How do jellyfish swim?
The basic cycle is egg, planula larva, polyp, medusa, with the medusa being the sexual stage. The polyp stage is sometimes secondarily lost. The subphylum include the major taxa, Scyphozoa large jellyfishCubozoa box jellyfish and Hydrozoa small jellyfishand excludes Anthozoa corals and sea anemones.
Scyphozoa are sometimes called true jellyfish, though they are no more truly jellyfish than the others listed here. They have tetra-radial symmetry. Most have tentacles around the outer margin of the bowl-shaped bell, and long, oral arms around the mouth in the center of the subumbrella.
Box jellyfish may be related more closely to scyphozoan jellyfish than either are to the Hydrozoa. Hydrozoa show great diversity of lifestyle. Some species maintain the polyp form for their entire life and do not form medusae at all such as Hydrawhich is hence not considered a jellyfishand a few are entirely medusal and have no polyp form.
At least some Staurozoa also have a polyp form that alternates with the medusoid portion of the life cycle.
Until recently, Staurozoa were classified within the Scyphozoa. The oldest conulariid scyphozoans appeared between and mya in the Neoproterozoic of the Lantian formation in China; others are found in the youngest Ediacaran rocks of the Tamengo formation of Brazil, c.
This is a hollow structure consisting of a mass of transparent jelly-like matter known as mesogleawhich forms the hydrostatic skeleton of the animal. The mesogloea is contained by the epidermis on the outside and the gastrodermis on the inside.
The edge of the bell is often divided into rounded lobes known as lappetswhich allow the bell to flex. In the niches between the lappets are sensory organs known as rhopaliaand the margin of the bell often bears tentacles. There are often four oral arms connected to the manubrium, streaming away into the water below.
This is subdivided by four thick septa into a central stomach and four gastric pockets. The four pairs of gonads are attached to the septa, and close to them four septal funnels open to the exterior, perhaps supplying good oxygenation to the gonads.
Near the free edges of the septa, gastric filaments extend into the gastric cavity; these are armed with nematocysts and enzyme-producing cells and play a role in subduing and digesting the prey. In some scyphozoans, the gastric cavity is joined to radial canals which branch extensively and may join a marginal ring canal.
Cilia in these canals circulate the fluid in a regular direction. It has a squarish, box-like bell from each of the four lower corners of which hang a short pedalium or stalk which bears one or more long, slender tentacles.
In some species, a non-detachable bud known as a gonophore is formed that contains a gonad but is missing many other medusal features such as tentacles and rhopalia.
Nematocystswhich deliver the sting, are located mostly on the tentacles; scyphozoans also have them around the mouth and stomach. They have limited control over their movement, but can navigate with the pulsations of the bell-like body; some species are active swimmers most of the time, while others largely drift.
The rhopalial ganglia contain pacemaker neurones which control swimming rate and direction.
These are generally pigment spot ocelli, which have some of their cells pigmented. The rhopalia are suspended on stalks with heavy crystals at one end, acting like gyroscopes to orient the eyes skyward. Certain jellyfish look upward at the mangrove canopy while making a daily migration from mangrove swamps into the open lagoon, where they feed, and back again.
Each individual has 24 eyestwo of which are capable of seeing colorand four parallel information processing areas that act in competition,  supposedly making them one of the few kinds of animal to have a degree view of its environment.
Other very small jellyfish, which have bells about one millimeter, are the hydromedusae of many species that have just been released from their parent polyps;  some of these live only a few minutes before shedding their gametes in the plankton and then dying, while others will grow in the plankton for weeks or months.
The hydromedusae Cladonema radiatum and Cladonema californicum are also very small, living for months, yet never growing beyond a few mm in bell height and diameter. Sperm fertilize eggs, which develop into larval planulae, become polyps, bud into ephyrae and then transform into adult medusae.
In some species certain stages may be skipped. In most species, spawning is controlled by light, with all individuals spawning at about the same time of day, in many instances this is at dawn or dusk. In most cases, adults release sperm and eggs into the surrounding water, where the unprotected eggs are fertilized and develop into larvae.
In moon jellies, the eggs lodge in pits on the oral arms, which form a temporary brood chamber for the developing planula larvae. When sufficiently developed, it settles onto a firm surface and develops into a polyp. The polyp generally consists of a small stalk topped by a mouth that is ringed by upward-facing tentacles.
The polyps resemble those of closely related anthozoanssuch as sea anemones and corals. The jellyfish polyp may be sessileliving on the bottom, boat hulls or other substrates, or it may be free-floating or attached to tiny bits of free-living plankton  or rarely, fish   or other invertebrates.Jellyfish and comb jellies are gelatinous animals that drift through the ocean's water column around the world.
They are both beautiful—the jellyfish with their pulsating bells and long, trailing tentacles, and the comb jellies with their paddling combs generating rainbow-like colors. Yet though. Jellyfish form large masses or blooms in certain environmental conditions of ocean currents, nutrients, sunshine, temperature, season, prey availability, reduced predation and oxygen concentration.
Currents collect jellyfish together, especially in years with unusually high populations. Mastigias jellyfish flood Jellyfish Lake, a marine lake in Palau, an island nation in the Pacific Ocean. Here, researchers found that pulsating jellyfish stir up the oceans with as much vigor as.
Some jellyfish are not mere drifters as they also possess a unique ability that helps them swim against strong ocean currents, according to a .
Based on the first comprehensive data collection on the occurrence of this invasive jellyfish in Europe, scientists have now shown that ocean currents play a key role for this successful invasion. Jellyfish and Ocean Currents Mrs. Haske English 11 December 4, Outline I Introduction A. Statements about jellyfish B.
Thesis statement: Jellyfish are mysterious creatures that live almost anywhere in the water and depend on ocean currents to move as well as create them.