Salp

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Sea Salp
A chain of salps near the surface in the Red Sea.
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Tunicata
Class: Thaliacea
Order: Salpida
Family: Salpidae
Genera and species

See text.

A salp (plural salps) or salpa (plural salpae or salpas[1]) 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.

Distribution[edit]

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[2] (near Antarctica). Here they sometimes form enormous swarms, often in deep water, and are sometimes even more abundant than krill.[3] 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.[4]

Life history[edit]

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 3.94 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[edit]

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[edit]

Salps are related to the pelagic tunicate groups doliolida and pyrosoma, as well as to other bottom-living (benthic) tunicates.

Although salps appear similar to jellyfish because of the simple body form and planktonic behavior, they are structurally most closely related to vertebrates, animals with true backbones.

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.[5]

Classification[edit]

The World Register of Marine Species lists the following genera and species in the order Salpida:[6]

  • Order Salpida
    • Family Salpidae
      • Genus Brooksia Metcalf, 1918 [7]
        • Brooksia berneri van Soest, 1975
        • Brooksia rostrata (Traustedt, 1893)
      • Genus Cyclosalpa de Blainville, 1827[8]
        • 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[9]
        • Helicosalpa komaii (Ihle & Ihle-Landenberg, 1936)
        • Helicosalpa virgula (Vogt, 1854)
        • Helicosalpa younti Kashkina, 1973
      • Genus Ihlea Metcalf, 1919[10]
        • Ihlea magalhanica (Apstein, 1894)
        • Ihlea punctata (Forskål, 1775)
        • Ihlea racovitzai (van Beneden & Selys Longchamp, 1913)
      • Genus Metcalfina[11]
        • Metcalfina hexagona (Quoy & Gaimard, 1824)
      • Genus Pegea Savigny, 1816[12]
        • Pegea bicaudata (Quoy & Gaimard, 1826)
        • Pegea confederata (Forsskål, 1775)
      • Genus Ritteriella Metcalf, 1919[13]
        • Ritteriella amboinensis (Apstein, 1904)
        • Ritteriella picteti (Apstein, 1904)
        • Ritteriella retracta (Ritter, 1906)
      • Genus Salpa Forskål, 1775[14]
        • Salpa aspera Chamisso, 1819
        • Salpa fusiformis Cuvier, 1804
        • Salpa gerlachei Foxton, 1961
        • Salpa maxima Forskål, 1775
        • Salpa thompsoni (Foxton, 1961)
        • Salpa tuberculata Metcalf, 1918
        • Salpa younti van Soest, 1973
      • Genus Soestia (also accepted as Iasis)[15]
        • Soestia cylindrica (Cuvier, 1804)
        • Soestia zonaria (Pallas, 1774)
      • Genus Thalia[16]
        • 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[17]
      • Genus Traustedtia [18]
        • Traustedtia multitentaculata (Quoy & Gaimard, 1834)
      • Genus Weelia Yount, 1954[19]
        • Weelia cylindrica (Cuvier, 1804)

Bibliography[edit]

Bone, Q. editor (1998) The Biology of Pelagic Tunicates. Oxford University Press, Oxford. 340 pp.

References[edit]

  1. ^ "salp - Definitions from Dictionary.com". Retrieved 2008-09-28. 
  2. ^ "Now that's a jelly fish!". Daily Mail. 22 January 2014. Retrieved 22 January 2014. 
  3. ^ "Dive and Discover: Scientific Expedition 10: Antarctica". Retrieved 2008-09-03. 
  4. ^ "Odd creatures wash ashore on Washington beach". NBC. 16 February 2013. Retrieved 17 February 2013. 
  5. ^ Lacalli, T.C.; Holland, L.Z. (1998). "The developing dorsal ganglion of the salp Thalia democratica, and the nature of the ancestral chordate brain". Philosophical Transactions of the Royal Society B 353 (1378): 1943–1967. doi:10.1098/rstb.1998.0347. 
  6. ^ Salpida World Register of Marine Species. Retrieved 2011-11-16.
  7. ^ Brooksia Metcalf, 1918 World Register of Marine Species. Retrieved 2011-11-16.
  8. ^ Cyclosalpa de Blainville, 1827 World Register of Marine Species. Retrieved 2011-11-16.
  9. ^ Helicosalpa Todaro, 1902 World Register of Marine Species. Retrieved 2011-11-16.
  10. ^ Ihlea World Register of Marine Species. Retrieved 2011-11-16.
  11. ^ Metcalfina World Register of Marine Species. Retrieved 2011-11-16.
  12. ^ Pegea World Register of Marine Species. Retrieved 2011-11-16.
  13. ^ Ritteriella World Register of Marine Species. Retrieved 2012-9-17.
  14. ^ Salpa World Register of Marine Species. Retrieved 2011-11-16.
  15. ^ Soestia World Register of Marine Species. Retrieved 2011-11-16.
  16. ^ Thalia World Register of Marine Species. Retrieved 2011-11-16.
  17. ^ Thetys de Blainville, 1827 World Register of Marine Species. Retrieved 2011-11-16.
  18. ^ Traustedtia World Register of Marine Species. Retrieved 2011-11-16.
  19. ^ Weelia Yount, 1954 World Register of Marine Species. Retrieved 2011-11-16.

External links[edit]