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|A chain of salps near the surface in the Red Sea.|
|Genera and species|
A salp (plural salps) or salpa (plural salpae or salpas) is a barrel-shaped, planktonic tunicate. It moves by contracting, thus pumping water through its gelatinous body. The salp strains the pumped water through its internal feeding filters, feeding on phytoplankton.
Salps are common in equatorial, temperate, and cold seas, where they can be seen at the surface, singly or in long, stringy colonies. The most abundant concentrations of salps are in the Southern Ocean (near Antarctica). Here they sometimes form enormous swarms, often in deep water, and are sometimes even more abundant than krill. 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 State.
Life history 
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 1 and 10 cm (0.39 and 3.9 in) tall. The solitary life history phase, also known as an oozoid, is a single barrel-shaped animal that reproduces asexually 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, first maturing as females, and are fertilized by male gametes produced by older chains), with a growing embryo oozoid attached to the body wall of the parent. The growing oozoids are eventually released from the parent blastozooids, and then continue to feed and grow as the solitary asexual phase, thus 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 are abundant, this rapid reproduction leads to fairly short-lived blooms of salps, which eventually filter out most of the phytoplankton. The bloom ends when there is no longer enough food to sustain the enormous population of salps.
Oceanographic importance 
One reason for the success of salps is how they respond to phytoplankton blooms. When there is plenty of food, salps can quickly bud off clones, which graze the phytoplankton and can grow at a rate which is probably faster than that of any other multicellular animal, quickly stripping the phytoplankton from the sea. But if the phytoplankton are 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 planktonic species can experience fluctuations in their numbers due to competition with the salps.
Sinking fecal pellets and bodies of salps carry carbon to the sea floor, and salps are abundant enough to have an effect on the ocean's biological pump. Consequently, large changes in their abundance or distribution may alter the ocean's carbon cycle, and potentially play a role in climate change.
Nervous systems and relationships to other animals 
Salps appear to have a form preliminary to vertebrates, and are used as a starting point in models of how vertebrates evolved. Scientists speculate that the tiny groups of nerves in salps are one of the first instances of a primitive nervous system, which eventually evolved into the more complex central nervous systems of vertebrates.
Bone, Q. editor (1998) The Biology of Pelagic Tunicates. Oxford University Press, Oxford. 340 pp.
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- Lacalli, T.C.; Holland, L.Z. (1998). "The developing dorsal ganglion of the salp Thalia democratica, and the nature of the ancestral chordate brain". Phil. Trans. Royal Society B. Biological Sciences 353 (1378): 1943–1967. doi:10.1098/rstb.1998.0347.
- Salpida World Register of Marine Species. Retrieved 2011-11-16.
- Brooksia Metcalf, 1918 World Register of Marine Species. Retrieved 2011-11-16.
- Cyclosalpa de Blainville, 1827 World Register of Marine Species. Retrieved 2011-11-16.
- Helicosalpa Todaro, 1902 World Register of Marine Species. Retrieved 2011-11-16.
- Ihlea World Register of Marine Species. Retrieved 2011-11-16.
- Metcalfina World Register of Marine Species. Retrieved 2011-11-16.
- Pegea World Register of Marine Species. Retrieved 2011-11-16.
- Ritteriella World Register of Marine Species. Retrieved 2012-9-17.
- Salpa World Register of Marine Species. Retrieved 2011-11-16.
- Soestia World Register of Marine Species. Retrieved 2011-11-16.
- Thalia World Register of Marine Species. Retrieved 2011-11-16.
- Thetys de Blainville, 1827 World Register of Marine Species. Retrieved 2011-11-16.
- Traustedtia World Register of Marine Species. Retrieved 2011-11-16.
- Weelia Yount, 1954 World Register of Marine Species. Retrieved 2011-11-16.
|Wikimedia Commons has media related to: Salpidae|
|Wikispecies has information related to: Salpidae|
- Plankton Chronicles Short documentary films & photos
- Pelagic tunicates (including salps) overview
- Scientific expedition to study salps near Antarctica - many details, with interviews, photos, videos, graphs
- Sludge of slimy organisms coats beaches of New England Boston Globe October 9, 2006
- The salps on earthlife.net
- The role of salps in the study of origin of the vertebrate brain
- 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
- Jelly blobs may hold key to climate change ABC Radio, The World Today - Monday, 17 November, 2008
- Salp Fact Sheet