Sea cucumber
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2008-07-06T23:50:19Z
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robot Adding: [[ms:Gamat]]
{{Taxobox
| name = Sea Cucumbers
| image =Sea cucumber in kona.jpg
| image_width = 250px
| image_caption = A Sea Cucumber
| regnum = [[Animalia]]
| phylum = [[Echinodermata]]
| subphylum = [[Echinozoa]]
| classis = '''Holothuroidea'''
| subdivision_ranks = [[Order (biology)|Orders]]
| subdivision =
*Subclass [[Apodacea]]
**[[Apodida]]
**[[Molpadiida]]
*Subclass [[Aspidochirotacea]]
**[[Aspidochirotida]]
**[[Elasipodida]]
*Subclass [[Dendrochirotacea]]
**[[Dactylochirotida]]
**[[Dendrochirotida]]
}}
The '''sea cucumber''' is an [[echinoderm]] of the [[class (biology)|class]] '''Holothuroidea''', with an elongated body and leathery skin, which is found on the sea floor worldwide. It is so named because of its [[cucumber]]-like shape. The body contains a single, branched [[gonad]].
Like all echinoderms, sea cucumbers have an [[endoskeleton]] just below the skin, calcified structures that are usually reduced to isolated microscopic ossicles (or sclerietes) joined by connective tissue. These can sometimes be enlarged to flattened plates, forming an armour. In pelagic species (Order Elasipodida, family Pelagothuriidae), the skeleton is often absent<ref>[http://www.geobiologie.uni-goettingen.de/people/mreich/pdf/PDFs/POST_Dijon_Seegurken1.pdf Cambrian holothurians ? – The early fossil record and evolution of Holothuroidea]</ref>.
==Overview==
[[Image:Conspicuous Sea Cucumber, Coconut Island, Hawaii.JPG|thumb|200px|right|Conspicuous Sea Cucumber, [[Coconut Island]], Hawaii]]
[[Image:Holothuroidea (Sea cucumber feeding).jpg|thumb|200px|right|A sea cucumber feeding while on gravel]]
[[Image:Sea cucumber defence.JPG|Sea cucumber in [[Mahé, Seychelles]] ejects sticky filaments from the anus in self-defence. |200px|thumb|right]]
Sea cucumbers are generally [[scavenger]]s, feeding on debris in the [[benthic zone]] of the ocean. Exceptions include [[Pelagic zone|pelagic]] cucumbers and the species ''Rynkatropa pawsoni'', which has a commensal relationship with deep-sea [[anglerfish]].<ref> Brusca, R.C., Brusca, G.J.; ''Invertebrates''. Sinauer Associates, Massachusetts, 1990.</ref> The [[diet (nutrition)|diet]] of most cucumbers consists of [[plankton]] and decaying organic matter found in the sea. Some sea cucumbers position themselves in [[Ocean current|currents]] and catch food that flows by with their open [[tentacle]]s. They also sift through the bottom [[sediment]]s using their tentacles.
Some species of coral-reef sea cucumbers within the order [[Aspidochirotida]] can defend themselves by expelling their sticky cuvierian tubules (enlargements of the respiratory tree that float freely in the [[Body cavity|coelom]]) to entangle potential predators. When startled, these cucumbers may expel some of them through a tear in the wall of the [[cloaca]] in an [[Autotomy|autotomic]] process known as [[Evisceration (autotomy)|evisceration]]. Replacement tubules grow back in one-and-a-half to five weeks, depending on the species.<ref>{{cite journal | title = Biomechanics of adhesion in sea cucumber cuvierian tubules (echinodermata, holothuroidea) | journal = Integrative and Comparative Biology | date = 2002-12-01 | last = Flammang | first = Patrick | coauthors = Ribesse, Jerome & Jangoux, Michel | url = http://findarticles.com/p/articles/mi_qa4054/is_200212/ai_n9160035/pg_1 | accessdate = 2007-10-03 | language = English }}</ref>
They can be found in great numbers on the deep sea floor, where they often make up the majority of the animal biomass.<ref>{{cite web | url = http://jrscience.wcp.muohio.edu/fieldcourses05/PapersMarineEcologyArticles/SeaCucumbers.html | title = Sea Cucumbers | last = Miller | first = Nat | accessdate = 2007-10-03 | language = English}}</ref> At depths deeper than 5.5 mi (8.8 km), sea cucumbers comprise 90% of the total mass of the macrofauna<ref>[http://www.answers.com/topic/sea-cucumber Sci-Tech Encyclopedia: Holothuroidea]</ref>. The body of deep water holothurians is made of a tough gelatinous tissue with unique properties that makes the animals able to control their own buoyancy, making it possible for them to either live on the ocean floor or to float over it to move to new locations with a minimum of energy.<ref>{{cite web | url = http://www.oceanexplorer.noaa.gov/explorations/07mexico/logs/june18/june18.html | title = The Kingdom of the Echinoderm | date = 2007-06-18 | first = Bob | last = Carney | accessdate = 2007-10-03 | language = English}}</ref>
In more shallow waters, sea cucumbers can form dense populations. The strawberry sea cucumber (''Squamocnus brevidentis'') of [[New Zealand]] lives on rocky walls around the southern coast of the South Island where populations sometimes reach densities of 1,000 animals per square metre. For this reason, one such area in [[Fiordland]] is simply called the strawberry fields.<ref>{{cite web | url = http://www.niwascience.co.nz/ncabb/abb/ma/pi/2003-03/cucumber | title = Aquatic Biodiversity & Biosecurity: Shedding new light on the humble sea cucumber | accessdate = 2007-10-03 | last = Alcock | first = Nick | date = 2007 | language = English}}</ref>
Sea cucumbers extract oxygen from water in a pair of 'respiratory trees' that branch off the [[cloaca]] just inside the [[anus]], so that they 'breathe' by drawing water in through the anus and then expelling it.<ref>{{cite web | url = http://www.fegi.ru/prim/sea/golot.htm
| title = Holothurians or sea cucumbers | accessdate = 2007-10-03}}</ref><ref>{{cite web | url = http://www.comoxvalleynaturalist.bc.ca/knowing_nature/2006/sea_cucumbers.html | title = Knowing Nature... Cool as a Sea Cucumber | accessdate = 2007-10-03 | last = Ingram | first = Jocie | date = 2006-06-16 | language = English }}</ref> A variety of [[fish]], most commonly [[pearl fish]], have evolved a [[commensalism|commensalistic]] symbiotic relationship with sea cucumbers in which the pearl fish will live in sea cucumber's cloaca using it for protection from predation, a source of food (the nutrients passing in and out of the anus from the water), and to develop into their adult stage of life. Many [[polychaete]] worms and [[crab]]s have also specialized to use the cloacal respiratory trees for protection by living inside the sea cucumber.<ref>{{cite web | url = http://www.advancedaquarist.com/issues/mar2003/invert.htm | title = Aquarium Invertebrates | first = Rob, Ph.D.| last = Toonen | accessdate = 2007-10-03 | date = 2003 | language = English}}</ref>
Ten percent of the [[blood cell]] pigment of the sea cucumber is [[vanadium]]. Just as the [[horseshoe crab]] has blue blood rather than [[red blood cell|red blood]] (colored by iron in [[hemoglobin]]) because of [[copper]] in the [[hemocyanin]] pigment, the blood of the sea cucumber is yellow because of the vanadium in the [[vanabins|vanabin]] pigment<ref>{{cite web | last = Natkin | first = Michael | title = Blood Color | work = Science Facts | publisher = Soak (Source Of All Knowledge) | date = 2007 | url = http://www.soak.com/topic/sciencefacts/article/tshow/98556/blood+color | accessdate = 2007-11-16 }}</ref>. Nonetheless, there is no evidence that vanabins carry [[oxygen]], in contrast to hemoglobin and hemocyanin.
Sea cucumbers reproduce by releasing [[sperm]] and [[ova]] into the ocean water. Depending on conditions, one organism can produce thousands of gametes.
The largest [[Americas|American]] species is ''Holothuria floridana'', which abounds just below low-water mark on the [[Florida]] reefs.
The most common way to separate the subclasses is by looking at their oral tentacles. Subclass Dendrochirotacea has 8-30 oral tentacles, subclass Aspidochirotacea has 10-30 leaflike or shieldlike oral tentacles, while subclass Apodacea may have up to 25 simple or [[pinnate]] oral tentacles and is also characterized by reduced or absent tube feet, as in the order [[Apodida]].{{fact|date=July 2007}}
==Sea cucumbers as food and medicine==
[[Image:Yokohama Chinese Medicine Sea cucumber 2.jpg|thumb|200px|Dried sea cucumbers in a Chinese pharmacy]]"To supply the markets of [[Southern China]], [[Makassar|Macassan]] [[trepanger]]s traded with the [[Indigenous Australians]] of [[Arnhem Land]]. This [[Macassan contact with Australia]] is the first recorded example of trade between the inhabitants of the Australian continent and their Asian neighbours."
Some varieties of sea cucumber (known as ''[[gamat]]'' in Malaysia or ''trepang'' in Indonesia) are said to have excellent healing properties. There are pharmaceutical companies being built based on this gamat product. Extracts are prepared and made into oil, cream or cosmetics. Some products are intended to be taken internally. The effectiveness of sea cucumber extract in tissue repair has been the subject of serious study<ref>[http://www.ansinet.org/fulltext/pjbs/pjbs6242068-2072.pdf Study of healing properties] (PDF format)</ref>. It is believed that the sea cucumber contains all the fatty acids necessary to play an active role in tissue repair.<ref>[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10523072&dopt=Abstract/ Effects on tissue repair]</ref>.
Sea cucumbers are believed to be endowed with aphrodisiac powers in the Far East. The reason for this belief is the peculiar reaction of the creature on being kneaded or disturbed slightly with fingers. It swells and stiffens and a jet of water is released from one end. This behaviour is similar to the [[erection]] and subsequent [[ejaculation]] of the male human [[penis]]. After releasing the jet which is a defensive mechanism and contains irritants the creature loses its stiffness and reverts to its original state.{{Fact|date=September 2007}}
On [[December 21]], [[2007]], a study published in [[PLoS Pathogens]] found that a [[lectin]] from ''[[Dendrochirotida|Cucumaria echinata]]'' impaired the development of the [[malaria]] parasite when produced by transgenic [[Anopheles|mosquitoes]].<ref>{{cite journal |author=Yoshida S, Shimada Y, Kondoh D, ''et al'' |title=Hemolytic C-type lectin CEL-III from sea cucumber expressed in transgenic mosquitoes impairs malaria parasite development |journal=PLoS Pathog. |volume=3 |issue=12 |pages=e192 |year=2007 |pmid=18159942 |doi=10.1371/journal.ppat.0030192 |url=http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.0030192}}</ref>.
==Sea cucumbers in art==
[[Image:Sjogurka stor ugglan.gif|thumb|300px|'''Sea cucumber''' (a - Tentacles, b - Cloaca, c - Ambulacral feet on the ventral side, d - Papillae on the back)]]
Sea cucumbers have inspired musical composition: in the first of his ''[[Embryons desséchés]]'' for [[piano]] solo, [[Erik Satie]] presents the "(Desiccated embryo) of a Holothurian" and inserts a description of the animal in the score:
:The Holothurian crawls across boulders and rocky surfaces.
:This sea-animal purrs like a cat; also, it produces disgusting silky threads.
:Light appears to have an incommodating effect on it.
Nonetheless it is the sea cucumber's closest relative (the [[sea urchin|echinoidea or sea urchin]]) that gets the most attention from scientists, both as an [[embryo]] and as a [[fossil]].
Sea cucumbers have also inspired thousands of [[haiku]] in [[Japan]], where they are called ''namako'' (ナマコ), written with characters that can be translated "sea mice". In English translations of these haiku, they are usually called "sea slugs"; according to the [[Oxford English Dictionary]], the term "sea slug" originally referred to holothurians (in the 18th century), though biologists now use the name only for the [[nudibranch]] molluscs, marine relatives of land slugs. Almost 1,000 Japanese holothurian haiku translated into English appear in the book ''Rise, Ye Sea Slugs!'' by Robin D. Gill (ISBN 0-9742618-0-7).
==See also==
[[Image:Sea cucumber in fuji.JPG|Sea cucumber in [[Fiji]]|200px|thumb|right]]
* [[Trepanging]]
* [[Gamat]]
==Notes==
{{reflist}}
== External links ==
{{wikispecies|Holothuroidea}}
*[http://chekjawa.nus.edu.sg/ria/text/cucumbers.htm Chek Jawa Link for more photos of sea cucumber and more.]
[[Category:Echinoderms]]
[[Category:Edible shellfish]]
[[Category:Commercial echinoderms]]
[[Category:Chinese ingredients]]
[[Category:Korean ingredients]]
[[Category:Fauna of Japan]]
[[Category:Japanese seafood]]
[[Category:Seafood]]
[[Category:Indonesian cuisine]]
[[ar:خيار البحر]]
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[[es:Holothuroidea]]
[[fa:خیار دریایی]]
[[fr:Holothurie]]
[[io:Holoturio]]
[[id:Teripang]]
[[it:Holothuroidea]]
[[he:מלפפון ים]]
[[ka:ჰოლოთურიები]]
[[lt:Holoturijos]]
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[[oc:Oloturia]]
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[[ru:Голотурии]]
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