Jellyfish

Jellyfish

Overview
Jellyfish are free-swimming members of the phylum Cnidaria
Cnidaria
Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...

. Medusa
Medusa (biology)
In biology, a medusa is a form of cnidarian in which the body is shaped like an umbrella, in contrast with polyps. Medusae vary from bell-shaped to the shape of a thin disk, scarcely convex above and only slightly concave below...

is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria. Jellyfish have several different morphologies
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

 that represent several different cnidarian classes including the Scyphozoa
Scyphozoa
Scyphozoa is a class within the phylum Cnidaria, sometimes referred to as the "true jellyfish".The class name Scyphozoa comes from the Greek word skyphos , denoting a kind of drinking cup and alluding to the cup shape of the organism....

 (over 200 species), Staurozoa (about 50 species), Cubozoa (about 20 species), and Hydrozoa
Hydrozoa
Hydrozoa are a taxonomic class of very small, predatory animals which can be solitary or colonial and which mostly live in saltwater. A few genera within this class live in freshwater...

 (about 1000–1500 species that make jellyfish and many more that do not).

Jellyfish are found in every ocean, from the surface to the deep sea.
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Encyclopedia
Jellyfish are free-swimming members of the phylum Cnidaria
Cnidaria
Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...

. Medusa
Medusa (biology)
In biology, a medusa is a form of cnidarian in which the body is shaped like an umbrella, in contrast with polyps. Medusae vary from bell-shaped to the shape of a thin disk, scarcely convex above and only slightly concave below...

is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria. Jellyfish have several different morphologies
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

 that represent several different cnidarian classes including the Scyphozoa
Scyphozoa
Scyphozoa is a class within the phylum Cnidaria, sometimes referred to as the "true jellyfish".The class name Scyphozoa comes from the Greek word skyphos , denoting a kind of drinking cup and alluding to the cup shape of the organism....

 (over 200 species), Staurozoa (about 50 species), Cubozoa (about 20 species), and Hydrozoa
Hydrozoa
Hydrozoa are a taxonomic class of very small, predatory animals which can be solitary or colonial and which mostly live in saltwater. A few genera within this class live in freshwater...

 (about 1000–1500 species that make jellyfish and many more that do not).

Jellyfish are found in every ocean, from the surface to the deep sea. Some hydrozoan jellyfish, or hydromedusae, are also found in fresh water; freshwater jellyfish
Craspedacusta sowerbyi
Craspedacusta sowerbyi is a freshwater jellyfish in the phylum Cnidaria. Since it is classified as a hydrozoan, it is one of many jellyfish that are also known as hydromedusae...

 are less than an inch (25 mm) in diameter, are colorless and do not sting. Large, often colorful, jellyfish are common in coastal zones worldwide. Scientists have evidence of jellyfish roaming the seas for about 500 million years.

In its broadest sense, the term jellyfish also generally refers to members of the phylum Ctenophora. Although not closely related to cnidarian jellyfish, ctenophores are also free-swimming planktonic carnivores, are generally transparent or translucent, and exist in shallow to deep portions of all the world's oceans.

Alternative names for groups of jellyfish are scyphomedusae, stauromedusae
Stauromedusae
Stauromedusae are the stalked jellyfishes, of the class Staurozoa within the phylum Cnidaria. They are unique in that they do not have an alternation of polyp and medusa life cycle phases, but are interpreted as an attached medusa stage, with a life style more resembling that of polypoid forms...

, cubomedusae, and hydromedusae. These may relate to an entire order or class.

Terminology


The word jellyfish (which has been in common usage for more than a century) is used to denote several different kinds of cnidarians, all of which have a basic body structure that resembles an umbrella, including scyphozoans, staurozoans
Stauromedusae
Stauromedusae are the stalked jellyfishes, of the class Staurozoa within the phylum Cnidaria. They are unique in that they do not have an alternation of polyp and medusa life cycle phases, but are interpreted as an attached medusa stage, with a life style more resembling that of polypoid forms...

 (stalked jellyfish), hydrozoa
Hydrozoa
Hydrozoa are a taxonomic class of very small, predatory animals which can be solitary or colonial and which mostly live in saltwater. A few genera within this class live in freshwater...

ns, and cubozoans
Box jellyfish
Box jellyfish are cnidarian invertebrates distinguished by their cube-shaped medusae. Box jellyfish are known for the extremely potent venom produced by some species: Chironex fleckeri, Carukia barnesi and Malo kingi are among the most venomous creatures in the world...

 (box jellyfish). Some textbooks and websites refer to scyphozoans as "true jellyfish".

As jellyfish are not even vertebrates, let alone true fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

, the usual word jellyfish is considered by some to be a misnomer
Misnomer
A misnomer is a term which suggests an interpretation that is known to be untrue. Such incorrect terms sometimes derive their names because of the form, action, or origin of the subject becoming named popularly or widely referenced—long before their true natures were known.- Sources of misnomers...

, and American public aquariums have popularized use of the terms jellies or sea jellies instead.

In its broadest usage, some scientists occasionally include members of the phylum Ctenophora (comb jellies) when they are referring to jellyfish. Other scientists prefer to use the more all-encompassing term "gelatinous zooplankton
Gelatinous zooplankton
Gelatinous zooplankton is the term used to describe the fragile animals that live in the water column in the ocean. They have very delicate bodies that are easily damaged or destroyed. Gelatinous zooplankton are often transparent. All jellyfish are gelatinous zooplankton, but not all gelatinous...

", when referring to these, together with other soft-bodied animals in the water column.

A group of jellyfish is sometimes called a bloom or a swarm. "Bloom
Algal bloom
An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration...

" is usually used for a large group of jellyfish that gather in a small area, but may also have a time component, referring to seasonal increases, or numbers beyond what was expected.
Another collective name for a group of jellyfish is a smack.

Jellyfish are "bloomy" by nature of their life cycles, being produced by their benthic polyps usually in the spring when sunshine and plankton increase, so they appear rather suddenly and often in large numbers, even when an ecosystem is in balance. Using "swarm
Swarm
Swarm behaviour, or swarming, is a collective behaviour exhibited by animals of similar size which aggregate together, perhaps milling about the same spot or perhaps moving en masse or migrating in some direction. As a term, swarming is applied particularly to insects, but can also be applied to...

" usually implies some kind of active ability to stay together, which a few species like Aurelia, the moon jelly, demonstrate.

Most jellyfish have a second part of their life cycle, which is called the polyp phase. When single polyps, arising from a single fertilized egg, develop into a multiple-polyp cluster, connected to each other by strands of tissue called stolons, they are said to be "colonial". A few polyps never proliferate and are referred to as "solitary" species.

Anatomy


Most Jellyfish do not have specialized digestive
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....

, osmoregulatory
Osmoregulation
Osmoregulation is the active regulation of the osmotic pressure of an organism's fluids to maintain the homeostasis of the organism's water content; that is it keeps the organism's fluids from becoming too diluted or too concentrated. Osmotic pressure is a measure of the tendency of water to move...

, central nervous
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

, respiratory
Respiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...

, or circulatory
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...

 systems. They digest using the gastrodermal
Gastrodermis
The gastrodermis is the inner layer of cells that lines a gastrovascular cavity of Cnidarians....

 lining of the gastrovascular cavity
Gastrovascular cavity
Gastro vascular cavity, as the name indicates, functions in both digestion and the distribution of nutrients and particles to all parts of the body...

, where nutrients are absorbed. They do not need a respiratory system since their skin is thin enough that the body is oxygenated by diffusion
Diffusion
Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...

. They have limited control over movement, but can use their hydrostatic skeleton
Hydrostatic skeleton
A hydrostatic skeleton or hydroskeleton is a structure found in many cold-blooded organisms and soft-bodied animals consisting of a fluid-filled cavity, the coelom, surrounded by muscles. The pressure of the fluid and action of the surrounding circular and longitudinal muscles are used to change an...

 to accomplish movement through contraction-pulsations of the bell-like body; some species actively swim most of the time, while others are passive much of the time. Jellyfish are composed of more than 90% water; most of their umbrella mass is a gelatinous material — the jelly — called mesoglea
Mesoglea
Mesoglea is the translucent, inert, jelly-like substance that makes up most of the bodies of jellyfish, comb jellies and certain primitive sea creatures in the phyla Cnidaria and Ctenophora. It acts as the creatures' structural support in water, as they lack bones or cartilage, endo- or...

 which is surrounded by two layers of epithelial cells which form the umbrella (top surface) and subumbrella (bottom surface) of the bell, or body.

Most jellyfish do not have a brain or central nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...

, but rather has a loose network of nerves, located in the epidermis
Squamous epithelium
In anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scale-like cells called squamous epithelial cells...

, which is called a "nerve net
Nerve net
A nerve net is a type of simple nervous system that is found in members of the cnidaria, ctenophora, and echinodermata phyla. Nerve nets consist of interconnected neurons lacking a brain or any form of cephalization. This nervous system allows cnidarians to respond to physical contact. They may...

". A jellyfish detects various stimuli including the touch of other animals via this nerve net, which then transmits impulses both throughout the nerve net and around a circular nerve ring, through the rhopalial lappet, located at the rim of the jellyfish body, to other nerve cells. Some jellyfish also have ocelli
Ocellus
A simple eye refers to a type of eye design or optical arrangement that contains a single lens which detect light. A "simple eye" is so-called in distinction from a multi-lensed "compound eye", and is not necessarily at all simple in the usual sense of the word...

: light-sensitive organs that do not form images but which can detect light, and are used to determine up from down, responding to sunlight shining on the water's surface. These are generally pigment spot ocelli, which have some cells (not all) pigmented.

Certain species of jellyfish, such as the Box jellyfish
Box jellyfish
Box jellyfish are cnidarian invertebrates distinguished by their cube-shaped medusae. Box jellyfish are known for the extremely potent venom produced by some species: Chironex fleckeri, Carukia barnesi and Malo kingi are among the most venomous creatures in the world...

, have been revealed to be more advanced than their primitive counterparts. The Box jellyfish has 24 eyes, two of which are capable of seeing color, and four parallel brains that act in competition, supposedly making it one of the only creatures to have a 360 degree view of its environment. It is suggested that the two eyes that contain cornea and retina are attached to a central nervous system which enables the four brains to process images. It is unknown how this works, as the creature has an as yet unseen type of central nervous system.

It has also been found that certain species of the Box Jellyfish sleep on the sea bed in shallow water.

Jellyfish blooms


The presence of ocean blooms is usually seasonal, responding to prey availability and increasing with temperature and sunshine. Ocean currents tend to congregate jellyfish into large swarm
Swarm
Swarm behaviour, or swarming, is a collective behaviour exhibited by animals of similar size which aggregate together, perhaps milling about the same spot or perhaps moving en masse or migrating in some direction. As a term, swarming is applied particularly to insects, but can also be applied to...

s or "blooms", consisting of hundreds or thousands of individuals. In addition to sometimes being concentrated by ocean currents, blooms can result from unusually high populations in some years. Bloom formation is a complex process that depends on ocean current
Ocean current
An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect, cabbeling, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun...

s, nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

s, temperature, predation
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...

, and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 concentrations. Jellyfish are better able to survive in oxygen-poor water than competitors, and thus can thrive on plankton without competition. Jellyfish may also benefit from saltier waters, as saltier waters contain more iodine, which is necessary for polyps to turn into jellyfish. Rising sea temperatures caused by climate change may also contribute to jellyfish blooms, because many species of jellyfish are better able to survive in warmer waters.
Jellyfish are likely to stay in blooms that are quite large and can reach up to 100,000 in each.

There is very little data about changes in global jellyfish populations over time, besides "impressions" in the public memory. Scientists have little quantitative data of historic or current jellyfish populations. Recent speculation about increases in jellyfish populations are based on no "before" data.

The global increase in jellyfish bloom frequency may stem from human impact. In some locations jellyfish may be filling ecological niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...

s formerly occupied by now overfished
Overfishing
Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....

 creatures, but this hypothesis lacks supporting data. Jellyfish researcher Marsh Youngbluth further clarifies that "jellyfish feed on the same kinds of prey as adult and young fish, so if fish are removed from the equation, jellyfish are likely to move in."

Some jellyfish populations that have shown clear increases in the past few decades are "invasive" species, newly arrived from other habitats: examples include the Black Sea and the Caspian Sea, the Baltic Sea, the eastern Mediterranean coasts of Egypt and Israel, and the American coast of the Gulf of Mexico. Populations of invasive species can expand rapidly because there are often no natural predators in the new habitat to check their growth. Such blooms would not necessarily reflect overfishing or other environmental problems.

Increased nutrients, ascribed to agricultural runoff, have also been cited as an antecedent to the proliferation of jellyfish. Monty Graham, of the Dauphin Island Sea Lab
Dauphin Island Sea Lab
The Dauphin Island Sea Lab is Alabama's primary marine education and research center. DISL is the home site of the Marine Environmental Sciences Consortium and was founded by an act of the Alabama State Legislature in 1971. It also has a public aquarium specializing in estuarine organisms, the...

 in Alabama, says that "ecosystems in which there are high levels of nutrients ... provide nourishment for the small organisms on which jellyfish feed. In waters where there is eutrophication
Eutrophication
Eutrophication or more precisely hypertrophication, is the movement of a body of water′s trophic status in the direction of increasing plant biomass, by the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system...

, low oxygen levels often result, favoring jellyfish as they thrive in less oxygen-rich water than fish can tolerate. The fact that jellyfish are increasing is a symptom of something happening in the ecosystem."

Life cycle



Jellyfish are usually either male or female (occasionally hermaphroditic specimens are found). In most cases, both release sperm
Spermatozoon
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...

 and eggs into the surrounding water, where the (unprotected) eggs are fertilized and mature into new organisms. In a few species, the sperm swim into the female's mouth fertilizing the eggs within the female's body where they remain for the early stages of development. In moon jellies, the eggs lodge in pits on the oral arms, which form a temporary brood chamber for the developing planula larvae.

Most jellyfish undergo two distinct life history stages (body forms) during their life cycle
Biological life cycle
A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...

. The first is the polyp
Polyp
A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are approximately cylindrical in shape and elongated at the axis of the body...

oid stage. After fertilization and initial growth, a larval form, called the planula
Planula
A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species. The planula forms from the fertilized egg of a medusa, as the case in scyphozoans and some hydrozoans, or from a polyp, as in the case of anthozoans...

, develops. The planula is a small larva covered with cilia
Cilium
A cilium is an organelle found in eukaryotic cells. Cilia are slender protuberances that project from the much larger cell body....

. It settles onto a firm surface and develops into a polyp
Polyp
A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are approximately cylindrical in shape and elongated at the axis of the body...

. The polyp is generally a small stalk with a mouth surrounded by upward-facing tentacles like miniatures of the closely related anthozoa
Anthozoa
Anthozoa is a class within the phylum Cnidaria that contains the sea anemones and corals. Unlike other cnidarians, anthozoans do not have a medusa stage in their development. Instead, they release sperm and eggs that form a planula, which attaches to some substrate on which the cnidarian grows...

n polyps (sea anemones and corals), also of the phylum Cnidaria. This polyp may be sessile
Sessility (zoology)
In zoology, sessility is a characteristic of animals which are not able to move about. They are usually permanently attached to a solid substrate of some kind, such as a part of a plant or dead tree trunk, a rock, or the hull of a ship in the case of barnacles. Corals lay down their own...

, living on the bottom or on similar substrata such as floats or boat-bottoms, or it may be free-floating or attached to tiny bits of free-living plankton or rarely, fish or other invertebrates. Polyps may be solitary or colonial, and some bud asexually by various means, making more polyps. Most are very small, measured in millimeters.

After a growth interval, the polyp begins reproducing asexually by budding
Budding
Budding is a form of asexual reproduction in which a new organism grows on another one. The new organism remains attached as it grows, separating from the parent organism only when it is mature. Since the reproduction is asexual, the newly created organism is a clone and is genetically identical...

 and, in the Scyphozoa
Scyphozoa
Scyphozoa is a class within the phylum Cnidaria, sometimes referred to as the "true jellyfish".The class name Scyphozoa comes from the Greek word skyphos , denoting a kind of drinking cup and alluding to the cup shape of the organism....

, is called a segmenting polyp, or a scyphistoma. New scyphistomae may be produced by budding or new, immature jellies called ephyra
Ephyra
Ephyra may refer to:* The city of Kichyro, later known as Ephyra.* Ephyra, one of the Oceanids* Ephyra, one of the Nereids* Ephyra, a stage of the life cycle of jellyfish* Efyra, a village and an archeological site in Elis, Greece...

e may be formed. A few jellyfish species can produce new medusae by budding directly from the medusan stage. Budding sites vary by species; from the tentacle bulbs, the manubrium (above the mouth), or the gonads of hydromedusae. A few of species of hydromedusae reproduce by fission (splitting in half).

In the second stage, the tiny polyps asexually produce jellyfish, each of which is also known as a medusa
Medusa (biology)
In biology, a medusa is a form of cnidarian in which the body is shaped like an umbrella, in contrast with polyps. Medusae vary from bell-shaped to the shape of a thin disk, scarcely convex above and only slightly concave below...

. Tiny jellyfish (usually only a millimeter or two across) swim away from the polyp and then grow and feed in the plankton. Medusae have a radially symmetric, umbrella-shaped body called a bell, which is usually supplied with marginal tentacles - fringe-like protrusions from the bell's border that capture prey. A few species of jellyfish do not have the polyp portion of the life cycle, but go from jellyfish to the next generation of jellyfish through direct development of fertilized eggs.

Other species of jellyfish are among the most common and important jellyfish predators, some of which specialize in jellies. Other predators include tuna, shark, swordfish, sea turtles and at least one species of Pacific salmon. Sea birds sometimes pick symbiotic crustaceans from the jellyfish bells near the sea's surface, inevitably feeding also on the jellyfish hosts of these amphipods or young crabs and shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...

.

Jellyfish lifespans typically range from a few hours (in the case of some very small hydromedusae) to several months. Life span and maximum size varies by species. One unusual species is reported to live as long as 30 years. Another species, Turritopsis dohrnii as T. nutricula
Turritopsis nutricula
Turritopsis nutricula, the immortal jellyfish, is a hydrozoan whose medusa, or jellyfish, form can revert to the polyp stage after becoming sexually mature. It is the only known case of a metazoan capable of reverting completely to a sexually immature, colonial stage after having reached sexual...

, may be effectively immortal because of its ability to transform between medusa and polyp, thereby escaping death. Most large coastal jellyfish live 2 to 6 months, during which they grow from a millimeter or two to many centimeters in diameter. They feed continuously and grow to adult size fairly rapidly. After reaching adult size, jellyfish spawn daily if there is enough food. In most species, spawning is controlled by light, so the entire population spawns at about the same time of day, often at either dusk or dawn.

Culinary



Only scyphozoan jellyfish belonging to the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Rhizostomeae are harvested for food; about 12 of the approximately 85 species are harvested and sold on international markets. Most of the harvest takes place in southeast Asia. Rhizostomes, especially Rhopilema
Rhopilema
Rhopilema is a genus of jellyfishes.Species include* R. esculentum Kishinouye 1891 * R. hispidum Vanhoffen 1888...

 esculentum in China ( hǎizhē, "sea stings") and Stomolophus meleagris (cannonball jellyfish) in the United States, are favored because of their larger and more rigid bodies and because their toxins are harmless to humans.


Traditional processing methods, carried out by a Jellyfish Master, involve a 20 to 40 day multi-phase procedure in which after removing the gonads and mucous membranes, the umbrella and oral arms are treated with a mixture of table salt and alum
Alum
Alum is both a specific chemical compound and a class of chemical compounds. The specific compound is the hydrated potassium aluminium sulfate with the formula KAl2.12H2O. The wider class of compounds known as alums have the related empirical formula, AB2.12H2O.-Chemical properties:Alums are...

, and compressed. Processing reduces liquefaction, off-odors and the growth of spoilage organisms, and makes the jellyfish drier and more acidic, producing a "crunchy and crispy texture." Jellyfish prepared this way retain 7-10% of their original weight, and the processed product contains approximately 94% water and 6% protein. Freshly processed jellyfish has a white, creamy color and turns yellow or brown during prolonged storage.

In China, processed jellyfish are desalted by soaking in water overnight and eaten cooked or raw. The dish is often served shredded with a dressing of oil, soy sauce, vinegar and sugar, or as a salad with vegetables. In Japan, cured jellyfish are rinsed, cut into strips and served with vinegar as an appetizer. Desalted, ready-to-eat products are also available.

Fisheries have begun harvesting the American cannonball jellyfish, Stomolophus meleagris, along the southern Atlantic coast of the United States and in the Gulf of Mexico for export to Asia.

In biotechnology



In 1961, Osamu Shimomura
Osamu Shimomura
is a Japanese organic chemist and marine biologist, and Professor Emeritus at Marine Biological Laboratory in Woods Hole, Massachusetts and Boston University Medical School...

 of Princeton University extracted green fluorescent protein
Green fluorescent protein
The green fluorescent protein is a protein composed of 238 amino acid residues that exhibits bright green fluorescence when exposed to blue light. Although many other marine organisms have similar green fluorescent proteins, GFP traditionally refers to the protein first isolated from the...

 (GFP) and another bioluminescent protein, called aequorin
Aequorin
Aequorin is a photoprotein isolated from luminescent jellyfish and a variety of other marine organisms...

, from the large and abundant hydromedusa Aequorea victoria
Aequorea victoria
Aequorea victoria, also sometimes called the crystal jelly, is a bioluminescent hydrozoan jellyfish, or hydromedusa, that is found off the west coast of North America. This species is thought to be synonymous with Aequorea aequorea of Osamu Shimomura, the discoverer of green fluorescent protein . ...

, while studying photoproteins that cause bioluminescence
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...

 by this species of jellyfish. Three decades later, Douglas Prasher
Douglas Prasher
Douglas C. Prasher is an American molecular biologist. He is known for his work to clone and sequence the gene for green fluorescent protein and for his proposal to use GFP as a tracer molecule.-Career:...

, a post-doctoral scientist at Woods Hole Oceanographic Institution, sequenced and cloned the gene for GFP. Martin Chalfie
Martin Chalfie
Martin Chalfie is an American scientist. He is the William R. Kenan, Jr. Professor of Biological Sciences at Columbia University, where he is also chair of the department of biological sciences. He shared the 2008 Nobel Prize in Chemistry along with Osamu Shimomura and Roger Y. Tsien "for the...

 of Columbia University soon figured out how to use GFP as a fluorescent marker of genes inserted into other cells or organisms. Roger Tsien of University of California, San Diego, later chemically manipulated GFP in order to get other colors of fluorescence to use as markers. In 2008, Shimomura, Chalfie, and Tsien won the Nobel Prize in Chemistry
Nobel Prize in Chemistry
The Nobel Prize in Chemistry is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in chemistry, physics, literature,...

 for their work with GFP.

Man-made GFP is now commonly used as a fluorescent tag
Fluorescent tag
In molecular biology and biotechnology, a fluorescent tag is a part of a molecule that researchers have attached chemically to aid in detection of the molecule to which it has been attached. The tag is some kind of fluorescent molecule...

 to show which cells or tissues express specific genes. The genetic engineering technique fuses the gene of interest to the GFP gene. The fused DNA is then put into a cell, to generate either a cell line or (via IVF techniques) an entire animal bearing the gene. In the cell or animal, the artificial gene turns on in the same tissues and the same time as the normal gene. But instead of making the normal protein, the gene makes GFP. One can then find out what tissues express that protein—or at what stage of development—by shining light on the animal or cell and observing fluorescence. The fluorescence shows where the gene is expressed.

Jellyfish are also harvested for their collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...

, which can be used for a variety of applications including the treatment of rheumatoid arthritis
Rheumatoid arthritis
Rheumatoid arthritis is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks synovial joints. The process produces an inflammatory response of the synovium secondary to hyperplasia of synovial cells, excess synovial fluid, and the development...

.

In captivity



Jellyfish are displayed in aquariums in many countries. Often the tank's background is blue and the animals are illuminated by side light, increasing the contrast between the animal and the background. In natural conditions, many jellies are so transparent that they are nearly invisible.

Jellyfish are not adapted to closed spaces. They depend on currents to transport them from place to place. Professional exhibits feature precise water flows, typically in circular tanks to prevent specimens from becoming trapped in corners. The Monterey Bay Aquarium
Monterey Bay Aquarium
The Monterey Bay Aquarium is located on the former site of a sardine cannery on Cannery Row of the Pacific Ocean shoreline in Monterey, California. It has an annual attendance of 1.8 million visitors. It holds thousands of plants and animals, representing 623 separate named species on display...

 uses a modified version of the kreisel (German for "spinning top") for this purpose. Jellyfish are becoming a popular trend in home aquaria. It is now possible to buy jellyfish aquaria and live jellyfish online. It is also possible to assemble a jellyfish aquarium for personal use.

Toxicity


All jellyfish sting their prey using nematocysts, also called cnidocysts, stinging structures located in specialized cells called cnidocytes, which are characteristic of all Cnidaria
Cnidaria
Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...

. Contact with a jellyfish tentacle can trigger millions of nematocysts to pierce the skin and inject venom, yet only some species have a sting that will cause an adverse reaction in humans. When a nematocyst is triggered by contact by predator or prey, pressure builds up rapidly inside it up to 2,000 lbs/sq. inch until it bursts open. A lance inside the nematocyst pierces the victim's skin, and poison flows through into the victim. Touching or being touched by a jellyfish can be very uncomfortable, sometimes requiring medical assistance; sting effects range from no effect to extreme pain or even death. Because of the wide variation in response to jellyfish stings, it is wisest not to contact any jellyfish with bare skin. Even beached and dying jellyfish can still sting when touched.

Scyphozoan jellyfish stings range from a twinge to tingling to savage agony. Most jellyfish stings are not deadly, but stings of some species of the class Cubozoa and the Box jellyfish
Box jellyfish
Box jellyfish are cnidarian invertebrates distinguished by their cube-shaped medusae. Box jellyfish are known for the extremely potent venom produced by some species: Chironex fleckeri, Carukia barnesi and Malo kingi are among the most venomous creatures in the world...

, such as the famous and especially toxic Irukandji jellyfish
Irukandji jellyfish
Irukandji jellyfish are tiny and extremely venomous jellyfish that inhabit marine waters of Australia and which are able to fire their stingers into their victim, causing symptoms collectively known as Irukandji syndrome. Its size is roughly no larger than a cubic centimetre...

, can be deadly. Stings may cause anaphylaxis
Anaphylaxis
Anaphylaxis is defined as "a serious allergic reaction that is rapid in onset and may cause death". It typically results in a number of symptoms including throat swelling, an itchy rash, and low blood pressure...

, which can be fatal. Medical care may include administration of an antivenom.

In 2010 at a New Hampshire
New Hampshire
New Hampshire is a state in the New England region of the northeastern United States of America. The state was named after the southern English county of Hampshire. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Atlantic Ocean to the east, and the Canadian...

 beach, pieces of a single dead lion's mane jellyfish
Lion's mane jellyfish
The lion's mane jellyfish is the largest known species of jellyfish. Its range is confined to cold, boreal waters of the Arctic, northern Atlantic, and northern Pacific Oceans, seldom found farther south than 42°N latitude. Similar jellyfish, which may be the same species, are known to inhabit...

 stung between 125 and 150 people. Jellyfish kill 20 to 40 people a year in the Philippines alone. In 2006 the Spanish Red Cross treated 19,000 stung swimmers along the Costa Brava
Costa Brava
The Costa Brava is a coastal region of northeastern Catalonia, Spain, in the comarques of Alt Empordà, Baix Empordà and Selva, in the province of Girona. Costa is the Catalan and Spanish word for 'coast', and Brava means 'rugged' or 'wild'...

.

Treatment


The three goals of first aid for uncomplicated jellyfish stings are to prevent injury to rescuers, deactivate the nematocysts
Cnidocyte
A cnidocyte, cnidoblast, or nematocyte is a type of venomous cell unique to the phylum Cnidaria . The cnidocyte cell provides a means for them to catch prey and defend themselves from predators. Despite being morphologically simple, lacking a skeleton and usually being sessile, cnidarians prey on...

, and remove tentacles attached to the patient. Rescuers need to wear barrier clothing, such as pantyhose
Pantyhose
Pantyhose are sheer, close-fitting legwear, covering the wearer's body from the waist to the feet. Mostly considered to be a woman's and girl's garment, pantyhose appeared in the 1960s, and they provided a convenient alternative to stockings...

, wet suits or full-body sting-proof suits. Deactivating the nematocysts (stinging cells) prevents further injection of venom.

Vinegar
Vinegar
Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...

 (3 to 10% aqueous acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

) is a common remedy to help with box jellyfish
Box jellyfish
Box jellyfish are cnidarian invertebrates distinguished by their cube-shaped medusae. Box jellyfish are known for the extremely potent venom produced by some species: Chironex fleckeri, Carukia barnesi and Malo kingi are among the most venomous creatures in the world...

 stings, but not the stings of the Portuguese Man o' War
Portuguese Man o' War
The Portuguese Man o' War , also known as the Portuguese man-of-war, man-of-war, or bluebottle, is a jelly-like marine invertebrate of the family Physaliidae...

 (which is not a true jellyfish, but a colony). For stings on or around the eyes, a towel dampened with vinegar is used to dab around the eyes, with care taken to avoid the eyeballs. Salt water is also used if vinegar is unavailable. Fresh water is not used if the sting occurs in salt water, as changes in tonicity
Tonicity
Tonicity is a measure of the osmotic pressure gradient of two solutions separated by a semipermeable membrane. It is commonly used when describing the response of cells immersed in an external solution...

 can release additional venom. Rubbing wounds, or using alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

, spirits, ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

, or urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

 may have strongly negative effects as these can also encourage the release of venom.

Clearing the area of jelly, tentacles, and wetness further reduces nematocyst firing. Scraping the affected skin with a knife edge, safety razor, or credit card can remove remaining nematocysts.

Beyond initial first aid, antihistamine
Antihistamine
An H1 antagonist is a histamine antagonist of the H1 receptor that serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions...

s such as diphenhydramine
Diphenhydramine
Diphenhydramine hydrochloride is a first-generation antihistamine possessing anticholinergic, antitussive, antiemetic, and sedative properties which is mainly used to treat allergies. Like most other first-generation antihistamines, the drug also has a powerful hypnotic effect, and for this reason...

 (Benadryl
Histamine antagonist
A histamine antagonist, commonly referred to as antihistamine, is a pharmaceutical drug that inhibits action of histamine by blocking it from attaching to histamine receptors.- Clinical effects :...

) can control skin irritation (pruritus
Itch
Itch is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to classify it as any one type of sensory experience. Modern science has shown that itch has many similarities to pain, and while both are unpleasant sensory experiences, their behavioral response...

). For removal of venom in the skin, a paste of baking soda and water can be applied with a cloth covering on the sting. In some cases it is necessary to reapply paste every 15–20 minutes. Ice or fresh water should not be applied to the sting, as this may help the nematocysts to continue releasing their toxin.

Overpopulation


Evidence in recent years suggest that the population of jellyfish has swelled as a result of overfishing which reduces the number of predatory organisms that feed on them. This has allowed jellyfish to proliferate to the extent that they adversely affect humanity by interfering with public systems and harming swimmers. Jellyfish blooms cause problems for mankind. The most obvious are stings to humans (sometimes deadly), and causing coastal tourism to decline. Other problems are destroying fish nets, poisoning or crushing captured fish, and consuming fish eggs and young fish.

By clogging cooling equipment en masse, jellyfish have disabled power plants in several countries, including a cascading blackout in the Philippines in 1999 as well as in the Diablo Canyon Power Plant
Diablo Canyon Power Plant
Diablo Canyon Power Plant is an electricity-generating nuclear power plant at Avila Beach in San Luis Obispo County, California. The plant has two Westinghouse-designed 4-loop pressurized-water nuclear reactors operated by Pacific Gas & Electric. The facility is located on about in Avila Beach,...

 in California in 2010. Clogging also causes many problems including stoppage of nuclear power plant
Nuclear power plant
A nuclear power plant is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity.Nuclear power plants are usually...

s and desalination plants, as well as clogging engines of ships and making pull in of fishing nets hazardous.

In media


New discoveries about jellyfish and their prevalence are reflected on television in programs such as in "Jellyfish Invasion," which is an episode of the National Geographic Channel
National Geographic Channel
National Geographic Channel, also commercially abbreviated and trademarked as Nat Geo, is a subscription television channel that airs non-fiction television programs produced by the National Geographic Society. Like History and the Discovery Channel, the channel features documentaries with factual...

 documentary series Explorer
National Geographic Explorer
National Geographic Explorer is an American documentary television series that originally premiered on Nickelodeon on April 7, 1985, after having been produced as a less costly and intensive alternative to PBS's National Geographic Specials by Pittsburgh station WQED...

, which includes research conducted by scientists in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

 and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

.

The Disney Pixar animated film Finding Nemo
Finding Nemo
Finding Nemo is a 2003 American comi-drama animated film written by Andrew Stanton, directed by Andrew Stanton and Lee Unkrich and produced by Pixar. It tells the story of the overly protective clownfish Marlin who, along with a regal tang called Dory , searches for his abducted son Nemo...

 shows the near fatal effects of swimming through a jellyfish bloom. The opening sequence of the animated film Ponyo depicts a massive jellyfish bloom off the coast of Japan.

The Japanese science fiction
Science fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...

 film Dogora
Dogora
Dogora may refer to:* Dogora , a Japanese film, 1964* Dogora: Ouvrons les yeux, a French film, 2004...

 features jellyfish-like space creatures.
The Japanese anime Kuragehime
Kuragehime
is a Japanese josei manga series written and illustrated by Akiko Higashimura. It began serialization in the Kodansha manga magazine Kiss on November 10, 2008. An 11-episode anime television series based on the manga was produced by Brain's Base and aired on Fuji TV's Noitamina programming block...

 features a main character who is obsessed with jellyfish, and has jellyfish related plotlines.

In the Will Smith movie Seven Pounds
Seven Pounds
Seven Pounds is a 2008 film, directed by Gabriele Muccino. Will Smith stars as a man who sets out to change the lives of seven people. Rosario Dawson, Woody Harrelson, and Barry Pepper star. The film was released in theaters in the United States and Canada on December 19, 2008, by Columbia Pictures...

, Will Smith's character had a pet jellyfish which was an important piece to the end of the movie.

On an episode of Survivor Palau, the team winning the reward challenge got to swim in Jellyfish Lake
Jellyfish Lake
Jellyfish Lake is a marine lake located on Eil Malk island in Palau. Eil Malk is part of the Rock Islands, a group of small, rocky, mostly uninhabited islands in Palau's Southern Lagoon, between Koror and Peleliu. There are about 70 other marine lakes located throughout the Rock Islands. Jellyfish...

, a lake full of golden jellyfish, which are harmless to Humans.

On the "A Star is Born Again" episode of The Simpsons
The Simpsons
The Simpsons is an American animated sitcom created by Matt Groening for the Fox Broadcasting Company. The series is a satirical parody of a middle class American lifestyle epitomized by its family of the same name, which consists of Homer, Marge, Bart, Lisa and Maggie...

, the fictional town of Springfield holds a Jellyfish Festival, portrayed as a magical evening celebrating the waters and beach being overrun with jellyfish.

Taxonomy


Taxonomic classification systematics within the Cnidaria, as with all organisms, are always in flux. Many scientists who work on relationships between these groups are reluctant to assign ranks, although there is general agreement on the different groups, regardless of their absolute rank. Presented here is one scheme, which includes all groups that produce medusae (jellyfish), derived from several expert sources:
Jellyfish taxonomy (phylum Cnidaria
Cnidaria
Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...

: subphylum Medusozoa)
Class Subclass Order Suborder Families
Hydrozoa
Hydrozoa
Hydrozoa are a taxonomic class of very small, predatory animals which can be solitary or colonial and which mostly live in saltwater. A few genera within this class live in freshwater...

 
Hydroidolina Anthomedusae
Anthomedusae
Anthomedusae or Anthomedusa, the athecate hydroids, are an order of the Hydrozoa, a class of marine invertebrates belonging to the phylum Cnidaria...

Filifera see
Capitata see
Leptomedusae
Leptomedusae
Leptomedusae or Leptomedusa, commonly called thecate hydroids, are a cnidarian order in the subclass Leptolinae. They were formerly placed at suborder rank in the paraphyletic "Hydroida"...

Conica
Conica (Hydrozoa)
Conica are a cnidarian suborder of the Leptomedusae . They make up the bulk of their order; their internal relationships are not well resolved, and most of the roughly 30 families are not yet assigned to a superfamily....

see
Proboscoida see
Siphonophorae Physonectae Agalmatidae
Agalmatidae
Agalmatidea, or Agalmidae, is a family of siphonophores.-Genera:*Agalma Eschscholtz, 1825*Cordagalma Totton, 1932*Erenna Bedot, 1904*Frillagalma Daniel, 1966*Halistemma Huxley, 1859*Lychnagalma Haeckel, 1888...

, Apolemiidae, Erennidae, Forskaliidae, Physophoridae, Pyrostephidae, Rhodaliidae
Calycophorae Abylidae
Abylidae
Abylidae is a family of marine invertebrates in the order Siphonophora. They are colonial, but the colonies can superficially resemble jellyfish; although they appear to be a single organism, each specimen is actually a colony of Siphonophora....

, Clausophyidae, Diphyidae, Hippopodiidae, Prayidae
Prayidae
Prayidae is a family of marine invertebrates in the order Siphonophora. They are colonial, but the colonies can superficially resemble jellyfish; although they appear to be a single organism, each specimen is actually a colony of Siphonophora....

, Sphaeronectidae
Cystonectae Physaliidae, Rhizophysidaev
Trachylina Limnomedusae Olindiidae, Monobrachiidae, Microhydrulidae, Armorhydridae
Trachymedusae
Trachymedusae
Trachymedusae are an order in the cnidarian class Hydrozoa. They contain some 50 species, divided among about 30 genera and 5 families, of which the Rhopalonematidae are by far the most diverse. They only reproduce sexually as medusa, never forming polyps...

Geryoniidae, Halicreatidae, Petasidae, Ptychogastriidae, Rhopalonematidae
Narcomedusae
Narcomedusae
Narcomedusae is an order of hydrozoans in the subclass Trachylinae.-Characteristics:Members of this order do not normally have a polyp stage. The medusa has a dome-shaped bell with thin sides. The tentacles are attached above the lobed margin of the bell with usually a gastric pouch above each....

Cuninidae
Cuninidae
Cuninidae is a family of jellyfish in the order Narcomedusae.-Characteristics:Members of this family have dome-shaped bells and tentacles set above the undulating margin of the bell. There are gastric pouches containing the gonads situated in line with the tentacles, the number of pouches being the...

, Solmarisidae
Solmarisidae
Solmarisidae is a family of jellyfish in the order Narcomedusae. The name is sometimes spelled "Solmaridae".-Characteristics:Members of this family have dome-shaped bells and numerous tentacles set above the undulating margin of the bell. They do not have gastric pouches as do other members of the...

, Aeginidae
Aeginidae
Aeginidae is a family of jellyfish in the order Narcomedusae. Most of the genera include only a single species.-Characteristics:Jellyfish with dome-shaped bells and tentacles set above the undulating margin of the bell. There are gastric pouches containing the gonads situated between the tentacles,...

, Tetraplatiidae
Actinulidae Halammohydridae, Otohydridae
Staurozoa Eleutherocarpida
Eleutherocarpida
Eleutherocarpida is a stalked jellyfish order in the class Staurozoa....

Lucernariidae
Lucernariidae
Lucernariidae is a family of stalked jellyfish containing four genera. It is considered to be non-monophyletic.-External links:*...

, Kishinouyeidae
Kishinouyeidae
Kishinouyeidae is a stalked jellyfish family in the order Eleutherocarpida.-References:* Synopsis of the medusae of the world. Kramp, P. L., 1961, Journal of the Marine Biological Association of the United Kingdom, vol. 40, Page: 1-469...

, Lipkeidae, Kyopodiidae
Cleistocarpida Depastridae, Thaumatoscyphidae, Craterolophinae
Cubozoa  Carybdeidae
Carybdeidae
Carybdeidae is a family of venomous box jellyfish within class Cubozoa.-Carybdea:* Carybdea arborifera Maas, 1897* Carybdea branchi Gershwin & Gibbons, 2009* Carybdea brevipedalia Kishinouyea, 1891...

, Alatinidae
Alatinidae
Alatinidae is a family of box jellyfish within class Cubozoa.-Alatina:Contains the following species:* Alatina alata * Alatina grandis * Alatina madraspatana...

, Tamoyidae, Chirodropidae
Chirodropidae
Chirodropidae is a family of venomous box jellyfish within class Cubozoa.One of the species of jellyfish that belongs to this class is the Chironex fleckeri.-Chirodectes:* Chirodectes maculatus...

, Chiropsalmidae
Scyphozoa
Scyphozoa
Scyphozoa is a class within the phylum Cnidaria, sometimes referred to as the "true jellyfish".The class name Scyphozoa comes from the Greek word skyphos , denoting a kind of drinking cup and alluding to the cup shape of the organism....

 
Coronatae Atollidae, Atorellidae, Linuchidae
Linuchidae
Linuchidae is a family of jellyfish.-Linuche:Contains the following species:*Linuche aquila*Linuche unguiculata...

, Nausithoidae
Nausithoidae
Nausithoidae is a family of jellyfish.-Nausithoe:Contains the following species:* Nausithoe albatrossi* Nausithoe atlantica* Nausithoe aurea* Nausithoe challengeri* Nausithoe clausi* Nausithoe eumedusoides...

, Paraphyllinidae, Periphyllidae
Periphyllidae
Periphyllidae is a family of jellyfish, a type of animal.-Pericolpa:Contains the following species:* Pericolpa campana* Pericolpa quadrigata-Periphyllopsis:Contains the following species:* Periphyllopsis braueri...

Semaeostomeae
Semaeostomeae
Semaeostomeae is an order of large jellyfish characterized by four long, frilly oral arms flanking their quadrate mouths. The umbrella is domed with scalloped margins, and the gastrovascular system consists of four unbranched pouches radiating outwards from the central stomach; there is no ring...

Cyaneidae
Cyaneidae
Cyaneidae is a family of jellyfish. There are 14 species in this family. They are most commonly found in the southern part of the Atlantic Ocean.-Species:*Cyanea**Cyanea annasethe Haeckel 1880**Cyanea annaskala von Lendenfeld,1884...

, Pelagiidae
Pelagiidae
Pelagiidae is a family of jellyfish. There are 15 species in this family.-Genera:*Chrysaora**Chrysaora achlyos Martin, Gershwin, Burnett, Cargo & Bloom 1997**Chrysaora africana **Chrysaora blossevillei Lesson 1830...

, Ulmaridae
Ulmaridae
Ulmaridae is a family of jellyfish.-Genera:*Aurelia *Aurosa*Deepstaria*Diplulmaris*Discomedusa*Floresca*Parumbrosa*Phacellophora - Phacellophora camtschatica*Poralia...

Rhizostomeae Cassiopeidae, Catostylidae
Catostylidae
Catostylidae is a family of small jellyfish. Members of this family are characterized by their thick, sausage-like oral arms.-Description:Members of the Catostylidae family are small marine jellyfish with domed bells. The eight short oral arms are broad and three-sided...

, Cepheidae
Cepheidae
Cepheidae is a family of jellyfish....

, Lychnorhizidae, Lobonematidae, Mastigiidae, Rhizostomatidae, Stomolophidae
Stomolophidae
Stopmolophidae is a family of jellyfish.-Species:*Nemopilema nomurai - Nomura's jellyfish*Stomolophus meleagris - the cannonball or cabbage head jellyfish...


Largest jellyfish


The lion's mane jellyfish
Lion's mane jellyfish
The lion's mane jellyfish is the largest known species of jellyfish. Its range is confined to cold, boreal waters of the Arctic, northern Atlantic, and northern Pacific Oceans, seldom found farther south than 42°N latitude. Similar jellyfish, which may be the same species, are known to inhabit...

, Cyanea capillata, have long been cited as the largest known jellyfish, and are arguably the longest animal in the world, with fine, thread-like tentacles up to 36.5 m (120 feet) long (though most are nowhere near that large). They have a painful, but rarely fatal, sting.

The increasingly common giant Nomura's jellyfish, Nemopilema nomurai, found some, but not all years in the waters of Japan, Korea and China in summer and autumn is probably a much better candidate for "largest jellyfish", since the largest Nomura's jellyfish in late autumn can reach 200 cm (79 inches) in bell (body) diameter and about 200 kg (440 lbs) in weight, with average specimens frequently reaching 90 cm (35 inches) in bell diameter and about 150 kg (330 lbs) in weight. The large bell mass of the giant Nomura's jellyfish can dwarf a diver and is nearly always much greater than the up-to-100 cm bell diameter Lion's Mane.

The rarely-encountered deep-sea jellyfish Stygiomedusa gigantea
Stygiomedusa gigantea
Stygiomedusa gigantea is a species of giant deep sea jellyfish in the Ulmaridae family.With only 114 sightings in the last 110 years it is a jellyfish that is rarely seen, but believed to be widespread throughout the world....

 is another solid candidate for "largest jellyfish", with its 100 cm wide, and thick, massive bell and four thick, "paddle-like" oral arms extending up to 600 cm in length, very different than the typical fine, threadlike tentacles that rim the umbrella of more-typical-looking jellyfish, including the Lion's Mane.

External links




Photos: