Difference between revisions of "Electric eel" - New World Encyclopedia
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Electric eels have a vascularized respiratory organ in their oral cavity (Nelson 2006; Valasco 2003). These fish are obligate air-breathers; rising to the surface every 10 minutes or so, the animal will gulp air before returning to the bottom. Nearly 80% of the oxygen used by the fish is taken through their mouth, rather than their gills (Valasco 2003). | Electric eels have a vascularized respiratory organ in their oral cavity (Nelson 2006; Valasco 2003). These fish are obligate air-breathers; rising to the surface every 10 minutes or so, the animal will gulp air before returning to the bottom. Nearly 80% of the oxygen used by the fish is taken through their mouth, rather than their gills (Valasco 2003). | ||
| − | The electric eel's vital organs are all in the anterior part of their body, taking up about twenty percent of the fish, while the electric organs are located in the posterior portion (Valasco 2003; Agbayani 2008). | + | The electric eel's vital organs are all in the anterior part of their body, taking up about twenty percent of the fish, while the electric organs are located in the posterior portion and take up eighty percent of the body (Valasco 2003; Agbayani 2008). |
==Electric organs and discharge== | ==Electric organs and discharge== | ||
[[Image:Electric-eel2.jpg|thumb|left|200px|Electric eel at the [[New England Aquarium]].]] | [[Image:Electric-eel2.jpg|thumb|left|200px|Electric eel at the [[New England Aquarium]].]] | ||
| − | The electric eel has three abdominal pairs of organs that produce electricity. They are the main organ, the hunter's organ, and the sachs’ organ. | + | The electric eel has three abdominal pairs of organs that produce electricity. They are the main organ, the hunter's organ, and the sachs’ organ. These organs are made of flattened [[electrocyte]]s lined up in series and number to about hundreds of thousands (Agbayani 2008). The electrocytes are lined up so the current flows through them and produces an electrical charge. The brain sends a signal through the [[nervous system]] to the electric cells. This opens the [[ion]] channel, allowing positively-charged [[sodium]] to flow through, reversing the charges momentarily. By doing that it creates electricity. The electric eel generates its characteristic electrical pulse in a manner similar to a battery, in which stacked plates produce an electrical charge. |
| − | The | + | The organs give the electric eel the ability to generate two types of [[electric organ discharge]]s (EODs), low voltage and high voltage. Low-voltage EODs are about 10 volts and are emitted by the Sach's organ at rates of up to 25 Hz, while high-voltage EODS are about 50-fold and emitted by the main and Hunter's organs at peak rates of up to several hundred Hz (Agbayani 2008). |
| − | + | The Sachs organ with its low-voltage discharge is associated with [[electrolocation]] (Agbayani 2008). Each of the muscle-like cells or electrocytes, can only produce 0.15V, though working together the organ transmits a signal of about 10V in amplitude. These signals are what is thought to be used for communication as well as orientation; useful not only for finding prey, but also in finding and choosing a mate. | |
| − | The | + | The high-voltage discharge from the main organ and Hunter's organ is associated with predatory attacks and defense. Some 5,000 to 6,000 stacked [[electroplaques]] in the organs are capable of producing a shock at up to 500 [[volts]] and 1 [[ampere]] of current (500 [[watt]]s); an EOD of 500 volts was recorded from an individual one meter in length (Agbayani 2008). The shock could be harmful for an adult human. |
| − | + | The electric eel is unique among the gymnotiforms in having large electric organs capable of producing lethal discharges that allows them to stun prey (Nelson 2006). There are reports of animals producing larger voltages, but the typical output is sufficient to stun or deter virtually any other animal. Juveniles produce smaller voltages (about 100 volts). Electric eels are capable of varying the intensity of the electrical discharge, using lower discharges for "hunting" and higher intensities for stunning prey, or defending themselves. When agitated, it is capable of producing these intermittent electrical shocks over a period of at least an hour without signs of tiring. | |
| − | The electric eel | ||
| − | + | The electric eel also possesses high-frequency sensitive tuberous receptors patchily distributed over the body that seem useful for hunting other gymnotiformes (Agbayani 2008). | |
| + | ==Distribution and habitat== | ||
| + | |||
| + | The electric eel is found in northeastern portions of South America, incluidng the Guyana and Orinoco River Basins, and the middle and lower Amazon Basin (Valasco 2003). | ||
| + | |||
| + | Electric eels are freshwater fish. They tend to live on muddy bottoms of rivers, swamps, coastal pains, and creeks, often in calm waters (Agbayani 2008; Valasco 2003). They must surface frequently to breath air. Because of this [[adaptation]] as an obligatory air breather, they are able to survive well in water that is very poorly oxygenated (Valasco 2003; Agbayani 2008). | ||
| + | |||
| + | ==Behavior, feeding, and reproduction== | ||
| + | |||
| + | Electric eels are nocturnal animals, generally living in muddy dark waters and relying on electricity for sensing (Valasco 2003). | ||
It is an [[Apex_predator|apex predator]] in its [[South America]]n range. | It is an [[Apex_predator|apex predator]] in its [[South America]]n range. | ||
| Line 53: | Line 61: | ||
===Habitat=== | ===Habitat=== | ||
| − | + | ||
| − | |||
===Feeding ecology=== | ===Feeding ecology=== | ||
electris eels feed on [[invertebrate]]s, while adult eels feed on [[fish]] and small [[mammal]]s. First-born hatchlings will even prey on other eggs and embryos from later batches..<ref name=Fishbase/> | electris eels feed on [[invertebrate]]s, while adult eels feed on [[fish]] and small [[mammal]]s. First-born hatchlings will even prey on other eggs and embryos from later batches..<ref name=Fishbase/> | ||
| + | |||
| + | ==Importance== | ||
| + | The species is of some interest to researchers, who make use of its [[acetylcholinesterase]] and [[Adenosine triphosphate|ATP]].<ref name=AChE>{{cite journal | last = Simon | first = Stéphanie | coauthors = Jean Massoulié | title = Cloning and Expression of Acetylcholinesterase from Electrophorus | journal = Journal of Biological Chemistry | volume = 272 | issue = 52 | pages = 33045-33055 | date = [[1997-12-26]] | url = http://www.jbc.org/cgi/content/full/272/52/33045 | accessdate = 2008-02-07}}</ref><ref name=ATP>{{cite journal |author=Zimmermann, H | coauthors = CR Denston |title=Adenosine triphosphate in cholinergic vesicles isolated from the electric organ of Electrophorus electricus |journal=Brain Res. |volume=111 |issue=2 |pages=365–76 |year=1976 |pmid=949609 |doi=10.1016/0006-8993(76)90780-0}}</ref> | ||
Revision as of 20:26, 30 May 2008
| Electric eel | ||||||||||||||
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| Electrophorus electricus (Linnaeus, 1766) |
Electric eel is the common name for a South American freshwater fish, Electrophorus electricus, that is characterized by an elongated, cylindrical, snake-like body, absence of dorsal, pelvic, and caudal fins, and the capability of generating strong and weak electric organ discharges, which are used for hunting, self-defense, and electrolocation. Although the electric eel has gills, they are obligatory air breathers, using their gills only as a secondary source of oxygen, with their highly vascularized mouth as their primary source.
Despite its name and strong physical resemblance, the electric eel is not a "true eel," which are various members of the fish order Anguilliformes. The electric eel is placed in the order Gymnotiformes (knifefishes). The common name eel also is applied to members of the marine family Cyematidae (bobtail snipe eels) in the order Saccopharyngiformes and to members of the largely freshwater order Synbranchifromes. Electrophorus electricus is variously placed in the Gymnotidae family within Gymnotiformes (ITIS; Agbayani 2008) or within its own family Electrophoridae (Valasco 2003; Nelson 1994).
Overview and description
Electric eels (Electrophorus electricus) are members of the Gymnotiformes order of fishes, commonly known as knifefishes. Members of this order have a compressed or rounded eel-like body, the absence of pelvic and dorsal fins, an extremely long anal fin (from near the origin of the pectoral fin to near the tip of the tail), an absent or greatly reduced caudal fin, and electric organs. Nelson (1994) recognizes six families of this freshwater order: Sternopygidae (glass knifefishes), Rhamphichthyidae (sand knifefishes), Hypopomidae, Apteronotidae (ghost knifefishes), Gymnotidae (naked-back knifefishes), and Electrophoridae (electric knifefish).
E. electricus is so unusual that it has been reclassified several times. In some taxonomies currently, it is placed in its own family Electrophoridae, for which it is the only representative, while others place it in Gymnotidae (naked-back knifefishes), either part of the genus Gymnotus (G. electricus or G. regius) or as E. electricus alongside the Gymnotus species (Nelson 2006; ITIS; Valasco 2003; Agbayani 2008).
The electric eel is characterized by an elongated, cylindrical body, a flattened head, and an overall dark color on their dorsal surface (dark grayish green, or black, or brownish) shifting to yellowish on the bottom (Agbayani 2008). They have almost no scales. The large mouth is square, placed right at the end of the snout, and has a row of conical teeth in each jaw (Agbayani 2008). As with other members of Gymnotiformes, they lack pelvic and dorsal fins, and also lack a caudal fin. The anal fin continues down the length of the body to the tip of their tail (Nelson 2006). This elongated anal fin is used in locomotion, providing forward and backward movement as with the other Gymnotiformes. There are about 240 vertebrae (Nelson 1994).
The electric eel can grow up to 2.5 meters (about 8.2 feet) in length and 20 kilograms (about 44 pounds) in weight, making them the largest Gymnotiform (Agbayani 2008; Nelson 2006). Their entire body is covered by a thick, slimy skin, which provides a protective layer, including from their own electric current (Valasco 2003).
Electric eels have a vascularized respiratory organ in their oral cavity (Nelson 2006; Valasco 2003). These fish are obligate air-breathers; rising to the surface every 10 minutes or so, the animal will gulp air before returning to the bottom. Nearly 80% of the oxygen used by the fish is taken through their mouth, rather than their gills (Valasco 2003).
The electric eel's vital organs are all in the anterior part of their body, taking up about twenty percent of the fish, while the electric organs are located in the posterior portion and take up eighty percent of the body (Valasco 2003; Agbayani 2008).
Electric organs and discharge
The electric eel has three abdominal pairs of organs that produce electricity. They are the main organ, the hunter's organ, and the sachs’ organ. These organs are made of flattened electrocytes lined up in series and number to about hundreds of thousands (Agbayani 2008). The electrocytes are lined up so the current flows through them and produces an electrical charge. The brain sends a signal through the nervous system to the electric cells. This opens the ion channel, allowing positively-charged sodium to flow through, reversing the charges momentarily. By doing that it creates electricity. The electric eel generates its characteristic electrical pulse in a manner similar to a battery, in which stacked plates produce an electrical charge.
The organs give the electric eel the ability to generate two types of electric organ discharges (EODs), low voltage and high voltage. Low-voltage EODs are about 10 volts and are emitted by the Sach's organ at rates of up to 25 Hz, while high-voltage EODS are about 50-fold and emitted by the main and Hunter's organs at peak rates of up to several hundred Hz (Agbayani 2008).
The Sachs organ with its low-voltage discharge is associated with electrolocation (Agbayani 2008). Each of the muscle-like cells or electrocytes, can only produce 0.15V, though working together the organ transmits a signal of about 10V in amplitude. These signals are what is thought to be used for communication as well as orientation; useful not only for finding prey, but also in finding and choosing a mate.
The high-voltage discharge from the main organ and Hunter's organ is associated with predatory attacks and defense. Some 5,000 to 6,000 stacked electroplaques in the organs are capable of producing a shock at up to 500 volts and 1 ampere of current (500 watts); an EOD of 500 volts was recorded from an individual one meter in length (Agbayani 2008). The shock could be harmful for an adult human.
The electric eel is unique among the gymnotiforms in having large electric organs capable of producing lethal discharges that allows them to stun prey (Nelson 2006). There are reports of animals producing larger voltages, but the typical output is sufficient to stun or deter virtually any other animal. Juveniles produce smaller voltages (about 100 volts). Electric eels are capable of varying the intensity of the electrical discharge, using lower discharges for "hunting" and higher intensities for stunning prey, or defending themselves. When agitated, it is capable of producing these intermittent electrical shocks over a period of at least an hour without signs of tiring.
The electric eel also possesses high-frequency sensitive tuberous receptors patchily distributed over the body that seem useful for hunting other gymnotiformes (Agbayani 2008).
Distribution and habitat
The electric eel is found in northeastern portions of South America, incluidng the Guyana and Orinoco River Basins, and the middle and lower Amazon Basin (Valasco 2003).
Electric eels are freshwater fish. They tend to live on muddy bottoms of rivers, swamps, coastal pains, and creeks, often in calm waters (Agbayani 2008; Valasco 2003). They must surface frequently to breath air. Because of this adaptation as an obligatory air breather, they are able to survive well in water that is very poorly oxygenated (Valasco 2003; Agbayani 2008).
Behavior, feeding, and reproduction
Electric eels are nocturnal animals, generally living in muddy dark waters and relying on electricity for sensing (Valasco 2003).
It is an apex predator in its South American range.
Habitat
Feeding ecology
electris eels feed on invertebrates, while adult eels feed on fish and small mammals. First-born hatchlings will even prey on other eggs and embryos from later batches..[1]
Importance
The species is of some interest to researchers, who make use of its acetylcholinesterase and ATP.[2][3]
ReferencesISBN links support NWE through referral fees
- ↑ Cite error: Invalid
<ref>tag; no text was provided for refs namedFishbase - ↑ Simon, Stéphanie and Jean Massoulié (1997-12-26). Cloning and Expression of Acetylcholinesterase from Electrophorus. Journal of Biological Chemistry 272 (52): 33045-33055.
- ↑ Zimmermann, H and CR Denston (1976). Adenosine triphosphate in cholinergic vesicles isolated from the electric organ of Electrophorus electricus. Brain Res. 111 (2): 365–76.
- Agbayani, E. 2008. Electrophorus electricus (Linnaeus, 1766), electric eel. FishBase. Retrieved May 30, 2008.
- Integrated Taxonomic Information System (ITIS). n.d. Electrophorus electricus (Linnaeus, 1766). ITIS Taxonomic Serial No.: 163322. Retrieved May 30, 2008.
- .[1]
- Valasco, T. 2003. Electrophorus electricus. Animal Diversity Web. Retrieved May 30, 2008.
External links
- 1954 educational film about the electric eel from the [[Moody Institute 22|taxon=Electrophorus electricus|year=2006|date=11 March}}
- Interview with Fear Factor contestant
Credits
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- ↑ Nelson, Joseph, S. (2006). Fishes of the World. John Wiley & Sons, Inc.. ISBN 0471250317.
