The dwarf lanternshark (''Etmopterus perryi'') is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of dogfish shark in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Etmopteridae The Etmopteridae are a family of sharks in the order Squaliformes, commonly known as lantern sharks. Their name comes from the presence of light-producing photophore A photophore is a glandular organ that appears as luminous spots on vari ...

and is the smallest shark in the world, reaching a maximum known length of . It is known to be present only on the upper

continental slope A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margin ...

s off

Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...

and

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...

, at a depth of . 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 ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

, it is capable of producing light from a distinctive array of

photophore A photophore is a glandular organ that 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 Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...

, with females

gestating Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregnanc ...

two or three young at a time. The dwarf lanternshark is not significant to

commercial fisheries 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 ...

, but could be threatened by

mortality Mortality is the state of being mortal, or susceptible to death; the opposite of immortality. Mortality may also refer to: * Fish mortality, a parameter used in fisheries population dynamics to account for the loss of fish in a fish stock throug ...

from

bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

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

Taxonomy and phylogeny

American

ichthyologist Ichthyology is the branch of zoology devoted to the study of fish, including bony fish ( Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 33,400 species of fish had been described as of Octobe ...

s Stewart Springer and George H. Burgess described the dwarf lanternshark from specimens collected via

trawl Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch different speci ...

ing by the

U.S. Fish and Wildlife Service The United States Fish and Wildlife Service (USFWS or FWS) is an agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats. The mission of the agency is "working with othe ...

research ship ''Oregon'' in 1964. They dubbed the new species in honor of noted shark biologist Perry W. Gilbert, and published their findings in a 1985 ''Copeia'' paper. The

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

is a long female caught in the Caribbean Sea off the coast of

. This species is grouped with the

velvet belly lantern shark The velvet belly lanternshark (or simply velvet belly) (''Etmopterus spinax'') 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 I ...

(''E. spinax''), Caribbean lanternshark (''E. hillianus''),

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. It is endemic to this area. It is a deep water shark and ...

(''E. schultzi''),

brown lanternshark The brown lanternshark or bristled lanternshark (''Etmopterus unicolor'') 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, typi ...

(''E. unicolor''),

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. Its length is up to 35 ...

(''E. gracilispinis''), and combtooth lanternshark (''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 The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

off the coasts of

and

, occurring between

Barranquilla Barranquilla () is the capital district of Atlántico Department in Colombia. It is located near the Caribbean Sea and is the largest city and third port in the Caribbean Coast region; as of 2018 it had a population of 1,206,319, making it Col ...

and

Santa Marta Santa Marta (), officially Distrito Turístico, Cultural e Histórico de Santa Marta ("Touristic, Cultural and Historic District of Santa Marta"), is a city on the coast of the Caribbean Sea in northern Colombia. It is the capital of Magdalena ...

, near the

Guajira Peninsula The Guajira Peninsula ( es, Península de La Guajira, links=no, also spelled ''Goajira'', mainly in colonial period texts, guc, Hikükariby) is a peninsula in northern Colombia and northwestern Venezuela in the Caribbean. It is the northernm ...

, and between the Los Testigos Islands and

Grenada Grenada ( ; Grenadian Creole French: ) is an island country in the West Indies in the Caribbean Sea at the southern end of the Grenadines island chain. Grenada consists of the island of Grenada itself, two smaller islands, Carriacou and Pe ...

. This shark apparently inhabits the upper

at a depth of .

Description

The dwarf lanternshark appears to reach a maximum length of about (female). It has a long, wide, flattened head comprising a fourth to a fifth of its 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. Scattered, sparse

papilla Papilla (Latin, 'nipple') or papillae may refer to: In animals * Papilla (fish anatomy), in the mouth of fish * Basilar papilla, a sensory organ of lizards, amphibians and fish * Dental papilla, in a developing tooth * Dermal papillae, part of ...

e are inside the mouth and on the edges of the

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

arches. The five pairs of

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 and rays, as well as deep-branching vertebrates such as lampreys. In con ...

s are small. The trunk is short, with two relatively closely spaced, large

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

s bearing grooved spines in front. The first dorsal fin originates over the trailing margins of the

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

s. The second dorsal fin has twice the area of the first and is larger than the pectoral or

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

s, and originates over the end of the pelvic fin bases. There is no

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

. The

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

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

s, while others (including the patch behind the pelvic fins) are composed of

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...

-containing

chromatophore Chromatophores are cells that produce color, of which many types are Biological pigment, pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and ...

s. The largest known individual is long.

Biology and ecology

Perhaps the smallest living shark species, male dwarf lanternsharks mature at a length of and females from a length of with long pregnant individuals known. The spined pygmy shark (''Squaliolus laticaudus'') and the pygmy ribbontail catshark (''Eridacnis radcliffei'') are known to attain maturity at comparably small sizes; difficulties in assessing the reproductive maturity of sharks precludes stating one of these species as definitively smaller than the others. This species is

, with the developing

fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal deve ...

es being sustained by a

yolk sac The yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac'' is far ...

until birth. Females bear litters of two or three young, each measuring long.

Human interactions

Because of its very small size, the dwarf lanternshark is of no economic value. Its low

fecundity Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to pr ...

and limited known range may merit concern if

in the region are taking it as

. The

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

assesses it as least concern.

References

{{Taxonbar, from=Q243971 Etmopterus Taxa named by Stewart Springer Taxa named by George H. Burgess Fish described in 1985