Thaliacea

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Thaliacea
Pyrosoma atlanticum, a pyrosome
doliolid
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Subphylum: Tunicata
Class: Thaliacea
Nielsen, 1995
Orders

Thaliacea is a class of marine animals within the subphylum

pelagic) for their entire lifespan. The group includes species with complex life cycles, with both solitary and colonial
forms.

Anatomy

The three orders of thaliaceans are

cilia
.

Doliolids and salps alternate between asexual and sexual life stages. Salp colonies can be several meters in length. Doliolids and salps rely on muscular action to propel themselves through surrounding seawater.

Thaliaceans have complex lifecycles. Doliolid eggs hatch into swimming tadpole larvae, which are the common larval stage for other

viviparous, meaning the embryos are linked to the "mother" by a placenta. This then develops into an oozoid, which reproduces asexually by budding to produce a number of blastozoids
, which form long chains (see image). The individual blastozoids then reproduce sexually to produce the eggs and the next generation of oozoids.

The dorsal, hollow nerve cord and notochord found in Chordata has been lost, except for a rudimentary one in some doliolid larvae.[1]

The jell pump and the carbon cycle

See also: Jelly-falls and Gelatinous zooplankton

Thaliaceans play an important role in the ecology of the sea. Their dense faecal pellets sink to the bottom of the oceans, and this may be a major part of the worldwide carbon cycle.[2]

Taxonomy

The class is a relatively small one, and is divided into three orders:

Class Thaliacea[3]

  • Order
    Pyrosomida
    Jones 1848
  • Order
    Salpida
    [Hemimyaria; Desmomyaria Uljanin 1884]
    • Family
      Salpidae
      Franstedt 1885
      • Subfamily
        Cyclosalpinae
        Yount 1954
        • Genus Cyclosalpa Blainville 1827 [Orthocoela Macdonald 1864; Pyrosomopsis Macdonald 1864]
        • Genus Helicosalpa Todaro 1902
      • Subfamily
        Salpinae
        Lahille 1888
        • Genus Brooksia (tunicate) Metcalf 1918
        • Genus Iasis (tunicate) Savigny 1816 [Weelia Yount 1954; Salpa (Iasis) Savigny 1816]
        • Genus Ihlea Metcalf 1919 non Metcalf 1918 [Apsteinia Metcalf 1918 non Schmeil 1894]
        • Genus Metcalfina Ihle & Ihle-Landenberg 1933
        • Genus Pegea Savigny 1816
        • Genus Ritteriella Metcalf 1919 [Ritteria Metcalf 1918 non Kramer 1877]
        • Genus Salpa Forskål 1775 [Biphora Bruguière 1789; Bifora Agassiz 1846; Dagysa Banks & Solander 1773]
        • Genus Soestia [Holothurium sensu Pallas 1774]
        • Genus
          Thetys
           Tilesius 1802 [Salpa (Thetys) Tilesius 1802]
        • Genus Thalia Blumenbach 1798 [Dubreuillia Lesson 1832; Edusa Gistl 1848]
        • Genus Traustedtia Metcalf 1918 [Salpa (Traustedtia) Metcalf 1918]
  • Order Doliolida [Cyclomyaria Uljanin 1884]

References

  • Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 1042–1043.
    ISBN 978-0-03-056747-6
    .
  • Bone, Quentin (1998). The pelagic Tunicates. Oxford: Oxford University Press.
    ISBN 978-0-19-854024-3
    .
  1. S2CID 235602431
    .
  2. ^ "The jelly cycle". The Economist. May 21, 2009.
  3. ^ [1] World Register of Marine Species. Retrieved 2014-02-13.

External links

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