Sea cucumber
From Wikipedia, the free encyclopedia
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 A Sea Cucumber
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Subclass Apodacea |
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.
Sea cucumbers are generally scavengers, feeding on debris in the benthic layer. Their diet consists of plankton and other organic matter found in the sea. One way they might get a supply of food is to position themselves in a current where they can catch food that flow by with their tentacles when they open. Another way is to sift through the bottom sediments using their tentacles. They can be found in great numbers beneath fish farms.
They have the peculiar adaptation of expelling first sticky threads, perhaps to incapacitate predators, and then their internal organs when startled by a potential predator. These organs can then be regrown. (See defensive vomiting).
Sea cucumbers extract oxygen from water in a pair of 'lungs' or 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.[1][2] A variety of fishes, most commonly pearl fishes, have evolved a commensalistic symbiotic relationship (commensalism) 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.[3]
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.
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[edit] Sea cucumber as food and medicine
Sea cucumber is considered a delicacy in Far East countries such as Malaysia, China, Japan, and Indonesia. It is highly valued for its supposed medicinal properties. The flesh of the animal is "cleaned" in a process that takes several days. The food item is often purchased dried, and then rehydrated before use. The product is used in soups, stews and braised dishes due to its gelatinous texture but may be unappetising on its own.
In Japanese cuisine, Konowata is made of sea cucumber entrails which are extracted, salted, and cured.
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) 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[4]. It not only helps a wound heal more quickly but is also said to reduce scarring.[5].
[edit] Sea cucumbers in art
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 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"; there is a book with almost 1000 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.
[edit] See also
[edit] Notes
- ^ Holothurians or sea cucumbers (describes breathing processes)
- ^ Cool as a Sea Cucumber - URL retireved August 19, 2005
- ^ Aquarium Invertebrates by Rob Toonen, Ph.D.
- ^ Study of healing properties (PDF format)
- ^ Effects on tissue repair
[edit] External links
