Editing Sponge (section)

=== Taxonomy ===

<!-- [[File:Sponge in papua new guinea.jpg|thumb|A sponge in [[Papua New Guinea]]]] -->
<!-- [[File:Biological classification L Pengo.svg|thumb|right|100px|Levels in the [[Linnean taxonomy]].]] -->


[[Carl Linnaeus]], who classified most kinds of sessile animals as belonging to the order [[Vermes in the 10th edition of Systema Naturae#Zoophyta|Zoophyta]] in the class [[Vermes]], mistakenly identified the genus ''[[Spongia]]'' as plants in the order [[Algae]].<ref name=worms>{{cite web |url=http://www.marinespecies.org/aphia.php?p=sourceget&id=44036 |title=Spongia Linnaeus, 1759 |publisher=[[World Register of Marine Species]] |access-date=18 July 2012 |archive-url=https://web.archive.org/web/20160327183441/http://www.marinespecies.org/aphia.php?p=sourceget&id=44036 |archive-date=27 March 2016 |url-status=live }}</ref>{{Explain |date=May 2024 |reason=Spongia 1st genus dedicated to sea sponges during time Linnaeus studied them? }} For a long time thereafter, sponges were assigned to subkingdom [[Parazoa]] ("beside the animals") separated from the [[Eumetazoa]] which formed the rest of the [[Kingdom (biology)|kingdom]] [[Animalia]].<ref name="Rowland_2001"/>

The phylum Porifera is further divided into [[Class (biology)|classes]] mainly according to the composition of their [[skeleton]]s:<ref name="Hooper_2002"/><ref name="Bergquist_2001"/>
* [[Hexactinellida]] (glass sponges) have silicate spicules, the largest of which have six rays and may be individual or fused.<ref name="Hooper_2002"/> The main components of their bodies are [[syncytia]] in which large numbers of cell share a single external [[Cell membrane|membrane]].<ref name="Bergquist_2001"/>
* [[Calcarea]] have skeletons made of [[calcite]], a form of [[calcium carbonate]], which may form separate spicules or large masses. All the cells have a single nucleus and membrane.<ref name="Bergquist_2001"/>
* Most [[Demospongiae]] have silicate spicules or [[spongin]] fibers or both within their soft tissues. However, a few also have massive external skeletons made of [[aragonite]], another form of calcium carbonate.<ref name="Hooper_2002"/><ref name="Bergquist_2001"/> All the cells have a single nucleus and membrane.<ref name="Bergquist_2001"/>
* [[Archeocyatha]] are known only as fossils from the [[Cambrian]] period.<ref name="Rowland_2001"/>

In the 1970s, sponges with massive calcium carbonate skeletons were assigned to a separate class, [[Sclerospongiae]], otherwise known as "coralline sponges".<ref>{{cite journal |last1=Hartman |first1=W.D. |last2=Goreau |first2=T.F. |year=1970|title=Jamaican coralline sponges: Their morphology, ecology and fossil relatives|journal=Symposium of the Zoological Society of London|volume=25|pages=205–243}} [http://mgg.rsmas.miami.edu/groups/sil/work1.htm (cited by MGG.rsmas.miami.edu).] {{Webarchive|url=https://web.archive.org/web/20180818135926/http://mgg.rsmas.miami.edu/groups/sil/work1.htm |date=2018-08-18 }}</ref> However, in the 1980s, it was found that these were all members of either the Calcarea or the Demospongiae.<ref>{{cite book |last=Vacelet |first=J. |year=1985 |contribution=Coralline sponges and the evolution of the Porifera |pages=1–13 |editor1=Conway Morris, S. |editor2=George, J.D. |editor3=Gibson, R. |editor4=Platt, H.M. |title=The Origins and Relationships of Lower Invertebrates |publisher=[[Oxford University Press]]|isbn=978-0-19-857181-0}}</ref>

So far scientific publications have identified about 9,000 poriferan species,<ref name="Bergquist_2001"/> of which about 400 are glass sponges, about 500 are calcareous species, and the rest are demosponges.<ref name="Ruppert_2004"/> However, some types of habitat, such as vertical rock and cave walls and galleries in rock and coral boulders, have been investigated very little, even in shallow seas, and may harbor many more species.<ref name="Bergquist_2001"/>