Green lanternshark
Encyclopedia
The green lanternshark (Etmopterus virens) is a species
of dogfish shark
in the family
Etmopteridae
, found in the western central Atlantic Ocean
. This species usually occurs on the upper continental slope below a depth of 350 m (1,148.3 ft). Reaching 26 cm (10.2 in) in length, the green lanternshark has a slender body with a long, thin tail and low, conical dermal denticles on its flanks. It is dark brown or gray with ventral black coloration, which contain light-emitting photophore
s that may serve a cryptic
and/or social function. Green lanternsharks are thought to be gregarious and may attack their prey, squid
and octopus
often larger than themselves, in packs. Reproduction is aplacental viviparous, with females giving birth to litters of 1–3 young. This relatively common shark is an occasional, valueless bycatch
of commercial fisheries; currently it does not appear to be significantly threatened by human activities.
, William C. Schroeder, and Stewart Springer
, in the Bulletin of the Museum of Comparative Zoology at Harvard University. The type specimen was a 20.3 cm (8 in) long male caught at a depth of 403 m (1,322.2 ft) in the northern Gulf of Mexico. The specific epithet virens is Latin
for "green".
to Florida
and Cuba
, and off the Yucatan Peninsula
. In the Caribbean Sea, it is found off Honduras
and Nicaragua
, and from Panama
to Venezuela
and perhaps as far as Brazil
. This largely bottom-dwelling species has been caught at a depth of 196–915 m (643–3,002 ft), with most individuals being found deeper than 350 m (1,148.3 ft).
s are very short, comparable to the spiracle
in size.
The first dorsal fin
bears a spine in front and originates over the trailing margin of the broad and rounded pectoral fins. The second dorsal fin also bears a spine in front and is over twice as large as the first in area, with the span between it and the first dorsal fin approximate equal to the distance between the snout tip and first gill slit. There is no anal fin. The caudal fin is low and narrow, with an indistinct lower lobe and an upper lobe about as long as the head. The dermal denticles on the sides of the body are stout and thorn-shaped, widely spaced without any regular pattern; the snout is mostly covered by denticles. The dorsal coloration is dark brown to gray; the underside of the body and snout are black, with a broad black marking above and behind each pelvic fin, and thin black marks on the tail. These black markings contain numerous light-emitting
photophore
s.
. Like many other bioluminescent deep-sea sharks, it has a yellow spot over its pineal gland
that acts as a "window" for the detection of ambient light levels. This shark is caught sporadically but in large numbers at a time, suggesting that they may travel in schools
. If so, their photophores may also allow individual sharks in a group to keep sight of and coordinate with its cohorts.
Green lanternsharks feed mainly on squid
and octopus
, and are frequently found with cephalopod
eyes and beaks in their stomach
s so large that the sharks would have had to distend their jaws considerably to swallow them. It is uncertain how these diminutive sharks manage to overwhelm prey often much larger than themselves; Stewart Springer has proposed that they may attack in packs, "swarming" over a single large squid or octopus with each shark sawing off pieces of flesh. As with other members of its family, this species is aplacental viviparous with females giving birth to litters of 1–3 young. The newborn pups measure 9 cm (3.5 in) long; males attain sexual maturity
at a length of 18.3–23.6 cm (7.2–9.3 in), and females at a length of 22–25.7 cm (8.7–10.1 in).
in deepwater fisheries but has no commercial value because of its small size. The International Union for Conservation of Nature (IUCN) has assessed it as of Least Concern
, as at present it appears to face no substantial threats. However, like many other deep-sea sharks there is a paucity of information on this species, and vigilance is warranted regarding expanding fisheries within its range.
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 dogfish shark
Squaliformes
Squaliformes is an order of sharks that includes about 97 species in seven families.Members of the order have two dorsal fins, which usually possess spines, no anal fin or nictitating membrane, and five gill slits. In most other respects, however, they are quite variable in form and size...
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...
Etmopteridae
Etmopteridae
Etmopteridae is a family of sharks in the order Squaliformes, commonly known as lantern sharks. Their name comes from the presence of light-producing photophores on their bodies. The members of this family are small, under long, and are found in deep waters worldwide. There are 45 species in five...
, found in the western central 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...
. This species usually occurs on the upper continental slope below a depth of 350 m (1,148.3 ft). Reaching 26 cm (10.2 in) in length, the green lanternshark has a slender body with a long, thin tail and low, conical dermal denticles on its flanks. It is dark brown or gray with ventral black coloration, which contain light-emitting photophore
Photophore
A photophore is a light-emitting organ which appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors...
s that may serve a cryptic
Crypsis
In ecology, crypsis is the ability of an organism to avoid observation or detection by other organisms. It may be either a predation strategy or an antipredator adaptation, and methods include camouflage, nocturnality, subterranean lifestyle, transparency, and mimicry...
and/or social function. Green lanternsharks are thought to be gregarious and may attack their prey, squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
and octopus
Octopus
The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...
often larger than themselves, in packs. Reproduction is aplacental viviparous, with females giving birth to litters of 1–3 young. This relatively common shark is an occasional, valueless bycatch
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...
of commercial fisheries; currently it does not appear to be significantly threatened by human activities.
Taxonomy
The green lanternshark was scientifically described in 1953 by Henry B. BigelowHenry Bryant Bigelow
Henry Bryant Bigelow was an American oceanographer and marine biologist.After graduating from Harvard in 1901, he began working with famed ichthyologist Alexander Agassiz. Bigelow accompanied Agassiz on several major marine science expeditions including one aboard the Albatross in 1907...
, William C. Schroeder, and Stewart Springer
Stewart Springer
Stewart Springer, was a world renowned expert on shark behavior, classification , and distribution of shark populations. There are more than 35 species of sharks, skates, rays, and other animals either classified originally by him or named after him.-Education:Springer was a field naturalist,...
, in the Bulletin of the Museum of Comparative Zoology at Harvard University. The type specimen was a 20.3 cm (8 in) long male caught at a depth of 403 m (1,322.2 ft) in the northern Gulf of Mexico. The specific epithet virens is Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
for "green".
Distribution and habitat
The range of the green lanternshark is restricted to the upper continental slopes of the western central Atlantic. In the Gulf of Mexico, it occurs from TexasTexas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
to Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
and Cuba
Cuba
The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...
, and off the Yucatan Peninsula
Yucatán Peninsula
The Yucatán Peninsula, in southeastern Mexico, separates the Caribbean Sea from the Gulf of Mexico, with the northern coastline on the Yucatán Channel...
. In the Caribbean Sea, it is found off Honduras
Honduras
Honduras is a republic in Central America. It was previously known as Spanish Honduras to differentiate it from British Honduras, which became the modern-day state of Belize...
and Nicaragua
Nicaragua
Nicaragua is the largest country in the Central American American isthmus, bordered by Honduras to the north and Costa Rica to the south. The country is situated between 11 and 14 degrees north of the Equator in the Northern Hemisphere, which places it entirely within the tropics. The Pacific Ocean...
, and from Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. 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 perhaps as far as 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...
. This largely bottom-dwelling species has been caught at a depth of 196–915 m (643–3,002 ft), with most individuals being found deeper than 350 m (1,148.3 ft).
Description
A slim-bodied shark with a short, blunt snout and a long, narrow tail, the green lanternshark attains a maximum known length of 26 cm (10.2 in). The eyes are very large and oval in shape. The nostrils are preceded by short skin flaps. There are 29–34 tooth rows in the upper jaw, each tooth with a narrow central cusp flanked by fewer than three pairs of lateral cusplets. The lower jaw contains 24–32 tooth rows, their bases interlocking to form a continuous cutting surface and each tooth bearing a horizontal narrow cusp. The five pairs of gill slitGill 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 very short, comparable to the 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...
in size.
The first 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...
bears a spine in front and originates over the trailing margin of the broad and rounded pectoral fins. The second dorsal fin also bears a spine in front and is over twice as large as the first in area, with the span between it and the first dorsal fin approximate equal to the distance between the snout tip and first gill slit. There is no anal fin. The caudal fin is low and narrow, with an indistinct lower lobe and an upper lobe about as long as the head. The dermal denticles on the sides of the body are stout and thorn-shaped, widely spaced without any regular pattern; the snout is mostly covered by denticles. The dorsal coloration is dark brown to gray; the underside of the body and snout are black, with a broad black marking above and behind each pelvic fin, and thin black marks on the tail. These black markings contain numerous light-emitting
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
photophore
Photophore
A photophore is a light-emitting organ which appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors...
s.
Biology and ecology
The ventrally positioned photophores of the green lanternshark may serve to disguise its silhouette from potential predators via counter-illuminationCountershading
Countershading, or Thayer's Law, is a form of camouflage. Countershading, in which an animal’s pigmentation is darker dorsally, is often thought to have an adaptive effect of reducing conspicuous shadows cast on the ventral region of an animal’s body...
. Like many other bioluminescent deep-sea sharks, it has a yellow spot over its pineal gland
Pineal gland
The pineal gland is a small endocrine gland in the vertebrate brain. It produces the serotonin derivative melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions...
that acts as a "window" for the detection of ambient light levels. This shark is caught sporadically but in large numbers at a time, suggesting that they may travel in schools
Shoaling and schooling
In biology, any group of fish that stay together for social reasons are said to be shoaling , and if, in addition, the group is swimming in the same direction in a coordinated manner, they are said to be schooling . In common usage, the terms are sometimes used rather loosely...
. If so, their photophores may also allow individual sharks in a group to keep sight of and coordinate with its cohorts.
Green lanternsharks feed mainly on squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
and octopus
Octopus
The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...
, and are frequently found with cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
eyes and beaks in their 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...
s so large that the sharks would have had to distend their jaws considerably to swallow them. It is uncertain how these diminutive sharks manage to overwhelm prey often much larger than themselves; Stewart Springer has proposed that they may attack in packs, "swarming" over a single large squid or octopus with each shark sawing off pieces of flesh. As with other members of its family, this species is aplacental viviparous with females giving birth to litters of 1–3 young. The newborn pups measure 9 cm (3.5 in) long; males attain 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 a length of 18.3–23.6 cm (7.2–9.3 in), and females at a length of 22–25.7 cm (8.7–10.1 in).
Human interactions
Relatively common, the green lanternshark is caught infrequently as bycatchBycatch
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...
in deepwater fisheries but has no commercial value because of its small size. The International Union for Conservation of Nature (IUCN) has assessed it as of Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
, as at present it appears to face no substantial threats. However, like many other deep-sea sharks there is a paucity of information on this species, and vigilance is warranted regarding expanding fisheries within its range.