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 appropriat ...
of
dogfish shark
Squalidae, more commonly known as dogfish, dog sharks, or spiny dogfish, are one of several families of sharks categorized under Squaliformes, making it the second largest order of sharks, numbering 119 species across 7 families. Having earned ...
in the
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Etmopteridae 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 ...
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 living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
, 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 ins ...
, 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 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, 33,400 species of fish had been described as of O ...
s
Stewart Springer
Stewart Springer (5 June 190623 August 1991) was an American ichthyologist and herpetologist. He was a world-renowned expert on shark behavior, classification ( taxonomy), and population distribution. More than 35 species of sharks, skates, ray ...
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 spec ...
ing 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 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 anchor or centralizes th ...
is a long female caught in the Caribbean Sea off the coast of
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 ...
. This species is grouped with the
velvet belly lantern shark (''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, typica ...
(''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
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 ...
(''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 scales, which can also provide effective camouflage through the use of reflection and colouration, as ...
s.
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 Mexic ...
off the coasts of
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 ...
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 ...
, 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 Co ...
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 northe ...
, and between the
Los Testigos Islands
Los Testigos Islands ( es, Islas Los Testigos, Witnesses Islands) are a group of islands in the southeastern Caribbean Sea. They are a part of the ''Dependencias Federales'' ( Federal Dependencies) of Venezuela.
Geography
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 Pet ...
.
This shark apparently inhabits 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 ...
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 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 ar ...
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 co ...
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 c ...
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 se ...
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 ...
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 see ...
. 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 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 scales, which can also provide effective camouflage through the use of reflection and colouration, as ...
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 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, 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 compou ...
-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 cephalopods. Mammals and birds, in contrast, ...
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
The spined pygmy shark (''Squaliolus laticaudus'') is a species of squaliform shark in the family Dalatiidae found widely in all oceans. Growing no larger than roughly , it is one of the smallest sharks alive, with this record beaten by the dwar ...
(''Squaliolus laticaudus'') and the
pygmy ribbontail catshark
The pygmy ribbontail catshark (''Eridacnis radcliffei'') 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 in ...
(''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
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 ins ...
, 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 dev ...
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 natural capability to pr ...
and limited known range may merit concern if
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 ...
in the region are taking it as
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
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