Sea cucumbers are

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the ...

s from the

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently ...

Holothuroidea (). They are

marine animal Marine life, sea life, or ocean life is the plants, animals and other organisms that live in the salt water of seas or oceans, or the brackish water of coastal estuaries. At a fundamental level, marine life affects the nature of the planet. M ...

s with a leathery skin and an elongated body containing a single, branched

gonad A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sp ...

. Sea cucumbers are found on the

sea floor The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

worldwide. The number of holothurian () species worldwide is about 1,717, with the greatest number being in the

Asia-Pacific Asia-Pacific (APAC) is the part of the world near the western Pacific Ocean. The Asia-Pacific region varies in area depending on context, but it generally includes East Asia, Russian Far East, South Asia, Southeast Asia, Australia and Paci ...

region. Many of these are gathered for human consumption and some species are cultivated in aquaculture systems. The harvested product is variously referred to as '' trepang'', ''namako'', ''bêche-de-mer'', or ''balate''. Sea cucumbers serve a useful role in the

marine ecosystem Marine ecosystems are the largest of Earth's aquatic ecosystems and exist in waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the sur ...

as they help recycle nutrients, breaking down

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts comm ...

and other

organic matter Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have c ...

, after which

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

can continue the

decomposition Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and ...

process. Like all

s, sea cucumbers have an

endoskeleton An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue. Overview An endoskeleton is a skeleton that is on the ...

just below the skin, calcified structures that are usually reduced to isolated microscopic

ossicles The ossicles (also called auditory ossicles) are three bones in either middle ear that are among the smallest bones in the human body. They serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea). The absence of the auditor ...

(or sclerietes) joined by connective tissue. In some species these can sometimes be enlarged to flattened plates, forming an armour. In

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...

species such as '' Pelagothuria natatrix'' (order Elasipodida, family Pelagothuriidae), the skeleton is absent and there is no calcareous ring. Sea cucumbers are named for their resemblance to the fruit of the

cucumber Cucumber (''Cucumis sativus'') is a widely-cultivated creeping vine plant in the Cucurbitaceae family that bears usually cylindrical fruits, which are used as culinary vegetables. Most sea cucumbers, as their name suggests, have a soft and cylindrical body, more or less lengthened, rounded off and occasionally fat in the extremities, and generally without solid appendages. Their shape ranges from almost spherical for "sea apples" (genus ''

Pseudocolochirus Sea apple is the common name for the colorful and somewhat round sea cucumbers of the genus ''Pseudocolochirus'', found in Indo-Pacific waters. Sea apples are filter feeders with tentacles, ovate bodies, and tube-like feet. As with many other ho ...

'') to serpent-like for Apodida or the classic sausage-shape, while others resemble caterpillars. The mouth is surrounded by tentacles, which can be pulled back inside the animal. Holothurians measure generally between 10 and 30 centimetres long, with extremes of some millimetres for '' Rhabdomolgus ruber'' and up to more than 3 metres for '' Synapta maculata''. The largest

American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

species, '' Holothuria floridana'', which abounds just below low-water mark on the

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and ...

reefs, has a volume of well over , and long. Most possess five rows of tube feet (called " podia"), but Apodida lacks these and moves by crawling; the podia can be of smooth aspect or provided with fleshy appendages (like '' Thelenota ananas''). The podia on the dorsal surface generally have no locomotive role, and are transformed into papillae. At one of the extremities opens a rounded mouth, generally surrounded with a crown of tentacles which can be very complex in some species (they are in fact modified podia); the anus is postero-dorsal. Holothurians do not look like other echinoderms at first glance, because of their tubular body, without visible skeleton nor hard appendixes. Furthermore, the fivefold symmetry, classical for echinoderms, although preserved structurally, is doubled here by a bilateral symmetry which makes them look like

chordate A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These fi ...

s. However, a central symmetry is still visible in some species through five 'radii', which extend from the mouth to the anus (just like for sea urchins), on which the tube feet are attached. There is thus no "oral" or "aboral" face as for sea stars and other echinoderms, but the animal stands on one of its sides, and this face is called ''trivium'' (with three rows of tube feet), while the dorsal face is named ''bivium''. A remarkable feature of these animals is the "catch"

collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whol ...

that forms their body wall."Catch" collagen has two states, soft and stiff, that are under neurological contro
Jose del Castillo and David S. Smith. (1996) "We Still Invoke Friction and Occam's Razor to Explain Catch in the Spines of ''Eucidaris Tribuloides''." ''Biological Bulletin'' 190:243-244
/ref> This can be loosened and tightened at will, and if the animal wants to squeeze through a small gap, it can essentially liquefy its body and pour into the space. To keep itself safe in these crevices and cracks, the sea cucumber will hook up all its collagen fibers to make its body firm again. The most common way to separate the subclasses is by looking at their oral tentacles. Order Apodida have a slender and elongate body lacking tube feet, with up to 25 simple or

pinnate Pinnation (also called pennation) is the arrangement of feather-like or multi-divided features arising from both sides of a common axis. Pinnation occurs in biological morphology, in crystals, such as some forms of ice or metal crystals, an ...

oral tentacles. Aspidochirotida are the most common sea cucumbers encountered, with a strong body and 10–30 leaflike or shield-like oral tentacles. Dendrochirotida are filter-feeders, with plump bodies and 8–30 branched oral tentacles (which can be extremely long and complex). Image:Apostichopus californicus.004 - Aquarium Finisterrae.jpg, Details of the mouth with its tentacles. Image:Synaptula lamberti.JPG, ''

Synaptula lamperti ''Synaptula lamperti'' is a species of sea cucumber in the family Synaptidae in the phylum Echinodermata, found on coral reefs in the Indo-Pacific region. The echinoderms are marine invertebrates and include the sea urchins, starfish and sea cuc ...

'' lives on sponges (here in

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Gui ...

). Image:Reef1118 - Flickr - NOAA Photo Library.jpg, '' Synapta maculata'', the longest known sea cucumber ( Apodida). Image:Thelenota anax géante.JPG, The king sea cucumber ('' Thelenota anax'', family Stichopodidae) is one of the heaviest known holothurians. Image:Chiridota heheva.jpg, ''

Chiridota heheva ''Chiridota heheva'' is a species of sea cucumber Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found o ...

'', abyssal species. Image:Cucumaria big.jpg, ''

Cucumaria miniata ''Cucumaria miniata'' is a species of sea cucumber. It is commonly known as the orange sea cucumber or red sea cucumber due to its striking color. This northeast Pacific species is often found wedged in between rocks or crevices at the coast or ...

'', a filter-feeding sea cucumber. Image:Pseudocolochirus axiologus.jpg, ''

'' ("sea apple"). Image:Holothuria leucospilota.jpg, ''

Holothuria leucospilota ''Holothuria leucospilota'', commonly known as the black sea cucumber or black tarzan, is a species of marine invertebrate in the family Holothuriidae. It is placed in the subgenus ''Mertensiothuria'' making its full scientific name ''Holothuria ...

'' Image:Isostichopus badionotus.jpg, '' Isostichopus badionotus'' Image:Treasure chest candycane sea cucumber 2.jpg, '' Thelenota rubralineata'' Image:Holothuria fuscopunctata.jpg, ''

Holothuria fuscopunctata ''Holothuria fuscopunctata'', the elephant trunkfish, is a species of sea cucumber in the family Holothuriidae native to shallow water in the tropical Indo-Pacific. It is placed in the subgenus ''Microthele'', making its full name ''Holothuria ( ...

'' Image:Bohadschia argus.jpg, ''

Bohadschia argus ''Bohadschia argus'', the leopard sea cucumber, is a species of marine invertebrate in the family Holothuriidae. It is the type species of the genus ''Bohadschia''; Jaeger, 1833. Description ''Bohadschia argus'' is sausage-shaped with a smooth, ...

Anatomy

Sea cucumbers are typically in length, although the smallest known species are just long, and the largest can reach . The body ranges from almost spherical to worm-like, and lacks the arms found in many other echinoderms, such as

starfish Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish a ...

. The anterior end of the animal, containing the mouth, corresponds to the oral pole of other echinoderms (which, in most cases, is the underside), while the posterior end, containing the anus, corresponds to the aboral pole. Thus, compared with other echinoderms, sea cucumbers can be said to be lying on their side. Conspicuous Sea Cucumber, Coconut Island, Hawaii

Conspicuous Sea Cucumber, Coconut Island, Hawaii

Body plan

The body of a holothurian is roughly cylindrical. It is radially symmetrical along its longitudinal axis, and has weak bilateral symmetry transversely with a dorsal and a ventral surface. As in other Echinozoans, there are five ambulacra separated by five ambulacral grooves, the interambulacra. The ambulacral grooves bear four rows of tube feet but these are diminished in size or absent in some holothurians, especially on the dorsal surface. The two dorsal ambulacra make up the bivium while the three ventral ones are known as the trivium.''Cucumaria frondosa''
Invertebrate anatomy online. ed2012-02-12. At the anterior end, the mouth is surrounded by a ring of tentacles which are usually retractable into the mouth. These are modified tube feet and may be simple, branched or arborescent. They are known as the introvert and posterior to them there is an internal ring of large calcareous ossicles. Attached to this are five bands of muscle running internally longitudinally along the ambulacra. There are also circular muscles, contraction of which cause the animal to elongate and the introvert to extend. Anterior to the ossicles lie further muscles, contraction of which cause the introvert to retract. The body wall consists of an epidermis and a dermis and contains smaller calcareous ossicles, the types of which are characteristics which help to identify different species. Inside the body wall is the coelom which is divided by three longitudinal

mesenteries In zoology, a mesentery is a membrane inside the body cavity of an animal. The term identifies different structures in different phyla: in vertebrates it is a double fold of the peritoneum enclosing the intestines; in other organisms it forms com ...

which surround and support the internal organs.

Digestive system

pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its st ...

lies behind the mouth and is surrounded by a ring of ten

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an ad ...

plates. In most sea cucumbers, this is the only substantial part of the skeleton, and it forms the point of attachment for muscles that can retract the tentacles into the body for safety as for the main muscles of the body wall. Many species possess an

oesophagus The esophagus ( American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to ...

and

stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

, but in some the pharynx opens directly into the

intestine The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans an ...

. The intestine is typically long and coiled, and loops through the body three times before terminating in a

cloaca In animal anatomy, a cloaca ( ), plural cloacae ( or ), is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles and birds, ...

l chamber, or directly as the

anus The anus (Latin, 'ring' or 'circle') is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, the residual semi-solid waste that remains after food digestion, which, ...

Nervous system

Sea cucumbers have no true

brain A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. I ...

. A ring of neural tissue surrounds the oral cavity, and sends nerves to the tentacles and the

. The animal is, however, quite capable of functioning and moving about if the nerve ring is surgically removed, demonstrating that it does not have a central role in nervous coordination. In addition, five major nerves run from the nerve ring down the length of the body beneath each of the ambulacral areas. Most sea cucumbers have no distinct sensory organs, although there are various nerve endings scattered through the skin, giving the animal a sense of touch and a sensitivity to the presence of light. There are, however, a few exceptions: members of the Apodida order are known to possess statocysts, while some species possess small eye-spots near the bases of their tentacles.

Respiratory system

Sea cucumbers extract oxygen from water in a pair of "respiratory trees" that branch in the

just inside the

, so that they "breathe" by drawing water in through the anus and then expelling it. The trees consist of a series of narrow tubules branching from a common duct, and lie on either side of the digestive tract. Gas exchange occurs across the thin walls of the tubules, to and from the fluid of the main body cavity. Together with the intestine, the respiratory trees also act as excretory organs, with nitrogenous waste diffusing across the tubule walls in the form of

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous ...

and

phagocytic Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is c ...

coelomocytes depositing particulate waste.

Circulatory systems

Like all echinoderms, sea cucumbers possess both a water vascular system that provides hydraulic pressure to the tentacles and tube feet, allowing them to move, and a ''haemal system''. The latter is more complex than that in other echinoderms, and consists of well-developed vessels as well as open

sinuses Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity. The maxillary sinuses are located under the eyes; the frontal sinuses are above the eyes; the ethmoidal sinuses are between the eyes and the spheno ...

. A central haemal ring surrounds the pharynx next to the ring canal of the water vascular system, and sends off additional vessels along the radial canals beneath the ambulacral areas. In the larger species, additional vessels run above and below the intestine and are connected by over a hundred small muscular ampullae, acting as miniature hearts to pump blood around the haemal system. Additional vessels surround the respiratory trees, although they contact them only indirectly, via the coelomic fluid. Indeed, the blood itself is essentially identical with the coelomic fluid that bathes the organs directly, and also fills the water vascular system. Phagocytic coelomocytes, somewhat similar in function to the

white blood cell White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...

s of

vertebrates Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with ...

, are formed within the haemal vessels, and travel throughout the body cavity as well as both circulatory systems. An additional form of coelomocyte, not found in other echinoderms, has a flattened discoid shape, and contains

hemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythroc ...

. As a result, in many (though not all) species, both the blood and the coelomic fluid are red in colour.

Vanadium Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer ( pass ...

has been reported in high concentrations in holothurian blood, however researchers have been unable to reproduce these results.

Locomotive organs

Like all echinoderms, sea cucumbers possess

pentaradial symmetry Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, take the face of a human being which has a pla ...

, with their bodies divided into five nearly identical parts around a central axis. However, because of their posture, they have secondarily evolved a degree of bilateral symmetry. For example, because one side of the body is typically pressed against the substratum, and the other is not, there is usually some difference between the two surfaces (except for Apodida). Like

sea urchin Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) o ...

s, most sea cucumbers have five strip-like ambulacral areas running along the length of the body from the mouth to the anus. The three on the lower surface have numerous

tube feet Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on br ...

, often with suckers, that allow the animal to crawl along; they are called ''trivium''. The two on the upper surface have under-developed or vestigial tube feet, and some species lack tube feet altogether; this face is called ''bivium''. In some species, the ambulacral areas can no longer be distinguished, with tube feet spread over a much wider area of the body. Those of the order Apodida have no tube feet or ambulacral areas at all, and burrow through sediment with muscular contractions of their body similar to that of worms, however five radial lines are generally still obvious along their body. Even in those sea cucumbers that lack regular tube feet, those that are immediately around the mouth are always present. These are highly modified into retractile

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s, much larger than the locomotive tube feet. Depending on the species, sea cucumbers have between ten and thirty such tentacles and these can have a wide variety of shapes depending on the diet of the animal and other conditions. Many sea cucumbers have papillae, conical fleshy projections of the body wall with sensory tube feet at their apices. These can even evolve into long antennae-like structures, especially on the abyssal genus ''

Scotoplanes ''Scotoplanes'' is a genus of deep-sea sea cucumbers of the family Elpidiidae. Its species are commonly known as sea pigs. Locomotion Members of the Elpidiidae have particularly enlarged tube "feet" that have taken on a leg-like appearance, u ...

''.

Endoskeleton

Echinoderms typically possess an internal skeleton composed of plates of calcium carbonate. In most sea cucumbers, however, these have become reduced to microscopic ossicles embedded beneath the skin. A few genera, such as '' Sphaerothuria'', retain relatively large plates, giving them a scaly armour.

Life history and behaviour

Habitat

Sea cucumbers can be found in great numbers on the deep seafloor, where they often make up the majority of the animal biomass. At depths deeper than , sea cucumbers comprise 90% of the total mass of the macrofauna. Sea cucumbers form large herds that move across the bathygraphic features of the ocean, hunting food. The body of some deep water holothurians, such as ''Enypniastes eximia'', ''Peniagone leander'' and ''Paelopatides confundens'', 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 actively swim or float over it in order to move to new locations, in a manner similar to how the group Torquaratoridae floats through water. Holothurians appear to be the echinoderms best adapted to extreme depths, and are still very diversified beyond 5,000 m deep: several species from the family

Elpidiidae Elpidiidae is a family of deep-sea sea cucumber Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found o ...

("sea pigs") can be found deeper than 9,500 m, and the record seems to be some species of the genus ''

Myriotrochus ''Myriotrochus'' is a genus of sea cucumber Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on th ...

'' (in particular ''

Myriotrochus bruuni ''Myriotrochus'' is a genus of sea cucumber Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on th ...

''), identified down to 10,687 meters deep. In more shallow waters, sea cucumbers can form dense populations. The strawberry sea cucumber (''Squamocnus brevidentis'') of

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...

lives on rocky walls around the southern coast of the South Island where populations sometimes reach densities of 1,000 animals per square meter (93 /sq ft). For this reason, one such area in

Fiordland Fiordland is a geographical region of New Zealand in the south-western corner of the South Island, comprising the westernmost third of Southland. Most of Fiordland is dominated by the steep sides of the snow-capped Southern Alps, deep lake ...

is called the strawberry fields.

Locomotion

Some abyssal species in the abyssal order Elasipodida have evolved to a "benthopelagic" behaviour: their body is nearly the same density as the water around them, so they can make long jumps (up to high), before falling slowly back to the ocean floor. Most of them have specific swimming appendages, such as some kind of umbrella (like ''

Enypniastes ''Enypniastes'' is a genus of deep-sea sea cucumber. It is monotypic, being represented by the single species ''Enypniastes eximia''. Due to its unique appearance, the species has been dubbed the headless chicken fish, headless chicken monster, a ...

''), or a long lobe on top of the body ('' Psychropotes''). Only one species is known as a true completely

species, that never comes close to the bottom: '' Pelagothuria natatrix''.

Diet

Holothuroidea are generally

scavenger Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feedin ...

s, feeding on debris in the

benthic zone The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning " ...

of the ocean. Exceptions include some

cucumbers and the species ''Rynkatorpa pawsoni'', which has a

commensal Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit fro ...

relationship with deep-sea

anglerfish The anglerfish are fish of the teleost order Lophiiformes (). They are bony fish named for their characteristic mode of predation, in which a modified luminescent fin ray (the esca or illicium) acts as a lure for other fish. The luminescence ...

. The

diet Diet may refer to: Food * Diet (nutrition), the sum of the food consumed by an organism or group * Dieting, the deliberate selection of food to control body weight or nutrient intake ** Diet food, foods that aid in creating a diet for weight loss ...

of most cucumbers consists of

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a cruc ...

and decaying organic matter found in the sea. Some sea cucumbers position themselves in currents and catch food that flows by with their open tentacles. They also sift through the bottom

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand ...

s using their tentacles. Other species can dig into bottom silt or sand until they are completely buried. They then extrude their feeding tentacles, ready to withdraw at any hint of danger. In the South Pacific sea cucumbers may be found in densities of 40 individuals per square meter (33 /sq yd). These populations can process 19 kilograms of sediment per square meter (34 lb /sq yd) per year. The shape of the tentacles is generally adapted to the diet, and to the size of the particles to be ingested: the filter-feeding species mostly have complex arborescent tentacles, intended to maximize the surface area available for filtering, while the species feeding on the substratum will more often need digitate tentacles to sort out the nutritional material; the detritivore species living on fine sand or mud more often need shorter "peltate" tentacles, shaped like shovels. A single specimen can swallow more than 45 kg of sediment a year, and their excellent digestive capacities allow them to reject a finer, purer and homogeneous sediment. Therefore, sea cucumbers play a major role in the biological processing of the sea bed (bioturbation, purge, homogenization of the substratum etc.). Image:Euapta godeffroyi, détail.jpg, The mouth of an ''

Euapta godeffroyi ''Euapta godeffroyi'', the sticky snake sea cucumber, is a species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defi ...

'', showing pinnate tentacles. Image:Apostichopus californicus.004 - Aquarium Finisterrae.jpg, Mouth of a '' Holothuria sp.'', showing peltate tentacles. Image:Cucumaria main.jpg, Mouth of a ''

'', with dendritic tentacles, for filtering the water. Image:Holothurie sp..jpg, Faeces of an holothurian. This participates in sediment homogenization and purification.

Communication and sociability

Reproduction

Most sea cucumbers reproduce by releasing

sperm Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, ...

and ova into the ocean water. Depending on conditions, one organism can produce thousands of

gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce ...

s. Sea cucumbers are typically

dioecious Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproducti ...

, with separate male and female individuals, but some species are protandric. The reproductive system consists of a single

, consisting of a cluster of tubules emptying into a single duct that opens on the upper surface of the animal, close to the tentacles. At least 30 species, including the red-chested sea cucumber (''

Pseudocnella insolens ''Hemiocnus insolens'' is a species of sea cucumber from the family Cucumariidae Cucumariidae is a family of sea cucumbers, marine animals with elongated bodies, leathery skins and tentacles that are found on the sea bed. Description Members ...

''), fertilize their eggs internally and then pick up the fertilized zygote with one of their feeding tentacles. The egg is then inserted into a pouch on the adult's body, where it develops and eventually hatches from the pouch as a juvenile sea cucumber. A few species are known to brood their young inside the body cavity, giving birth through a small rupture in the body wall close to the anus.

Development

In all other species, the egg develops into a free-swimming

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...

, typically after around three days of development. The first stage of larval development is known as an auricularia, and is only around in length. This larva swims by means of a long band of

cilia The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike proje ...

wrapped around its body, and somewhat resembles the bipinnaria larva of starfish. As the larva grows it transforms into the doliolaria, with a barrel-shaped body and three to five separate rings of cilia. The pentacularia is the third larval stage of sea cucumber, where the tentacles appear. The tentacles are usually the first adult features to appear, before the regular tube feet.

Symbiosis and commensalism

Numerous small animals can live in

symbiosis Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or para ...

commensalism Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit fr ...

with sea cucumbers, as well as some parasites. Some cleaner shrimps can live on the tegument of holothurians, in particular several species of the genus ''

Periclimenes ''Periclimenes'', commonly known as glass shrimp or cleaner shrimp, is a commensal and often symbiotic genus of semi-transparent shrimp within the family Palaemonidae. Species of this large genus feature a wide variety of coloration and patterns, ...

'' (genus which is specialized in echinoderms), in particular ''

Periclimenes imperator ''Periclimenes imperator'', known as the emperor shrimp, is a species of shrimp with a wide distribution across the Indo-Pacific. It lives commensally on a number of hosts, including the sea slug Sea slug is a common name for some marin ...

''.. A variety of fish, most commonly pearl fish, have evolved a 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 Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made ...

worms (family Polynoidae) and

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all th ...

s (like ''

Lissocarcinus orbicularis ''Lissocarcinus orbicularis'', common names sea cucumber crab, red-spotted white crab, and harlequin crab is a species of crab in the family Portunidae. This species gains one of its names from its close-knit relationship with holothuroids, the ...

'') have also specialized to use the mouth or the cloacal respiratory trees for protection by living inside the sea cucumber. Nevertheless, holothurians species of the genus ''

Actinopyga ''Actinopyga'' is a genus of sea cucumbers found in coastal waters in tropical and temperate regions. Species There are 18 recognized species: Image:Actinopyga capillata.jpg, '' Actinopyga capillata'' Image:Actinopyga caerulea.JPG, '' Actin ...

'' have anal teeth that prevent visitors from penetrating their anus. Sea cucumbers can also shelter bivalvia as endocommensals, such as ''

Entovalva ''Entovalva'' is a genus of bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting ...

sp''. Image:Swimming Crab - Lissocarcinus Orbicularis on Sea Cucumber.jpg, ''

'', a symbiotic crab. Image:Shrimp on Sea Cucumber.jpg, ''

'', a symbiotic shrimp. Image:Polychètes sur T. anax.JPG, Polynoid worms on a king sea cucumber.

Predators and defensive systems

Sea cucumbers are often ignored by most of the marine predators because of the toxins they contain (in particular

holothurin The holothurins are a group of toxins originally isolated from the sea cucumber '' Actinopyga agassizii''. They are contained within clusters of sticky threads called Cuvierian tubules which are expelled from the sea cucumber as a mode of sel ...

) and because of their often spectacular defensive systems. However, they remain a prey for some highly specialized predators which are not affected by their toxins, such as the big mollusks ''

Tonna galea ''Tonna galea'', commonly known as the giant tun, is a species of marine gastropod mollusc in the family Tonnidae (also known as the tun shells). This very large sea snail or tun snail is found in the North Atlantic Ocean as far as the coast of ...

'' and '' Tonna perdix'', which paralyzes them using powerful poison before swallowing them completely. Some other less specialized and opportunist predators can also prey on sea cucumbers sometimes when they cannot find any better food, such as certain species of fish (

triggerfish Triggerfish are about 40 species of often brightly colored fish of the family Balistidae. Often marked by lines and spots, they inhabit tropical and subtropical oceans throughout the world, with the greatest species richness in the Indo-Pacif ...

pufferfish Tetraodontidae is a family of primarily marine and estuarine fish of the order Tetraodontiformes. The family includes many familiar species variously called pufferfish, puffers, balloonfish, blowfish, blowies, bubblefish, globefish, swellfis ...

) and crustaceans (crabs, lobsters,

hermit crab Hermit crabs are anomuran decapod crustaceans of the superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit crab, most of which possess an as ...

s). Some species of coral-reef sea cucumbers within the order Aspidochirotida can defend themselves by expelling their sticky

cuvierian tubules Cuvierian tubules are clusters of fine tubes located at the base of the respiratory tree in some sea cucumbers in the genera '' Bohadschia'', ''Holothuria'' and '' Pearsonothuria'', all of which are included in the family Holothuriidae. The tubule ...

(enlargements of the respiratory tree that float freely in the

coelom The coelom (or celom) is the main body cavity in most animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, ...

) to entangle potential predators. When startled, these cucumbers may expel some of them through a tear in the wall of the

in an autotomic process known as

evisceration Evisceration (pronunciation: /ɪvɪsəˈreɪʃən/) is disembowelment, i.e., the removal of viscera (internal organs, especially those in the abdominal cavity). The term may also refer to: * Evisceration (autotomy), ejection of viscera as a defe ...

. Replacement tubules grow back in one and a half to five weeks, depending on the species. The release of these tubules can also be accompanied by the discharge of a toxic chemical known as

, which has similar properties to soap. This chemical can kill animals in the vicinity and is one more method by which these sedentary animals can defend themselves.

Estivation

If the water temperature becomes too high, some species of sea cucumber from temperate seas can

aestivate Aestivation ( la, aestas (summer); also spelled estivation in American English) is a state of animal dormancy, similar to hibernation, although taking place in the summer rather than the winter. Aestivation is characterized by inactivity and a ...

. While they are in this state of dormancy they stop feeding, their gut atrophies, their metabolism slows down and they lose weight. The body returns to its normal state when conditions improve.

Phylogeny and classification

Holothuroidea (sea cucumbers) are one of five

extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...

classes that make up the phylum Echinodermata. This is one of the most distinctive and diverse phyla, ranging from starfish to urchins to sea cucumbers and many other organisms. The echinoderms are mainly distinguished from other phyla by their body plan and organization. While the organisms in this phylum may not all look the same from the outside, their make-up is another story. The earlliest sea cucumbers are known from the middle

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. T ...

, over 450 million years ago. The apodida is the sister group to the other orders of sea cucumbers. All echinoderms share three main characteristics. When mature, echinoderms have a pentamerous radial symmetry. While this can easily be seen in a sea star or brittle star, in the sea cucumber it is less distinct and seen in their five primary tentacles. The pentamerous radial symmetry can also be seen in their five ambulacral canals. The ambulacral canals are used in their water vascular system which is another characteristic that binds this phylum together. The water vascular system develops from their middle coelom or hydrocoel. Echinoderms use this system for many things including movement by pushing water in and out of their podia or "tube feet". Echinoderms tube feet (including sea cucumbers) can be seen aligned along the side of their axes. While echinoderms are invertebrates, meaning they do not have a spine, they do all have an endoskeleton that is secreted by the

mesenchyme Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood or bone. The interactions between mesenchyme and epithelium help to form nearly every ...

. This endoskeleton is composed of plates called ossicles. They are always internal but may only be covered by a thin epidermal layer like in sea urchin's spines. In the sea cucumber the ossicles are only found in the dermis, making them a very supple organism. For most echinoderms, their ossicles are found in units making up a three dimensional structure. However, in sea cucumbers the ossicles are found in a two-dimensional network. All echinoderms also possess anatomical feature(s) called mutable collagenous tissues, or MCTs. Such tissues can rapidly change their passive mechanical properties from soft to stiff under the control of the nervous system and coordinated with muscle activity. Different echinoderm classes use MCTs in different ways. The asteroids, sea stars, can detach limbs for self-defense and then regenerate them. The Crinoidea, sea fans, can go from stiff to limp depending on the current for optimal filter feeding. The Echinoidea, sand dollars, use MCTs to grow and replace their rows of teeth when they need new ones. The Holothuroidea, sea cucumbers, use MCTs to eviscerate their gut as a self-defense response. MCTs can be used in many ways but are all similar at the cellular level and in mechanics of function. A common trend in the uses of MCTs is that they are generally used for self-defense mechanisms and in regeneration. Holothurian classification is complex and their paleontological phylogeny relies on a limited number of well-preserved specimens. The modern taxonomy is based first of all on the presence or the shape of certain soft parts (podia, lungs, tentacles, peripharingal crown) to determine the main orders, and secondarily on the microscopic examination of ossicles to determine the genus and the species. Contemporary genetic methods have been helpful in clarifying their classification. Taxonomic classification according to World Register of Marine Species: * subclass Actinopoda Ludwig, 1891 ** order Dendrochirotida Grube, 1840 *** family

Cucumariidae Cucumariidae is a family of sea cucumbers, marine animals with elongated bodies, leathery skins and tentacles that are found on the sea bed. Description Members of the family Cucumariidae are small to medium-sized sea cucumbers, characterised b ...

Ludwig, 1894 *** family

Cucumellidae ''Cucumella'' is a genus of sea cucumbers belonging to the monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies o ...

Thandar & Arumugam, 2011 *** family

Heterothyonidae Heterothyonidae is a family of sea cucumbers belonging to the order Dendrochirotida Dendrochirotida are an order of sea cucumbers. Members of this order have branched tentacles and are suspension feeders. Examples include '' Thyonella'' and '' ...

Pawson, 1970 *** family † Monilipsolidae Smith & Gallemí, 1991 *** family

Paracucumidae Paracucumidae is a family of sea cucumbers belonging to the order Dendrochirotida Dendrochirotida are an order of sea cucumbers. Members of this order have branched tentacles and are suspension feeders. Examples include '' Thyonella'' and '' Cu ...

Pawson & Fell, 1965 *** family

Phyllophoridae Phyllophoridae is a family of sea cucumbers, marine invertebrates with elongated bodies, leathery skins and feeding tentacles. Members of the family are characterised by a complex ring of calcareous ossicles arranged in a tube, making a mosaic ...

Östergren, 1907 *** family

Placothuriidae ''Placothuria'' is a genus of sea cucumbers Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the ...

Pawson & Fell, 1965 *** family

Psolidae Psolidae is a family of sea cucumbers, marine animals with elongated bodies, leathery skins and tentacles that are found on the sea bed. Description Members of the family Psolidae are small and inconspicuous sea cucumbers found in crevices and u ...

Burmeister, 1837 *** family

Rhopalodinidae Rhopalodinidae is a family of sea cucumbers belonging to the order Dendrochirotida Dendrochirotida are an order of sea cucumbers. Members of this order have branched tentacles and are suspension feeders. Examples include '' Thyonella'' and '' C ...

Théel, 1886 *** family Sclerodactylidae Panning, 1949 *** family

Vaneyellidae Vaneyellidae is a family of sea cucumbers belonging to the order Dendrochirotida Dendrochirotida are an order of sea cucumbers. Members of this order have branched tentacles and are suspension feeders. Examples include '' Thyonella'' and '' Cuc ...

Pawson & Fell, 1965 *** family

Ypsilothuriidae Ypsilothuriidae is a family of sea cucumbers belonging to the order Dendrochirotida Dendrochirotida are an order of sea cucumbers. Members of this order have branched tentacles and are suspension feeders. Examples include '' Thyonella'' and '' ...

Heding, 1942 ** order Elasipodida Théel, 1882 *** family

Théel, 1882 *** family

Laetmogonidae Laetmogonidae is a family of sea cucumbers Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the ...

Ekman, 1926 *** family † Palaeolaetmogonidae Reich, 2012 *** family Pelagothuriidae Ludwig, 1893 *** family

Psychropotidae Psychropotidae is a family of deep-sea swimming sea cucumbers. The geographic range of some psychropotids is very extensive at abyssal depths, whereas other species are found within more restricted ranges.P. A. Tyler & D. S. M. Billett (1988) The ...

Théel, 1882 ** order Holothuriida Miller, Kerr, Paulay, Reich, Wilson, Carvajal & Rouse, 2017 *** family Holothuriidae Burmeister, 1837 *** family

Mesothuriidae Mesothuriidae is a family of echinoderms belonging to the order Holothuriida Holothuriida is an order of sea cucumbers. Taxa within the order Holothuriida were previously classified in the order Aspidochirotida, which was determined to be poly ...

Smirnov, 2012 ** order Molpadida Haeckel, 1896 *** family Caudinidae Heding, 1931 *** family

Eupyrgidae ''Eupyrgus'' is a genus of sea cucumbers. It is the only genus in the monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include s ...

Semper, 1867 *** family

Gephyrothuriidae Gephyrothuriidae is a family of sea cucumbers belonging to the order Persiculida Persiculida is an order of sea cucumbers. Taxa within the order Persiculida were previously classified in an order called Aspidochirotida, which was determined to ...

Koehler & Vaney, 1905 *** family Molpadiidae Müller, 1850 ** order

Persiculida Persiculida is an order of sea cucumbers. Taxa within the order Persiculida were previously classified in an order called Aspidochirotida, which was determined to be polyphyletic A polyphyletic group is an assemblage of organisms or other e ...

Miller, Kerr, Paulay, Reich, Wilson, Carvajal & Rouse, 2017 *** family

Koehler & Vaney, 1905 *** family Molpadiodemidae Miller, Kerr, Paulay, Reich, Wilson, Carvajal & Rouse, 2017 *** family

Pseudostichopodidae ''Pseudostichopus'' is a genus of sea cucumbers belonging to the monotypic family Pseudostichopodidae. The genus has a cosmopolitan distribution In biogeography, cosmopolitan distribution is the term for the range of a taxon that extends acr ...

Miller, Kerr, Paulay, Reich, Wilson, Carvajal & Rouse, 2017 ** order

Synallactida Synallactida is a rankless clade of sea cucumbers, but is referred to as an order. Taxa within Synallactida were previously classified in an order called Aspidochirotida, which was determined to be polyphyletic in 2017. List of families Syna ...

Miller, Kerr, Paulay, Reich, Wilson, Carvajal & Rouse, 2017 *** family Deimatidae Théel, 1882 *** family Stichopodidae Haeckel, 1896 *** family Synallactidae Ludwig, 1894 * subclass †ArthrochirotaceaSmirnov, 2012 ** order † Arthrochirotida Brandt, 1835 *** family † Palaeocucumariidae Frizzell & Exline, 1966 * subclass Paractinopoda Ludwig, 1891 ** order Apodida Brandt, 1835Small text *** family

Chiridotidae 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. Sea cucumbers play a fundamental role in many marine ecosystems. Des ...

Östergren, 1898 *** family Myriotrochidae Théel, 1877 *** family Synaptidae Burmeister, 1837

Relation to humans

Food

Yokohama Chinese Medicine Sea cucumber 2

To supply the markets of

Southern China South China () is a geographical and cultural region that covers the southernmost part of China. Its precise meaning varies with context. A notable feature of South China in comparison to the rest of China is that most of its citizens are not n ...

Makassar Makassar (, mak, ᨆᨀᨔᨑ, Mangkasara’, ) is the capital of the Indonesian province of South Sulawesi. It is the largest city in the region of Eastern Indonesia and the country's fifth-largest urban center after Jakarta, Surabaya, Meda ...

trepanger Trepanging is the act of collection or harvesting of sea cucumbers, known in Indonesian as ''trepang'', Malay těripang, and used as food. The collector, or fisher, of ''trepang'' is a trepanger. Trepanging is comparable to clamming, crabbin ...

s traded with the

Indigenous Australians Indigenous Australians or Australian First Nations are people with familial heritage from, and membership in, the ethnic groups that lived in Australia before British colonisation. They consist of two distinct groups: the Aboriginal peoples ...

Arnhem Land Arnhem Land is a historical region of the Northern Territory of Australia, with the term still in use. It is located in the north-eastern corner of the territory and is around from the territory capital, Darwin. In 1623, Dutch East India Compa ...

from at least the 18th century and probably earlier. This is the first recorded example of trade between the inhabitants of the Australian continent and their Asian neighbours. There are many commercially important species of sea cucumber that are harvested and dried for export for use in

Chinese cuisine Chinese cuisine encompasses the numerous cuisines originating from China, as well as overseas cuisines created by the Chinese diaspora. Because of the Chinese diaspora and historical power of the country, Chinese cuisine has influenced many o ...

as ''hoisam''. Some of the more commonly found species in markets include: *'' Holothuria nobilis'' *'' Thelenota ananas'' *'' Actinopyga echinites'' *'' Actinopyga palauensis'' *'' Holothuria scabra'' *'' Holothuria fuscogilva'' *'' Actinopyga mauritiana'' *''

Stichius japonicus ''Bianor'' is a genus of boreal jumping spiders that can grow to . The robust shiny body and northerly distribution are distinctive. Males can be easily recognized by his swollen forelegs and females have orange legs. It was first described by ...

'' *''

Apostichopus californicus The California sea cucumber (''Apostichopus californicus''), also known as the giant California sea cucumber, is a sea cucumber that can be found from the Gulf of Alaska to Baja California. It is found from the low intertidal zone to a depth of . ...

'' *'' Acaudina molpadioides'' *'' Isostichopus fuscus''

Medicine

According to the

American Cancer Society The American Cancer Society (ACS) is a nationwide voluntary health organization dedicated to eliminating cancer. Established in 1913, the society is organized into six geographical regions of both medical and lay volunteers operating in more than ...

, although it has been used in traditional Asian folk medicine for a variety of ailments, "there is little reliable scientific evidence to support claims that sea cucumber is effective in treating cancer, arthritis, and other diseases" but research is examining "whether some compounds made by sea cucumbers may be helpful against cancer". Various pharmaceutical companies emphasize ''

gamat The word Gamat, the Malay word for sea cucumber, refers to medicinal remedies derived from several species of the Holothuroidea family. Uses The golden sea cucumber ('' Stichopus horrens'') is commonly used. Tripang Emas is usually the dried, ...

'', the traditional medicinal usage of this animal. Extracts are prepared and made into oil, cream or cosmetics. Some products are intended to be taken internally. A review article found that

chondroitin sulfate Chondroitin sulfate is a sulfated glycosaminoglycan (GAG) composed of a chain of alternating sugars ( N-acetylgalactosamine and glucuronic acid). It is usually found attached to proteins as part of a proteoglycan. A chondroitin chain can have ove ...

and related compounds found in sea cucumbers can help in treating joint-pain, and that dried sea cucumber is "medicinally effective in suppressing

arthralgia Arthralgia (from Greek ''arthro-'', joint + ''-algos'', pain) literally means ''joint pain''. Specifically, arthralgia is a symptom of injury, infection, illness (in particular arthritis), or an allergic reaction to medication. According to MeSH, ...

". Another study suggested that sea cucumbers contain all the fatty acids necessary to play a potentially active role in tissue repair. Sea cucumbers are under investigation for use in treating ailments including

colorectal cancer Colorectal cancer (CRC), also known as bowel cancer, colon cancer, or rectal cancer, is the development of cancer from the colon or rectum (parts of the large intestine). Signs and symptoms may include blood in the stool, a change in bowel ...

. Surgical probes made of nanocomposite material based on the sea cucumber have been shown to reduce brain scarring. One study found that a

lectin Lectins are carbohydrate-binding proteins that are highly specific for sugar groups that are part of other molecules, so cause agglutination of particular cells or precipitation of glycoconjugates and polysaccharides. Lectins have a role in rec ...

from '' Cucumaria echinata'' impaired the development of the

malaria parasite ''Plasmodium'' is a genus of unicellular eukaryotes that are obligate parasites of vertebrates and insects. The life cycles of ''Plasmodium'' species involve development in a blood-feeding insect host which then injects parasites into a verteb ...

when produced by transgenic

mosquitoes Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small Diptera, flies within the family Culicidae (from the Latin ''culex'' meaning "gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish ...

. File:Dried sea cucumber.jpg, "Teripang" in a market in Asia. File:Sea cucumber dish 2.jpg, Sea cucumber in sauce in China. File:Haisom Cah Jamur 1.JPG, ''Haisom cah jamur'',

Chinese Indonesian Chinese Indonesians ( id, Orang Tionghoa Indonesia) and colloquially Chindo or just Tionghoa are Indonesians whose ancestors arrived from China at some stage in the last eight centuries. Chinese people and their Indonesian descendants have ...

sea cucumber with mushroom. File:Sea cucumber dish 3.jpg, Deep fried sea cucumbers. File:Keripik teripang 1.JPG, '' Kripik teripang'', Indonesian sea cucumber cracker.

Procurement

Sea cucumbers are harvested from the environment, both legally and illegally, and are increasingly farmed via

aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...

. The harvested animals are normally dried for resale. In 2016, prices on Alibaba ranged up to $1,000/kg.

Commercial harvest

In recent years, the sea cucumber industry in Alaska has increased due to increased demand for the skins and muscles to China. Wild sea cucumbers are caught by divers. Wild Alaskan sea cucumbers have higher nutritional value and are larger than farmed Chinese sea cucumbers. Larger size and higher nutritional value has allowed the Alaskan fisheries to continue to compete for market share. One of Australia's oldest fisheries is the collection of sea cucumber, harvested by divers from throughout the

Coral Sea The Coral Sea () is a marginal sea of the South Pacific off the northeast coast of Australia, and classified as an interim Australian bioregion. The Coral Sea extends down the Australian northeast coast. Most of it is protected by the Fre ...

in far

North Queensland North Queensland or the Northern Region is the northern part of the Australian state of Queensland that lies just south of Far North Queensland. Queensland is a massive state, larger than many countries, and its tropical northern part has been ...

, Torres Straits and

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to t ...

. In the late 1800s as many as 400 divers operated from

Cook Town, Queensland Cooktown is a coastal town and locality in the Shire of Cook, Queensland, Australia. Cooktown is at the mouth of the Endeavour River, on Cape York Peninsula in Far North Queensland where James Cook beached his ship, the Endeavour, for repair ...

Overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in t ...

of sea cucumbers in the Great Barrier Reef is threatening their population. Their popularity as luxury seafood in

East Asia East Asia is the eastern region of Asia, which is defined in both geographical and ethno-cultural terms. The modern states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. China, North Korea, South Korea ...

n countries poses a serious threat.

Black market

As of 2013 a thriving

black market A black market, underground economy, or shadow economy is a clandestine market or series of transactions that has some aspect of illegality or is characterized by noncompliance with an institutional set of rules. If the rule defines the ...

was driven by demand in China where at its peak might have sold for the equivalent of US$300 and a single sea cucumber for about US$160. A crackdown by governments both in and out of China reduced both prices and consumption, particularly among government officials who had been known to eat (and were able to afford purchasing) the most expensive and rare species. In the

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexic ...

off the shores of the

Yucatán Peninsula The Yucatán Peninsula (, also , ; es, Península de Yucatán ) is a large peninsula in southeastern Mexico and adjacent portions of Belize and Guatemala. The peninsula extends towards the northeast, separating the Gulf of Mexico to the north ...

near fishing ports such as Dzilam de Bravo, illegal harvesting had devastated the population and resulted in conflict as rival gangs struggled to control the harvest.

Aquaculture

Overexploitation Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Continued overexploitation can lead to the destruction of the resource, as it will be unable to replenish. The term ap ...

of sea cucumber stocks in many parts of the world provided motivation for the development of sea cucumber

in the early 1980s. The Chinese and Japanese were the first to develop successful hatchery technology on '' Apostichopus japonicus'', prized for its high meat content and success in commercial hatcheries.James, B. D. (2004
Captive breeding of the sea cucumber, ''Holothuria scabra'', from India
In Lovatelli, A. (comp./ed.); Conand, C.; Purcell, S.; Uthicke, S.; Hamel, J.-F.; Mercier, A. (eds.) ''Advances in sea cucumber aquaculture and management''. FAO Fisheries Technical Paper. No. 463. Rome, FAO. 2004.425p. Using techniques pioneered by the Chinese and Japanese, a second species, '' Holothuria scabra'', was cultured for the first time in India in 1988.James, D. B., Gandhi, A. D., Palaniswamy, N., & Rodrigo, J. X. (1994
Techniques and Culture of the Sea-cucumber ''Holothuria scabra''
CMFRI Special Publication(57),1-40. In recent years Australia, Indonesia, New Caledonia, Maldives, Solomon Islands and Vietnam have successfully cultured ''H. scabra'' using the same technology, and now culture other species.

Conservation

In 2020, the Indian government created the world's first sea cucumber conservation area, the Dr KK Mohammed Koya Sea Cucumber Conservation Reserve, to protect the sea cucumber species. In India, the commercial harvesting and transportation of sea cucumbers is banned.

In popular culture

Edgar Allan Poe Edgar Allan Poe (; Edgar Poe; January 19, 1809 – October 7, 1849) was an American writer, poet, editor, and literary critic. Poe is best known for his poetry and short stories, particularly his tales of mystery and the macabre. He is wid ...

's only novel, ''

The Narrative of Arthur Gordon Pym of Nantucket ''The Narrative of Arthur Gordon Pym of Nantucket'' (1838) is the only complete novel written by American writer Edgar Allan Poe. The work relates the tale of the young Arthur Gordon Pym, who stows away aboard a whaling ship called the ''Grampus' ...

'' (1838), includes in its 20th chapter a long, detailed description of sea cucumbers, which the narrator calls ''biche de mer''. *In

Kir Bulychov Kir Bulychev (russian: Кир Булычёв ''Kir Bulychyov 18 October 1934 – 5 September 2003) is a pen name of Igor Vsevolodovich Mozheiko (И́горь Все́володович Може́йко), a Soviet Russian science fiction writer, c ...

's science-fiction novella, "Half a Life", a human being kidnapped by alien machines described her fellow alien prisoners as "trepangs". *The first movement of

French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...

composer

Erik Satie Eric Alfred Leslie Satie (, ; ; 17 May 18661 July 1925), who signed his name Erik Satie after 1884, was a French composer and pianist. He was the son of a French father and a British mother. He studied at the Paris Conservatoire, but was an und ...

Embryons desséchés ''Embryons desséchés'' ("''Desiccated embryos''") is a piano composition by Erik Satie, composed in the summer of 1913. The composition consists of three little "movements", each taking about two to three minutes to play. The music The parts ...

is titled "D'Holothournie". It is said to emulate the "

purring A purr is a tonal fluttering sound made by some species of felids and two species of genets. It varies in loudness and tone among species and in the same animal. Felids are a family of mammals that belong to the order Carnivora and are infor ...

" of the Holothourian. *Sea cucumbers have inspired thousands of

haiku is a type of short form poetry originally from Japan. Traditional Japanese haiku consist of three phrases that contain a '' kireji'', or "cutting word", 17 '' on'' (phonetic units similar to syllables) in a 5, 7, 5 pattern, and a '' kigo'', or ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...

, where they are called ''namako'' (海鼠), written with characters that can be translated as "sea mice" (an example of

gikun are the logographic Chinese characters taken from the Chinese script and used in the writing of Japanese. They were made a major part of the Japanese writing system during the time of Old Japanese and are still used, along with the subsequent ...

). In English translations of these haiku, they are usually called "sea slugs". According to the ''

Oxford English Dictionary The ''Oxford English Dictionary'' (''OED'') is the first and foundational historical dictionary of the English language, published by Oxford University Press (OUP). It traces the historical development of the English language, providing a c ...

'', the English term "sea slug" was originally applied to holothurians during the 18th century. The term is now applied to several groups of

sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the a ...

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

s that have no shell or only a very reduced shell, including the

nudibranch Nudibranchs () are a group of soft-bodied marine gastropod molluscs which shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames to match, ...

s. Almost 1,000 Japanese holothurian haiku translated into English appear in the book ''Rise, Ye Sea Slugs!'' by Robin D. Gill.Gill, Robin
''Rise, Ye Sea Slugs!''
Paraverse Press, 2003, *Nobel laureate poet

Wisława Szymborska Maria Wisława Anna SzymborskaVioletta Szosta gazeta.pl, 9 February 2012. ostęp 2012-02-11 (; 2 July 1923 – 1 February 2012) was a Polish poet, essayist, translator, and recipient of the 1996 Nobel Prize in Literature. Born in Prowent ( ...

wrote a poem which mentions holothurians, titled "Autotomy". *In the book ''

John Dies at the End ''John Dies at the End'' is a comic horror novel written by David Wong that was first published online as a webserial beginning in 2001, then as an edited manuscript in 2004, and a printed paperback in 2007, published by Permuted Press. An ...

'', the character Amy Sullivan was nicknamed "Cucumber" by the narrator/author when the two were children. This is assumed by other characters to have a sexual connotation but is actually a reference to her frequent nausea. The name is in reference to a sea cucumber's use of vomiting as a method of self-defense. *A descriptive passage in American novelist

Cormac McCarthy Cormac McCarthy (born Charles Joseph McCarthy Jr., July 20, 1933) is an American writer who has written twelve novels, two plays, five screenplays and three short stories, spanning the Western and post-apocalyptic genres. He is known for his g ...

's 1985 anti-Western ''

Blood Meridian ''Blood Meridian or the Evening Redness in the West'' is a 1985 in literature, 1985 Epic (genre), epic novel by American author Cormac McCarthy, classified under the Western (genre), Western, or sometimes the Revisionist Western, anti-Western, g ...

'' likens cactus embers to holothurians: "In the thorn forest through which they'd passed the little desert wolves yapped and on the dry plain before them others answered and the wind fanned the coals that he watched. The bones of cholla that glowed there in their incandescent basketry pulsed like burning holothurians in the phosphorous dark of the sea's deeps."

References

Informational notes Citations

External links

* {{Taxonbar, from=Q127470 Extant Ordovician first appearances Edible shellfish Commercial echinoderms

Anatomy

Body plan

Digestive system

Nervous system

Respiratory system

Circulatory systems

Locomotive organs

Endoskeleton

Life history and behaviour

Habitat

Locomotion

Diet

Communication and sociability

Reproduction

Development

Symbiosis and commensalism

Predators and defensive systems

Estivation

Phylogeny and classification

Relation to humans

Food

Medicine

Procurement

Commercial harvest

Black market

Aquaculture

Conservation

In popular culture

See also

References

External links