Smooth lanternshark
Encyclopedia
The smooth lanternshark or slender lanternshark (Etmopterus pusillus) is a species
of dogfish shark
in the family
Etmopteridae
, found widely in the Atlantic and Pacific Ocean
s. It inhabits benthic environments at a depth of 274–1000 m (899–3,280.8 ft), and pelagic environments at a depth of 0–708 m (0–2,322.8 ft). The smooth lanternshark forms a species group
with the larger blurred lanternshark (E. bigelowi), both of which are distinguished from other members of their family by small, irregularly arranged dermal denticles with a truncated shape. This species has a slender, dark brown body with an indistinct black band on the sides over the pelvic fins, and reaches 50 cm (19.7 in) in length. This slow-growing, ovoviviparous shark feeds on smaller squid
, fish
es, and fish eggs. Smooth lanternsharks are often caught as bycatch
in eastern Atlantic and Japan
ese commercial fisheries
. The International Union for Conservation of Nature (IUCN) has evaluated this species as of Least Concern
because of its wide distribution and limited threats.
, in an 1839 issue of the scientific journal
Transactions of the Zoological Society of London. This species was later moved to the genus
Etmopterus
. The specific epithet pusillus means "weak" in Latin
. The smooth lanternshark forms a species group
with the blurred lanternshark (E. bigelowi); these two species are distinguished from other lantern sharks by their irregularly arranged, truncated (ending in a flat crown as though the tip were cut off) dermal denticles.
, the smooth lanternshark occurs from the Gulf of Mexico
to Argentina
in the west, Portugal
to South Africa
(including Cape Verde
and the Azores
) in the east, and on the Mid-Atlantic Ridge
. In the Indian Ocean
, it is found off KwaZulu-Natal
and Madagascar
. In the Pacific Ocean
, it has been reported from the East China Sea
to southern Japan
, in the Hawaiian–Emperor seamount chain area, off Australia
and New Zealand
, and over the Nazca Plate
(including the Amber Seamount and off Isla Salas y Gómez).
Smooth lanternsharks are usually found on or near the bottom on continental and insular shelves
and slopes at a depth of 274–1000 m (899–3,280.8 ft), and possibly to as deep as 1998 m (6,555.1 ft). Catch data off southern Portugal
suggests that this species has a preference for rocky substrates, and may conduct a diel vertical migration
. In the South Atlantic, this shark also inhabits the open ocean from the surface to a depth of 708 m (2,322.8 ft). It has been observed swimming over fields of hydrothermal vent
s.
s with short anterior skin flaps. There are 22–31 tooth rows in the upper jaw and 30–53 tooth rows in the lower jaw. Each upper tooth has a narrow smooth-edged central cusp flanked by 1–2 tiny cusplets; mature males over 38 cm (15 in) long grow additional pairs of lateral cusplets with age. The lower teeth are smooth, knife-like, and angled, with their bases interlocking to form a continuous cutting surface. The five pairs of gill slit
s are long.
The first dorsal fin
bears a stout spine in front and originates over the free rear tips of the rounded pectoral fins. The second dorsal fin is much larger than the first and has a longer spine. The pelvic fins are low and angular, and there is no anal fin. The caudal fin is short and broad, with a well-developed lower lobe and a ventral notch near the tip of the upper lobe. The skin is covered by many widely spaced, small blocky denticles not arranged in regular rows, giving it a smooth appearance. The coloration is a uniform dark brown, with a faint black mark over the bases of the pelvic fins extending both forward and backward on the flank. The smooth lanternshark is very similar to but smaller than the blurry lanternshark, attaining a length of 50 cm (19.7 in). The two species differ in a number of anatomical characteristics, but can be most reliably distinguished by the number of turns in their spiral valve
intestine
s (10–13 in E. pusillus versus 16–19 in E. bigelowi).
, lanternfish
es, smaller dogfish sharks
, and fish eggs. This species is ovoviviparous, with the developing embryo
s being sustained by a yolk sac
. Females produce an average of 10 young per reproductive cycle. Males reach sexual maturity at a length of 31–39 cm (12.2–15.4 in), and females at a length of 38 centimetre. The length at maturity varies with geographical region, with sharks in the western Atlantic maturing larger than those from off KwaZulu-Natal
. This species grows at a slow rate, with the body becoming relatively longer with age. Off southern Portugal
, males live to at least 13 years of age, and females to at least 17 years.
by commercial longline fisheries
, and to a lesser extent in bottom trawls and fixed bottom nets, in the eastern Atlantic and off Japan. This species is one of the three most common sharks caught as bycatch in deepwater fisheries off southern Portugal, along with the velvet belly lantern shark
(E. spinax) and the blackmouth catshark
(Galeus melastomus). Most captured smooth lanternsharks are discarded, although some may be sold dried and salted for human consumption or processed into fishmeal. The smooth lanternshark's slow rates of reproduction and growth may render it vulnerable to population collapse under sustained fishing pressure. However, catch rates currently show no evidence of this occurring which, coupled with the smooth lanternshark's wide geographic range, has led to the International Union for Conservation of Nature (IUCN) assessing it as of Least Concern
.
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 widely in the Atlantic and Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
s. It inhabits benthic environments at a depth of 274–1000 m (899–3,280.8 ft), and pelagic environments at a depth of 0–708 m (0–2,322.8 ft). The smooth lanternshark forms a species group
Species group
A species group is an informal taxonomic rank into which an assemblage of closely related species within a genus are grouped because of their morphological similarities and their identity as a biological unit with a single monophyletic origin.-Use:...
with the larger blurred lanternshark (E. bigelowi), both of which are distinguished from other members of their family by small, irregularly arranged dermal denticles with a truncated shape. This species has a slender, dark brown body with an indistinct black band on the sides over the pelvic fins, and reaches 50 cm (19.7 in) in length. This slow-growing, ovoviviparous shark feeds on smaller 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...
, fish
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...
es, and fish eggs. Smooth lanternsharks are often caught as 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...
in eastern Atlantic and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese commercial fisheries
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...
. The International Union for Conservation of Nature (IUCN) has evaluated this species 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...
because of its wide distribution and limited threats.
Taxonomy and phylogeny
The first scientific description of the smooth lanternshark, as Acanthidium pusillum, was published by British biologist Richard Thomas LoweRichard Thomas Lowe
Richard Thomas Lowe was a British botanist, ichthyologist, malacologist, and clergyman. In 1825 he graduated from Christ's College, Cambridge and in the same year took holy orders. He became a clergyman in the Madeira Islands in 1832, where he was a part-time naturalist, extensively studying the...
, in an 1839 issue of the scientific journal
Scientific journal
In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. There are thousands of scientific journals in publication, and many more have been published at various points in the past...
Transactions of the Zoological Society of London. This species was later moved to the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Etmopterus
Etmopterus
Etmopterus, commonly known as lantern sharks, is a diverse genus of dogfish sharks in the family Etmopteridae. This genus has 35 described species.-Species:* Etmopterus baxteri...
. The specific epithet pusillus means "weak" in 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...
. The smooth lanternshark forms a species group
Species group
A species group is an informal taxonomic rank into which an assemblage of closely related species within a genus are grouped because of their morphological similarities and their identity as a biological unit with a single monophyletic origin.-Use:...
with the blurred lanternshark (E. bigelowi); these two species are distinguished from other lantern sharks by their irregularly arranged, truncated (ending in a flat crown as though the tip were cut off) dermal denticles.
Distribution and habitat
In 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...
, the smooth lanternshark occurs from the Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
to Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
in the west, Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
to 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...
(including Cape Verde
Cape Verde
The Republic of Cape Verde is an island country, spanning an archipelago of 10 islands located in the central Atlantic Ocean, 570 kilometres off the coast of Western Africa...
and 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...
) in the east, and on the Mid-Atlantic Ridge
Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. It separates the Eurasian Plate and North American Plate in the North Atlantic, and the African Plate from the South...
. 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...
, it is found off KwaZulu-Natal
KwaZulu-Natal
KwaZulu-Natal is a province of South Africa. Prior to 1994, the territory now known as KwaZulu-Natal was made up of the province of Natal and the homeland of KwaZulu....
and Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
. In the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
, it has been reported from the East China Sea
East China Sea
The East China Sea is a marginal sea east of China. It is a part of the Pacific Ocean and covers an area of 1,249,000 km² or 750,000 square miles.-Geography:...
to southern Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, in the Hawaiian–Emperor seamount chain area, off Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, and over the Nazca Plate
Nazca Plate
]The Nazca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The ongoing subduction along the Peru-Chile Trench of the Nazca Plate under the South American Plate is largely responsible for the...
(including the Amber Seamount and off Isla Salas y Gómez).
Smooth lanternsharks are usually found on or near the bottom on continental and insular shelves
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
and slopes at a depth of 274–1000 m (899–3,280.8 ft), and possibly to as deep as 1998 m (6,555.1 ft). Catch data off southern Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
suggests that this species has a preference for rocky substrates, and may conduct a diel vertical migration
Diel vertical migration
Diel vertical migration, also known as diurnal vertical migration, is a pattern of movement that some organisms living in the ocean and in lakes undertake each day. Usually organisms move up to the epipelagic zone at night and return to the mesopelagic zone of the oceans or to the hypolimnion zone...
. In the South Atlantic, this shark also inhabits the open ocean from the surface to a depth of 708 m (2,322.8 ft). It has been observed swimming over fields of hydrothermal vent
Hydrothermal vent
A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Hydrothermal vents exist because the earth is both...
s.
Description
Lightly built, the smooth lanternshark has a large head with a pointed snout, large oval eyes, and nostrilNostril
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 with short anterior skin flaps. There are 22–31 tooth rows in the upper jaw and 30–53 tooth rows in the lower jaw. Each upper tooth has a narrow smooth-edged central cusp flanked by 1–2 tiny cusplets; mature males over 38 cm (15 in) long grow additional pairs of lateral cusplets with age. The lower teeth are smooth, knife-like, and angled, with their bases interlocking to form a continuous cutting surface. The five pairs of 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 long.
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 stout spine in front and originates over the free rear tips of the rounded pectoral fins. The second dorsal fin is much larger than the first and has a longer spine. The pelvic fins are low and angular, and there is no anal fin. The caudal fin is short and broad, with a well-developed lower lobe and a ventral notch near the tip of the upper lobe. The skin is covered by many widely spaced, small blocky denticles not arranged in regular rows, giving it a smooth appearance. The coloration is a uniform dark brown, with a faint black mark over the bases of the pelvic fins extending both forward and backward on the flank. The smooth lanternshark is very similar to but smaller than the blurry lanternshark, attaining a length of 50 cm (19.7 in). The two species differ in a number of anatomical characteristics, but can be most reliably distinguished by the number of turns in their spiral valve
Spiral valve
A spiral valve is the lower portion of the intestine of some sharks, rays, skates and bichirs. A modification of the ileum, the spiral valve is internally twisted or coiled to increase the surface area of the intestine, to increase nutrient absorption....
intestine
Intestine
In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...
s (10–13 in E. pusillus versus 16–19 in E. bigelowi).
Biology and ecology
The smooth lanternshark feeds on squidSquid
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...
, lanternfish
Lanternfish
Cooper Lanternfishes are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represented by 246 species in 33 genera, and are found in oceans worldwide. They are aptly named after their conspicuous use of bioluminescence...
es, smaller dogfish sharks
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...
, and fish eggs. This species is ovoviviparous, with 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 being sustained by a yolk sac
Yolk sac
The yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals...
. Females produce an average of 10 young per reproductive cycle. Males reach sexual maturity at a length of 31–39 cm (12.2–15.4 in), and females at a length of 38 centimetre. The length at maturity varies with geographical region, with sharks in the western Atlantic maturing larger than those from off KwaZulu-Natal
KwaZulu-Natal
KwaZulu-Natal is a province of South Africa. Prior to 1994, the territory now known as KwaZulu-Natal was made up of the province of Natal and the homeland of KwaZulu....
. This species grows at a slow rate, with the body becoming relatively longer with age. Off southern Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
, males live to at least 13 years of age, and females to at least 17 years.
Human interactions
Large numbers of smooth lanternsharks, predominantly juvenile, are 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 longline fisheries
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 to a lesser extent in bottom trawls and fixed bottom nets, in the eastern Atlantic and off Japan. This species is one of the three most common sharks caught as bycatch in deepwater fisheries off southern Portugal, along with the velvet belly lantern shark
Velvet belly lantern shark
The velvet belly lantern shark is a species of dogfish shark in the family Etmopteridae. One of the most common deepwater sharks in the northeastern Atlantic Ocean, the velvet belly is found from Iceland and Norway to Gabon and South Africa at a depth of...
(E. spinax) and the blackmouth catshark
Blackmouth catshark
The blackmouth catshark is a species of catshark, family Scyliorhinidae, common in the northeastern Atlantic Ocean from Iceland to Senegal, including the Mediterranean Sea. It is typically found over the continental slope at depths of , on or near muddy bottoms. The youngest sharks generally...
(Galeus melastomus). Most captured smooth lanternsharks are discarded, although some may be sold dried and salted for human consumption or processed into fishmeal. The smooth lanternshark's slow rates of reproduction and growth may render it vulnerable to population collapse under sustained fishing pressure. However, catch rates currently show no evidence of this occurring which, coupled with the smooth lanternshark's wide geographic range, has led to the International Union for Conservation of Nature (IUCN) assessing 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...
.