Jellyfish
Jellyfish | |
---|---|
Pacific sea nettle (Chrysaora fuscescens) | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Cnidaria |
Subphylum: | Medusozoa |
Groups included | |
Cladistically included but traditionally excluded taxa | |
Jellyfish, also known as sea jellies, are the medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria.
Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle. The medusa is normally the sexual phase, which produces planula larvae. These then disperse widely and enter a sedentary polyp phase which may include asexual budding before reaching sexual maturity.
Jellyfish are found all over the world, from surface waters to the deep sea.
Jellyfish are eaten by humans in certain cultures. They are considered a delicacy in some Asian countries, where species in the Rhizostomeae order are pressed and salted to remove excess water. Australian researchers have described them as a "perfect food": sustainable and protein-rich but relatively low in food energy.[3]
They are also used in research, where the green fluorescent protein used by some species to cause bioluminescence has been adapted as a fluorescent marker for genes inserted into other cells or organisms.
The stinging cells used by jellyfish to subdue their prey can injure humans. Thousands of swimmers worldwide are stung every year, with effects ranging from mild discomfort to serious injury or even death. When conditions are favourable, jellyfish can form vast swarms, which can be responsible for damage to fishing gear by filling fishing nets, and sometimes clog the cooling systems of power and
Names
The name jellyfish, in use since 1796,
A group of jellyfish is called a "smack"[12] or a "smuck".[13]
Mapping to taxonomic groups
Phylogeny
Definition
The term jellyfish broadly corresponds to medusae,[4] that is, a life-cycle stage in the Medusozoa. The American evolutionary biologist Paulyn Cartwright gives the following general definition:
Typically, medusozoan cnidarians have a pelagic, predatory jellyfish stage in their life cycle; staurozoans are the exceptions [as they are stalked].[14]
The Merriam-Webster dictionary defines jellyfish as follows:
A free-swimming marine coelenterate that is the sexually reproducing form of a hydrozoan or scyphozoan and has a nearly transparent saucer-shaped body and extensible marginal tentacles studded with stinging cells.[15]
Given that jellyfish is a common name, its mapping to biological groups is inexact. Some authorities have called the comb jellies[16] and certain salps[16] jellyfish, though other authorities state that neither of these are jellyfish, which they consider should be limited to certain groups within the medusozoa.[17][18]
The non-medusozoan clades called jellyfish by some but not all authorities (both agreeing and disagreeing citations are given in each case) are indicated with "???" on the following cladogram of the animal kingdom:
Animalia
|
| ||||||||||||
Medusozoan jellyfish
Jellyfish are not a clade, as they include most of the Medusozoa, barring some of the Hydrozoa.[19][20] The medusozoan groups included by authorities are indicated on the following phylogenetic tree by the presence of citations. Names of included jellyfish, in English where possible, are shown in boldface; the presence of a named and cited example indicates that at least that species within its group has been called a jellyfish.
Cnidaria |
| ||||||||||||||||||||||||||||||||||||||||||||||||
Taxonomy
The subphylum Medusozoa includes all cnidarians with a medusa stage in their life cycle. The basic cycle is egg,
The four major classes of medusozoan Cnidaria are:
- 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.[25]
- Cubozoa (box jellyfish) have a (rounded) box-shaped bell, and their velarium assists them to swim more quickly. Box jellyfish may be related more closely to scyphozoan jellyfish than either are to the Hydrozoa.[26]
- Hydrozoa medusae also have tetra-radial symmetry, nearly always have a velum (diaphragm used in swimming) attached just inside the bell margin, do not have oral arms, but a much smaller central stalk-like structure, the manubrium, with terminal mouth opening, and are distinguished by the absence of cells in the mesoglea. 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 Hydra, which is hence not considered a jellyfish), and a few are entirely medusal and have no polyp form.[25]
- Staurozoa (stalked jellyfish) are characterized by a medusa form that is generally sessile, oriented upside down and with a stalk emerging from the apex of the "calyx" (bell), which attaches to the substrate. 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.[25]
There are over 200 species of Scyphozoa, about 50 species of Staurozoa, about 50 species of Cubozoa, and the Hydrozoa includes about 1000–1500 species that produce medusae, but many more species that do not.[27][28]
Fossil history
Since jellyfish have no hard parts, fossils are rare. The oldest unambiguous fossil of a free-swimming medusa is
Anatomy
The main feature of a true jellyfish is the umbrella-shaped bell. This is a hollow structure consisting of a mass of transparent jelly-like matter known as mesoglea, which forms the hydrostatic skeleton of the animal.[25] The mesoglea is 95% or more composed of water,[30] and also contains collagen and other fibrous proteins, as well as wandering amebocytes that can engulf debris and bacteria. The mesogloea is bordered 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 lappets, which allow the bell to flex. In the gaps or niches between the lappets are dangling rudimentary sense organs known as rhopalia, and the margin of the bell often bears tentacles.[25]
On the underside of the bell is the manubrium, a stalk-like structure hanging down from the centre, with the mouth, which also functions as the anus, at its tip. There are often four oral arms connected to the manubrium, streaming away into the water below.
The box jellyfish is largely similar in structure. It has a squarish, box-like bell. A short pedalium or stalk hangs from each of the four lower corners. One or more long, slender tentacles are attached to each pedalium.[32] The rim of the bell is folded inwards to form a shelf known as a velarium which restricts the bell's aperture and creates a powerful jet when the bell pulsates, allowing box jellyfish to swim faster than true jellyfish.[25] Hydrozoans are also similar, usually with just four tentacles at the edge of the bell, although many hydrozoans are colonial and may not have a free-living medusal stage. 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.[25] Stalked jellyfish are attached to a solid surface by a basal disk, and resemble a polyp, the oral end of which has partially developed into a medusa with tentacle-bearing lobes and a central manubrium with four-sided mouth.[25]
Most jellyfish do not have specialized systems for osmoregulation, respiration and circulation, and do not have a central nervous system. Nematocysts, which deliver the sting, are located mostly on the tentacles; true jellyfish also have them around the mouth and stomach.[33] Jellyfish do not need a respiratory system because sufficient oxygen diffuses through the epidermis. 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.[34]
The rhopalia contain rudimentary sense organs which are able to detect light, water-borne vibrations, odour and orientation.
In many species of jellyfish, the rhopalia include
Box jellyfish have more advanced vision than the other groups. Each individual has 24 eyes, two of which are capable of seeing colour, and four parallel information processing areas that act in competition,[38] supposedly making them one of the few kinds of animal to have a 360-degree view of its environment.[39]
Box jellyfish eye
The study of jellyfish eye evolution is an intermediary to a better understanding of how visual systems evolved on Earth.[40] Jellyfish exhibit immense variation in visual systems ranging from photoreceptive cell patches seen in simple photoreceptive systems to more derived complex eyes seen in box jellyfish.[40] Major topics of jellyfish visual system research (with an emphasis on box jellyfish) include: the evolution of jellyfish vision from simple to complex visual systems), the eye morphology and molecular structures of box jellyfish (including comparisons to vertebrate eyes), and various uses of vision including task-guided behaviors and niche specialization.
Evolution
Experimental evidence for photosensitivity and photoreception in cnidarians antecedes the mid 1900s, and a rich body of research has since covered evolution of visual systems in jellyfish.[41] Jellyfish visual systems range from simple photoreceptive cells to complex image-forming eyes. More ancestral visual systems incorporate extraocular vision (vision without eyes) that encompass numerous receptors dedicated to single-function behaviors. More derived visual systems comprise perception that is capable of multiple task-guided behaviors.
Although they lack a true brain, cnidarian jellyfish have a "ring" nervous system that plays a significant role in motor and sensory activity. This net of nerves is responsible for muscle contraction and movement and culminates the emergence of photosensitive structures.[40] Across Cnidaria, there is large variation in the systems that underlie photosensitivity. Photosensitive structures range from non-specialized groups of cells, to more "conventional" eyes similar to those of vertebrates.[41] The general evolutionary steps to develop complex vision include (from more ancestral to more derived states): non-directional photoreception, directional photoreception, low-resolution vision, and high-resolution vision.[40] Increased habitat and task complexity has favored the high-resolution visual systems common in derived cnidarians such as box jellyfish.[40]
The low-resolution visual system of box jellyfish is more derived than directional photoreception, and thus box jellyfish vision represents the most basic form of true vision in which multiple directional photoreceptors combine to create the first imaging and
Box jellyfish possess "proper eyes" (similar to vertebrates) that allow them to inhabit environments that lesser derived medusae cannot. In fact, they are considered the only class in the clade Medusozoa that have behaviors necessitating spatial resolution and genuine vision.[41] However, the lens in their eyes are more functionally similar to cup-eyes exhibited in low-resolution organisms, and have very little to no focusing capability.[44][43] The lack of the ability to focus is due to the focal length exceeding the distance to the retina, thus generating unfocused images and limiting spatial resolution.[41] The visual system is still sufficient for box jellyfish to produce an image to help with tasks such as object avoidance.
Utility as a model organism
Box jellyfish eyes are a visual system that is sophisticated in numerous ways. These intricacies include the considerable variation within the morphology of box jellyfishes' eyes (including their task/behavior specification), and the molecular makeup of their eyes including: photoreceptors, opsins, lenses, and synapses.[41] The comparison of these attributes to more derived visual systems can allow for a further understanding of how the evolution of more derived visual systems may have occurred, and puts into perspective how box jellyfish can play the role as an evolutionary/developmental model for all visual systems.[45]
Characteristics
Box jellyfish visual systems are both diverse and complex, comprising multiple photosystems.[41] There is likely considerable variation in visual properties between species of box jellyfish given the significant inter-species morphological and physiological variation. Eyes tend to differ in size and shape, along with number of receptors (including opsins), and physiology across species of box jellyfish.[41]
Box jellyfish have a series of intricate lensed eyes that are similar to those of more derived multicellular organisms such as vertebrates. Their 24 eyes fit into four different morphological categories.[46] These categories consist of two large, morphologically different medial eyes (a lower and upper lensed eye) containing spherical lenses, a lateral pair of pigment slit eyes, and a lateral pair of pigment pit eyes.[43] The eyes are situated on rhopalia (small sensory structures) which serve sensory functions of the box jellyfish and arise from the cavities of the exumbrella (the surface of the body) on the side of the bells of the jellyfish.[41] The two large eyes are located on the mid-line of the club and are considered complex because they contain lenses. The four remaining eyes lie laterally on either side of each rhopalia and are considered simple. The simple eyes are observed as small invaginated cups of epithelium that have developed pigmentation.[47] The larger of the complex eyes contains a cellular cornea created by a mono ciliated epithelium, cellular lens, homogenous capsule to the lens, vitreous body with prismatic elements, and a retina of pigmented cells. The smaller of the complex eyes is said to be slightly less complex given that it lacks a capsule but otherwise contains the same structure as the larger eye.[47]
Box jellyfish have multiple photosystems that comprise different sets of eyes.[41] Evidence includes immunocytochemical and molecular data that show photopigment differences among the different morphological eye types, and physiological experiments done on box jellyfish to suggest behavioral differences among photosystems. Each individual eye type constitutes photosystems that work collectively to control visually guided behaviors.[41]
Box jellyfish eyes primarily use c-PRCs (ciliary photoreceptor cells) similar to that of vertebrate eyes. These cells undergo
Comparison with other organisms
Comparative research on genetic and molecular makeup of box jellyfishes' eyes versus more derived eyes seen in vertebrates and cephalopods focuses on: lenses and crystallin composition, synapses, and Pax genes and their implied evidence for shared primordial (ancestral) genes in eye evolution.[49]
Box jellyfish eyes are said to be an evolutionary/developmental model of all eyes based on their evolutionary recruitment of crystallins and Pax genes.[45] Research done on box jellyfish including Tripedalia cystophora has suggested that they possess a single Pax gene, PaxB. PaxB functions by binding to crystallin promoters and activating them. PaxB in situ hybridization resulted in PaxB expression in the lens, retina, and statocysts.[45] These results and the rejection of the prior hypothesis that Pax6 was an ancestral Pax gene in eyes has led to the conclusion that PaxB was a primordial gene in eye evolution, and that the eyes of all organisms likely share a common ancestor.[45]
The lens structure of box jellyfish appears very similar to those of other organisms, but the crystallins are distinct in both function and appearance.[49] Weak reactions were seen within the sera and there were very weak sequence similarities within the crystallins among vertebrate and invertebrate lenses.[49] This is likely due to differences in lower molecular weight proteins and the subsequent lack of immunological reactions with antisera that other organisms' lenses exhibit.[49]
All four of the visual systems of box jellyfish species investigated with detail (Carybdea marsupialis, Chiropsalmus quadrumanus, Tamoya haplonema and Tripedalia cystophora) have invaginated synapses, but only in the upper and lower lensed eyes. Different densities were found between the upper and lower lenses, and between species.[46] Four types of chemical synapses have been discovered within the rhopalia which could help in understanding neural organization including: clear unidirectional, dense-core unidirectional, clear bidirectional, and clear and dense-core bidirectional. The synapses of the lensed eyes could be useful as markers to learn more about the neural circuit in box jellyfish retinal areas.[46]
Evolution as a response to natural stimuli
The primary adaptive responses to environmental variation observed in box jellyfish eyes include pupillary constriction speeds in response to light environments, as well as photoreceptor tuning and lens adaptations to better respond to shifts between light environments and darkness. Interestingly, some box jellyfish species' eyes appear to have evolved more focused vision in response to their habitat.[50]
Pupillary contraction appears to have evolved in response to variation in the light environment across ecological niches across three species of box jellyfish (Chironex fleckeri, Chiropsella bronzie, and Carukia barnesi). Behavioral studies suggest that faster pupil contraction rates allow for greater object avoidance,[50] and in fact, species with more complex habitats exhibit faster rates. Ch. bronzie inhabit shallow beach fronts that have low visibility and very few obstacles, thus, faster pupil contraction in response to objects in their environment is not important. Ca. barnesi and Ch. fleckeri are found in more three-dimensionally complex environments like mangroves with an abundance of natural obstacles, where faster pupil contraction is more adaptive.[50] Behavioral studies support the idea that faster pupillary contraction rates assist with obstacle avoidance as well as depth adjustments in response to differing light intensities.
Light/dark adaptation via pupillary light reflexes is an additional form of an evolutionary response to the light environment. This relates to the pupil's response to shifts between light intensity (generally from sunlight to darkness). In the process of light/dark adaptation, the upper and lower lens eyes of different box jellyfish species vary in specific function.[43] The lower lens-eyes contain pigmented photoreceptors and long pigment cells with dark pigments that migrate on light/dark adaptation, while the upper-lens eyes play a concentrated role in light direction and phototaxis given that they face upward towards the water surface (towards the sun or moon).[43] The upper lens of Ch. bronzie does not exhibit any considerable optical power while Tr. cystophora (a box jellyfish species that tends to live in mangroves) does. The ability to use light to visually guide behavior is not of as much importance to Ch. bronzie as it is to species in more obstacle-filled environments.[43] Differences in visually guided behavior serve as evidence that species that share the same number and structure of eyes can exhibit differences in how they control behavior.
Largest and smallest
Jellyfish range from about one millimeter in bell height and diameter,[51] to nearly 2 metres (6+1⁄2 ft) in bell height and diameter; the tentacles and mouth parts usually extend beyond this bell dimension.[25]
The smallest jellyfish are the peculiar creeping jellyfish in the genera Staurocladia and Eleutheria, which have bell disks from 0.5 millimetres (1⁄32 in) to a few millimeters in diameter, with short tentacles that extend out beyond this, which these jellyfish use to move across the surface of seaweed or the bottoms of rocky pools;[51] many of these tiny creeping jellyfish cannot be seen in the field without a hand lens or microscope. They can reproduce asexually by fission (splitting in half). 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;[52] 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.[53]
The lion's mane jellyfish, Cyanea capillata, was long-cited as the largest jellyfish, and arguably the longest animal in the world, with fine, thread-like tentacles that may extend up to 36.5 m (119 ft 9 in) long (though most are nowhere near that large).[54][55] They have a moderately painful, but rarely fatal, sting.[56] The increasingly common giant
The rarely encountered deep-sea jellyfish
Desmonema glaciale, which lives in the Antarctic region, can reach a very large size (several meters).[62][63] Purple-striped jelly (Chrysaora colorata) can also be extremely long (up to 15 feet).[64]
Life history and behavior
Life cycle
Jellyfish have a complex life cycle which includes both sexual and asexual phases, with the medusa being the sexual stage in most instances. 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.[65]
Upon reaching adult size, jellyfish spawn regularly if there is a sufficient supply of food. 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.[66] Jellyfish are usually either male or female (with occasional hermaphrodites). In most cases, adults release sperm and eggs into the surrounding water, where the unprotected eggs are fertilized and develop into larvae. In a few species, the sperm swim into the female's mouth, fertilizing the eggs within her body, where they remain during early development stages. In moon jellies, the eggs lodge in pits on the oral arms, which form a temporary brood chamber for the developing planula larvae.[67]
The planula is a small
After an interval and stimulated by seasonal or hormonal changes, the polyp may begin reproducing asexually by budding and, in the Scyphozoa, is called a segmenting polyp, or a scyphistoma. Budding produces more scyphistomae and also ephyrae.[25] Budding sites vary by species; from the tentacle bulbs, the manubrium (above the mouth), or the gonads of hydromedusae.[68] In a process known as strobilation, the polyp's tentacles are reabsorbed and the body starts to narrow, forming transverse constrictions, in several places near the upper extremity of the polyp. These deepen as the constriction sites migrate down the body, and separate segments known as ephyra detach. These are free-swimming precursors of the adult medusa stage, which is the life stage that is typically identified as a jellyfish.[25][72] The ephyrae, usually only a millimeter or two across initially, swim away from the polyp and grow. Limnomedusae polyps can asexually produce a creeping frustule larval form, which crawls away before developing into another polyp.[25] A few species can produce new medusae by budding directly from the medusan stage. Some hydromedusae reproduce by fission.[68]
Lifespan
Little is known of the life histories of many jellyfish as the places on the seabed where the benthic forms of those species live have not been found. However, an asexually reproducing strobila form can sometimes live for several years, producing new medusae (ephyra larvae) each year.[73]
An unusual species, Turritopsis dohrnii, formerly classified as Turritopsis nutricula,[74] might be effectively immortal because of its ability under certain circumstances to transform from medusa back to the polyp stage, thereby escaping the death that typically awaits medusae post-reproduction if they have not otherwise been eaten by some other organism. So far this reversal has been observed only in the laboratory.[75]
Locomotion
Using the moon jelly Aurelia aurita as an example, jellyfish have been shown to be the most energy-efficient swimmers of all animals.[76] They move through the water by radially expanding and contracting their bell-shaped bodies to push water behind them. They pause between the contraction and expansion phases to create two vortex rings. Muscles are used for the contraction of the body, which creates the first vortex and pushes the animal forward, but the mesoglea is so elastic that the expansion is powered exclusively by relaxing the bell, which releases the energy stored from the contraction. Meanwhile, the second vortex ring starts to spin faster, sucking water into the bell and pushing against the centre of the body, giving a secondary and "free" boost forward. The mechanism, called passive energy recapture, only works in relatively small jellyfish moving at low speeds, allowing the animal to travel 30 percent farther on each swimming cycle. Jellyfish achieved a 48 percent lower cost of transport (food and oxygen intake versus energy spent in movement) than other animals in similar studies. One reason for this is that most of the gelatinous tissue of the bell is inactive, using no energy during swimming.[77]
Ecology
Diet
Jellyfish are, like other cnidarians, generally carnivorous (or parasitic),[78] feeding on planktonic organisms, crustaceans, small fish, fish eggs and larvae, and other jellyfish, ingesting food and voiding undigested waste through the mouth. They hunt passively using their tentacles as drift lines, or sink through the water with their tentacles spread widely; the tentacles, which contain nematocysts to stun or kill the prey, may then flex to help bring it to the mouth.[25] Their swimming technique also helps them to capture prey; when their bell expands it sucks in water which brings more potential prey within reach of the tentacles.[79]
A few species such as
Predation
Other species of jellyfish are among the most common and important jellyfish predators. Sea anemones may eat jellyfish that drift into their range. Other predators include tunas, sharks, swordfish, sea turtles and penguins.[84][85] Jellyfish washed up on the beach are consumed by foxes, other terrestrial mammals and birds.[86] In general however, few animals prey on jellyfish; they can broadly be considered to be top predators in the food chain. Once jellyfish have become dominant in an ecosystem, for example through overfishing which removes predators of jellyfish larvae, there may be no obvious way for the previous balance to be restored: they eat fish eggs and juvenile fish, and compete with fish for food, preventing fish stocks from recovering.[87]
Symbiosis
Some small fish are immune to the stings of the jellyfish and live among the tentacles, serving as bait in a fish trap; they are safe from potential predators and are able to share the fish caught by the jellyfish.[88] The cannonball jellyfish has a symbiotic relationship with ten different species of fish, and with the longnose spider crab, which lives inside the bell, sharing the jellyfish's food and nibbling its tissues.[89]
Blooms
Jellyfish form large masses or blooms in certain environmental conditions of
As suspected at the turn of this century,
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, Caspian Sea, Baltic Sea, central and eastern Mediterranean, Hawaii, and tropical and subtropical parts of the West Atlantic (including the Caribbean, Gulf of Mexico and Brazil).[105][106]
Jellyfish blooms can have significant impact on community structure. Some carnivorous jellyfish species prey on zooplankton while others graze on primary producers.[110] Reductions in zooplankton and ichthyoplankton due to a jellyfish bloom can ripple through the trophic levels. High-density jellyfish populations can outcompete other predators and reduce fish recruitment.[111] Increased grazing on primary producers by jellyfish can also interrupt energy transfer to higher trophic levels.[112]
During blooms, jellyfish significantly alter the nutrient availability in their environment. Blooms require large amounts of available organic nutrients in the water column to grow, limiting availability for other organisms.[113] Some jellyfish have a symbiotic relationship with single-celled dinoflagellates, allowing them to assimilate inorganic carbon, phosphorus, and nitrogen creating competition for phytoplankton.[113] Their large biomass makes them an important source of dissolved and particulate organic matter for microbial communities through excretion, mucus production, and decomposition.[90][114] The microbes break down the organic matter into inorganic ammonium and phosphate. However, the low carbon availability shifts the process from production to respiration creating low oxygen areas making the dissolved inorganic nitrogen and phosphorus largely unavailable for primary production.
These blooms have very real impacts on industries. Jellyfish can outcompete fish by utilizing open niches in over-fished fisheries.[115] Catch of jellyfish can strain fishing gear and lead to expenses relating to damaged gear. Power plants have been shut down due to jellyfish blocking the flow of cooling water.[116] Blooms have also been harmful for tourism, causing a rise in stings and sometimes the closure of beaches.[117]
Jellyfish form a component of
Habitats
Most jellyfish are marine animals, although a few hydromedusae inhabit
Although most jellyfish live well off the ocean floor and form part of the plankton, a few species are closely associated with the bottom for much of their lives and can be considered
Some species explicitly adapt to
Parasites
Jellyfish are
Relation to humans
Fisheries
Jellyfish have long been eaten in some parts of the world.
Jellyfish are also harvested for their collagen, which is being investigated for use in a variety of applications including the treatment of rheumatoid arthritis.[127]
Aquaculture and fisheries of other species often suffer severe losses – and so losses of productivity – due to jellyfish.[128][129]
Products
Aristotle stated in the Parts of Animals IV, 6 that jellyfish (sea-nettles) were eaten in wintertime in a fish stew.[130]
In some countries, including China, Japan, and Korea, jellyfish are a delicacy. The jellyfish is dried to prevent spoiling. Only some 12 species of scyphozoan jellyfish belonging to the order Rhizostomeae are harvested for food, mostly in southeast Asia.[131] Rhizostomes, especially Rhopilema esculentum in China (海蜇 hǎizhé, 'sea stingers') 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.[126]
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
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.[126][132] Desalted, ready-to-eat products are also available.[126]
Biotechnology
Pliny the Elder reported in his Natural History that the slime of the jellyfish "Pulmo marinus" produced light when rubbed on a walking stick.[133]
In 1961,
Aquarium display
Jellyfish are displayed in many public aquariums. 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.[138] Jellyfish are not adapted to closed spaces. They depend on currents to transport them from place to place. Professional exhibits as in the Monterey Bay Aquarium feature precise water flows, typically in circular tanks to avoid trapping specimens in corners. The outflow is spread out over a large surface area and the inflow enters as a sheet of water in front of the outflow, so the jellyfish do not get sucked into it.[139] As of 2009, jellyfish were becoming popular in home aquariums, where they require similar equipment.[140]
Stings
Jellyfish are armed with nematocysts, a type of specialized stinging cell.[141] Contact with a jellyfish tentacle can trigger millions of nematocysts to pierce the skin and inject venom,[142] but only some species' venom causes an adverse reaction in humans.[143] In a study published in Communications Biology, researchers found a jellyfish species called Cassiopea xamachana which when triggered will release tiny balls of cells that swim around the jellyfish stinging everything in their path. Researchers described these as "self-propelling microscopic grenades" and named them cassiosomes.[144]
The effects of stings range from mild discomfort to extreme pain and death.
Vinegar (3–10% aqueous
In Elba Island and Corsica dittrichia viscosa is now used by residents and tourists to heal stings from jellyfish, bees and wasps by pressing fresh leaves on the skin with quick results.
-
Box jellyfish are small and venomous.
-
Jellyfish dermatitis
-
A flag in the beach of Zarautz alerting about the presence of jellyfish in the water
Mechanical issues
Jellyfish in large quantities can fill and split fishing nets and crush captured fish.
See also
- Jellyfish dermatitis
- List of prehistoric medusozoans
- Ocean sunfish, a significant jellyfish predator
- Ctenophora
Notes
References
- ^ "Fossil Record Reveals Elusive Jellyfish More Than 500 Million Years Old". ScienceDaily. Retrieved 10 February 2023.
- ^ a b c Angier, Natalie (6 June 2011). "So Much More Than Plasma and Poison". The New York Times. Archived from the original on 18 May 2013. Retrieved 2 December 2011.
- ^ a b Isabelle Rodd (20 October 2020). "Why jellyfish could be a 'perfect food'". BBC News. Retrieved 7 May 2023.
- ^ a b "jellyfish". Online Etymology Dictionary. Retrieved 9 June 2018.
- OL 7043926M.
- ISBN 978-0-618-00211-5.
- ^ "Flower Hat Jelly". 6 April 2009. Archived from the original on 6 April 2009. Retrieved 10 February 2023.
- ^ "What is a Fish?". Encyclopedia of Life. Archived from the original on 24 March 2018. Retrieved 13 October 2018.
And most people know that lampreys, sharks, rays, eels, seahorses, and other strange-looking aquatic creatures are fishes, while shellfish, cuttlefish, starfish, crayfish, and jellyfish (despite their names) are not fishes.
- ^ Brotz, Lucas. Changing Jellyfish Populations: Trends in Large Marine Ecosystems Archived 16 April 2013 at the Wayback Machine. 2011. p.1.
- ISBN 978-0-671-76503-3. Archivedfrom the original on 31 December 2013. Retrieved 20 March 2013.
- ^ Klappenbach, Laura. "Ten Facts about Jellyfish". Archived from the original on 26 February 2009. Retrieved 24 January 2010.
- ISBN 978-0-670-30044-0.
- ISBN 978-1-444-19376-3.
- PMID 17971881.
- ^ "Jellyfish". Merriam-Webster. 1 September 2018. Retrieved 11 September 2018.
- ^ a b c d e f g h i "Jellyfish Spotting | Species of Jellyfish". Policy-oriented marine Environmental Research in the Southern European Seas (PERSEUS). Retrieved 28 August 2018.
- ^ a b Mills, C. E. (8 November 2010). "Ctenophores". University of Washington. Retrieved 28 August 2018.
- ^ a b "Our jelly-like relatives: Common misconceptions about salps". Nereus Program. Retrieved 28 August 2018.
- ^ PMID 26465609.
- PMC 5932825.
- ^ "STAUROMEDUSAE UK An online guide to the Stalked jellyfish (Stauromedusae) found around the coastal waters of the United Kingdom and Ireland. Includes notes on their identification, and where and how to find them. BACK UK Checklist for Stalked jellyfish (Stauromedusae)". Stauromedusae UK. Retrieved 28 August 2018.
- PMID 29281657.
- ^ Osborn, K. J. (2014). "Red Paper Lantern Jellyfish". Smithsonian. Retrieved 13 October 2018.
- ^ Daley, Jason (1 March 2017). "Take a Peek at the Mesmerizing 'Cosmic Jellyfish'". Smithsonian. Retrieved 28 August 2018.
- ^ ISBN 978-81-315-0104-7.)
{{cite book}}
: CS1 maint: multiple names: authors list (link - ^ a b Cnidaria Archived 2012-09-21 at the Wayback Machine, Tree of Life.
- S2CID 28342963.
- .
- PMID 37528711.
- .
- ^ "Jellyfish - Visual Dictionary". infovisual.info. Retrieved 10 February 2023.
- ^ Waggoner, Ben; Collins, Allen G. "Cubozoa: More on Morphology". University of California Museum of Paleontology. Retrieved 6 January 2019.
- ^ "Nematocysts". Jellieszone. 2 April 2015. Archived from the original on 2 April 2015. Retrieved 29 March 2014.
- PMID 22442361.
- doi:10.1139/z02-138. Archived from the original(PDF) on 12 July 2013.
- PMID 23885868.
- PMID 21430196.
- (PDF) from the original on 29 July 2013.
- ^ "Multi-eyed jellyfish helps with Darwin's puzzle". New Scientist. Retrieved 10 February 2023.
- ^ PMID 23578808.
- ^ )
- PMID 20660753.
- ^ S2CID 9563849.
- S2CID 4418085.
- ^ PMID 15558464.
- ^ S2CID 24400231.
- ^ S2CID 85422599.
- S2CID 13344739.
- ^ S2CID 19797109.
- ^ S2CID 219759193.
- ^ ISBN 978-0-520-25118-2.
- JSTOR 1540715.
- .
- ^ "Rare sighting of a lion's mane jellyfish in Tramore Bay". Waterford Today. 1 August 2007. Archived from the original on 30 May 2010. Retrieved 18 October 2010.
- ^ "Lion's Mane Jellyfish – Reference Library". redOrbit. 12 June 2003. Archived from the original on 30 July 2010. Retrieved 18 October 2010.
- ^ "150 Stung By Jellyfish At Rye Beach". Wmur.com. 21 July 2010. Archived from the original on 14 October 2011. Retrieved 11 June 2018.
- ^ Omori, Makoto; Kitamura, Minoru (2004). "Taxonomic review of three Japanese species of edible jellyfish (Scyphozoa: Rhizostomeae)" (PDF). Plankton Biology and Ecology. 51 (1): 36–51. Archived (PDF) from the original on 23 March 2012.
- (PDF) from the original on 16 May 2013.
- ^ "Giant Echizen jellyfish off Japan coast". BBC. 30 November 2009. Archived from the original on 1 January 2011.
- .
- ^ Bourton, Jody (23 April 2010). "Giant deep sea jellyfish filmed in Gulf of Mexico". BBC Earth News. Archived from the original on 5 July 2010.
- ^ "Photos of Antarctic Giant Jelly (Desmonema glaciale) • iNaturalist".
- ^ League, Michael (11 October 2011). "The Way to End a Dive". PolarTREC. McMurdo Station, Antarctica.
- ^ "Diving underwater with giant jellyfish". 26 April 2010.
- ^ "How do jellyfish reproduce? What effect does their sting have on humans? What's the difference between red and translucent jellyfish?". Scientific American. 15 October 2013. Archived from the original on 23 October 2013. Retrieved 22 October 2013.
- S2CID 13914997.
- ^ Bishop, Andrew. "Moon Jelly (Aurelia aurita)". Marine Invertebrates of Bermuda. Retrieved 11 June 2018.
- ^ )
- S2CID 4078889.
- ^ Schuchert, Peter. "The Hydrozoa". Archived from the original on 4 February 2010. Retrieved 24 January 2010.
- ^ "How Jellyfish Grow, From Eggs to Polyps to Medusas". ThoughtCo. Retrieved 10 February 2023.
- ^ Hughes, Clare. "Lifecycle of the Box Jellyfish". Artforlibraries.org. Archived from the original on 4 March 2016. Retrieved 2 January 2016.
- ISBN 978-1-60535-375-3.
- .
- S2CID 3956265.
- ^ Rathi, Akshat (15 May 2014). "Jellyfish are the most energy-efficient swimmers, new metric confirms". Ars Technica. Archived from the original on 3 November 2014. Retrieved 3 December 2014.
- PMID 24101461.
- ISBN 978-1-60535-375-3.
All cnidarians are carnivores (or parasites). Typically, nematocyst-laden feeding tentacles capture animal prey and carry it to the mouth region where it is ingested whole.
- ^ "Bigger jellyfish inheriting the ocean, study finds". msnbc.com. 15 September 2011. Archived from the original on 14 July 2014. Retrieved 3 December 2014.
- ^ Davies, C.H.; Slotwinski, A.S. "Australian Marine Zooplankton-Jellyfish, Cladocerans" (PDF). Institute for Marine and Antarctic Studies, University of Tasmania. Retrieved 12 October 2018.
- .
- ^ )
- ^ Nemo, Leslie (13 February 2020). "Venomous Snot Helps These Jellyfish Sting Without Their Tentacles". Discover. Retrieved 11 July 2021.
- ^ Yin, Steph (29 September 2017). "Who's Eating Jellyfish? Penguins, That's Who". The New York Times. Archived from the original on 1 October 2017. Retrieved 4 October 2017.
- S2CID 90152409.
- ISBN 978-0-226-28767-6.
- ISBN 978-0-226-02010-5. Archivedfrom the original on 6 August 2016.
- ^ colugo7 (2006). "The jellyfish". Tree of Life Web Project. Archived from the original on 12 June 2018. Retrieved 7 June 2018.
{{cite web}}
: CS1 maint: numeric names: authors list (link) - ^ Griffin, DuBose B.; Murphy, Thomas M. "Cannonball Jellyfish" (PDF). South Carolina Department of Natural Resources. Archived from the original (PDF) on 19 January 2008. Retrieved 7 June 2018.
- ^ .
- ^ Gill, Victoria. "Jellyfish 'can sense ocean currents'". BBC News. Archived from the original on 26 January 2015. Retrieved 26 January 2015.
- PMID 28586681.
- ^ Shubin, Kristie (10 December 2008). "Anthropogenic Factors Associated with Jellyfish Blooms – Final Draft II". Tropical Field Courses: Western Program: Miami University. Archived from the original on 14 June 2010. Retrieved 19 November 2009.
- ^ "What is a dead zone?". National Ocean Service. Retrieved 3 October 2018.
- ^ Yong, Ed (6 June 2011). "Jellyfish shift ocean food webs by feeding bacteria with mucus and excrement". Discover Magazine. Archived from the original on 6 November 2018. Retrieved 3 October 2018.
- ^ a b "Jellyfish blooms could be sign of ailing seas". www.eurocbc.org. Retrieved 10 February 2023.
- (PDF) from the original on 25 December 2012.
- (PDF) from the original on 10 July 2012.
- PMID 19324452.[permanent dead link]
- .
- (PDF) from the original on 23 March 2011.
- S2CID 12415790. Archived from the original(PDF) on 12 July 2013.
- PMID 16103373.
- S2CID 189820003.
- ^ a b Rinat, Zafrir (15 June 2009). "World's Most Invasive Jellyfish Spreading Along Israel Coast". Haaretz. Retrieved 13 October 2018.
- ^ Briand, Frederic; Boero, Ferdinando (2001). "Gelatinous zooplankton outbreaks - an overview on jellyfish blooms". CIESM Monographs. 14: 5-17.
- (PDF) from the original on 3 March 2016.
- ^ "CIESM GIS". www.ciesm.org. Retrieved 10 February 2023.
- S2CID 27615539.
- .
- .
- ^ S2CID 22838905.
- PMID 23277544.
- S2CID 62793057.
- ^ Masilamani, J; Jesudoss, K; Kanavillil, Nandakumar; et al. (10 September 2000). "Jellyfish ingress: A threat to the smooth operation of coastal power plants". Current Science. 79: 567–569.
- .
- PMID 25320167.
- S2CID 3693276.
- ^ Didžiulis, Viktoras. "Invasive Alien Species Fact Sheet: Craspedacusta sowerbyi" (PDF). NOBANIS. Archived (PDF) from the original on 17 May 2014. Retrieved 16 June 2016.
- )
- ^ Mills, C. E.; Hirano, Y. M. (2007). "Stauromedusae". Encyclopedia of Tidepools and Rocky Shores: 541–543.
- from the original on 4 November 2017.
- ^ Leung, Tommy (26 May 2016). "Opechona olssoni". Blog: Parasite of the Day. Archived from the original on 30 June 2016. Retrieved 1 June 2016.
- ^ "FAOSTAT". www.fao.org. Retrieved 10 February 2023.
- ^ S2CID 20719121.
- ^ George, Aleta (1 November 2012). "Jellies in the Spotlight". Endocrine News. Endocrine Society. Retrieved 16 June 2018.
- ISSN 1054-3139.
- S2CID 225330785.
- ]
- S2CID 6518460.
- ISBN 978-0-442-22399-1.
- ^ "How the Jelly Got Its Glow". American Museum of Natural History. Archived from the original on 12 June 2018. Retrieved 11 June 2018.
- ^ PMID 13911999.
- PMID 1347277.
- S2CID 9043327.
- ISBN 978-0-674-02413-7.
- ISBN 978-0-19-854956-7.
- ^ "US Patent for Jellyfish Tank". Archived from the original on 20 February 2015.
- ^ Richtel, Matt (14 March 2009). "How to Avoid Liquefying Your Jellyfish". The New York Times. Archived from the original on 26 March 2010. Retrieved 6 May 2010.
- PMID 37272501.
- ^ Purves, W.K.; Sadava, D.; Orians, G.H.; Heller, H.C. 1998. Life. The Science of Biology. Part 4: The Evolution of Diversity. Chapter 31
- ^ "Jellyfish Tanks and live pet Jellyfish for sale at Jellyfish Art – Buy Jellyfish and Jellyfish tanks". jellyfishart.com. Archived from the original on 2 March 2012. Retrieved 3 December 2014.
- ISSN 0362-4331. Retrieved 27 February 2020.
- S2CID 225837493.
- ^ S2CID 12532183.
- ^ Adams, Julie (13 August 2016). "Box Jellyfish: Why are they so deadly?". Our Beautiful Planet. Archived from the original on 10 September 2016. Retrieved 17 September 2016.
- ^ S2CID 42453046.
- S2CID 19857333.
- S2CID 204054168.
- ^ PMID 14989575.
- PMID 25517656.
- PMID 4156430.
- ^ "Jellyfish Stings: Treatment and Drugs". Mayo Clinic. Mayo Foundation for Medical Education and Research. 1 September 2011. Archived from the original on 20 May 2013. Retrieved 15 April 2013.
- ^ a b "Jellyfish Gone Wild — Text-only". Nsf.gov. Archived from the original on 12 July 2010. Retrieved 18 October 2010.
- ^ "Current Event Notification Report". NRC. 22 October 2008. Archived from the original on 5 June 2011. Retrieved 14 July 2010.
- ^ Ryall, Julian (2 November 2009). "Japanese fishing trawler sunk by giant jellyfish". London: Telegraph.co.uk. Archived from the original on 4 November 2009.
Further reading
- Juli Berwald (2017). Spineless: The Science of Jellyfish and the Art of Growing a Backbone. Riverhead Books. ISBN 978-0-7352-1126-1.
External links
- Jellyfish and Comb Jellies – Smithsonian Ocean Portal
- Jellyfish Facts – Information on Jellyfish and Jellyfish Safety
- "There's no such thing as a jellyfish" from The MBARI YouTube channel
- "Vicious beauties – Jellyfish" – a documentary about jellyfish
- They're Taking Over! nybooks.com September 26, 2013. Tim Flannery
- Photos