Atlantic torpedo
Encyclopedia
The Atlantic torpedo or dark electric ray (Torpedo nobiliana) is a species
of electric ray
in the family
Torpedinidae. It is found in the Atlantic Ocean
, from Nova Scotia
to Brazil
in the west and from Scotland
to West Africa
and off southern Africa
in the east, occurring at depths of up to 800 m (2,624.7 ft). Younger individuals generally inhabit shallower, sandy or muddy habitat
s, whereas adults are more pelagic
in nature and frequent open water. Up to 1.8 m (6 ft) long and weighing 90 kg (198.4 lb), the Atlantic torpedo is the largest known electric ray. Like other members of its genus, it has an almost circular pectoral fin disk with a nearly straight leading margin, and a robust tail with a large triangular caudal fin. Distinctive characteristics include its uniform dark color, smooth-rimmed spiracle
s (paired respiratory openings behind the eyes), and two dorsal fin
s of unequal size.
Solitary and nocturnal, the Atlantic torpedo is capable of generating up to 220 volt
s of electricity
to subdue its prey or defend itself against predators. Its diet consists mainly of bony fishes, though it also feeds on small shark
s and crustacean
s. It is an aplacental viviparous species, wherein the developing embryo
s are nourished by yolk and later maternally provided histotroph ("uterine milk"). Females give birth to up to 60 young following a gestation period
of one year. The electric shock
of this species can be quite severe and painful, though it is not fatal. Because of its electrogenic properties, the Atlantic torpedo was used in medicine
by the Ancient Greeks and Romans
and became the namesake of the naval weapon
. Prior to the 19th century, its liver
oil was used as lamp fuel, but it is no longer of any economic value. The International Union for Conservation of Nature (IUCN) has listed this species as Data Deficient
; it is caught unintentionally
by commercial
and recreational fisher
s, but the impact of these activities on its population is unknown.
Charles Lucien Bonaparte
, in his principal work Iconografia della Fauna Italica. Sixteen specimens were designated as the syntype
s. The assignment of the southern Africa
n "great torpedo" to this species is provisional. Another type of electric ray found in the Indian Ocean
off Mozambique
may also belong to T. nobiliana. The Atlantic torpedo is placed in the subgenus Tetronarce, which differs from the other Torpedo subgenus Torpedo in having generally plain coloration and smooth-margined spiracle
s. Other common name
s include Atlantic electric ray, Atlantic New British torpedo, black torpedo, crampfish, electric ray, numbfish, or torpedo.
. In the east, it is found from northern Scotland
to the Gulf of Guinea
, including the entire Mediterranean Sea
(but not the Black Sea
), the Azores
, and Madeira
, as well as from Namibia
to western South Africa
. In the west, it occurs from southern Nova Scotia
to Venezuela
and Brazil
. It is rare in the North Sea
and the Mediterranean and south of North Carolina
.
Juvenile Atlantic torpedoes are primarily bottom-dwelling and usually found at depths of 10–50 m (32.8–164 ft) over sandy or muddy flats, or near coral reef
s. As they mature, they become more pelagic
in habits, and adults are often encountered swimming in the open ocean. This species has been recorded from the surface to a depth of 800 m (2,624.7 ft); in the Mediterranean, it is most common at depths of 200–500 m (656.2–1,640.4 ft). It is said to make long migratory movements
.
e on their inner rims. The nostril
s are close to the mouth; there is a flap of skin between them three times as wide as long, with a sinuous rear margin. The mouth is wide and arched, with prominent furrows at the corners. The teeth are pointed and increase in number with age, ranging from 38 rows in juveniles to 66 rows in adults; the first several series of teeth are functional. The gill slit
s are small, with the first and fifth pairs shorter than the others.
The pelvic fins are rounded and slightly overlapped by the disc at the front. The first dorsal fin is triangular with a rounded apex, originating in front of the pelvic fin insertions. The second dorsal fin is only one-half to two-thirds as large as the first; the distance between the dorsal fins is less than the length of the first dorsal fin base. The stout tail comprises about one-third of the total length, terminating in a caudal fin shaped like an equilateral triangle with slightly convex margins. The skin is soft and completely devoid of dermal denticles (scales). The dorsal coloration is a plain dark brown to gray, sometimes with a few diffuse spots, and darkening at the fin margins. The underside is white, with dark fin margins. The largest of the electric rays, the Atlantic torpedo can measure 1.8 m (6 ft) long and weigh 90 kg (198.4 lb). However, a length of 0.6–1.5 m (2–4.9 ft) and weight of 30 lb (13.6 kg) is more typical. Females attain a larger size than males.
from a pair of kidney-shaped electric organ
s in its disc, for both attack and defense. These organs comprise one-sixth of the ray's total weight and contain around half a million jelly-filled "electric plates" arranged in an average of 1,025–1,083 vertical hexagonal columns (visible beneath the skin). These columns essentially act as batteries
connected in parallel, enabling a large Atlantic torpedo to produce up to a kilowatt of electricity at 170–220 volt
s, provided that it is well-fed and rested. The discharges from the electric organ occur in a series, or train, of closely spaced pulses each lasting around 0.03 seconds. Trains contain on average 12 pulses, but trains of over 100 pulses have been recorded. The ray regularly emits pulses even without an obvious external stimulus.
Solitary in nature, the Atlantic torpedo is often seen resting on or half-buried in the substrate during the day, becoming more active at night. Large and well-defended from attack, it seldom falls prey to other animals. Known parasites of the Atlantic torpedo include the tapeworms Calyptrobothrium occidentale and C. minus, Grillotia microthrix, Monorygma sp., and Phyllobothrium gracile, the monogenea
ns Amphibdella flabolineata and Amphibdelloides maccallumi, and the copepod
Eudactylina rachelae. Some accounts suggest that this ray may be able to survive out of water for up to a day.
es, salmon
, eel
s, and mullet
, though it has also been known to take small catshark
s and crustacean
s. Captive rays have been observed lying still on the bottom and "pouncing" on fish that pass in front of them. At the moment of contact, the ray traps the prey against its body or the bottom by curling its pectoral fin disc around it, while delivering strong electric shocks. This strategy allows the sluggish ray to capture relatively fast-moving fish. Once subdued, the prey is maneuvered to the mouth with rippling motions of the disc and swallowed whole, head-first. The ray's highly distensible jaws allow surprisingly large prey to be ingested: an intact salmon weighing 2 kg (4 lb) has been found in the stomach
of one individual, and another contained a summer flounder
(Paralichthys dentatus) 37 cm (14.6 in) long. This ray has been known to kill fish much larger than it can eat.
s are sustained by yolk, which is later supplemented by protein
and fat
-enriched histotroph ("uterine milk") produced by the mother. Females have two functional ovaries and uterus
es, and a possibly biennial reproductive cycle. After a year-long gestation period
, females bear up to 60 pups during the summer; the litter size increases with the size of the female. When the embryo is 14 cm (5.5 in) long, it has a pair of deep notches at the front of the disc marking the origin of the pectoral fins, and the curtain of skin between the nostrils has not yet developed; on the other hand, the eyes, spiracles, dorsal fins, and tail have reached adult proportions. Newborn rays measure 17–25 cm (6.7–9.8 in) long, and still have the anterior notches in the disc. Males and females reach sexual maturity
at lengths of 55 cm (21.7 in) and 90 cm (35.4 in) respectively.
by commercial
and recreational fisheries
in bottom trawls and on hook-and-line. When caught at sea, it is generally discarded or cut up for bait. The International Union for Conservation of Nature (IUCN) does not yet have enough data to assess the Atlantic torpedo beyond Data Deficient
; it could be negatively affected by fishing mortality, though specific data on catch rates and population trends are lacking, as well as by the degradation of coral reefs that are important to juveniles. Its slow reproductive rate would limit its capacity to recover from population depletion.
Various electric fish
es, including the Atlantic torpedo, were used in medicine
during the classical era
. In the 1st century, Roman
physician Scribonius Largus
wrote of the application of live "dark torpedo" to patients afflicted with gout
or chronic headaches. In 1800, the Atlantic torpedo became the namesake for the naval weapon
when American inventor Robert Fulton
began using the word "torpedo" to describe bomb
s that submarine
s could attach to ships (although these early devices were more akin to modern-day mines
). Before the widespread introduction of kerosene
in the 19th century, the liver
oil of this species was regarded as of equal quality to sperm whale
(Physeter macrocephalus) oil
for use in lamps. Before the 1950s, its oil was also used in small quantities by fishermen in the United States as a treatment for muscle and stomach cramp
s, as well as to lubricate
farm machinery. Along with several other species of electric rays, the Atlantic torpedo is used as a model organism
in biomedical research because its electric organs are rich in acetylcholine receptor
protein
s. These proteins play an important role in mediating many neurological
processes, such as those involved in the functioning of anesthesia
.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of electric ray
Electric ray
The electric rays are a group of rays, flattened cartilaginous fish with enlarged pectoral fins, comprising the order Torpediniformes. They are known for being capable of producing an electric discharge, ranging from as little as 8 volts up to 220 volts depending on species, used to stun prey and...
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Torpedinidae. It is found in the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, from Nova Scotia
Nova Scotia
Nova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...
to Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
in the west and from Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
to West Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
and off southern Africa
Southern Africa
Southern Africa is the southernmost region of the African continent, variably defined by geography or geopolitics. Within the region are numerous territories, including the Republic of South Africa ; nowadays, the simpler term South Africa is generally reserved for the country in English.-UN...
in the east, occurring at depths of up to 800 m (2,624.7 ft). Younger individuals generally inhabit shallower, sandy or muddy habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s, whereas adults are more pelagic
Pelagic fish
Pelagic fish live near the surface or in the water column of coastal, ocean and lake waters, but not on the bottom of the sea or the lake. They can be contrasted with demersal fish, which do live on or near the bottom, and reef fish which are associated with coral reefs.The marine pelagic...
in nature and frequent open water. Up to 1.8 m (6 ft) long and weighing 90 kg (198.4 lb), the Atlantic torpedo is the largest known electric ray. Like other members of its genus, it has an almost circular pectoral fin disk with a nearly straight leading margin, and a robust tail with a large triangular caudal fin. Distinctive characteristics include its uniform dark color, smooth-rimmed spiracle
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...
s (paired respiratory openings behind the eyes), and two dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
s of unequal size.
Solitary and nocturnal, the Atlantic torpedo is capable of generating up to 220 volt
Volt
The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
s of electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...
to subdue its prey or defend itself against predators. Its diet consists mainly of bony fishes, though it also feeds on small shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
s and crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s. It is an aplacental viviparous species, wherein the developing embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
s are nourished by yolk and later maternally provided histotroph ("uterine milk"). Females give birth to up to 60 young following a gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
of one year. The electric shock
Electric shock
Electric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....
of this species can be quite severe and painful, though it is not fatal. Because of its electrogenic properties, the Atlantic torpedo was used in medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
by the Ancient Greeks and Romans
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....
and became the namesake of the naval weapon
Torpedo
The modern torpedo is a self-propelled missile weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with it or in proximity to it.The term torpedo was originally employed for...
. Prior to the 19th century, its liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
oil was used as lamp fuel, but it is no longer of any economic value. The International Union for Conservation of Nature (IUCN) has listed this species as Data Deficient
Data Deficient
Data Deficient is a category applied by the IUCN, other agencies, and individuals to a species when the available information is not sufficient for a proper assessment of conservation status to be made...
; it is caught unintentionally
Bycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
by commercial
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...
and recreational fisher
Recreational fishing
Recreational fishing, also called sport fishing, is fishing for pleasure or competition. It can be contrasted with commercial fishing, which is fishing for profit, or subsistence fishing, which is fishing for survival....
s, but the impact of these activities on its population is unknown.
Taxonomy
The first scientific description of the Atlantic torpedo was published in 1835 by French naturalistNaturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
Charles Lucien Bonaparte
Charles Lucien Bonaparte
Charles Lucien Jules Laurent Bonaparte, 2nd Prince of Canino and Musignano was a French naturalist and ornithologist.-Biography:...
, in his principal work Iconografia della Fauna Italica. Sixteen specimens were designated as the syntype
Syntype
In biological nomenclature, a syntype is a term used to indicate a specimen with a special status.In zoological nomenclature, a syntype is defined as "Each specimen of a type series from which neither a holotype nor a lectotype has been designated [Arts. 72.1.2, 73.2, 74]. The syntypes...
s. The assignment of the southern Africa
Southern Africa
Southern Africa is the southernmost region of the African continent, variably defined by geography or geopolitics. Within the region are numerous territories, including the Republic of South Africa ; nowadays, the simpler term South Africa is generally reserved for the country in English.-UN...
n "great torpedo" to this species is provisional. Another type of electric ray found in the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
off Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...
may also belong to T. nobiliana. The Atlantic torpedo is placed in the subgenus Tetronarce, which differs from the other Torpedo subgenus Torpedo in having generally plain coloration and smooth-margined spiracle
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...
s. Other common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
s include Atlantic electric ray, Atlantic New British torpedo, black torpedo, crampfish, electric ray, numbfish, or torpedo.
Distribution and habitat
The Atlantic torpedo is widely distributed in cool waters on both sides of the Atlantic OceanAtlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
. In the east, it is found from northern Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
to the Gulf of Guinea
Gulf of Guinea
The Gulf of Guinea is the northeasternmost part of the tropical Atlantic Ocean between Cape Lopez in Gabon, north and west to Cape Palmas in Liberia. The intersection of the Equator and Prime Meridian is in the gulf....
, including the entire Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
(but not the Black Sea
Black Sea
The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...
), the Azores
Azores
The Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the...
, and Madeira
Madeira
Madeira is a Portuguese archipelago that lies between and , just under 400 km north of Tenerife, Canary Islands, in the north Atlantic Ocean and an outermost region of the European Union...
, as well as from Namibia
Namibia
Namibia, officially the Republic of Namibia , is a country in southern Africa whose western border is the Atlantic Ocean. It shares land borders with Angola and Zambia to the north, Botswana to the east and South Africa to the south and east. It gained independence from South Africa on 21 March...
to western South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
. In the west, it occurs from southern Nova Scotia
Nova Scotia
Nova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...
to Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
and Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. It is rare in the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
and the Mediterranean and south of North Carolina
North Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
.
Juvenile Atlantic torpedoes are primarily bottom-dwelling and usually found at depths of 10–50 m (32.8–164 ft) over sandy or muddy flats, or near coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
s. As they mature, they become more pelagic
Pelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...
in habits, and adults are often encountered swimming in the open ocean. This species has been recorded from the surface to a depth of 800 m (2,624.7 ft); in the Mediterranean, it is most common at depths of 200–500 m (656.2–1,640.4 ft). It is said to make long migratory movements
Fish migration
Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...
.
Description
The Atlantic torpedo has a nearly circular pectoral fin disc 1.2 times as wide as it is long, with a thick and nearly straight front margin. The eyes are small and are followed by much larger spiracles, which do not have papillaFish 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 :...
e on their inner rims. The nostril
Nostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
s are close to the mouth; there is a flap of skin between them three times as wide as long, with a sinuous rear margin. The mouth is wide and arched, with prominent furrows at the corners. The teeth are pointed and increase in number with age, ranging from 38 rows in juveniles to 66 rows in adults; the first several series of teeth are functional. The gill slit
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...
s are small, with the first and fifth pairs shorter than the others.
The pelvic fins are rounded and slightly overlapped by the disc at the front. The first dorsal fin is triangular with a rounded apex, originating in front of the pelvic fin insertions. The second dorsal fin is only one-half to two-thirds as large as the first; the distance between the dorsal fins is less than the length of the first dorsal fin base. The stout tail comprises about one-third of the total length, terminating in a caudal fin shaped like an equilateral triangle with slightly convex margins. The skin is soft and completely devoid of dermal denticles (scales). The dorsal coloration is a plain dark brown to gray, sometimes with a few diffuse spots, and darkening at the fin margins. The underside is white, with dark fin margins. The largest of the electric rays, the Atlantic torpedo can measure 1.8 m (6 ft) long and weigh 90 kg (198.4 lb). However, a length of 0.6–1.5 m (2–4.9 ft) and weight of 30 lb (13.6 kg) is more typical. Females attain a larger size than males.
Biology and ecology
Like other members of its family, the Atlantic torpedo is capable of generating a powerful electric shockElectric shock
Electric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....
from a pair of kidney-shaped electric organ
Electric organ
In biology, the electric organ is an organ common to all electric fish used for the purposes of creating an electric field. The electric organ is derived from modified nerve or muscle tissue...
s in its disc, for both attack and defense. These organs comprise one-sixth of the ray's total weight and contain around half a million jelly-filled "electric plates" arranged in an average of 1,025–1,083 vertical hexagonal columns (visible beneath the skin). These columns essentially act as batteries
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
connected in parallel, enabling a large Atlantic torpedo to produce up to a kilowatt of electricity at 170–220 volt
Volt
The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
s, provided that it is well-fed and rested. The discharges from the electric organ occur in a series, or train, of closely spaced pulses each lasting around 0.03 seconds. Trains contain on average 12 pulses, but trains of over 100 pulses have been recorded. The ray regularly emits pulses even without an obvious external stimulus.
Solitary in nature, the Atlantic torpedo is often seen resting on or half-buried in the substrate during the day, becoming more active at night. Large and well-defended from attack, it seldom falls prey to other animals. Known parasites of the Atlantic torpedo include the tapeworms Calyptrobothrium occidentale and C. minus, Grillotia microthrix, Monorygma sp., and Phyllobothrium gracile, the monogenea
Monogenea
Monogenea are a group of largely ectoparasitic members of the flatworm phylum Platyhelminthes, class Monogenea.-Characteristics:Monogenea are very small parasitic flatworms mainly found on skin or gills of fish....
ns Amphibdella flabolineata and Amphibdelloides maccallumi, and the copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
Eudactylina rachelae. Some accounts suggest that this ray may be able to survive out of water for up to a day.
Feeding
The diet of the Atlantic torpedo consists mainly of bony fishes, including flatfishFlatfish
The flatfish are an order of ray-finned fish, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the head, one or the other migrating through and around the head during development...
es, salmon
Salmon
Salmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...
, eel
Eel
Eels are an order of fish, which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators...
s, and mullet
Mullet (fish)
The mullets or grey mullets are a family and order of ray-finned fish found worldwide in coastal temperate and tropical waters, and in some species in fresh water. Mullets have served as an important source of food in Mediterranean Europe since Roman times...
, though it has also been known to take small catshark
Catshark
Catsharks are ground sharks of the family Scyliorhinidae, with over 150 known species. While they are generally known as catsharks, many species are commonly called dogfish....
s and crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s. Captive rays have been observed lying still on the bottom and "pouncing" on fish that pass in front of them. At the moment of contact, the ray traps the prey against its body or the bottom by curling its pectoral fin disc around it, while delivering strong electric shocks. This strategy allows the sluggish ray to capture relatively fast-moving fish. Once subdued, the prey is maneuvered to the mouth with rippling motions of the disc and swallowed whole, head-first. The ray's highly distensible jaws allow surprisingly large prey to be ingested: an intact salmon weighing 2 kg (4 lb) has been found in the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
of one individual, and another contained a summer flounder
Summer flounder
The Summer Flounder is a marine flatfish that is found in the Atlantic Ocean off the East coast of the United States and Canada. It is especially abundant in waters from North Carolina to Massachusetts.-Description:...
(Paralichthys dentatus) 37 cm (14.6 in) long. This ray has been known to kill fish much larger than it can eat.
Life history
The Atlantic torpedo is aplacental viviparous: the developing embryoEmbryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
s are sustained by yolk, which is later supplemented by protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
and fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...
-enriched histotroph ("uterine milk") produced by the mother. Females have two functional ovaries and uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
es, and a possibly biennial reproductive cycle. After a year-long gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
, females bear up to 60 pups during the summer; the litter size increases with the size of the female. When the embryo is 14 cm (5.5 in) long, it has a pair of deep notches at the front of the disc marking the origin of the pectoral fins, and the curtain of skin between the nostrils has not yet developed; on the other hand, the eyes, spiracles, dorsal fins, and tail have reached adult proportions. Newborn rays measure 17–25 cm (6.7–9.8 in) long, and still have the anterior notches in the disc. Males and females reach sexual maturity
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
at lengths of 55 cm (21.7 in) and 90 cm (35.4 in) respectively.
Human interactions
Though seldom life-threatening, the electric discharge of an Atlantic torpedo is quite severe and may be enough to knock a person unconscious. However, a greater danger to divers is the disorientation that follows the shock. The Atlantic torpedo is of no commercial value, as its meat is flabby and tasteless. It is caught incidentallyBycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
by commercial
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...
and recreational fisheries
Recreational fishing
Recreational fishing, also called sport fishing, is fishing for pleasure or competition. It can be contrasted with commercial fishing, which is fishing for profit, or subsistence fishing, which is fishing for survival....
in bottom trawls and on hook-and-line. When caught at sea, it is generally discarded or cut up for bait. The International Union for Conservation of Nature (IUCN) does not yet have enough data to assess the Atlantic torpedo beyond Data Deficient
Data Deficient
Data Deficient is a category applied by the IUCN, other agencies, and individuals to a species when the available information is not sufficient for a proper assessment of conservation status to be made...
; it could be negatively affected by fishing mortality, though specific data on catch rates and population trends are lacking, as well as by the degradation of coral reefs that are important to juveniles. Its slow reproductive rate would limit its capacity to recover from population depletion.
Various electric fish
Electric fish
An electric fish is a fish that can generate electric fields. It is said to be electrogenic; a fish that has the ability to detect electric fields is said to be electroreceptive. Most electrogenic fish are also electroreceptive. Electric fish species can be found both in the sea and in freshwater...
es, including the Atlantic torpedo, were used in medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
during the classical era
Classical antiquity
Classical antiquity is a broad term for a long period of cultural history centered on the Mediterranean Sea, comprising the interlocking civilizations of ancient Greece and ancient Rome, collectively known as the Greco-Roman world...
. In the 1st century, Roman
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....
physician Scribonius Largus
Scribonius Largus
Scribonius Largus was the court physician to the Roman emperor Claudius.About 47 AD, at the request of Gaius Julius Callistus, the emperor's freedman, he drew up a list of 271 prescriptions , most of them his own, although he acknowledged his indebtedness to his tutors, to friends and to the...
wrote of the application of live "dark torpedo" to patients afflicted with gout
Gout
Gout is a medical condition usually characterized by recurrent attacks of acute inflammatory arthritis—a red, tender, hot, swollen joint. The metatarsal-phalangeal joint at the base of the big toe is the most commonly affected . However, it may also present as tophi, kidney stones, or urate...
or chronic headaches. In 1800, the Atlantic torpedo became the namesake for the naval weapon
Torpedo
The modern torpedo is a self-propelled missile weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with it or in proximity to it.The term torpedo was originally employed for...
when American inventor Robert Fulton
Robert Fulton
Robert Fulton was an American engineer and inventor who is widely credited with developing the first commercially successful steamboat...
began using the word "torpedo" to describe bomb
Bomb
A bomb is any of a range of explosive weapons that only rely on the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy...
s that submarine
Submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...
s could attach to ships (although these early devices were more akin to modern-day mines
Naval mine
A naval mine is a self-contained explosive device placed in water to destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, an enemy vessel...
). Before the widespread introduction of kerosene
Kerosene
Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...
in the 19th century, the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
oil of this species was regarded as of equal quality to sperm whale
Sperm Whale
The sperm whale, Physeter macrocephalus, is a marine mammal species, order Cetacea, a toothed whale having the largest brain of any animal. The name comes from the milky-white waxy substance, spermaceti, found in the animal's head. The sperm whale is the only living member of genus Physeter...
(Physeter macrocephalus) oil
Whale oil
Whale oil is the oil obtained from the blubber of various species of whales, particularly the three species of right whale and the bowhead whale prior to the modern era, as well as several other species of baleen whale...
for use in lamps. Before the 1950s, its oil was also used in small quantities by fishermen in the United States as a treatment for muscle and stomach cramp
Cramp
Cramps are unpleasant, often painful sensations caused by muscle contraction or over shortening. Common causes of skeletal muscle cramps include muscle fatigue, low sodium, and low potassium...
s, as well as to lubricate
Lubricant
A lubricant is a substance introduced to reduce friction between moving surfaces. It may also have the function of transporting foreign particles and of distributing heat...
farm machinery. Along with several other species of electric rays, the Atlantic torpedo is used as a model organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
in biomedical research because its electric organs are rich in acetylcholine receptor
Acetylcholine receptor
An acetylcholine receptor is an integral membrane protein that responds to the binding of acetylcholine, a neurotransmitter.-Classification:...
protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s. These proteins play an important role in mediating many neurological
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
processes, such as those involved in the functioning of anesthesia
Anesthesia
Anesthesia, or anaesthesia , traditionally meant the condition of having sensation blocked or temporarily taken away...
.