep  swarm of these jellyfish attacked a 100,000-fish salmon farm. Workers from The Northern Salmon Co. Ltd went out on boats to try to save the fish and fought to push through all the jellyfish for hours, but all the fish were either dead or dying from stings or stress.  It cost 1 million pounds in damages. 
Purplestriped jellyfish are what tend to scare tourists away from the beaches. Fishermen are hurt by the jellyfish. In France the jellyfish have burned holes into nets.
Researchers are looking for ways that the jellyfish can be made useful, like other jellyfish. 
Differences from other jellyfish
The difference between the Cyaneidae and Pelagiidae is that the Pelagiidea has simple and unbranched pouches, whereas the Cyaneidea has branched pouches. 
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