Editing Ctenophora (section)

== Distinguishing features ==

{{Further|Sponge|Cnidaria|Bilateria}}

[[File:Pelagic ctenophores.png|thumb|upright=1.5| {{center|'''Pelagic ctenophores'''}}<br/>'''a'''&nbsp;''[[Beroe ovata]]'', '''b'''&nbsp; unidentified cydippid, '''c'''&nbsp;"Tortugas red" cydippid, '''d'''&nbsp;''[[Bathocyroe fosteri]]'', '''e'''&nbsp;''[[Mnemiopsis leidyi]]'', and '''f'''&nbsp;''[[Ocyropsis]]'' sp.<ref>{{cite journal |last1=Ryan |first1=Joseph F. |last2=Schnitzler |first2=Christine E. |last3=Tamm |first3=Sidney L. |date=December 2016 |title=Meeting report of Ctenopalooza: The first international meeting of ctenophorologists |journal=[[EvoDevo]] |volume=7 |issue=1 |page=19 |doi=10.1186/s13227-016-0057-3 |doi-access=free |s2cid=931968 |hdl=1912/8430 |hdl-access=free}}</ref>]]

Ctenophores are distinguished from all other animals by having [[colloblast]]s, which are sticky and adhere to prey, although a few ctenophore species lack them.<ref name=Hinde2001CnidariaAndCtenophoraInAnderson>{{cite book |last=Hinde |first=R.T. |year=1998 |chapter=The Cnidaria and Ctenophora |editor-last=Anderson |editor-first=D.T. |title=Invertebrate Zoology |pages=28–57 |publisher=Oxford University Press |isbn=978-0-19-551368-4}}</ref><ref name=MillsNotesFromExpert/>

Like cnidarians, ctenophores have two main layers of cells that sandwich a middle layer of jelly-like material, which is called the [[mesoglea]] in cnidarians and ctenophores; more complex animals have three main cell layers and no intermediate jelly-like layer. Hence ctenophores and cnidarians have traditionally been labelled [[diploblastic]].<ref name=Hinde2001CnidariaAndCtenophoraInAnderson/><ref name=RuppertBarnes2004CnidariaGeneral>{{cite book | last1=Ruppert |first1=E.E. | last2=Fox |first2=R.S. | last3=Barnes |first3=R.D. | year=2004 | title=Invertebrate Zoology | edition=7 | publisher=Brooks / Cole | isbn=978-0-03-025982-1 | pages=[https://archive.org/details/isbn_9780030259821/page/111 111–124] | url=https://archive.org/details/isbn_9780030259821/page/111}}</ref> Both ctenophores and cnidarians have a type of [[muscle]] that, in more complex animals, arises from the [[mesoderm|middle cell layer]],<ref name=SeipelSchmid2005EvolutionOfStriatedMuscle>{{cite journal | last1=Seipel |first1=K. | last2=Schmid |first2=V. | date=June 2005 | title=Evolution of striated muscle: Jellyfish and the origin of triploblasty | journal=Developmental Biology | volume=282 | issue=1 | pages=14–26 | pmid=15936326 | doi=10.1016/j.ydbio.2005.03.032 | doi-access=free }}</ref> and as a result some text books classify ctenophores as [[triploblastic]],<ref name=RuppertBarnes2004Ctenophora/> while others still regard them as diploblastic.<ref name="Hinde2001CnidariaAndCtenophoraInAnderson"/> The comb jellies have more than 80&nbsp;different [[cell type]]s, exceeding the numbers from other groups like placozoans, sponges, cnidarians, and some deep-branching bilaterians.<ref>{{cite bioRxiv |last1=Moroz |first1=Leonid L. |last2=Norekian |first2=Tigran P. |date=16 August 2018 |title=Atlas of Neuromuscular Organization in the Ctenophore, Pleurobrachia bachei {{small|(A. Agassiz, 1860)}} |biorxiv=10.1101/385435}}</ref>

Ranging from about {{convert|1|mm|in|sp=us|sigfig=1}} to {{convert|1.5|m|ft|sp=us|sigfig=1}} in size,<ref name="RuppertBarnes2004Ctenophora"/><ref>{{cite journal | last1=Viitasalo |first1=S. | last2=Lehtiniemi |first2=M. | last3=Katajisto |first3=T. | year=2008 | title=The invasive ctenophore ''Mnemiopsis leidyi'' overwinters in high abundances in the subarctic Baltic Sea | journal=Journal of Plankton Research | volume=30 | issue=12 | pages=1431–1436 | doi=10.1093/plankt/fbn088 | doi-access=}}</ref> ctenophores are the largest non-colonial animals that use [[cilia]] as their main method of locomotion.<ref name=RuppertBarnes2004Ctenophora/> Most species have eight strips, called comb rows, that run the length of their bodies and bear comb-like bands of cilia, called "ctenes", stacked along the comb rows so that when the cilia beat, those of each comb touch the comb below.<ref name="RuppertBarnes2004Ctenophora"/> The name "ctenophora" means "comb-bearing", from the [[Greek Language|Greek]] ''{{lang|grc|κτείς}}'' (stem-form {{lang|grc|κτεν-}}) meaning "comb" and the Greek suffix ''{{lang|grc|-φορος}}'' meaning "carrying".<ref>{{cite encyclopedia | last1=Trumble |first1=W. | last2=Brown |first2=L. | year=2002 | title=Ctenophore | dictionary=Shorter Oxford English Dictionary | publisher=Oxford University Press}}</ref>{{-}}

{| class="wikitable" style="margin-left:4px"
|+ Comparison with other major animal groups
! &nbsp; 
! [[Sponges]]<ref name=RuppertBarnes2004Porifera>{{cite book | last1=Ruppert |first1=E.E. | last2=Fox |first2=R.S. | last3=Barnes |first3=R.D. | year=2004 | title=Invertebrate Zoology | edition=7 | pages=[https://archive.org/details/isbn_9780030259821/page/76 76–97] | publisher=Brooks / Cole | isbn=978-0-03-025982-1 | url=https://archive.org/details/isbn_9780030259821/page/76}}</ref><ref name=Bergquist2001PoriferaInAnderson>{{cite book | last=Bergquist |first=P.R. | year=1998 | chapter=Porifera | pages=10–27 | editor-last=Anderson |editor-first=D.T. | title=Invertebrate Zoology | publisher=Oxford University Press | isbn=978-0-19-551368-4}}</ref>
! [[Cnidarian]]s<ref name=Hinde2001CnidariaAndCtenophoraInAnderson/><ref name=RuppertBarnes2004CnidariaGeneral/><ref name=Moroz2014>{{cite journal |last1=Moroz |first1=Leonid L. |last2=Kocot |first2=Kevin M. |last3=Citarella |first3=Mathew R. |last4=Dosung |first4=Sohn |last5=Norekian |first5=Tigran P. |last6=Povolotskaya |first6=Inna S. |last7=Grigorenko |first7=Anastasia P. |last8=Dailey |first8=Christopher |last9=Berezikov |first9=Eugene |last10=Buckley |first10=Katherine M. |last11=Ptitsyn |first11=Andrey |last12=Reshetov |first12=Denis |last13=Mukherjee |first13=Krishanu |last14=Moroz |first14=Tatiana P. |last15=Bobkova |first15=Yelena |last16=Yu |first16=Fahong |last17=Kapitonov |first17=Vladimir V. |last18=Jurka |first18=Jerzy |last19=Bobkov |first19=Yuri V. |last20=Swore |first20=Joshua J. |last21=Girardo |first21=David O. |last22=Fodor |first22=Alexander |last23=Gusev |first23=Fedor |last24=Sanford |first24=Rachel |last25=Bruders |first25=Rebecca |last26=Kittler |first26=Ellen |last27=Mills |first27=Claudia E. |last28=Rast |first28=Jonathan P. |last29=Derelle |first29=Romain |last30=Solovyev |first30=Victor V. |last31=Kondrashov |first31=Fyodor A. |last32=Swalla |first32=Billie J. |last33=Sweedler |first33=Jonathan V. |last34=Rogaev |first34=Evgeny I. |last35=Halanych |first35=Kenneth M. |last36=Kohn |first36=Andrea B. |display-authors=6 |date=June 2014 |title=The ctenophore genome and the evolutionary origins of neural systems |journal=[[Nature (journal)|Nature]] |volume=510 |issue=7503 |pages=109–114 |doi=10.1038/nature13400 |pmid=24847885 |pmc=4337882 |bibcode=2014Natur.510..109M}}</ref>
! Ctenophores<ref name=Hinde2001CnidariaAndCtenophoraInAnderson/><ref name=RuppertBarnes2004Ctenophora>
{{cite book | last1=Ruppert |first1=E.E. | last2=Fox |first2=R.S. | last3=Barnes |first3=R.D. | year=2004
 | title=Invertebrate Zoology | edition=7 | publisher=Brooks/Cole | isbn=978-0-03-025982-1 | pages=[https://archive.org/details/isbn_9780030259821/page/182 182–195] | url=https://archive.org/details/isbn_9780030259821/page/182}}</ref>
! [[Bilateria]]<ref name="Hinde2001CnidariaAndCtenophoraInAnderson"/>
|- align="center"
! [[Cnidocyte]]s
| No 
| Yes
|colspan="2"| Only in some species<br/>{{small|(obtained from ingested cnidarians)}} 
|- align="center"
! [[microRNA]]
|colspan="2"| Yes 
| No 
| Yes
|- align="center"
! [[Hox gene]]s
| No 
| Yes 
| No 
| Yes
|- align="center"
! [[Colloblast]]s
|colspan="2"| No 
| In most species<ref name=MillsNotesFromExpert>
{{cite web | last=Mills |first=C.E. | title=Ctenophores – some notes from an expert | publisher=[[University of Washington]] | place=Seattle, WA | url=http://faculty.washington.edu/cemills/Ctenophores.html | access-date=2009-02-05}}</ref>
| No
|- align="center"
! [[Digestive system|Digestive]] and [[circulatory system|circulatory]] [[organ (anatomy)|organ]]s
|colspan="3"| No 
| Yes
|- align="center"
! Anal pores
|colspan="2"| No 
| Yes 
| Mostly Yes
|- align="center"
! Number of main cell layers
|colspan="2"| Two, with jelly-like layer between them 
| Debate about whether two<ref name=Hinde2001CnidariaAndCtenophoraInAnderson/> or three<ref name=SeipelSchmid2005EvolutionOfStriatedMuscle/><ref name=RuppertBarnes2004Ctenophora/>
| Three
|- align="center"
! {{small|Cells in each layer bound together}}
| No, except that [[Homoscleromorpha]] have [[basement membrane]]s<ref name=ExpositoCluzelEtAl2002EvolutionOfCollagens>
{{cite journal | last1=Exposito | first1=J-Y. | last2=Cluzel | first2=C. | last3=Garrone | first3=R. | last4=Lethias | first4=C. | year=2002 | title=Evolution of collagens | journal=The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology | volume=268 | issue=3 | pages=302–316 | doi=10.1002/ar.10162 | doi-access=free | pmid=12382326 | s2cid=12376172}}</ref>
|colspan="3"| Yes: Inter-cell connections; basement membranes
|- align="center"
! [[Sensory system|Sensory]] organs
| No
|colspan="3"| Yes
|- align="center"
! Eyes<br/>{{small|(e.g. [[ocelli]])}}
| No
| Yes
| No
| Yes
|- align="center"
! Apical organ
| No
|colspan="2"| Yes
| In species with primary ciliated larvae
|- align="center"
! Cell abundance<br/>{{small|in middle "jelly" layer}}
| Many
|colspan="2"| Few
|rowspan="2"| {{small|{{grey|[not applicable]}} }}
|- align="center"
! Outer layer cells
| can move inwards and change functions
|colspan="2"| do not move or change
|- align="center"
! Nervous system
| No
|colspan="2"| Yes, simple
| Simple to complex
|- align="center"
! [[Muscle]]s
| None
| Mostly epitheliomuscular
| Mostly [[myoepithelial]]
| Mostly [[myocyte]]s
|}