Swamp eel
| Swamp eels | |
|---|---|
| |
| Monopterus albus | |
Scientific classification
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Synbranchiformes |
| Suborder: | Synbranchoidei Boulenger,1904[2] |
| Family: | Synbranchidae Bonaparte,1835[1] |
| Type species | |
| Synbranchus marmoratus Bloch, 1795[3]
| |
| Genera | |
|
Macrotrema | |
Theswamp eels(also written "swamp-eels" ) are afamily(Synbranchidae) offreshwatereel-likefishesof the tropics and subtropics.[4]Most species are able to breathe air and typically live in marshes, ponds and damp places, sometimes burying themselves in the mud if the water source dries up. They have various adaptations to suit this lifestyle; they are long and slender, they lack pectoral and pelvic fins, and their dorsal and anal fins are vestigial, making themlimbless vertebrates.They lack scales and aswimbladder,and their gills open on the throat in a slit or pore. Oxygen can be absorbed through the lining of the mouth and pharynx, which is rich in blood vessels and acts as a "lung".
Although adult swamp eels have virtually no fins, the larvae have large pectoral fins which they use to fan water over their bodies, thus ensuring gas exchange before their adult breathing apparatus develops. When about a fortnight old they shed these fins and assume the adult form. Most species of swamp eel arehermaphrodite,starting life as females and later changing to males, though some individuals start life as males and do not change sex.
In theJiangnanregion of China, swamp eels are eaten as a delicacy, usually cooked as part of astir-fryorcasserole.
It is known as Kusia (কুচিয়া) inAssamand Bangladesh. It is considered a delicacy and cooked with curry as part ofAssamese cuisine.
Description[edit]
Themarbled swamp eel,Synbranchus marmoratus,has been recorded at up to 150 cm (59 in) in length,[5]while theBombay swamp eel,Monopterus indicus,reaches no more than 8.5 cm (3.3 in).
Swamp eels are almost entirely finless; thepectoralandpelvic finsare absent, thedorsalandanal finsare vestigial, reduced to rayless ridges, and thecaudal finranges from small to absent, depending on species. Almost all of the species lackscales.The eyes are small, and in somecave-dwellingspecies, they are beneath the skin, so the fish is blind. Thegillmembranes are fused, and the gill opening is either a slit or pore underneath the throat. Theswim bladderand ribs are also absent. These are all believed to be adaptations for burrowing into soft mud during periods of drought, and swamp eels are often found in the mud underneath a dried-up pond.[5]
Most of the species can breathe air, allowing them to survive in low-oxygenated water, and to migrate overland between ponds on wet nights. The linings of the mouth andpharynxare highly vascularised, acting as primitive but efficient lungs. Although swamp eels are not themselves related toamphibians,this lifestyle may well resemble those of the fish from which the land animals evolved during theDevonianperiod.[5]
Although the adults are virtually finless, the larvae are born with greatly enlarged pectoral fins. The fins are used to propel streams of oxygenated water from the surface along the larva's body. The skin of the larva is thin and vascularised, allowing it to extract oxygen from this stream of water. As the fish grows, the adult air-breathing organ begins to develop, and it no longer requires the fins. At the age of about two weeks, the larva suddenly sheds the pectoral fins, and takes on the adult form.[5]
Most species areprotogynoushermaphrodites, that is, most individuals begin life as females, but later change into males. This typically occurs around four years of age, although a small number of individuals are born male and remain so throughout their lives.[5]
Taxonomy[edit]
The family Synbranchidae is divided into sixgeneraas follows:[6]
- genusMacrotremaRegan,1912
- genusOphisternonMcClelland,1844
- genusSynbranchusBloch,1795
- genusMonopterusLacepède,1800
- genusRakthamichthysBritz,Dahanukar,Standing,Philip,Kumar&Raghavan,2020
- genusTyphlosynbranchusPellegrin,1922
In cooking[edit]
InIndonesiaswamp eel is calledbelut,and are commonly harvested from water ponds ofrice paddiesand become the protein source for rural population in Indonesia. Swamp eel is usually stir fried served withsambalhot chili sauce asbelut penyet,curried, or deep fried to achieve crispy texture askripikbelut.[7]
In the Jiangnan region of China, swamp eels are a delicacy, usually cooked in stirfries or casseroles. The recipe usually calls for garlic, scallions, bamboo shoots, rice wine, sugar, starch, and soy sauce with prodigious amounts of vegetable oil. It is popular in the region from Shanghai to Nanjing. The Chinese name in pinyin of this dish ischao shan hu.The name of the swamp eel isshan yuorhuang shan.
InAssamswamp eels are considered a delicacy and prepared as curry or dry fry. It is believed there that these are good source of iron and good for blood deficiency.
Conservation status[edit]
As of 2021, eleven species were listed by theIUCNas species of special concern:Typhlosynbranchus boueti(Liberian swamp eel),Rakthamichthys indicus(Malabar swamp eel),Rakthamichthys roseni,Rakthamichthys digressus,andOphichthys hodgartihave been classified asdata deficient,meaning that they require more study to determine their conservation status.Ophichthys indicus(Bombay swamp eel) is classified asvulnerable.Ophichthys fossorius(Malabar swampeel),Ophisternon infernale(blind swamp eel),Ophisternon candidum(the blind cave eel), andOphisternon afrum(Guinea swamp eel) are classified asendangered.Ophichthys desilvai(Desilvai's blind eel) is classified ascritically endangered.[8]
On the other side of the endangerment issue,invasiveswamp eels inFloridaare a major threat to populations ofcrayfishand some other small species.[9][10]
References[edit]
- ^Richard van der Laan; William N. Eschmeyer & Ronald Fricke (2014)."Family-group names of Recent fishes".Zootaxa.3882(2): 001–230.
- ^Robert A. Travers (1985)."A review of the Mastacembeloidei, a suborder of Synbranchoform teleost fish Part 2: Phylogenetic analysis".Bulletin of the British Museum (Natural History).47:83–151.
- ^Eschmeyer, William N.;Fricke, Ron & van der Laan, Richard (eds.)."Synbranchus".Catalog of Fishes.California Academy of Sciences.Retrieved11 November2019.
- ^Perdices, A.; Doadrio, I.; Bermingham, E. (November 2005). "Evolutionary history of the synbranchid eels (Teleostei: Synbranchidae) in Central America and the Caribbean islands inferred from their molecular phylogeny".Molecular Phylogenetics and Evolution.37(2): 460–473.doi:10.1016/j.ympev.2005.01.020.PMID16223677.
- ^abcdeLiem, Karel F. (1998). Paxton, J.R.; Eschmeyer, W.N. (eds.).Encyclopedia of Fishes.San Diego: Academic Press. pp. 173–174.ISBN0-12-547665-5.
- ^J. S. Nelson; T. C. Grande; M. V. H. Wilson (2016).Fishes of the World(5th ed.). Wiley. pp. 381–383.ISBN978-1-118-34233-6.
- ^Media, Kompas Cyber (2022-05-11)."7 Cara Masak Belut Bebas Amis, Cocok Jadi Keripik atau Penyetan Halaman all".KOMPAS(in Indonesian).Retrieved2023-02-28.
- ^"The IUCN Red List of Threatened Species".IUCN Red List of Threatened Species.Retrieved2021-01-29.
- ^[1]
- ^[2]
