Dwarf lanternshark

Dwarf lanternshark

Overview
The dwarf lanternshark (Etmopterus perryi) is a little-known species
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...

 and possibly the smallest shark in the world, reaching a maximum known length of 21.2 cm (8.3 in). It is known to be present only on the upper continental slopes off Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

 and 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...

, at a depth of 283–439 m (928.5–1,440.3 ft). This species can be identified by its small size at maturity, long flattened head, and pattern of black ventral markings and a mid-dorsal line.
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Encyclopedia
The dwarf lanternshark (Etmopterus perryi) is a little-known species
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...

 and possibly the smallest shark in the world, reaching a maximum known length of 21.2 cm (8.3 in). It is known to be present only on the upper continental slopes off Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

 and 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...

, at a depth of 283–439 m (928.5–1,440.3 ft). This species can be identified by its small size at maturity, long flattened head, and pattern of black ventral markings and a mid-dorsal line. Like other members of its 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...

, it is capable of producing light from a distinctive array of 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. Reproduction is aplacental viviparous, with females gestating
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....

 2–3 young at a time. The dwarf lanternshark is not significant to commercial fisheries but could be threatened by mortality
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....

 from 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...

; the degree of impact from human activities on its population is presently unknown.

Taxonomy and phylogeny


American ichthyologists 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,...

 and George H. Burgess
George H. Burgess
George H. Burgess is an ichthyologist and fisheries biologist with the Florida Museum of Natural History, University of Florida. He is the director of the International Shark Attack File and author/coauthor of numerous books and papers on sharks and other fish.George Burgess also appeared on...

 described the dwarf lanternshark from specimens collected via trawling by the U.S. Fish and Wildlife Service research ship Oregon in 1964. They named the new species in honor of noted shark biologist Perry W. Gilbert, and published their findings in a 1985 Copeia paper. The type specimen is a 18.2 cm (7.2 in) long female caught in the Caribbean Sea off the coast of Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

. This species is grouped 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), Caribbean lanternshark
Caribbean lanternshark
The Caribbean lanternshark, Etmopterus hillianus, is a shark of the family Etmopteridae found in the eastern and western Atlantic at depths of between 180 and 720 m. Its length is up to 50 cm.Reproduction is ovoviviparous.-References:...

 (E. hillianus), fringefin lanternshark
Fringefin lanternshark
The fringefin lanternshark, Etmopterus schultzi, is a shark of the family Etmopteridae found in the western central Atlantic from Texas to Florida, northern Gulf of Mexico, and Mexico.-References:...

 (E. schultzi), brown lanternshark
Brown lanternshark
The brown lanternshark is a little-known species of deep-sea dogfish shark in the family Etmopteridae. It is found off Japan and New Zealand, and possibly also South Africa and Australia, typically deeper than...

 (E. unicolor), broadbanded lanternshark
Broadbanded lanternshark
The broadbanded lanternshark, Etmopterus gracilispinis, is a shark of the family Etmopteridae found in the western and southeast Atlantic, between latitudes 40°N and 45°S, at depths of between 70 and 1,000 m...

 (E. gracilispinis), and combtooth lanternshark
Combtooth lanternshark
The combtoothed lanternshark, Etmopterus decacuspidatus, is a shark of the family Etmopteridae the only specimen, and holotype, being found from the South China Sea between the Viet Nam coast and Hainan Island, at a depth of between 510 and 690 m...

 (E. decacuspidatus) in having irregularly arranged, needle-shaped dermal denticles.

Distribution and habitat


At present, the dwarf lanternshark has only been reported from a small area of the Caribbean Sea
Caribbean Sea
The Caribbean Sea is a sea of the Atlantic Ocean located in the tropics of the Western hemisphere. It is bounded by Mexico and Central America to the west and southwest, to the north by the Greater Antilles, and to the east by the Lesser Antilles....

 off the coasts of Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

 and 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...

, occurring between Barranquilla
Barranquilla
Barranquilla is an industrial port city and municipality located in northern Colombia, near the Caribbean Sea. The capital of the Atlántico Department, it is the largest industrial city and port in the Colombian Caribbean region with a population of 1,148,506 as of 2005, which makes it Colombia's...

 and Santa Marta
Santa Marta
Santa Marta is the capital city of the Colombian department of Magdalena in the Caribbean Region. It was founded in July 29, 1525 by the Spanish conqueror Rodrigo de Bastidas, which makes it the oldest remaining city in Colombia...

, near the Guajira Peninsula
Guajira Peninsula
Guajira Peninsula , is a peninsula in northern Colombia and northwestern Venezuela in the Caribbean Sea...

, and between the Los Testigos Islands
Los Testigos Islands
Los Testigos Islands are a group of islands in the southeastern Caribbean Sea. They are a part of the Dependencias Federales of Venezuela.-Geography:...

 and Grenada
Grenada
Grenada is an island country and Commonwealth Realm consisting of the island of Grenada and six smaller islands at the southern end of the Grenadines in the southeastern Caribbean Sea...

. This shark apparently inhabits the upper continental slope at a depth of 283–439 m (928.5–1,440.3 ft).

Description


The dwarf lanternshark has a long, wide, flattened head comprising a fourth to a fifth of the total length. The eyes are large, twice as long as high, with the anterior and posterior corners acute. The nares are large and preceded by poorly developed flaps of skin. There are 25–32 tooth rows in the upper jaw and 30–34 tooth rows in the lower jaw. The upper teeth of adult males have a single cusp flanked by two pairs of smaller cusplets, while the upper teeth of females are more robust and have only one pair of lateral cusplets flanking the central cusp. The lower teeth each have a single, strongly oblique cusp, and their bases are interlocked to form a continuous cutting surface. There are scattered, sparse papilla
Papilla (fish mouth structure)
The papilla, in certain kinds of fish, particularly rays, sharks, and catfish, are small lumps of dermal tissue found in the mouth, where they are "distributed uniformly on the tongue, palate, and pharynx"...

e inside the mouth and on the edges of the gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...

 arches. 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 small.

The trunk is short, with two relatively closely spaced, large 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 bearing grooved spines in front. The first dorsal fin originates over the trailing margins of the pectoral fins. The second dorsal fin has twice the area of the first and is larger than the pectoral or pelvic fins, and originates over the end of the pelvic fin bases. There is no anal fin. The caudal fin is low, with a moderate lower lobe and a ventral notch near the tip of the upper lobe. The skin is densely covered by thin, needle-like dermal denticles in a random pattern, except for the lips and the tips of the fins. This shark is dark brown with a striking and distinctive pattern of black markings on its ventral surface, a continuous or broken fine black line along the middle of its back (but without a white band like in the similar Caribbean lanternshark), a black band on the end of its caudal fin, and a dark blotch on its lower caudal fin lobe. Curiously, some of the ventral black markings are composed of light-producing 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, while others (including the patch behind the pelvic fins) are composed of pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...

-containing chromatophore
Chromatophore
Chromatophores are pigment-containing and light-reflecting cells found in amphibians, fish, reptiles, crustaceans, and cephalopods. They are largely responsible for generating skin and eye colour in cold-blooded animals and are generated in the neural crest during embryonic development...

s. The largest known individual is 21.2 cm (8.3 in) long.

Biology and ecology


Perhaps the smallest living shark species, male dwarf lanternsharks mature at a length of 16–17.5 cm (6.3–6.9 in) and females from a length of 15.5 cm (6.1 in) with 19–20 cm (7.5–7.9 in) long pregnant individuals known. The spined pygmy shark
Spined pygmy shark
The spined pygmy shark is a species of dogfish shark in the family Dalatiidae found widely in all oceans. With a maximum known length of , it is one of the smallest living sharks. This shark has a slender, cigar-shaped body with a sizable conical snout, a long but low second dorsal fin, and an...

 (Squaliolus laticaudus) and the pygmy ribbontail catshark
Pygmy ribbontail catshark
The pygmy ribbontail catshark is a species of finback catshark, family Proscylliidae, distributed patchily in the western Indo-Pacific from Tanzania to the Philippines. It occurs around the edges of continental and insular shelves at a depth of , typically on or near mud bottoms...

 (Eridacnis radcliffei) are known to attain maturity at comparably small sizes; difficulties in assessing the reproductive maturity of sharks currently precludes stating one of these species as definitively smaller than the others. This species is aplacental viviparous, with the developing fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

es 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...

 until birth. Females bear litters of 2–3 young, each measuring 5.5–6 cm (2.2–2.4 in) long.

Human interactions


Because of its very small size, the dwarf lanternshark is of no economic value. Its low fecundity
Fecundity
Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...

 and limited known range may merit concern if commercial fisheries in the region are taking it 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...

, though presently there is insufficient information for the International Union for Conservation of Nature (IUCN) to assess it 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...

.