
The Scyphozoa are an exclusively marine class of the
phylum
In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead ...
Cnidaria
Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), including jellyfish, hydroid (zoology), hydroids, ...
, referred to as the true
jellyfish
Jellyfish, also known as sea jellies or simply jellies, are the #Life cycle, 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 animal ...
(or "true jellies").
The class name Scyphozoa comes from the
Greek
Greek may refer to:
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group
*Greek language, a branch of the Indo-European language family
**Proto-Greek language, the assumed last common ancestor of all kno ...
word ''
skyphos
A skyphos (; : skyphoi) is a two-handled deep wine-cup on a low flanged base or none. The handles may be horizontal ear-shaped thumbholds that project from the rim (in both Corinthian and Athenian shapes), or they may be loop handles at the rim ...
'' (), denoting a kind of drinking cup and alluding to the cup shape of the organism.
Scyphozoans have existed from the earliest
Cambrian
The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...
to the present.
Biology
Most species of Scyphozoa have two life-history phases, including the planktonic
medusa
In Greek mythology, Medusa (; ), also called Gorgo () or the Gorgon, was one of the three Gorgons. Medusa is generally described as a woman with living snakes in place of hair; her appearance was so hideous that anyone who looked upon her wa ...
or
polyp form, which is most evident in the warm summer months, and an inconspicuous, but longer-lived, bottom-dwelling polyp, which seasonally gives rise to new medusae. Most of the large, often colorful, and conspicuous jellyfish found in coastal waters throughout the world are Scyphozoa.
They typically range from in diameter, but the largest species, ''
Cyanea capillata
The lion's mane jellyfish (''Cyanea capillata'') is one of the Largest organisms#Cnidarians (Cnidaria), largest known species of jellyfish. Its range is confined to cold, boreal ecosystem, boreal waters of the Arctic Ocean, Arctic, northern Atla ...
'' can reach across. Scyphomedusae are found throughout the world's oceans, from the surface to great depths; no Scyphozoa occur in freshwater (or on land).
As medusae, they eat a variety of crustaceans and fish, which they capture using stinging cells called
nematocysts
A cnidocyte (also known as a cnidoblast) is a type of cell containing a large secretory organelle called a ''cnidocyst'', that can deliver a sting to other organisms as a way to capture prey and defend against predators. A cnidocyte explosively ...
. The nematocysts are located throughout the tentacles that radiate downward from the edge of the umbrella dome, and also cover the four or eight oral arms that hang down from the central mouth. Some species, however, are instead filter feeders, using their tentacles to strain
plankton
Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...
from the water.
Anatomy
Scyphozoans usually display a four-part symmetry and have an internal gelatinous material called
mesoglea
Mesoglea refers to the extracellular matrix found in cnidarians like coral or jellyfish as well as ctenophores that functions as a hydrostatic skeleton. It is related to but distinct from mesohyl, which generally refers to extracellular material f ...
, which provides the same structural integrity as a skeleton. The mesoglea includes mobile amoeboid cells originating from the epidermis.
Scyphozoans have no durable hard parts, including no head, no skeleton, and no specialized organs for respiration or excretion. Marine jellyfish can consist of as much as 98% water, so are rarely found in fossil form.
Unlike the
hydrozoan
Hydrozoa (hydrozoans; from Ancient Greek ('; "water") and ('; "animals")) is a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial sp ...
jellyfish, Hydromedusae, Scyphomedusae lack a vellum, which is a circular membrane beneath the umbrella that helps propel the (usually smaller) Hydromedusae through the water. However, a ring of muscle fibres is present within the mesoglea around the rim of the dome, and the jellyfish swims by alternately contracting and relaxing these muscles. The periodic contracting and relaxing propels the jellyfish through the water, allowing it to escape predation or catch its prey.
The mouth opens into a central stomach, from which four interconnected
diverticula
In medicine or biology, a diverticulum is an outpouching of a hollow (or a fluid-filled) structure in the body. Depending upon which layers of the structure are involved, diverticula are described as being either true or false.
In medicine, t ...
radiate outwards. In many species, this is further elaborated by a system of radial canals, with or without an additional ring canal towards the edge of the dome. Some genera, such as ''
Cassiopea
''Cassiopea'' (upside-down jellyfish) is a genus of Scyphozoa, true jellyfish and members of the family Cassiopeidae. They are found in warmer coastal regions around the world, including shallow mangrove swamps, mudflats, canals, and turtle gras ...
'', even have additional, smaller mouths in the oral arms. The lining of the digestive system includes further stinging nematocysts, along with cells that secrete
digestive enzyme
Digestive enzymes take part in the chemical process of digestion, which follows the mechanical process of digestion. Food consists of macromolecules of proteins, carbohydrates, and fats that need to be broken down chemically by digestive enzymes ...
s.
[
The nervous system usually consists of a distributed net of cells, although some species possess more organised nerve rings. In species lacking nerve rings, the nerve cells are instead concentrated into small structures called '']rhopalia
Rhopalia (singular: rhopalium) from Ancient Greek ῥόπαλον (''rhópalon'') 'club' are small sensory structures of certain Scyphozoan (true jellyfish) and Cubozoan (box jellyfish) species.
Description
The structures typically occur in mul ...
''. There are between four and sixteen of these small lobes arranged around the rim of the umbrella, where they coordinate the muscular action allowing the animal to move. Each rhopalium is typically associated with a pair of sensory pits, a statocyst
The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, ctenophorans, echinoderms, cephalopods, crustaceans, and gastropods, A similar structure is also found in '' Xenoturbella''. T ...
, and sometimes a pigment-cup ocellus
A simple eye or ocellus (sometimes called a pigment pit) is a form of eye or an optical arrangement which has a single lens without the sort of elaborate retina that occurs in most vertebrates. These eyes are called "simple" to distinguish the ...
.[
]
Reproduction
Most species appear to be gonochorists
In biology, gonochorism is a sexual system where there are two sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric.
Gonochorism contrast ...
, with separate male and female individuals. The gonad
A gonad, sex gland, or reproductive gland is a Heterocrine gland, mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gon ...
s are located in the stomach lining, and the mature gamete
A gamete ( ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also referred to as s ...
s are expelled through the mouth. After fertilization, some species brood their young in pouches on the oral arms, but they are more commonly planktonic.[
]
Growth and development
The fertilized egg produces a planula
A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species and also in some species of Ctenophores, which are not related to cnidarians at all. Some groups of Nemerteans also produce larva ...
r larva which, in most species, quickly attaches itself to the sea bottom. The larva develops into the hydroid stage of the lifecycle, a tiny sessile polyp called a scyphistoma. The scyphistoma reproduces asexually, producing similar polyps by budding, and then either transforming into a medusa, or budding several medusae off from its upper surface via a process called strobilation
Strobilation or transverse fission is a form of asexual reproduction consisting of the spontaneous transverse segmentation of the body. It is observed in certain cnidarians and helminths. This mode of reproduction is characterized by high offspri ...
. The medusae are initially microscopic and may take years to reach sexual maturity.[
]
Commercial importance
Scyphozoa include the moon jelly ''Aurelia aurita
''Aurelia aurita'' (also called the common jellyfish, moon jellyfish, moon jelly or saucer jelly) is a species of the family (biology), family Ulmaridae. All species in the genus are very similar, and it is difficult to identify ''Aurelia (cnida ...
'', in the order Semaeostomeae, and the enormous ''Nemopilema nomurai
is a very large rhizostome jellyfish, in the same size class as the lion's mane jellyfish, the largest cnidarian in the world. It is edible but not considered high quality. It is the only species in the monotypic genus ''Nemopilema.'' Commonl ...
'', in the order Rhizostomeae, found between Japan and China and which in some years causes major fisheries disruptions.
The jellyfish fished commercially for food are Scyphomedusae in the order Rhizostomeae
Rhizostomeae is an order of jellyfish. Species of this order have neither tentacles nor other structures at the bell's edges. Instead, they have eight highly branched oral arms, along which there are suctorial minimouth orifices. (This is in cont ...
. Most rhizostome jellyfish live in warm water.
Taxonomy
Although the Scyphozoa were formerly considered to include the animals now referred to as the classes Cubozoa
Box jellyfish (class Cubozoa) are cnidarian invertebrates distinguished by their box-like (i.e., cube-shaped) body. Some species of box jellyfish produce potent venom (poison), venom delivered by contact with their tentacles. Stings from some spec ...
and Staurozoa
Staurozoa is a class of Medusozoa (or jellyfish). It has one extant order: Stauromedusae (stalked jellyfishes) with a total of 50 known species. A fossil group called Conulariida has been proposed as a second order, although this is highly spec ...
, they now include just three extant
Extant or Least-concern species, least concern is the opposite of the word extinct. It may refer to:
* Extant hereditary titles
* Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English
* Exta ...
orders (two of which are in Discomedusae, a subclass of Scyphozoa).[Daly, Brugler, Cartwright, Collins, Dawson, Fautin, France, McFadden, Opresko, Rodriguez, Romano & Stake (2007). ]
The phylum Cnidaria: A review of phylogenetic patterns and diversity 300 years after Linnaeus.
' Zootaxa 1668: 127–182 About 200 extant species are recognized at present, but the true diversity is likely to be at least 400 species.[
Class Scyphozoa
*Subclass ]Coronamedusae
Coronamedusae is a subclass of jellyfish
Jellyfish, also known as sea jellies or simply jellies, are the #Life cycle, medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria. Jell ...
:* Order Coronatae
Crown jellyfishes are the six families of true jellyfish that belong to the order Coronatae.Daly, Brugler, Cartwright, Collins, Dawson, Fautin, France, McFadden, Opresko, Rodriguez, Romano & Stake (2007). The phylum Cnidaria: A review of phyloge ...
:::* Family Atollidae
''Atolla'' is a genus of crown jellyfish in the order Coronatae. The genus ''Atolla'' was originally proposed by Haeckel in 1880 and elevated to the monotypic family level, as Atollidae by Henry Bigelow in 1913. The six known species inhabit t ...
:::* Family Atorellidae
''Atorella'' is a genus of crown jellyfish. It is the only genus in the monotypic family Atorellidae and includes five species. Members of this family are known from the eastern coast of Africa and the western coast of Panama.
Characteristics
Me ...
:::* Family Linuchidae
Linuchidae is a family of crown jellyfish.Collins, A.G.; Morandini, A.C. (2023). World List of ScyphozoaLinuchidae Haeckel, 1880 Accessed through World Register of Marine Species on 2023-06-06.
Species
*'' Linantha''
**'' Linantha lunulata''
*' ...
:::* Family Nausithoidae
Nausithoidae is a family of jellyfish.
Genera
*''Nausithoe''
** '' Nausithoe albatrossi'' (Maas, 1897)
** '' Nausithoe atlantica'' (Broch, 1914)
** '' Nausithoe aurea'' Da Silveira & Morandini, 1997
** '' Nausithoe challengeri'' (Haeckel, 1880)
...
:::* Family Paraphyllinidae
:::* Family Periphyllidae
Periphyllidae is a family of jellyfish containing four genera and six species. The most well-known member of the family, ''Periphylla periphylla'', is usually considered a deep-sea species, but it forms large blooms in surface waters of Norwegian ...
* Subclass Discomedusae
Discomedusae is a subclass of jellyfish in the class Scyphozoa. It is the sister taxon of Coronamedusae. Discomedusae contains about 155 named species and there are likely to be many more as yet Undescribed taxon, undescribed. Jellyfish in this ...
:* Order Rhizostomeae
Rhizostomeae is an order of jellyfish. Species of this order have neither tentacles nor other structures at the bell's edges. Instead, they have eight highly branched oral arms, along which there are suctorial minimouth orifices. (This is in cont ...
::* Suborder Daktyliophorae
:::* Family Catostylidae
Catostylidae is a family of jellyfish, their common name is fat-armed jellies. Members of this family are characterized by their thick, sausage-like oral arms. Members of the family Catostylidae are small marine jellyfish with domed bells. The ei ...
:::* Family Lobonematidae
Lobonematidae is a family of jellyfishes belonging to the order Rhizostomeae
Rhizostomeae is an order of jellyfish. Species of this order have neither tentacles nor other structures at the bell's edges. Instead, they have eight highly branche ...
:::* Family Lychnorhizidae
Lychnorhizidae is a family of Scyphozoa, true jellyfish.
Species
The following species are recognized in the family Lychnorhizidae:
* ''Anomalorhiza''
:*''Anomalorhiza shawi'' Light, 1921
* ''Lychnorhiza''
:*''Lychnorhiza arubae'' Stiasny, 192 ...
:::* Family Rhizostomatidae
Rhizostomatidae is a family of cnidarians in the class Scyphozoa.
Genera and species
According to the World Register of Marine Species, 11 extant species are in four extant genera within this family:
*Genus ''Eupilema''
**'' Eupilema inexpectat ...
:::* Family Stomolophidae
''Stomolophus'' is a genus of true jellyfish from the West Atlantic and Pacific. It is the only genus in the monotypic family Stomolophidae. Formerly, Nomura's jellyfish (''Nemopilema nomurai'') was also included in this genus, but has now been r ...
::* Suborder Kolpophorae
:::* Family Cassiopeidae
''Cassiopea'' (upside-down jellyfish) is a genus of true jellyfish and members of the family Cassiopeidae. They are found in warmer coastal regions around the world, including shallow mangrove swamps, mudflats, canals, and turtle grass flats in ...
:::* Family Cepheidae
Cepheidae may refer to:
* Cepheidae (jellyfish), a family of jellyfish in the order Rhizostomeae
* Cepheidae (mite), a family of mites in the order Sarcoptiformes
The Sarcoptiformes are an order (biology), order of mites comprising over 15,000 d ...
:::* Family Mastigiidae
Mastigiidae is a family of Scyphozoa, true jellyfish. The family is native to the Indo-Pacific, but a species of ''Mastigias'' has been Introduced species, introduced to the West Atlantic, and ''Phyllorhiza punctata'' has been introduced to the W ...
:::* Family Thysanostomatidae
:::* Family Versurigidae
''Versuriga'' is a monotypic genus of jellyfishes belonging to the monotypic family Versurigidae. The only species is ''Versuriga anadyomene''. This species is rare, only having been sighted in a limited region. However, it can be identified by ...
:* Order Semaeostomeae
Semaeostomeae (literally "flag mouths") 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 unbra ...
:::* Family Cyaneidae
The Cyaneidae are a family of true jellyfish. About 20 species are in this family, including the well-known lion's mane jellyfish, lion's-mane jellyfish.
Species
The following species are recognized within the family Cyaneidae. Formerly, this f ...
:::* Family Drymonematidae
''Drymonema'' is a genus of true jellyfish, placed in its own family, the Drymonematidae. There are three species: '' Drymonema dalmatinum'', '' Drymonema gorgo'', and '' Drymonema larsoni'', which are found in the Gulf of Mexico, Atlantic Ocean ...
[Bayha, K. M., and M. N. Dawson (2010). ''New family of allomorphic jellyfishes, Drymonematidae (Scyphozoa, Discomedusae), emphasizes evolution in the functional morphology and trophic ecology of gelatinous zooplankton.'' ]The Biological Bulletin
''The Biological Bulletin'' is a peer review, peer-reviewed scientific journal covering the field of biology. The journal was established in 1897 as the ''Zoological Bulletin'' by Charles Otis Whitman and William Morton Wheeler. In 1899 the title ...
219(3): 249–267
:::* Family Pelagiidae
The Pelagiidae are a family of jellyfish. Members of the family ''Pelagiidae'' have no ring canal, and the marginal tentacles arise from umbrella margin.
Genera
There are four genera currently recognized:
*Genus '' Chrysaora'' – (14 species)
...
:::* Family Phacellophoridae
''Phacellophora'', commonly known as the fried egg jellyfish or egg-yolk jellyfish, is a very large jellyfish in the monotypic family Phacellophoridae containing a single species ''Phacellophora camtschatica''. This genus can be easily identified ...
:::* Family Ulmaridae
The Ulmaridae are a family of jellyfish, which includes the famous moon jellies, and other jellyfish with unique characteristics like '' Tiburonia granrojo''.
Genera
Formerly, the genus '' Phacellophora'' was also included in this family, but ...
References
External links
The Classification and Distribution of the Class Scyphozoa
*
{{Authority control
Medusozoa
Ediacaran first appearances