Coelenterata: Difference between revisions
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{{Short description|Term encompassing animal phyla Cnidaria and Ctenophora}} |
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{{Taxobox | color = pink |
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{{automatic_Taxobox |
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| name = Coelenterates |
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| image= Comb_jellies-mba.jpg |
| image= Comb_jellies-mba.jpg |
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| image_caption = [[Ctenophora|Comb jellies]] (''Beroe'' spp.) |
| image_caption = [[Ctenophora|Comb jellies]] (''Beroe'' spp.) |
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| regnum = [[Animal]]ia |
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| authority = [[Hatschek]], 1888 |
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| unranked_phylum = ''Coelenterata'' |
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| subdivision_ranks = [[Phylum|Phyla]] |
| subdivision_ranks = [[Phylum|Phyla]] |
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| subdivision = |
| subdivision = |
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[[Ctenophora]] |
*[[Ctenophora]] |
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[[Cnidaria]] |
*[[Cnidaria]] |
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}} |
}} |
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'''Coelenterata''' is |
'''Coelenterata''' is a term encompassing the animal [[phylum|phyla]] [[Cnidaria]] ([[coral|corals]], [[Scyphozoa|true jellies]], [[Sea anemone|sea anemones]], [[sea pen]]s, and their relatives) and [[Ctenophora]] (comb jellies). The name comes {{etymology|grc|''{{wikt-lang|grc|κοῖλος}}'' ({{grc-transl|κοῖλος}})|hollow||''{{wikt-lang|grc|ἔντερον}}'' ({{grc-transl|ἔντερον}})|intestine}}, referring to the hollow [[body cavity]] common to these two phyla.<ref name="OED">{{Cite OED|coelenterate}}</ref><ref name="MW">{{cite Merriam-Webster|coelenterate|access-date=2017-02-25}}</ref> They have very simple [[tissue (biology)|tissue]] organization, with only two layers of cells ([[ectoderm]] and [[endoderm]]), along with a middle undifferentiated layer called the [[mesoglea]], and radial symmetry. Coelenterata lack a specialized circulatory system, relying instead on diffusion across the tissue layers. |
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==Characteristics== |
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All coelenterates are [[aquatic animal|aquatic]], mostly [[marine life|marine]], animals. The body form is [[symmetry in biology|radially symmetrical]], [[diploblastic]] and does not have a [[coelom]]. The body has a single opening, the ''{{wikt-lang|en|hypostome}}'', surrounded by sensory [[tentacle]]s equipped with either [[nematocyst]]s or [[colloblast]]s to capture mostly [[plankton]]ic prey. These tentacles are surrounded by a spacious cavity called the [[gastrovascular cavity]], or coelenteron. Digestion is both intracellular and extracellular. Respiration and excretion are accomplished by simple diffusion. A [[nerve net]] is spread throughout the body. Many Cnidaria exhibit [[Polymorphism (biology)|polymorphism]], wherein different types of individuals are present in a colony for different functions. These individuals are called [[zooid]]s. These animals generally reproduce asexually by budding, though sexual reproduction does occur in some groups. |
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The term ''coelenterate'' is no longer recognized as scientifically valid, as the Cnidaria and Ctenophora have placed at equal rank under the [[Metazoa]] with the other phyla of animals.<ref>[http://www.britannica.com/eb/article-1647 Excerpt from Britannica article regarding Ctenophore classification] |
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</ref> A single term encompassing these two phyla but leaving out all others of equal rank would be considered [[polyphyletic]]. Nonetheless, the term ''coelenterate'' is still used in informal settings to refer to the Cnidaria and Ctenophora. |
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| ⚫ | Complicating the issue is the 1997 work of [[Lynn Margulis]] (revising an earlier model by [[Thomas Cavalier-Smith]]) that placed the Cnidaria and Ctenophora alone |
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The scientific validity of the term ''coelenterate'' is currently rejected, as the Cnidaria and Ctenophora have less in common than previously assumed.<ref name="Dunn2015">{{cite journal|last1=Dunn|first1=Casey W.|last2=Leys|first2=Sally P.|last3=Haddock|first3=Steven H.D.|title=The hidden biology of sponges and ctenophores|journal=Trends in Ecology & Evolution|date=May 2015|volume=30|issue=5|pages=282–291|doi=10.1016/j.tree.2015.03.003|doi-access=free|pmid=25840473}}</ref> Coelentera may only be monophyletic if both [[Placozoa]] and [[Bilateria]] are included.<ref name="Pisani">{{Cite journal|last1=Pisani|first1=Davide|last2=Pett|first2=Walker|last3=Dohrmann|first3=Martin|last4=Feuda|first4=Roberto|last5=Rota-Stabelli|first5=Omar|last6=Philippe|first6=Hervé|last7=Lartillot|first7=Nicolas|last8=Wörheide|first8=Gert|date=2015-12-15|title=Genomic data do not support comb jellies as the sister group to all other animals|journal=Proceedings of the National Academy of Sciences|language=en|volume=112|issue=50|pages=15402–15407|doi=10.1073/pnas.1518127112|issn=0027-8424|pmc=4687580|pmid=26621703|bibcode=2015PNAS..11215402P|doi-access=free}}</ref> In particular, the phylogenetic position of [[Ctenophora]] is controversial; it was first considered a sub-group of coelenterata but Hyman regarded it as a separate phylum.<ref name="Pisani" /><ref>{{Cite journal|title = Error, signal, and the placement of Ctenophora sister to all other animals|journal = Proceedings of the National Academy of Sciences|date = 2015-05-05|issn = 0027-8424|pmc = 4426464|pmid = 25902535|pages = 5773–5778|volume = 112|issue = 18|doi = 10.1073/pnas.1503453112|first1 = Nathan V.|last1 = Whelan|first2 = Kevin M.|last2 = Kocot|first3 = Leonid L.|last3 = Moroz|first4 = Kenneth M.|last4 = Halanych|bibcode = 2015PNAS..112.5773W|doi-access = free}}</ref> Most researchers think that Coelenterata is not [[Monophyly|monophyletic]], and therefore any group containing Cnidaria and Ctenophora but excluding other phyla would be [[paraphyletic]]. |
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Previously, some genomic studies have found support for monophyletic coelenterates.<ref name="Philippe2009">{{Cite journal|title = Phylogenomics Revives Traditional Views on Deep Animal Relationships|journal = Current Biology|issn = 0960-9822|pmid = 19345102|pages = 706–712|volume = 19|issue = 8|doi = 10.1016/j.cub.2009.02.052|first1 = Hervé|last1 = Philippe|first2 = Romain|last2 = Derelle|first3 = Philippe|last3 = Lopez|first4 = Kerstin|last4 = Pick|first5 = Carole|last5 = Borchiellini|first6 = Nicole|last6 = Boury-Esnault|first7 = Jean|last7 = Vacelet|first8 = Emmanuelle|last8 = Renard|first9 = Evelyn|last9 = Houliston|date=April 2009|doi-access = free}}</ref><ref>{{Cite journal|title = Deep metazoan phylogeny: When different genes tell different stories|journal = Molecular Phylogenetics and Evolution|date = 2013-04-01|pages = 223–233|volume = 67|issue = 1|doi = 10.1016/j.ympev.2013.01.010|first1 = Tetyana|last1 = Nosenko|first2 = Fabian|last2 = Schreiber|first3 = Maja|last3 = Adamska|first4 = Marcin|last4 = Adamski|first5 = Michael|last5 = Eitel|first6 = Jörg|last6 = Hammel|first7 = Manuel|last7 = Maldonado|first8 = Werner E. G.|last8 = Müller|first9 = Michael|last9 = Nickel|pmid=23353073}}</ref> Despite this uncertainty, the term ''coelenterate'' is still used in informal settings to refer to the Cnidaria and Ctenophora. |
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<references /> |
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| ⚫ | Complicating the issue is the 1997 work of [[Lynn Margulis]] (revising an earlier model by [[Thomas Cavalier-Smith]]) that placed the Cnidaria and Ctenophora alone in the branch [[Radiata]] within [[Eumetazoa]].<ref>Margulis, Lynn and Karlene V. Schwartz, 1997, ''Five Kingdoms: An Illustrated Guide to the Phyla of Life on Earth'', W.H. Freeman & Company, {{ISBN|0-613-92338-3}}</ref> (The latter refers to all the animals except the [[Porifera|sponges]] and [[Placozoa]]). Neither grouping is accepted universally;<ref>{{Cite web|url=https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=6072&lvl=3&p=mapview&p=has_linkout&p=blast_url&p=genome_blast&lin=f&keep=1&srchmode=1&unlock|title=Taxonomy browser (Eumetazoa)|website=www.ncbi.nlm.nih.gov}}</ref> however, both are commonly encountered in taxonomic literature.<ref name="Dunn2015"/><ref name="Philippe2009"/> |
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{{Reflist}} |
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{{Taxonbar|from=Q387474}} |
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{{biology-stub}} |
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{{Authority control}} |
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[[Category:Obsolete animal taxa]] |
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[[de:Hohltiere]] |
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[[fa:کیسهتنان]] |
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[[pl:jamochłony]] |
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[[ru:Кишечнополостные]] |
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[[uk:Кишковопорожнинні]] |
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Latest revision as of 12:52, 6 January 2025
| Coelenterates | |
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| Comb jellies (Beroe spp.) | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Subkingdom: | Eumetazoa |
| Phylum: | Coelenterata Hatschek, 1888 |
| Phyla | |
Coelenterata is a term encompassing the animal phyla Cnidaria (corals, true jellies, sea anemones, sea pens, and their relatives) and Ctenophora (comb jellies). The name comes from Ancient Greek κοῖλος (koîlos) 'hollow' and ἔντερον (énteron) 'intestine', referring to the hollow body cavity common to these two phyla.[1][2] They have very simple tissue organization, with only two layers of cells (ectoderm and endoderm), along with a middle undifferentiated layer called the mesoglea, and radial symmetry. Coelenterata lack a specialized circulatory system, relying instead on diffusion across the tissue layers.
Characteristics
[edit]All coelenterates are aquatic, mostly marine, animals. The body form is radially symmetrical, diploblastic and does not have a coelom. The body has a single opening, the hypostome, surrounded by sensory tentacles equipped with either nematocysts or colloblasts to capture mostly planktonic prey. These tentacles are surrounded by a spacious cavity called the gastrovascular cavity, or coelenteron. Digestion is both intracellular and extracellular. Respiration and excretion are accomplished by simple diffusion. A nerve net is spread throughout the body. Many Cnidaria exhibit polymorphism, wherein different types of individuals are present in a colony for different functions. These individuals are called zooids. These animals generally reproduce asexually by budding, though sexual reproduction does occur in some groups.
History of classification
[edit]The scientific validity of the term coelenterate is currently rejected, as the Cnidaria and Ctenophora have less in common than previously assumed.[3] Coelentera may only be monophyletic if both Placozoa and Bilateria are included.[4] In particular, the phylogenetic position of Ctenophora is controversial; it was first considered a sub-group of coelenterata but Hyman regarded it as a separate phylum.[4][5] Most researchers think that Coelenterata is not monophyletic, and therefore any group containing Cnidaria and Ctenophora but excluding other phyla would be paraphyletic.
Previously, some genomic studies have found support for monophyletic coelenterates.[6][7] Despite this uncertainty, the term coelenterate is still used in informal settings to refer to the Cnidaria and Ctenophora.
Complicating the issue is the 1997 work of Lynn Margulis (revising an earlier model by Thomas Cavalier-Smith) that placed the Cnidaria and Ctenophora alone in the branch Radiata within Eumetazoa.[8] (The latter refers to all the animals except the sponges and Placozoa). Neither grouping is accepted universally;[9] however, both are commonly encountered in taxonomic literature.[3][6]
References
[edit]- ^ "coelenterate". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
- ^ "coelenterate". Merriam-Webster.com Dictionary. Merriam-Webster. Retrieved 2017-02-25.
- ^ a b Dunn, Casey W.; Leys, Sally P.; Haddock, Steven H.D. (May 2015). "The hidden biology of sponges and ctenophores". Trends in Ecology & Evolution. 30 (5): 282–291. doi:10.1016/j.tree.2015.03.003. PMID 25840473.
- ^ a b Pisani, Davide; Pett, Walker; Dohrmann, Martin; Feuda, Roberto; Rota-Stabelli, Omar; Philippe, Hervé; Lartillot, Nicolas; Wörheide, Gert (2015-12-15). "Genomic data do not support comb jellies as the sister group to all other animals". Proceedings of the National Academy of Sciences. 112 (50): 15402–15407. Bibcode:2015PNAS..11215402P. doi:10.1073/pnas.1518127112. ISSN 0027-8424. PMC 4687580. PMID 26621703.
- ^ Whelan, Nathan V.; Kocot, Kevin M.; Moroz, Leonid L.; Halanych, Kenneth M. (2015-05-05). "Error, signal, and the placement of Ctenophora sister to all other animals". Proceedings of the National Academy of Sciences. 112 (18): 5773–5778. Bibcode:2015PNAS..112.5773W. doi:10.1073/pnas.1503453112. ISSN 0027-8424. PMC 4426464. PMID 25902535.
- ^ a b Philippe, Hervé; Derelle, Romain; Lopez, Philippe; Pick, Kerstin; Borchiellini, Carole; Boury-Esnault, Nicole; Vacelet, Jean; Renard, Emmanuelle; Houliston, Evelyn (April 2009). "Phylogenomics Revives Traditional Views on Deep Animal Relationships". Current Biology. 19 (8): 706–712. doi:10.1016/j.cub.2009.02.052. ISSN 0960-9822. PMID 19345102.
- ^ Nosenko, Tetyana; Schreiber, Fabian; Adamska, Maja; Adamski, Marcin; Eitel, Michael; Hammel, Jörg; Maldonado, Manuel; Müller, Werner E. G.; Nickel, Michael (2013-04-01). "Deep metazoan phylogeny: When different genes tell different stories". Molecular Phylogenetics and Evolution. 67 (1): 223–233. doi:10.1016/j.ympev.2013.01.010. PMID 23353073.
- ^ Margulis, Lynn and Karlene V. Schwartz, 1997, Five Kingdoms: An Illustrated Guide to the Phyla of Life on Earth, W.H. Freeman & Company, ISBN 0-613-92338-3
- ^ "Taxonomy browser (Eumetazoa)". www.ncbi.nlm.nih.gov.
