Demosponge

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Demosponge
Temporal range: Cryogenian – present, 650–0 Ma[1]
Included are the yellow tube sponge, Aplysina fistularis, the purple vase sponge, Niphates digitalis, the red encrusting sponge, Spiratrella coccinea, and the gray rope sponge, Callyspongia sp.
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Porifera
Class: Demospongiae
Sollas, 1885
Subclasses
The carnivorous ping-pong tree sponge, Chondrocladia lampadiglobus [2][3]
Monanchora arbuscula (Poecilosclerida)
Geodia barretti (Tetractinellida)
Chondrosia reniformis (Chondrosiida)
Spongia officinalis (Dictyoceratida)
Spongilla lacustris (Spongillida)

Demosponges (Demospongiae) are the most diverse

diatoms.[6]

The many diverse

methylate sterols at the 26-position, a fact used to identify the presence of demosponges before their first known unambiguous fossils.[8][9]

Because of many species' long life span (500–1,000 years) it is thought that analysis of the aragonite skeletons of these sponges could extend data regarding ocean temperature, salinity, and other variables farther into the past than has been previously possible. Their dense skeletons are deposited in an organized chronological manner, in concentric layers or bands. The layered skeletons look similar to reef corals. Therefore, demosponges are also called coralline sponges.

Classification and systematics

The Demospongiae have an ancient history. The first demosponges may have appeared during the

Tommotian stage about 530 Ma, found in southeast Siberia.[12] A major radiation occurred in the Lower Cambrian and further major radiations in the Ordovician possibly from the middle Cambrian.[13]

The Systema Porifera (2002) book (2 volumes)[1] was the result of a collaboration of 45 researchers from 17 countries led by editors J. N. A. Hooper and R. W. M. van Soest. This milestone publication provided an updated comprehensive overview of sponge systematics, the largest revision of this group (from genera, subfamilies, families, suborders, orders and class) since the start of spongiology in the mid-19th century. In this large revision, the extant Demospongiae were organized into 14 orders that encompassed 88 families and 500 genera. Hooper and van Soest (2002) gave the following classification of demosponges into orders:

  • Subclass
    Homoscleromorpha
     Bergquist 1978
  • Subclass
    Tetractinomorpha
    • Astrophorida
      Sollas 1888
    • Chondrosida
      Boury-Esnault & Lopès 1985
    • Hadromerida
      Topsent 1894
    • Lithistida
      Sollas 1888
    • Spirophorida
      Bergquist & Hogg 1969
  • Subclass
    Ceractinomorpha
     Lévi 1953

However, molecular and morphological evidence show that the

Homoscleromorpha was therefore officially taken out of the Demospongiae in 2012, and became the fourth class of phylum Porifera.[14]

Morrow & Cárdenas (2015)

Trachycladida). These added to the recently created orders (Biemnida and Chondrillida) make a total of 22 orders in the revised classification. These changes are now implemented in the World Porifera Database[16]
part of the World Register of Marine Species.

Sclerosponges

Sclerosponges were first proposed as a class of sponges, Sclerospongiae, in 1970 by Hartman and Goreau.

Porifera.[18] That means that sclerosponges are not a closely related (taxonomic) group of sponges and are considered to be a polyphyletic grouping and contained within the Demospongiae. Like bats and birds that independently developed the ability to fly, different sponges developed the ability to build a calcareous skeleton independently and at different times in Earth's history. Fossil sclerosponges are already known from the Cambrian period.[19]

Chaetetids

Chaetetids, more formally called "chaetetid hyper-calcified demosponges" (West, 2011), are common calcareous

sclerosponges
. The chaetetid skeleton has now been shown to be of polyphyletic origin and with little systematic value. Extant chaetetids are also described. This skeleton is now known from three demosponge orders (Hadromerida, Poecilosclerida, and Agelasida). Fossil chaetetid hyper-calcified demosponges can only be classified with information on their spicule forms and the original mineralogy of their skeletons (West, 2011).

  • Fossil chaetetid from the Bird Spring Formation (Upper Carboniferous) of southern Nevada.
    Fossil chaetetid from the
    Upper Carboniferous) of southern Nevada
    .
  • Cross-section of a fossil chaetetid (Bird Spring Formation, Upper Carboniferous, Nevada.
    Cross-section of a fossil chaetetid (Bird Spring Formation, Upper Carboniferous, Nevada.

Reproduction

Red volcano sponge (Acarnus erithacus, Poecilosclerida).

Spermatocytes develop from the transformation of

flagellated
cells. The resulting swimming larva enters a canal of the central cavity and is expelled with the exhalant current.

Methods of asexual reproduction include both budding and the formation of gemmules. In budding, aggregates of cells differentiate into small sponges that are released superficially or expelled through the oscula. Gemmules are found in the freshwater family Spongillidae. They are produced in the mesohyl as clumps of archeocytes, are surrounded with a hard layer secreted by other amoebocytes. Gemmules are released when the parent body breaks down, and are capable of surviving harsh conditions. In a favorable situation, an opening called the micropyle appears and releases amoebocytes, which differentiate into cells of all the other types.

Meiosis and recombination

The cytological progression of porifera oogenesis and spermatogenesis (gametogenesis) shows great similarity to other metazoa.[20] Most of the genes from the classic set of meiotic genes conserved in eukaryotes are upregulated in the sponges Geodia hentscheli and Geodia phlegraei including genes for DNA recombination.[20] Since porifera are the earliest divergent animals, these findings indicate that the basic toolkit of meiosis and recombination were present early in eukaryote evolution.[20]

Economic importance

The most economically important group of demospongians to human are the bath sponges. These are harvested by divers and can also be grown commercially. They are bleached and marketed; the spongin gives the sponge its softness.

Citations

  1. doi:10.1038/nature07673
    .
  2. doi:10.1111/j.1096-3642.2006.00234.x
  3. PMID 22558119
    .
  4. ^ "World Porifera Database". marinespecies.org. Retrieved 21 October 2015.
  5. ^
    ISBN 978-0-03-056747-6
    .
  6. doi:10.1093/zoolinnean/zlaa058
    .
  7. ^ Divergence times in demosponges (Porifera) - bioRxiv
  8. PMID 26507690
    .
  9. S2CID 4314662. Archived from the original
    (PDF) on 2018-07-24. Retrieved 2019-01-27.
  10. ^ Gordon D, Love et al., "Fossil steroids record the appearance of Demospongiae during the Cryogenian period", Nature, 2009
  11. doi:10.1111/pala.12133
    .
  12. doi:10.1130/0091-7613(1995)023<0649:SADOOS>2.3.CO;2
    .
  13. ^ Finks, R.M. (1970). "The evolution and ecologic history of sponges during Palaeozoic times". Symposium of the Zoological Society of London. 25: 3–22.
  14. S2CID 14468684
    .
  15. PMID 25901176
    .
  16. ^ "World Porifera Database".
  17. ^ Hartman, W.D.; Goreau, T.F. (1970). "Jamaican coralline sponges: Their morphology, ecology and fossil relatives". Symp. Zool. Soc. Lond. 25: 205–243. (Cited by "Notes of the Sclerosponge Workshop". Stable Isotope Laboratory, Rosenstiel School of Marine and Atmospheric Science. Miami, FL: University of Miami. 21–23 March 1998. Archived from the original on 18 August 2018. Retrieved 19 December 2018.)
  18. ^ Vacelet, J. (1985). "Coralline sponges and the evolution of the Porifera". System. Assoc. Spec. 28: 1–13.
  19. ^ Reitner, J. (1992). "Coralline Spongien. der Versuch einer phylogenetisch-taxonomischen Analyse". Berliner Geowissenschaftliche Abhandlungen Reihe e (Paläobiologie). 1: 1–352.
  20. ^ a b c Koutsouveli V, Cárdenas P, Santodomingo N, Marina A, Morato E, Rapp HT, Riesgo A. The Molecular Machinery of Gametogenesis in Geodia Demosponges (Porifera): Evolutionary Origins of a Conserved Toolkit across Animals. Mol Biol Evol. 2020 Dec 16;37(12):3485-3506. doi: 10.1093/molbev/msaa183. PMID: 32929503; PMCID: PMC7743902
  1. ^ J. N. A. Hooper and R. W. M. van Soest (2002). "Class Demospongiae Sollas, 1885". Systema Porifera. A guide to the classification of sponges. New York, Boston, Dordrecht, London, Moscow: Kluwer Academic/Plenum Publishers.
  2. PMID 15288059
    .

General references
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