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| Sea Cucumbers | ||||||||
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 A Sea Cucumber | ||||||||
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Wikispecies has information related to:
The sea cucumber is an echinoderm of the 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. Like all echinoderms, sea cucumbers have an endoskeleton just below the skin, but this can actually be absent in some species.[citation needed]
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Sea cucumbers are generally scavengers, feeding on debris in the benthic zone of the ocean. Exceptions include pelagic cucumbers and the species Rynkatropa pawsoni, which has a commensal relationship with deep-sea anglerfish. Brusca, R.C., Brusca, G.J.; Invertebrates. Sinauer Associates, Massachusetts, 1990. The diet of most cucumbers consists of plankton 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 sediments using their tentacles. Sea Cucumbers live in Tropical Reefs.
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 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 autotomic process known as evisceration. Replacement tubules grow back in one-and-a-half to five weeks, depending on the species.Flammang, Patrick; Ribesse, Jerome & Jangoux, Michel (2002-12-01). "Biomechanics of adhesion in sea cucumber cuvierian tubules (echinodermata, holothuroidea)" (in English). Integrative and Comparative Biology. Retrieved on 2007-10-03.
They can be found in great numbers on the deep sea floor, where they often make up the majority of the animal biomass.Miller, Nat. Sea Cucumbers (English). Retrieved on 2007-10-03. 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.Carney, Bob (2007-06-18). The Kingdom of the Echinoderm (English). Retrieved on 2007-10-03.
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.Alcock, Nick (2007). Aquatic Biodiversity & Biosecurity: Shedding new light on the humble sea cucumber (English). Retrieved on 2007-10-03.
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.Holothurians or sea cucumbers. Retrieved on 2007-10-03.Ingram, Jocie (2006-06-16). Knowing Nature... Cool as a Sea Cucumber (English). Retrieved on 2007-10-03. 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 worms and crabs have also specialized to use the cloacal respiratory trees for protection by living inside the sea cucumber.Toonen, Rob, Ph.D. (2003). Aquarium Invertebrates (English). Retrieved on 2007-10-03.
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 (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 vanabin pigmentNatkin, Michael (2007). Blood Color. Science Facts. Soak (Source Of All Knowledge). Retrieved on 2007-11-16.. 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 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.[citation needed]
Dried sea cucumbers in a Chinese pharmacy
"To supply the markets of Southern China, Macassan trepangers 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 studyStudy of healing properties (PDF format). It is believed that the sea cucumber contains all the fatty acids necessary to play an active role in tissue repair.Effects on tissue repair.
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.[citation needed]
On December 22, 2007, the PLoS Pathogens study found that sea cucumbers block transmission of the malaria parasite, since they produce the protein, lectin (which retards growth of the parasites).BBC NEWS, Sea cucumber \'new malaria weapon\'
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:
Nonetheless it is the sea cucumber\'s closest relative (the echinoidea or sea urchin) that gets the most attention from scientists, both as an embryo and as a fossil. H. edmondia, an ancient relative of the sea cucumber, is often seen throughout art history as a mythical asexual being, often portrayed as dancing.
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"; there is a book with almost 1,000 holothurian haiku translated from Japanese titled "Rise, Ye Sea Slugs!" by Robin D. Gill (ISBN 0-9742618-0-7). According to the Oxford English Dictionary, the "sea slug" is a holothurian first, but biologists insist on using "sea slug" only for the nudibranch, a marine-dwelling relative of land slugs.
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A sea cucumber feeding on gravel
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