A salp (plural salps, also known colloquially as “sea grape”) or salpa (plural salpae or salpas) is a barrel-shaped, planktic

tunicate A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata (). It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time ...

. It moves by contracting, thereby pumping water through its gelatinous body, one of the most efficient examples of

jet propulsion Jet propulsion is the propulsion of an object in one direction, produced by ejecting a jet of fluid in the opposite direction. By Newton's third law, the moving body is propelled in the opposite direction to the jet. Reaction engines operatin ...

in the animal kingdom. The salp strains the pumped water through its internal feeding filters, feeding on phytoplankton.

Distribution

Salps are common in equatorial, temperate, and cold seas, where they can be seen at the surface, singly or in long, stringy

colonies In modern parlance, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the '' metropolitan state'' ...

. The most abundant concentrations of salps are in the

Southern Ocean The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-small ...

(near

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...

), where they sometimes form enormous swarms, often in deep water, and are sometimes even more abundant than

krill Krill are small crustaceans of the order Euphausiacea, and are found in all the world's oceans. The name "krill" comes from the Norwegian word ', meaning "small fry of fish", which is also often attributed to species of fish. Krill are consi ...

. Since 1910, while krill populations in the Southern Ocean have declined, salp populations appear to be increasing. Salps have been seen in increasing numbers along the coast of

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

Life cycle

Salps have a complex life cycle, with an obligatory alternation of generations. Both portions of the life cycle exist together in the seas—they look quite different, but both are mostly transparent, tubular, gelatinous animals that are typically between long. The

solitary Solitary is the state of being alone or in solitude. The term may refer to: * shortened form of solitary confinement * Solitary animal, an animal that does not live with others in its species * Solitary but social, a type of social organization ...

life history phase, also known as an oozooid, is a single, barrel-shaped animal that

reproduces asexually Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the fu ...

by producing a chain of tens to hundreds of individuals, which are released from the parent at a small size. The chain of salps is the 'aggregate' portion of the life cycle. The aggregate individuals are also known as blastozooids; they remain attached together while swimming and feeding, and each individual grows in size. Each blastozooid in the chain reproduces sexually (the blastozooids are sequential

hermaphrodites In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have sep ...

, first maturing as females, and are fertilized by male gametes produced by older chains), with a growing embryo oozooid attached to the body wall of the parent. The growing oozooids are eventually released from the parent blastozooids, and then continue to feed and grow as the solitary asexual phase, closing the life cycle of salps. The alternation of generations allows for a fast generation time, with both solitary individuals and aggregate chains living and feeding together in the sea. When phytoplankton is abundant, this rapid reproduction leads to fairly short-lived blooms of salps, which eventually filter out most of the phytoplankton. The bloom ends when enough food is no longer available to sustain the enormous population of salps. Occasionally,

mushroom coral The Fungiidae () are a family of Cnidaria, commonly known as mushroom corals or plate corals. The family contains thirteen extant genera. They range from solitary corals to colonial species. Some genera such as ''Cycloseris'' and '' Fungia'' ar ...

s and those of the genus ''

Heteropsammia ''Heteropsammia'' is a genus of apozooxanthellate corals that belong to the family Dendrophylliidae. Anatomy These corals consist of free-living, single polyps, of a diameter of around 2.5 cm. They form a symbiotic relationship with a sip ...

'' are known to feed on salps during blooms.

History

The incursion of a large number of salps (''

Salpa fusiformis ''Salpa fusiformis'', sometimes known as the common salp, is the most widespread species of salp. They have a cosmopolitan distribution, and can be found at depths of . They exhibit diel vertical migration, moving closer to the surface at night ...

'') into the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea, epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the ...

in 1920 led to a failure of the Scottish herring fishery.

Oceanographic importance

One reason for the success of salps is how they respond to phytoplankton blooms. When food is plentiful, salps can quickly bud off

clones Clone or Clones or Cloning or Cloned or The Clone may refer to: Places * Clones, County Fermanagh * Clones, County Monaghan, a town in Ireland Biology * Clone (B-cell), a lymphocyte clone, the massive presence of which may indicate a pathologi ...

, which graze on the phytoplankton and can grow at a rate which is probably faster than that of any other

multicellular A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism. All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially un ...

animal, quickly stripping the phytoplankton from the sea. But if the phytoplankton is too dense, the salps can clog and sink to the bottom. During these blooms, beaches can become slimy with mats of salp bodies, and other

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...

ic species can experience fluctuations in their numbers due to competition with the salps. Sinking

fecal Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...

pellets and bodies of salps carry

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...

to the seafloor, and salps are abundant enough to have an effect on the ocean's

biological pump The biological pump (or ocean carbon biological pump or marine biological carbon pump) is the ocean's biologically driven sequestration of carbon from the atmosphere and land runoff to the ocean interior and seafloor sediments.Sigman DM & GH ...

. Consequently, large changes in their abundance or distribution may alter the ocean's

carbon cycle The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. Carbon is the main component of biological compounds as well as a major componen ...

, and potentially play a role in

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

Nervous systems and relationships to other animals

Salps are closely related to the pelagic tunicate groups

Doliolida The Doliolida are an order of small marine animals of the subphylum Tunicata. They are in the class Thaliacea, which also includes the salps and pyrosomes. The doliolid body is small, typically 1–2 mm long, and barrel-shaped; it featu ...

and Pyrosoma, as well as to other bottom-living (benthic)

tunicates A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata (). It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one tim ...

. Although salps appear similar to

jellyfish 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 umbrell ...

because of their simple body form and planktonic behavior, they are

chordate A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These fi ...

s: animals with dorsal nerve cords, related to

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...

s (animals with

backbone The backbone is the vertebral column of a vertebrate. Arts, entertainment, and media Film * ''Backbone'' (1923 film), a 1923 lost silent film starring Alfred Lunt * ''Backbone'' (1975 film), a 1975 Yugoslavian drama directed by Vlatko Gilić ...

s). Small fish swim inside salps as protection from predators.

Classification

The

World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive list of names of marine organisms. Content The content of the registry is edited and maintained by scientific specialis ...

lists the following genera and

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

in the order Salpida: *Order Salpida **Family Salpidae ***Subfamily Cyclosalpinae **** Genus '' Cyclosalpa'' de Blainville, 1827 ***** '' Cyclosalpa affinis'' (Chamisso, 1819) ***** '' Cyclosalpa bakeri'' Ritter, 1905 ***** '' Cyclosalpa foxtoni'' Van Soest, 1974 ***** '' Cyclosalpa ihlei'' van Soest, 1974 ***** '' Cyclosalpa pinnata'' (Forskål, 1775) ***** '' Cyclosalpa polae'' Sigl, 1912 ***** '' Cyclosalpa quadriluminis'' Berner, 1955 ***** '' Cyclosalpa sewelli'' Metcalf, 1927 ***** '' Cyclosalpa strongylenteron'' Berner, 1955 **** Genus '' Helicosalpa'' Todaro, 1902 ***** '' Helicosalpa komaii'' (Ihle & Ihle-Landenberg, 1936) ***** '' Helicosalpa virgula'' (Vogt, 1854) ***** '' Helicosalpa younti'' Kashkina, 1973 ***Subfamily Salpinae **** Genus ''

Brooksia ''Brooksia'' is a genus of fungus, fungi in the class Dothideomycetes. The relationship of this taxon to other taxa within the class is unknown (''incertae sedis''). The genus name of ''Brooksia'' is in honour of Frederick Tom Brooks (1882 – ...

'' Metcalf, 1918 ***** '' Brooksia berneri'' van Soest, 1975 ***** '' Brooksia rostrata'' (Traustedt, 1893) **** Genus '' Ihlea'' Metcalf, 1919 ***** '' Ihlea magalhanica'' (Apstein, 1894) ***** '' Ihlea punctata'' (Forskål, 1775) ***** '' Ihlea racovitzai'' (van Beneden & Selys Longchamp, 1913) **** Genus '' Metcalfina'' ***** '' Metcalfina hexagona'' (Quoy & Gaimard, 1824) **** Genus ''

Pegea ''Pegea'' is a genus of tunicates A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata (). It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including verteb ...

'' Savigny, 1816 ***** ''

Pegea bicaudata ''Pegea'' is a genus of tunicates A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata (). It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including verteb ...

'' (Quoy & Gaimard, 1826) ***** '' Pegea confederata'' (Forsskål, 1775) **** Genus '' Ritteriella'' Metcalf, 1919 ***** '' Ritteriella amboinensis'' (Apstein, 1904) ***** '' Ritteriella picteti'' (Apstein, 1904) ***** '' Ritteriella retracta'' (Ritter, 1906) **** Genus '' Salpa'' Forskål, 1775 ***** '' Salpa aspera'' Chamisso, 1819 ***** ''

'' Cuvier, 1804 ***** '' Salpa gerlachei'' Foxton, 1961 ***** '' Salpa maxima'' Forskål, 1775 ***** '' Salpa thompsoni'' (Foxton, 1961) ***** '' Salpa tuberculata'' Metcalf, 1918 ***** ''

Salpa younti Salpa may refer to: * Salpa (singular salp), a barrel-shaped, planktic tunicate * ''Salpa'' (genus), a genus of tunicates in the family Salpidae * Salon Palloilijat, association football club from Salo, Finland. * Salpa Line, a bunker line on the ...

'' van Soest, 1973 **** Genus '' Soestia'' (also accepted as ''Iasis'') ***** '' Soestia cylindrica'' (Cuvier, 1804) ***** '' Soestia zonaria'' (Pallas, 1774) **** Genus '' Thalia'' ***** '' Thalia cicar'' van Soest, 1973 ***** '' Thalia democratica'' Forskål, 1775 ***** '' Thalia longicauda'' Quoy & Gaimard, 1824 ***** '' Thalia orientalis'' Tokioka, 1937 ***** '' Thalia rhinoceros'' Van Soest, 1975 ***** '' Thalia rhomboides'' Quoy & Gaimard, 1824 ***** '' Thalia sibogae'' Van Soest, 1973 **** Genus '' Thetys'' Tilesius, 1802 ***** '' Thetys vagina'' Tilesius, 1802 **** Genus '' Traustedtia'' ***** '' Traustedtia multitentaculata'' Quoy & Gaimard, 1834 **** Genus '' Weelia'' Yount, 1954''Weelia'' Yount, 1954
World Register of Marine Species. Retrieved 2011-11-16. ***** '' Weelia cylindrica'' (Cuvier, 1804)

References

External links

Plankton Chronicles
Short documentary films & photos
Pelagic tunicates (including salps) overview

*[http://www.boston.com/news/local/massachusetts/articles/2006/10/09/sludge_of_slimy_organisms_coats_beaches_of_new_england/ Sludge of slimy organisms coats beaches of New England Boston Globe October 9, 2006]
The salps on earthlife.net

* ttps://www.sciencedaily.com/releases/2006/07/060702085004.htm Jellyfish-like Creatures May Play Major Role In Fate Of Carbon Dioxide In The Ocean ScienceDaily.com, July 2, 2006
"Ocean 'Gummy Bears' Fight Global Warming"
LiveScience.com, July 20, 2006
How salps might help counteract global warming
BBC News, September 26, 2007

ABC Radio, The World Today - Monday, 17 November 2008

{{Authority control Thaliacea