Chiridotidae

{{Short description|Family of sea cucumbers}} {{Automatic taxobox | image = Chirodota heheva.jpg | image_caption = ''Chiridota hydrothermica'' | taxon = Chiridotidae | authority = Östergren, 1898 | subdivision = see Taxonomy }}

'''Chiridotidae''' is a family of sea cucumbers found in the order Apodida. Within the family, there are 16 recognized genera all with different ranges of body types and functions.<ref name=":43">{{Cite web |title=WoRMS - World Register of Marine Species - Chiridotidae Östergren, 1898 |url=http://www.marinespecies.org/aphia.php?p=taxdetails&id=123180 |access-date=2022-03-16 |website=www.marinespecies.org |language=en}}</ref> Sea cucumbers play a fundamental role in many marine ecosystems.<ref name=":74">{{Cite journal |last1=Sun |first1=Jiamin |last2=Hamel |first2=Jean-François |last3=Mercier |first3=Annie |date=2018-01-01 |title=Influence of flow on locomotion, feeding behaviour and spatial distribution of a suspension-feeding sea cucumber |journal=Journal of Experimental Biology |volume=221 |issue=20 |language=en |article-number=jeb.189597 |doi=10.1242/jeb.189597 |pmid=30127075 |s2cid=52051333 |issn=1477-9145|doi-access=free }}</ref>

== Description ==

Members in this family have 10, 12, or 18 pelto-digitate tentacles. They lack podia, radial canals, a respiratory tree, and papillae.<ref name=":03">{{Cite journal |last=KERR |first=ALEXANDER M. |date=September 2001 |title=Phylogeny of the Apodan Holothurians (Echinodermata) inferred from morphology |journal=Zoological Journal of the Linnean Society |volume=133 |issue=1 |pages=53–62 |doi=10.1111/j.1096-3642.2001.tb00622.x |issn=0024-4082|doi-access=free }}</ref><ref name=":16">{{Cite journal |last1=Souto |first1=Camilla |last2=Martins |first2=Luciana |last3=Menegola |first3=Carla |date=November 2018 |title=Giving up on elaborate dermal ossicles: a new genus of ossicleless Apodida (Holothuroidea) |url=https://www.cambridge.org/core/product/identifier/S0025315417001084/type/journal_article |journal=Journal of the Marine Biological Association of the United Kingdom |language=en |volume=98 |issue=7 |pages=1685–1688 |doi=10.1017/S0025315417001084 |bibcode=2018JMBUK..98.1685S |s2cid=90246363 |issn=0025-3154|url-access=subscription }}</ref><ref name=":26">{{Cite journal |last1=Martins |first1=Luciana |last2=Souto |first2=Camilla |date=2020-04-20 |title=Taxonomy of the Brazilian Apodida (Holothuroidea), with the description of two new genera |journal=Marine Biology Research |volume=16 |issue=4 |pages=219–255 |doi=10.1080/17451000.2020.1761027 |bibcode=2020MBioR..16..219M |s2cid=219917907 |issn=1745-1000}}</ref> However, their body structure does include ossicles, tentacles, a calcareous ring, and a ciliary urn.

Chiridotidae typically undergo direct development and can usually be found in benthic ecosystems. Within their benthic systems they feed off of detritus meaning they must have a digestive tract.

== Taxonomy == The following genera are recognised in the family Chiridotidae:<ref>Paulay, G. [http://www.marinespecies.org/aphia.php?p=taxdetails&id=123180 Chiridotidae Östergren, 1898.] Accessed through: World Register of Marine Species (WoRMS) 2025.</ref> * ''Archedota'' O'Loughlin in O'Loughlin & VandenSpiegel, 2007 -- 1 species * ''Chantalia'' Martins & Souto, 2020 -- 1 species * ''Chiridota'' Eschscholtz, 1829 -- 37 species * ''Gymnopipina'' Souto & Martins in Souto et al., 2017 -- 1 species * †''Jumaraina'' Soodan, 1973 -- 6 species * ''Kolostoneura'' Becher, 1909-- 2 species * ''Neotoxodora'' Liao, Pawson & Liu, 2007 -- 1 species * ''Ovalidota'' Pawson, 2004 -- 1 species * †''Palaeotrochodota'' Reich, 2003 -- 2 species * ''Paradota'' Ludwig & Heding, 1935 -- 4 species * ''Polycheira'' H.L. Clark, 1908 -- 2 species * ''Psammothuria'' Rao, 1968 -- 1 species * ''Rowedota'' O'Loughlin & VandenSpiegel, 2010 -- 7 species * ''Scoliorhapis'' Clark, 1946 -- 7 species * ''Sigmodota'' Studer, 1876 -- 4 species * ''Taeniogyrus'' Semper, 1867 -- 30 species * †''Theelia'' Schlumberger, 1890 -- 7 species There is a subfamily of Chiridotidae, Chiridotinae, that is classified by the absence of an even number of tentacles.<ref name=":85">{{Cite journal |last1=Martins |first1=Luciana |last2=Souto |first2=Camilla |date=2020-04-20 |title=Taxonomy of the Brazilian Apodida (Holothuroidea), with the description of two new genera |url=https://www.tandfonline.com/doi/full/10.1080/17451000.2020.1761027 |journal=Marine Biology Research |language=en |volume=16 |issue=4 |pages=219–255 |doi=10.1080/17451000.2020.1761027 |bibcode=2020MBioR..16..219M |s2cid=219917907 |issn=1745-1000|url-access=subscription }}</ref>

== Development == During the developmental stages of Chiridotidae, the gastrula develops directly into the doliolaria larvae, with no Auricularia stage, this means that they typically undergo direct development.<ref name=":32">{{Cite journal |last1=Samyn |first1=Yves |last2=Tallon |first2=Irena |date=2005 |title=Zoogeography of the Shallow-Water Holothuroids of the Western Indian Ocean |journal=Journal of Biogeography |volume=32 |issue=9 |pages=1523–1538 |doi=10.1111/j.1365-2699.2005.01295.x |jstor=3566324 |s2cid=85895787 |issn=0305-0270|doi-access=free |bibcode=2005JBiog..32.1523S }}</ref> Direct development allows for the internal brooding of their young within the coelom or ovaries.<ref name=":85"/> They gain their nutrition during developmental stages through a Lecithotrophic pathway, which is made easier by their benthic habitat during these stages.<ref name=":32"/> Researchers have discovered that Chiridotidae reach their asymptotic range size at 10 cells.<ref name=":32"/>

== Environment == Sea cucumbers are a mostly nocturnal animals.<ref name=":92">{{Cite journal |last1=Liu |first1=Xiaolu |last2=Lin |first2=Chenggang |last3=Sun |first3=Lina |last4=Liu |first4=Shilin |last5=Sun |first5=Jingchun |last6=Zhang |first6=Libin |last7=Yang |first7=Hongsheng |date=June 2020 |title=Transcriptome analysis of phototransduction-related genes in tentacles of the sea cucumber Apostichopus japonicus |url=https://doi-org.pallas2.tcl.sc.edu/10.1016/j.cbd.2020.100675 |journal=Comparative Biochemistry and Physiology Part D: Genomics and Proteomics |volume=34 |article-number=100675 |doi=10.1016/j.cbd.2020.100675 |pmid=32109670 |s2cid=211563936 |issn=1744-117X|url-access=subscription }}</ref> It has been found that they are dependent on light for the regulation of body processes.<ref name=":92"/>

In the family Chiridotidae, there are roughly 110 identifiable species.<ref name=":42">{{Cite web |title=WoRMS - World Register of Marine Species - Chiridotidae Östergren, 1898 |url=http://www.marinespecies.org/aphia.php?p=taxdetails&id=123180 |access-date=2022-03-16 |website=www.marinespecies.org |language=en}}</ref> Chiridotidae can be found worldwide. Although they develop in benthic ecosystems they can be found anywhere in the ocean once they are fully matured.<ref name=":32"/> Different species have adapted to the harsh conditions of deep-sea life, but because they primarily feed off detritus, they do not starve. Chiridotidae is specifically known for burrowing into the seafloor.<ref name=":32" />

== Body == Chiridotids have a very thin, mostly transparent body wall. There is an amino acid peptide called Stichopin that affects the stiffness in the body wall, connective tissues, and the contraction of muscles.<ref name=":102">{{Cite journal |last1=Tamori |first1=Masaki |last2=Saha |first2=Apurba Kumar |last3=Matsuno |first3=Akira |last4=Noskor |first4=Sukumar Chandra |last5=Koizumi |first5=Osamu |last6=Kobayakawa |first6=Yoshitaka |last7=Nakajima |first7=Yoko |last8=Motokawa |first8=Tatsuo |date=2007-07-10 |title=Stichopin-containing nerves and secretory cells specific to connective tissues of the sea cucumber |journal=Proceedings of the Royal Society B: Biological Sciences |volume=274 |issue=1623 |pages=2279–2285 |doi=10.1098/rspb.2007.0583 |issn=0962-8452 |pmc=2288486 |pmid=17623636}}</ref> They often range in lengths from a few millimeters to up to 3 meters.<ref name=":03"/> Because they lack podia, they also lack sensory cups.<ref name=":03"/><ref name=":16"/><ref name=":26"/>

The only remnants of a skeleton within this family of sea cucumbers are the calcareous ring, microscopic sclerites within the body wall, sometimes the walls of internal organs, and the tentacles that surround the organism's mouth.<ref name=":52">{{Cite journal |last=Smirnov |first=A. V. |date=December 2016 |title=Parallelisms in the evolution of sea cucumbers (Echinodermata: Holothuroidea) |url=http://link.springer.com/10.1134/S0031030116140082 |journal=Paleontological Journal |language=en |volume=50 |issue=14 |pages=1610–1625 |doi=10.1134/S0031030116140082 |bibcode=2016PalJ...50.1610S |s2cid=90804600 |issn=0031-0301|url-access=subscription }}</ref> However, the sclerites are absent in some genera of Chiridotidae (ex. Kolostoneura and Paradota).<ref name=":52"/>

=== Connective Tissues === Sea cucumbers have a number of connective tissues that suspend their organs. Cells that contain the amino acid peptide, Stichopin, have been found within the connective tissues of the Chiridotidae.<ref name=":102"/> These tissues perform in catch and autonomy manifestations.<ref name=":11">{{Cite journal |last=Byrne |first=M. |date=2001-03-01 |title=The morphology of autotomy structures in the sea cucumber Eupentacta quinquesemita before and during evisceration |journal=Journal of Experimental Biology |volume=204 |issue=5 |pages=849–863 |doi=10.1242/jeb.204.5.849 |pmid=11171409 |issn=0022-0949|doi-access=free }}</ref> The muscles that undergo catch manifestations exhibit reversible stiffening and softening properties.<ref name=":11" /><ref name=":102" /> The muscles that undergo autonomy manifestations exhibit irreversible softening allowing for the loss of body parts.<ref name=":11" />

The digestive system is anchored to the body wall by mediodorsal mesentery muscles.<ref name=":52"/> When sea cucumbers go through an autonomic loss of an organ, it regrows from the muscles that anchor them to the body wall.<ref name=":122">{{Cite journal |last1=Candelaria |first1=Ann Ginette |last2=Murray |first2=Gisela |last3=File |first3=Sharon K. |last4=García-Arrarás |first4=José E. |date=2006-07-01 |title=Contribution of mesenterial muscle dedifferentiation to intestine regeneration in the sea cucumber Holothuria glaberrima |journal=Cell and Tissue Research |language=en |volume=325 |issue=1 |pages=55–65 |doi=10.1007/s00441-006-0170-z |pmid=16541286 |s2cid=10540517 |issn=1432-0878}}</ref> This process starts with the thickening of the muscle along the mesentery edge.<ref name=":122" /> Then the new organ arises from these thick places along the muscle.<ref name=":122" />

Mesenteries are made up of a coelomic epithelium layer that lies over a layer of muscles, this is known as the mesothelium.<ref name=":122" /> The mesothelium is separated from the inner connective tissue layer by the basal lamina.<ref name=":122" />

=== Ossicles === alt=|left|thumb|320x320px|Chiridota rotifera a. dorsal view of animalb. wheel ossicle from body wallc. rods from body wall Ossicles are generally wheel-shaped with six spokes.<ref name=":85"/> Ossicles have rods, hooks, denticles, and miliary granules.<ref name=":16"/><ref name=":85"/> Many have even developed elaborate wheel and anchor-shaped ossicles contained in the body wall.<ref name=":16"/> The denticles are located on the inner rim and complex hub of the ossicles.<ref name=":85"/> On the lower side of the ossicles the denticles branch to the lower side of the hub and it forms a star-shape in the center.<ref name=":85"/> In the genus Chiridota, the ossicles attached to the body wall often occur in small clusters that are adjacent to the radii.<ref name=":03"/> Some genera of Chiridotidae are thought to have lost their body wall ossicles independently.<ref name=":26"/>

Hooks can only be found in three living genera of Chiridotidae: Taeniogyrus, Scoliorhapis, and Trochodota.<ref name=":03" /> In these genera, the ossicles are curved to form a loop, or eye.<ref name=":03" />

Wheel ossicles located in Chiridotidae contain numerous tiny teeth.<ref name=":03" /> For example, the Myriotrochid genus has teeth located in the inner margin and they can be either large and pronounced or completely absent.<ref name=":03" />

=== Calcareous Ring === The calcareous ring is made up of many small plates bound together by connective tissues.<ref name=":16"/> The radial plates contain a deep notch on the upper side of the ring.<ref name=":85"/> In Chiridotidae the ring is composed of dense labyrinthic stereom, that is thickest in the center of the plate.<ref name=":26"/> The stereom in this family is more porous than other families of sea cucumber.<ref name=":26"/>

The ring provides structural integrity in these animals by providing support to the pharynx, tentacles, water vascular system, and the radial nerve ring.<ref name=":26"/> Calcareous rings also serve as a point of insertion for the retractor muscle bands.<ref name=":26"/>

The genus Gymnopipina has short anterior projections in the calcareous ring and a madreporite sitting at the end of the long stone canal that has allowed scientists to classify it in the family Chiridotidae.<ref name=":16"/>

=== Ciliary Urns === Ciliary urns are a coelomic organ that gathers and excretes waste.<ref name=":6">{{Cite journal |last1=Curtis |first1=Michelle D. |last2=Turner |first2=Richard L. |date=2019-09-18 |title=Development and morphology of ciliary urns in the sea cucumberSynaptula hydriformis(Echinodermata: Holothuroidea) |url=https://doi-org.pallas2.tcl.sc.edu/10.1111/ivb.12264 |journal=Invertebrate Biology |volume=138 |issue=4 |doi=10.1111/ivb.12264 |s2cid=203895584 |issn=1077-8306|url-access=subscription }}</ref> It is thought that it aids in immunity.<ref name=":6" /> The Ciliary urn can also be called ciliated funnels or vibratile urnae.<ref name=":6" />

The echinoderm immune system has components of cellular and humoral defenses.<ref name=":6" /> Cellular defense comprises various types of coelomocytes with humoral defenses mediated by numerous immune-specific molecules.<ref name=":6" /> Invertebrate immunity is an innate defense.<ref name=":6" />

Ciliary urns have a cornucopia-shaped body and an invaginated ciliary field that collects and accumulates coelomocytes.<ref name=":6" /> They also take up waste materials from the coelom and dispose of them by deposition or release through the body wall.<ref name=":6" />

Ciliary urns vary in shape, size, and arrangement among species.<ref name=":6" /> Because ciliary urns run up the entire length of adult sea cucumbers, it is known that the urns are not associated with digestion, but rather they serve an excretory role in the immune system.<ref name=":6" />

The development and formation of the urn is still unknown; however, its function is clear.<ref name=":6" />

=== Movement === All families within Apodida do not have tube feet, including the Chiridotidae.<ref name=":26"/><ref name=":16"/> More recent studies have proven that anchors are important for movement.<ref name=":16" /> Other body parts used for movement include; the body wall, tentacles, papillae, and dermal ossicles.<ref name=":26" /> Apodids in general usually use peristaltic movements to navigate around the seafloor.<ref name=":16" /> Because of the lack of podia, tube feet, it is assumed that species use their anchors to hold onto the substratum.<ref name=":16" />

=== Tentacles === In the family Chiridotidae, the tentacles around the mouth are forked.<ref>{{Cite journal |last=Smirnov |first=A. V. |date=December 2015 |title=Paedomorphosis and heterochrony in the origin and evolution of the class holothuroidea |url=http://link.springer.com/10.1134/S003103011514018X |journal=Paleontological Journal |language=en |volume=49 |issue=14 |pages=1597–1615 |doi=10.1134/S003103011514018X |bibcode=2015PalJ...49.1597S |s2cid=86879502 |issn=0031-0301|url-access=subscription }}</ref> For species within the family, there are always an even number of tentacles, except for in the subfamily Chiridotinae<ref name=":85"/>'''.''' Tentacles are present in order to help the sea cucumbers guide food into their mouths.<ref name=":133">{{Cite journal |last1=Sun |first1=Jiamin |last2=Zhang |first2=Libin |last3=Pan |first3=Yang |last4=Lin |first4=Chenggang |last5=Wang |first5=Fang |last6=Kan |first6=Rentao |last7=Yang |first7=Hongsheng |date=February 2015 |title=Feeding behavior and digestive physiology in sea cucumber Apostichopus japonicus |url=https://doi-org.pallas2.tcl.sc.edu/10.1016/j.physbeh.2014.11.051 |journal=Physiology & Behavior |volume=139 |pages=336–343 |doi=10.1016/j.physbeh.2014.11.051 |pmid=25449414 |s2cid=25799235 |issn=0031-9384|url-access=subscription }}</ref><ref name=":74"/> frame The movement of tentacles changes with the movement of the water.<ref name=":74"/> There are two different responses to flow rheotaxis response, direct, and rheokinesis response, non-direct.<ref name=":74"/>

== Feeding == Sea cucumbers within the family Chiridotidae, feed on benthic sediments causing a change within the stability and stratification of the sediment.<ref name=":74"/> The benthic sediments that they consume as food contain fungal, bacterial, and detrital organic matter.<ref name=":143">{{Cite journal |last1=Navarro |first1=Pablo G. |last2=García-Sanz |first2=Sara |last3=Tuya |first3=Fernando |date=April 2014 |title=Contrasting displacement of the sea cucumber Holothuria arguinensis between adjacent nearshore habitats |url=https://doi-org.pallas2.tcl.sc.edu/10.1016/j.jembe.2014.01.008 |journal=Journal of Experimental Marine Biology and Ecology |volume=453 |pages=123–130 |doi=10.1016/j.jembe.2014.01.008 |bibcode=2014JEMBE.453..123N |issn=0022-0981|url-access=subscription }}</ref> The availability of food is the main driver for the Chiridotidae to move around the seafloor.<ref name=":74"/>

There are two different feeding strategies that have been observed; those that conduct a continuous search for food and those that shelter during periods when they reduce feeding activity.<ref name=":143"/>

Amongst all sea cucumbers, tentacles are linked to the mode of feeding conducted by the organism.<ref name=":133"/> The structure and type of feeding is different within even a species of sea cucumber.<ref name=":133" />

When collecting food the sea cucumbers extend their tentacles out to grab the particles.<ref name=":133" /><ref name=":74"/>

== Behavior == The Chiridotidae are a nocturnal family and because of this they contain light avoidance behaviors.<ref name=":92"/> This is behavior is thought to be a response to predation.<ref name=":143"/> Tentacles respond to changes in light at a molecular level, the response shown as a full body contraction when exposed.<ref name=":92" />

The rheotaxis response of their tentacles to water flow allows for muscles to turn when activated.<ref name=":74"/> During the rheokinesis response is a random movement in the water.<ref name=":74" />

The burrowing behavior of sea cucumbers within the family Chiridotidae is effected by the salinity and temperature of the water around them.<ref name=":152">{{Cite journal |last1=Mercier |first1=Annie |last2=Battaglene |first2=Stephen C. |last3=Hamel |first3=Jean-François |date=2000 |title=Proxy Login - University Libraries - USC |url=https://doi-org.pallas2.tcl.sc.edu/10.1023/A:1004121818691 |journal=Hydrobiologia |volume=440 |issue=1/3 |pages=81–100 |doi=10.1023/a:1004121818691 |s2cid=22303000 |issn=0018-8158|url-access=subscription }}</ref>

It has been observed by many researchers that abundance of sea cucumbers is affected by the moon phases.<ref name=":143" /><ref name=":152" /> Specifically, Chiridotidae are spotted in larger groups closer to a new moon than when it is not a new moon, it is thought that this is due to the lack of light.<ref name=":143" /><ref name=":152" />

==References== {{commons category}} <references /> {{Taxonbar|from=Q3466786}}

Category:Echinoderm families Category:Chiridotidae Category:Apodida Category:Extant Pennsylvanian first appearances Category:Taxa named by Hjalmar Östergren