Monopterus albus
Encyclopedia
Monopterus albus (Synonym: Fluta alba (Bloch and Schneider, 1801)) is an important air-breathing commercial species of fish
in the Synbranchidae family. Originating in the waters of East and Southeast Asia, it has been identified as an invasive species in the North American Everglades
.
Monopterus albus comes from the class or subclass Actinopterygii
. It arose from the Osteichthyes
, the first bony fish, whose fossil record dates back to the Triassic period
. In turn, the bony fish came from the Acanthodii
class of bony and cartilaginous fish. The common name of M. albus is somewhat of a misnomer, as the Asian swamp eel is not an eel, per se. Eels are of the order Anguilliformes, while M. albus is of the order Synbranchiformes
.
, it has a tapering tail, blunt snout, and lacks pectoral and pelvic fins. The dorsal, anal, and caudal fins are rudimentary, with the caudal fin often absent. These fins serve to protect the swamp eel against rolling, and assist in sudden turns and stops (link
). Its gill membranes are fused, but one v-shaped gill is located beneath the head. Such a shape prevents reverse flow (link
). Its body and head are dark, with dark olive or brown dorsal coloring and light orange ventral coloring. This coloration camouflages the aquatic predator; however, some are brightly colored with yellow, black and gold spots(link). The bristle-like teeth of the M. albus, which are not easily seen, also indicate its carnivorous behavior (link).
M. albus is an evasive nocturnal animal (Source). Its diet includes other fish, shrimp, crayfish, frogs, turtle eggs, aquatic invertebrates like worms and insects, and occasionally detritus
. Unlike the traits of its diurnal counterparts, M. albus life history traits
(e.g. absolute density and survival) are difficult to accurately measure and can require decades of data to detect trends, as expressed by the lack of data available on the topic. This results in an increase in the population of the invasive species
without adequate time for population control methods.
The Asian swamp eel has versatile motility
and is even capable of moving over dry land for short distances. This behavior is used for relocation according to resource availability. In the absence of water and food, the Asian swamp eel is able to survive long periods of drought by burrowing in moist earth(link). If its home becomes unsuitable, M. albus simply crawls ashore and makes its way to a more suitable home by slithering over the land in a snake-like fashion. These characteristics enhance the ability of M. albus to disperse widely. The swamp eel is a voracious general predator, making it a threat to native fishes, amphibians, and aquatic invertebrates.
The survivorship
of a species or cohort can be found by calculating the number or proportion of individuals surviving at each age. Type I survivorship is characterized by high survival in early and middle life, followed by a rapid decline in survivorship in later life because of physiological changes. Type II survivorship exhibits a constant mortality rate regardless of age because of consistent environmental threats. M. albus survivorship falls between Type I, physiological, and Type II, ecological. They exhibit a great deal of parental care, indicative of physiological survivorship. Large males construct bubble nests at the mouth of burrows and guard the eggs and young. Additionally, eel populations are dependant upon resource abundance, making their survivorship partially ecological. Because of the aforesaid behaviors, removal of the invasive species might be best achieved in the juvenile stage or immediately after spawning, when parental care is at its highest.
. All young are females. As juvenile fish begin to mature, some take on the masculine phenotype. Males have transgendered capabilities, allowing them to replenish female populations when female densities are low. This change from one sex to another can take up to a year.
Spawning can occur throughout the year. Eggs are laid in bubble nests located in shallow waters. These bubble nests float at the water’s surface and are not attached to aquatic vegetation. Females produce up to 1,000 eggs, each, per spawning event. This characteristic is important when considering control of the invasive species. The greater the proportion of females in the population, the greater the amount of reproduction. Thus, it would be best to implement removal of the species at the juvenile stage of life cycle to obtain the largest number of the reproductive population.
s (e.g., rotenone
and antimycin-A
) that are transmitted across the gill membrane may not be effective. Serial piscicide dilutions of antimycin-A were tested and found to be innocuous. No change in morbidity and mortality
were observed.
. Eating raw or undercooked swamp eel can cause gnathostomiasis
, an important disease in Thailand
, Laos
, Burma and Vietnam
.
Neurognathostomiasis has been reported in the US, but a link to imported swamp eels has not been proven.
Gnathostoma binucleatum (which is native to the Americas) has not been previous been reported to cause neurognathostomiasis, suggesting that G. spinigerum has been introduced to the Americas, but a survey of Gnathostoma isolates has not confirmed this.
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
in the Synbranchidae family. Originating in the waters of East and Southeast Asia, it has been identified as an invasive species in the North American Everglades
Everglades
The Everglades are subtropical wetlands in the southern portion of the U.S. state of Florida, comprising the southern half of a large watershed. The system begins near Orlando with the Kissimmee River, which discharges into the vast but shallow Lake Okeechobee...
.
Taxonomy and Evolution
The Asian swamp eel is a freshwater eel-like fish belonging to the family Synbranchidae. This family is native to the fresh, brackish, tropical, and subtropical waters of Asia, but is now present in West Africa and North, Central and South America. Its taxonomy, however, is incorrect. Though Monopterus albus was initially thought to be a single species, four known populations of the “species” in the southeastern United States may actually be three distinct species or taxa, each originating from a different area in Asia.Monopterus albus comes from the class or subclass Actinopterygii
Actinopterygii
The Actinopterygii or ray-finned fishes constitute a class or sub-class of the bony fishes.The ray-finned fishes are so called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines , as opposed to the fleshy, lobed fins that characterize...
. It arose from the Osteichthyes
Osteichthyes
Osteichthyes , also called bony fish, are a taxonomic group of fish that have bony, as opposed to cartilaginous, skeletons. The vast majority of fish are osteichthyes, which is an extremely diverse and abundant group consisting of over 29,000 species...
, the first bony fish, whose fossil record dates back to the Triassic period
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
. In turn, the bony fish came from the Acanthodii
Acanthodii
Acanthodii is a class of extinct fishes, sharing features with both bony fish and cartilaginous fish. In form they resembled sharks, but their epidermis was covered with tiny rhomboid platelets like the scales of holosteans...
class of bony and cartilaginous fish. The common name of M. albus is somewhat of a misnomer, as the Asian swamp eel is not an eel, per se. Eels are of the order Anguilliformes, while M. albus is of the order Synbranchiformes
Synbranchiformes
Synbranchiformes, often called swamp eels, is an order of ray-finned fishes that are eel-like but have spiny rays, indicating that they belong to the superorder Acanthopterygii.-Taxonomy:...
.
Characteristics
The Asian swamp eel has a scaleless, anguilliform body that grows to a meter or less, typically 25 to 40 cm as an adult. As a SynbranchidaeSwamp eel
The swamp eels are a family of freshwater eel-like fishes of the worldwide tropics.-Description:...
, it has a tapering tail, blunt snout, and lacks pectoral and pelvic fins. The dorsal, anal, and caudal fins are rudimentary, with the caudal fin often absent. These fins serve to protect the swamp eel against rolling, and assist in sudden turns and stops (link
Fish anatomy
Fish anatomy is primarily governed by the physical characteristics of water, which is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does.- Body :...
). Its gill membranes are fused, but one v-shaped gill is located beneath the head. Such a shape prevents reverse flow (link
Gill slit
Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of Cartilaginous fish such as sharks, rays, sawfish, and guitarfish. Most of these have five pairs, but a few species have 6 or 7 pairs...
). Its body and head are dark, with dark olive or brown dorsal coloring and light orange ventral coloring. This coloration camouflages the aquatic predator; however, some are brightly colored with yellow, black and gold spots(link). The bristle-like teeth of the M. albus, which are not easily seen, also indicate its carnivorous behavior (link).
Appearance
Monopterus albus has a scaleless cylindrical snake-like body with tapered tail and small eyes. It grows to a meter or less, usually 25 to 40 cm as an adult. Its body color is brown or green-brown above and white or light-brown below. In adults, paired fins are lacking, and the dorsal, caudal and anal fins are reduced. Through its life, Monopterus Albus develops a small top fin near its rear. The gill openings are merged into a single slit underneath the head while the mouth is large and protractile and both upper and lower jaws have tiny teeth for eating fishes, worms, crustaceans, and other small aquatic animals at night.Life history
Life HistoryM. albus is an evasive nocturnal animal (Source). Its diet includes other fish, shrimp, crayfish, frogs, turtle eggs, aquatic invertebrates like worms and insects, and occasionally detritus
Detritus
Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...
. Unlike the traits of its diurnal counterparts, M. albus life history traits
Life history theory
Life history theory posits that the schedule and duration of key events in an organism's lifetime are shaped by natural selection to produce the largest possible number of surviving offspring...
(e.g. absolute density and survival) are difficult to accurately measure and can require decades of data to detect trends, as expressed by the lack of data available on the topic. This results in an increase in the population of the invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
without adequate time for population control methods.
The Asian swamp eel has versatile motility
Motility
Motility is a biological term which refers to the ability to move spontaneously and actively, consuming energy in the process. Most animals are motile but the term applies to single-celled and simple multicellular organisms, as well as to some mechanisms of fluid flow in multicellular organs, in...
and is even capable of moving over dry land for short distances. This behavior is used for relocation according to resource availability. In the absence of water and food, the Asian swamp eel is able to survive long periods of drought by burrowing in moist earth(link). If its home becomes unsuitable, M. albus simply crawls ashore and makes its way to a more suitable home by slithering over the land in a snake-like fashion. These characteristics enhance the ability of M. albus to disperse widely. The swamp eel is a voracious general predator, making it a threat to native fishes, amphibians, and aquatic invertebrates.
The survivorship
Survivorship curve
A survivorship curve is a graph showing the number or proportion of individuals surviving at each age for a given species or group...
of a species or cohort can be found by calculating the number or proportion of individuals surviving at each age. Type I survivorship is characterized by high survival in early and middle life, followed by a rapid decline in survivorship in later life because of physiological changes. Type II survivorship exhibits a constant mortality rate regardless of age because of consistent environmental threats. M. albus survivorship falls between Type I, physiological, and Type II, ecological. They exhibit a great deal of parental care, indicative of physiological survivorship. Large males construct bubble nests at the mouth of burrows and guard the eggs and young. Additionally, eel populations are dependant upon resource abundance, making their survivorship partially ecological. Because of the aforesaid behaviors, removal of the invasive species might be best achieved in the juvenile stage or immediately after spawning, when parental care is at its highest.
Life cycle
The Asian swamp eel is hermaphroditicHermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
. All young are females. As juvenile fish begin to mature, some take on the masculine phenotype. Males have transgendered capabilities, allowing them to replenish female populations when female densities are low. This change from one sex to another can take up to a year.
Spawning can occur throughout the year. Eggs are laid in bubble nests located in shallow waters. These bubble nests float at the water’s surface and are not attached to aquatic vegetation. Females produce up to 1,000 eggs, each, per spawning event. This characteristic is important when considering control of the invasive species. The greater the proportion of females in the population, the greater the amount of reproduction. Thus, it would be best to implement removal of the species at the juvenile stage of life cycle to obtain the largest number of the reproductive population.
Distribution and habitat
M. albus is native to the tropical and subtropical areas of northern India and Burma to China, Asiatic Russia, Japan, and Indo-Malayan Archipelago. It is one of the common fish found mainly in Asia, from India, Southern China to Malaysia and Indonesia. The fish is an important protein source for people in the northeastern part of Thailand. In Asia, the swamp eel is wide-ranging, occurring in both tropical and temperate climates. Endemic to southern and eastern Asia, swamp eels live in ditches, ponds, streams, and rice paddies.Native habitat
The preferred environment for the Asian swamp eel includes a wide variety of freshwater-like shallow wetlands, stagnant waters, marshes, streams, rivers, ditches, canals, lakes, reservoirs, and ponds. While they prefer freshwater, they are also able to tolerate brackish and saline conditions, as seen in their colonization of American marshlands. Depths of less than 3 m are optimal. M. albus also easily tolerates cold temperatures—well below 0 degrees C-- and a wide range of oxygen levels. This fish can obtain up to 25% oxygen from air cutaneously if not using gills underwater. This means that factors that typically limit dispersal—temperature, oxygen, and salinity—do not limit the Asian swamp eel.Nonnative habitats
The Asian swamp eels were first introduced to the Hawaiian islands around 1900. Locations in the southeastern United States were not colonized until the end of the 20th century. As early as 1990, Asian swamp eels were introduced to several ponds at a nature center near Atlanta, Georgia, within the Chattahoochee River drainage basin; individuals have since migrated to an adjacent marsh of the Chattahoochee River. As a general predator, the Asian swamp eel has disrupted the ecological balance of the Everglades. In 1994, eel specimen were collected in ponds at the Chattahoochee Nature Center north of Atlanta, Georgia. Subsequently, eels were collected from Florida waters in 1997 at two widely separated areas: one in southeast and the other in west-central Florida. Tens of thousands of swamp eels are estimated to inhabit nearly 55 miles of two water canal systems in southern Florida, one in the North Miami area and another on the eastern side of Everglades National Park. Two other populations of the eel have been discovered since 1993: one outside of Tampa, Florida, and one in southern Georgia near the Chattahoochee River. One or more of the populations are believed to be the result of an intentional or accidental release of the creature from a home aquarium or fish farm. Some populations may have been the result of an attempt by a few local residents to establish the eels as a food source. Asian swamp eels pose a threat to the homeostasis of Everglades National Park by disrupting the natural interactions between native species and their environment. The species has an incredible ability to survive in adverse conditions, and the Everglade food web presents no known natural predators. Swamp eels survive even in the dry season when other nonnative species normally die. To combat Asian swamp eel resilience, the American Fisheries Society is investigating methods for control, containment, and possible eradication.Control Plan
The United States Geological Survey (USGS) proposed and implemented several methods in controlling the Monopterus albus population in Southern Florida. Having documented eel distribution, behavior, and biology, the USGS discourages catching and transporting the eel for use as bait, food, or aquarium pets. Water management practices are also changing to combat the invasive species. Selected water-control structures near established swamp eel populations are not being opened to prevent or at least retard dispersal, particularly into the waters of Everglades National Park. Adult and juvenile swamp eels are obligate air-breathers, while young absorb oxygen directly through the skin. As such, standard fish poisons or piscicidePiscicide
A piscicide is a chemical substance which is poisonous to fish. The primary use for piscicides is to eliminate a dominant species of fish in a body of water, as the first step in attempting to populate the body of water with a different fish...
s (e.g., rotenone
Rotenone
Rotenone is an odorless chemical that is used as a broad-spectrum insecticide, piscicide, and pesticide. It occurs naturally in the roots and stems of several plants such as the jicama vine plant...
and antimycin-A
Antimycin A
Antimycins are a group of secondary metabolites produced by Streptomyces bacteria.-Uses:It is the active ingredient in Fintrol, a chemical piscicide used in fisheries management and in the catfish industry.-Mechanism of action:...
) that are transmitted across the gill membrane may not be effective. Serial piscicide dilutions of antimycin-A were tested and found to be innocuous. No change in morbidity and mortality
Mortality rate
Mortality rate is a measure of the number of deaths in a population, scaled to the size of that population, per unit time...
were observed.
Disease
Swamp eels are an important host for Gnathostoma spinigerumGnathostoma spinigerum
Gnathostoma spinigerum is a parasitic nematode that causes gnathostomiasis in humans, also known as its clinical manifestations are creeping eruption, larva migrans, Yangtze edema, Choko-Fuschu Tua chid and wandering swelling. Gnathostomiasis in animals can be serious, and even fatal...
. Eating raw or undercooked swamp eel can cause gnathostomiasis
Gnathostomiasis
Gnathostomiasis is the human infection by the nematode Gnathostoma spinigerum and/or Gnathostoma hispidum, which infects vertebrates.-Synonyms:...
, an important disease in Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
, Laos
Laos
Laos Lao: ສາທາລະນະລັດ ປະຊາທິປະໄຕ ປະຊາຊົນລາວ Sathalanalat Paxathipatai Paxaxon Lao, officially the Lao People's Democratic Republic, is a landlocked country in Southeast Asia, bordered by Burma and China to the northwest, Vietnam to the east, Cambodia to the south and Thailand to the west...
, Burma and Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
.
Neurognathostomiasis has been reported in the US, but a link to imported swamp eels has not been proven.
Gnathostoma binucleatum (which is native to the Americas) has not been previous been reported to cause neurognathostomiasis, suggesting that G. spinigerum has been introduced to the Americas, but a survey of Gnathostoma isolates has not confirmed this.
Sources and notes
External links
- Species Profile- Asian Swamp Eel (Monopterus albus), National Invasive Species Information Center, United States National Agricultural LibraryUnited States National Agricultural LibraryThe United States National Agricultural Library is one of the world's largest agricultural research libraries, and serves as a National Library of the United States and as the library of the United States Department of Agriculture...
. Lists general information and resources for Asian Swamp Eel. - http://el.erdc.usace.army.mil/ansrp/ANSIS/html/monopterus_albus_asian_swamp_eel.htm#Malbus_Distribution, US Army Corps of Engineers, responsible for investigating, developing and maintaining the nation's water and related environmental resources.
- http://www.fishbase.org/PopDyn/KeyfactsSummary_1.php?ID=4663&GenusName=Monopterus&SpeciesName=albus&vStockCode=4880&fc=262, Life History Data.