Scyphozoa

Last updated

Scyphozoa
Temporal range: Fortunian – Recent [1]
Cauliflour Jellyfish, Cephea cephea at Marsa Shouna, Red Sea, Egypt SCUBA.jpg
Cephea cephea
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Cnidaria
Subphylum: Medusozoa
Class: Scyphozoa
Götte, 1887
Subgroups

See text.

Fossilized stranded scyphozoans on a Cambrian tidal flat at Blackberry Hill, Wisconsin. Stranded Cambrian scyphozoans.jpg
Fossilized stranded scyphozoans on a Cambrian tidal flat at Blackberry Hill, Wisconsin.

The Scyphozoa are an exclusively marine class of the phylum Cnidaria, [2] referred to as the true jellyfish (or "true jellies").

Contents

The class name Scyphozoa comes from the Greek word skyphos ( σκύφος ), denoting a kind of drinking cup and alluding to the cup shape of the organism. [3]

Scyphozoans have existed from the earliest Cambrian to the present. [1]

Biology

Most species of Scyphozoa have two life-history phases, including the planktonic medusa 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. [4] They typically range from 2 to 40 cm (1 to 15+1⁄2 in) in diameter, but the largest species, Cyanea capillata can reach 2 metres (6 ft 7 in) 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. 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 from the water. [5]

Anatomy

Scyphozoans usually display a four-part symmetry and have an internal gelatinous material called mesoglea, 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. [6] [7] Marine jellyfish can consist of as much as 98% water, so are rarely found in fossil form.

Unlike the hydrozoan 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. [8] 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 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 , 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 enzymes. [5]

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 . 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, and sometimes a pigment-cup ocellus. [5]

Reproduction

The developmental stages of scyphozoan jellyfish's life cycle: 1-3 Larva searches for site 4-8 Polyp grows 9-11 Polyp strobilates 12-14 Medusa grows Schleiden-meduse-2.jpg
The developmental stages of scyphozoan jellyfish's life cycle:
1–3 Larva searches for site
4–8 Polyp grows
9–11 Polyp strobilates
12–14 Medusa grows

Most species appear to be gonochorists, with separate male and female individuals. The gonads are located in the stomach lining, and the mature gametes are expelled through the mouth. After fertilization, some species brood their young in pouches on the oral arms, but they are more commonly planktonic. [5]

Growth and development

The fertilized egg produces a planular 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. The medusae are initially microscopic and may take years to reach sexual maturity. [5]

Commercial importance

Scyphozoa include the moon jelly Aurelia aurita , [9] in the order Semaeostomeae, and the enormous Nemopilema nomurai , 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. [10] Most rhizostome jellyfish live in warm water. [4]

Taxonomy

Although the Scyphozoa were formerly considered to include the animals now referred to as the classes Cubozoa and Staurozoa, they now include just three extant orders (two of which are in Discomedusae, a subclass of Scyphozoa). [11] [12] About 200 extant species are recognized at present, but the true diversity is likely to be at least 400 species. [11]

Class Scyphozoa

Related Research Articles

<span class="mw-page-title-main">Cnidaria</span> Aquatic animal phylum having cnydocytes

Cnidaria is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter.

<span class="mw-page-title-main">Jellyfish</span> Soft-bodied, aquatic invertebrates

Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, 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 highly 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 that disperse widely and enter a sedentary polyp phase before reaching sexual maturity.

<i>Aurelia aurita</i> Species of jellyfish

Aurelia aurita is a species of the genus Aurelia. All species in the genus are very similar, and it is difficult to identify Aurelia medusae without genetic sampling; most of what follows applies equally to all species of the genus. The most common method used to identify the species consists of selecting a jellyfish from a harbour using a device, usually a drinking glass and then photographing the subject. This means that they can be released in to the harbour shortly afterwards and return to their natural habitat.

<span class="mw-page-title-main">Hydrozoa</span> Class of cnidarians

Hydrozoa are 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 species can be large, and in some cases the specialized individual animals cannot survive outside the colony. A few genera within this class live in freshwater habitats. Hydrozoans are related to jellyfish and corals and belong to the phylum Cnidaria.

<span class="mw-page-title-main">Rhizostomae</span> Order of jellyfish with eight branched oral arms

Rhizostomae or 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. These oral arms become fused as they approach the central part of the jellyfish. The mouth of the animal is also subdivided into minute pores that are linked to coelenteron.

<span class="mw-page-title-main">Medusozoa</span> Clade of marine invertebrates

Medusozoa is a clade in the phylum Cnidaria, and is often considered a subphylum. It includes the classes Hydrozoa, Scyphozoa, Staurozoa and Cubozoa, and possibly the parasitic Polypodiozoa. Medusozoans are distinguished by having a medusa stage in their often complex life cycle, a medusa typically being an umbrella-shaped body with stinging tentacles around the edge. With the exception of some Hydrozoa, all are called jellyfish in their free-swimming medusa phase.

<span class="mw-page-title-main">Semaeostomeae</span> Order of jellyfish with four long, frilly oral arms

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; no ring canal is present. They usually possess eight tentacles; four are per-radical and four are inter-radical.

<span class="mw-page-title-main">Jellyfish Lake</span> Marine lake in Palau

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. Millions of golden jellyfish migrate horizontally across the lake daily.

<i>Pelagia noctiluca</i> Species of cnidarian

Pelagia noctiluca is a jellyfish in the family Pelagiidae and the only currently recognized species in the genus Pelagia. It is typically known in English as the mauve stinger, but other common names are purple-striped jelly, purple stinger, purple people eater, purple jellyfish, luminous jellyfish and night-light jellyfish. In Greek, pelagia means "(she) of the sea", from pelagos "sea, open sea"; in Latin noctiluca is the combining form of nox, "night"", and lux, "light"; thus, Pelagia noctiluca can be described as a marine organism with the ability to glow in the dark (bioluminescence). It is found worldwide in tropical and warm temperate seas, although it is suspected that records outside the North Atlantic region, which includes the Mediterranean and Gulf of Mexico, represent closely related but currently unrecognized species.

<i>Phacellophora camtschatica</i> Species of jellyfish

Phacellophora camtschatica, commonly known as the fried egg jellyfish or egg-yolk jellyfish, is a very large jellyfish in the family Phacellophoridae. This species can be easily identified by the yellow coloration in the center of its body which closely resembles an egg yolk, hence how it got its common name. Some individuals can have a bell close to 60 cm (2 ft) in diameter, and most individuals have 16 clusters of up to a few dozen tentacles, each up to 6 m (20 ft) long. A smaller jellyfish, Cotylorhiza tuberculata, typically found in warmer water, particularly in the Mediterranean Sea, is also popularly called a fried egg jellyfish. Also, P. camtschatica is sometimes confused with the Lion's mane jellyfish.

<span class="mw-page-title-main">Discomedusae</span> Subclass of jellyfishes

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. Jellyfish in this subclass are much more likely to have swarming events or form blooms than those in Coronamedusae. Discomedusae consists of two orders, Rhizostomae and Semaeostomeae.

<i>Cotylorhiza tuberculata</i> Species of jellyfish

Cotylorhiza tuberculata is a species of jellyfish, of the phylum Cnidaria, also known as the Mediterranean jellyfish, Mediterranean jelly or fried egg jellyfish. It is commonly found in the Mediterranean Sea, Aegean Sea, and Adriatic Sea.

<i>Turritopsis dohrnii</i> Species of small, biologically immortal jellyfish

Turritopsis dohrnii, also known as the immortal jellyfish, is a species of small, biologically immortal jellyfish found worldwide in temperate to tropic waters. It is one of the few known cases of animals capable of reverting completely to a sexually immature, colonial stage after having reached sexual maturity as a solitary individual. Others include the jellyfish Laodicea undulata and species of the genus Aurelia.

<span class="mw-page-title-main">Atolla jellyfish</span> Species of jellyfish

Atolla wyvillei, also known as the Atolla jellyfish or Coronate medusa, is a species of deep-sea crown jellyfish. It lives in oceans around the world. Like many species of mid-water animals, it is deep red in color. This species was named in honor of Sir Charles Wyville Thomson, chief scientist on the Challenger expedition.

<i>Chrysaora hysoscella</i> Species of jellyfish

Chrysaora hysoscella, the compass jellyfish, is a common species of jellyfish that inhabits coastal waters in temperate regions of the northeastern Atlantic Ocean, including the North Sea and Mediterranean Sea. In the past it was also recorded in the southeastern Atlantic, including South Africa, but this was caused by confusion with close relatives; C. africana, C. fulgida and an undescribed species tentatively referred to as "C. agulhensis".

<i>Cyanea</i> (jellyfish) Genus of jellyfishes

Cyanea is a genus of jellyfish, primarily found in northern waters of the Atlantic and Pacific Oceans and southern Pacific waters of Australia and New Zealand, there are also several boreal, polar, tropical and sub-tropical species. Commonly found in and associated with rivers and fjords. The same genus name has been given to a genus of plants of the Hawaiian lobelioids, an example of a parahomonym.

<span class="mw-page-title-main">Thimble jellyfish</span> Species of cnidarian

The thimble jellyfish is a species of cnidarian found in the warm West Atlantic Ocean, including the Caribbean. It is a tiny jellyfish with a straight-sided, flat-topped bell. This jellyfish is the most common cause of seabather's eruption, a reaction caused by the injection of juvenile jellyfish nematocysts into human skin.

<i>Rhopilema verrilli</i> Species of jellyfish

Rhopilema verrilli, or mushroom cap jellyfish, is a species of jellyfish in the family Rhizostomatidae. They are cnidarian invertebrates distinguished by their mushroom-shaped medusae. The species does not have any tentacles; however, they still have stinging cells, called nematocysts, within their bells, which can produce mild stings to humans.

<i>Cyanea annaskala</i> Species of jellyfish

Cyanea annaskala is a species of jellyfish that was discovered in 1882 by Robert Lendlmayer von Lendenfeld.

<i>Desmonema</i> (jellyfish)

Desmonema is a genus of jellyfish under the Cyaneidae family found in colder waters near the Antarctic region and off of the coast of Argentina. They have a bell diameter that can extend over 1 meter and wide tentacles that are grouped together in clusters. They share similar anatomical and physiological structures to the genus Cyanea. Their sophisticated structures like the thick tentacles, sensory systems, and gastrovascular system allow Desmonema to easily capture and extracellularly digest their prey. In recent years, Desmonema were reported to have a commensal relationship with fishes under the Trachurus genus and a parasitic relationship with specimens of the Hyperia genus.

References

  1. 1 2 Liu, Yunhuan; Shao, Tiequan; Zhang, Huaqiao; Wang, Qi; Zhang, Yanan; Chen, Cheng; Liang, Yongchun; Xue, Jiaqi (2017). "A new scyphozoan from the Cambrian Fortunian Stage of South China". Palaeontology. 60 (4): 511–518. doi: 10.1111/pala.12306 .
  2. ↑ Dawson, Michael N. "The Scyphozoan" . Retrieved 2008-08-11.
  3. ↑ Towle, Albert (1989). Modern biology. Austin, Texas: Holt, Rinehart and Winston. ISBN   978-0030139192.
  4. 1 2 Kramp, P. L. (1961). "Synopsis of the medusae of the world". Journal of the Marine Biological Association of the United Kingdom. 40: 1–469. doi:10.1017/s0025315400007347.
  5. 1 2 3 4 5 Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 139–149. ISBN   978-0-03-056747-6.
  6. ↑ Cartwright, P., Halgedahl, S.L., Hendriks, J.R., Jarrad, R.D., Marques, A.C., Collins, A.G., and Lieberman, B.S., 2007, Exceptionally preserved jellyfishes from the Middle Cambrian. PLOSONE Issue 10: e1121, p.1-7.
  7. ↑ Richards, H.G., 1947, Preservation of fossil jellyfish: Bulletin of the Geological Society of America, v. 58, p. 1221.
  8. ↑ Morris, M., and Fautin, D., 2001, Animal Diversity Web: University of Michigan Museum of Zoology, "Scyphozoa., Accessed: September 28, 2008.
  9. ↑ Berking S, Herrmann K (2007). "Compartments in Scyphozoa". Int. J. Dev. Biol. 51 (3): 221–8. doi: 10.1387/ijdb.062215sb . PMID   17486542.
  10. ↑ Omori, Makoto; Eiji Nakano (2001). "Jellyfish fisheries in southeast Asia". Hydrobiologia. 451 (1/3): 19–26. doi:10.1023/A:1011879821323.
  11. 1 2 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
  12. ↑ "Scyphozoa". WoRMS. World Register of Marine Species . Retrieved 30 July 2012.
  13. ↑ 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 219(3): 249–267
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.