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

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of dogfish shark in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

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 photophores on their bodies. The members of this family are small, under long, and are ...

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 margi ...

s off

Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

and

Venezuela Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...

, 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 (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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

photophore A photophore is a specialized anatomical structure found in a variety of organisms that emits light through the process of boluminescence. This light may be produced endogenously by the organism itself (symbiotic) or generated through a mut ...

s. Reproduction is aplacental viviparous, with females gestating 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 p ...

, but could be threatened by mortality 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, 35,800 species of fish had been described as of March 2 ...

Stewart Springer Stewart Springer (5 June 190623 August 1991) was an American ichthyologist and herpetologist. He was an expert on shark behavior, classification (taxonomy), and population distribution. More than 35 species of sharks, skates, rays, and other cr ...

and George H. Burgess described the dwarf lanternshark from specimens collected via trawling by the U.S. Fish and Wildlife Service 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 wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...

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

. This species is grouped with the velvet belly lantern shark (''E. spinax''), Caribbean lanternshark (''E. hillianus''), fringefin lanternshark (''E. schultzi''), brown lanternshark (''E. unicolor''), broadbanded lanternshark (''E. gracilispinis''), and combtooth lanternshark (''E. decacuspidatus'') in having irregularly arranged, needle-shaped

dermal denticle A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scale (zoology), scales, which can also provide effective Underwater camouflage, camouflage through the us ...

Distribution and habitat

At present, the dwarf lanternshark has been reported only from a small area of the

Caribbean Sea The Caribbean Sea is a sea of the Atlantic Ocean, North Atlantic Ocean in the tropics of the Western Hemisphere, located south of the Gulf of Mexico and southwest of the Sargasso Sea. It is bounded by the Greater Antilles to the north from Cuba ...

off the coasts of

and

, occurring between

Barranquilla Barranquilla () is the capital district of the Atlántico department in Colombia. It is located near the Caribbean Sea and is the largest city and third port in the Caribbean region of Colombia, Caribbean coast region; as of 2018, it had a popul ...

and

Santa Marta Santa Marta (), officially the Distrito Turístico, Cultural e Histórico de Santa Marta (), is a port List of cities in Colombia, city on the coast of the Caribbean Sea in northern Colombia. It is the capital of Magdalena Department and the fou ...

, near the

Guajira Peninsula The Guajira Peninsula (, also spelled ''Goajira'', mainly in colonial period texts, ) is a peninsula in northern Colombia and northwestern Venezuela in the Caribbean. It is the northernmost peninsula in South America and has an area of exte ...

, and between the Los Testigos Islands and

Grenada Grenada is an island country of the West Indies in the eastern Caribbean Sea. The southernmost of the Windward Islands, Grenada is directly south of Saint Vincent and the Grenadines and about north of Trinidad and Tobago, Trinidad and the So ...

. 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 papillae are inside the mouth and on the edges of the

gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, 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 r ...

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 c ...

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

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

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

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

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 (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

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

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

. The

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

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

s 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 powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...

-containing

chromatophore Chromatophores are cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopod A cephalopod is any member o ...

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 aplacental viviparous, with the developing

fetus A fetus or foetus (; : fetuses, foetuses, rarely feti or foeti) is the unborn offspring of a viviparous animal that develops from an embryo. Following the embryonic development, embryonic stage, the fetal stage of development takes place. Pren ...

es being sustained by a

yolk sac The yolk sac is a membranous wikt:sac, 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' ...

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 capability to produc ...

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) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...

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