The smoothtooth blacktip shark (''Carcharhinus leiodon'') 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 ...

requiem shark Requiem sharks are sharks of the family Carcharhinidae in the order Carcharhiniformes. They are migratory, live-bearing sharks of warm seas (sometimes of brackish or fresh water) and include such species as the tiger shark, bull shark, le ...

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 ...

Carcharhinidae. It is known only from 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 ...

caught from the

Gulf of Aden The Gulf of Aden ( ar, خليج عدن, so, Gacanka Cadmeed 𐒅𐒖𐒐𐒕𐒌 𐒋𐒖𐒆𐒗𐒒) is a deepwater gulf of the Indian Ocean between Yemen to the north, the Arabian Sea to the east, Djibouti to the west, and the Guardafui Channe ...

, off eastern

Yemen Yemen (; ar, ٱلْيَمَن, al-Yaman), officially the Republic of Yemen,, ) is a country in Western Asia. It is situated on the southern end of the Arabian Peninsula, and borders Saudi Arabia to the Saudi Arabia–Yemen border, north and ...

, and a handful of additional specimens caught from the

Persian Gulf The Persian Gulf ( fa, خلیج فارس, translit=xalij-e fârs, lit=Gulf of Persis, Fars, ), sometimes called the ( ar, اَلْخَلِيْجُ ٱلْعَرَبِيُّ, Al-Khalīj al-ˁArabī), is a Mediterranean sea (oceanography), me ...

, off

Kuwait Kuwait (; ar, الكويت ', or ), officially the State of Kuwait ( ar, دولة الكويت '), is a country in Western Asia. It is situated in the northern edge of Eastern Arabia at the tip of the Persian Gulf, bordering Iraq to the nort ...

. Reaching in length, this species has a stocky greenish-colored body, a short snout, and black-tipped fins. It can be distinguished from similar species by its teeth, which are narrow, erect, and smooth-edged. Little is known of the smoothtooth blacktip shark's natural history; it likely inhabits shallow waters and feeds on small

bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilag ...

es. It is presumably

viviparous Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the m ...

like other members of its family. 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 ...

last assessed this species as

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inva ...

. Although more specimens have since been discovered, the conservation status of this species remains precarious due to heavy

fishing Fishing is the activity of trying to catch fish. Fish are often caught as wildlife from the natural environment, but may also be caught from stocked bodies of water such as ponds, canals, park wetlands and reservoirs. Fishing techniques inclu ...

and

habitat degradation Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

within its range.

Taxonomy and phylogeny

The first known specimen of the smoothtooth blacktip shark was a 75-cm-long, immature male caught by Wilhelm Hein in 1902 and deposited at the

Naturhistorisches Museum The Natural History Museum Vienna (german: Naturhistorisches Museum Wien) is a large natural history museum located in Vienna, Austria. It is one of the most important natural history museums worldwide. The NHM Vienna is one of the largest museum ...

Vienna en, Viennese , iso_code = AT-9 , registration_plate = W , postal_code_type = Postal code , postal_code = , timezone = CET , utc_offset = +1 , timezone_DST ...

. The location was recorded as the

near "Gischin", which likely refers to the town of

Qishn Qishn ( ar, قشن) is a coastal town in Al Mahrah Governorate, seat of Qishn District in southern Yemen. It is located at around . It has a landing strip, which is currently not in use. Historically, Qishn was a port from which incense was expo ...

in eastern

. In 1985, the shark was examined and described as a new species by

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

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 ...

Jack Garrick John Andrew Frank "Jack" Garrick (1928 – August 30, 2018) was a New Zealand ichthyologist. He specialized in elasmobranchs and published many books and articles about shark and ray biology. In 1982, he published a thorough taxonomy on sharks of ...

in a

National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...

technical report. He gave it the

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''leiodon'', from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''leios'' meaning "smooth", and ''odon'' meaning "tooth". This species was known only by the single specimen until 2008, when

fishery Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

surveys in

uncovered several more specimens. Based on

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

Leonard Compagno Leonard Joseph Victor Compagno is an international authority on shark taxonomy and the author of many scientific papers and books on the subject, best known of which is his 1984 catalogue of shark species produced for the Food and Agriculture Organi ...

in 1988 tentatively grouped the smoothtooth blacktip shark with the

spinner shark The spinner shark (''Carcharhinus brevipinna'') is a species of requiem shark, in the family Carcharhinidae, named for the spinning leaps it makes as a part of its feeding strategy. This species occurs in tropical and warm temperate waters worldw ...

(''C. brevipinna''), the

blacktip shark The blacktip shark (''Carcharhinus limbatus'') is a species of requiem shark, and part of the family Carcharhinidae. It is common to coastal tropical and subtropical waters around the world, including brackish habitats. Genetic analyses have re ...

(''C. limbatus''), the

graceful shark The graceful shark or Queensland shark (''Carcharhinus amblyrhynchoides'') is a species of requiem shark, in the family Carcharhinidae, found in the tropical Indo-Pacific, from the Gulf of Aden to northern Australia. It is a midwater species that ...

(''C. amblyrhynchoides''), and the finetooth shark (''C. isodon''). Using

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

techniques on

mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...

sequences, Alec Moore and colleagues reported in 2011 that this species is closely related to the graceful shark, the blacktip shark, and the

Australian blacktip shark The Australian blacktip shark (''Carcharhinus tilstoni'') is a species of requiem shark, in the family Carcharhinidae, endemic to northern and eastern Australia. Favoring the upper and middle parts of the water column, it can be found from the i ...

(''C. tilstoni'').

Description

Superficially, the smoothtooth blacktip shark resembles the

blacktip reef shark The blacktip reef shark (''Carcharhinus melanopterus'') is a species of requiem shark, in the family Carcharhinidae, which can be easily identified by the prominent black tips on its fins (especially on the first dorsal fin and its caudal fin). ...

(''C. melanopterus''). It is rather robust in build, with a short and blunt snout. The large nostrils are preceded by well-developed, triangular flaps of skin. The small, circular eyes are equipped with

nictitating membrane The nictitating membrane (from Latin '' nictare'', to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye from the medial canthus to protect and moisten it while maintaining vision. All ...

s. The mouth forms a wide arch and has very short furrows at the corners. Sixteen upper and 14–15 lower tooth rows are on either side, along with two or three small teeth at the symphysis (center) of either jaw. The teeth are distinctive in shape, having narrow, upright cusps without serrations; finetooth sharks and juvenile spinner sharks are the only other members of ''Carcharhinus'' with similar teeth. 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 long. The fairly long and pointed

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 are slightly sickle-shaped (falcate) and originate between the fourth and fifth gill slits. The first

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 ...

is medium-sized and triangular with a pointed apex, and originates over the rear of the pectoral fin bases. The second dorsal fin is small and positioned opposite the

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 ...

. No ridge exists between the dorsal fins. The

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 are triangular and larger than the anal fin, which has a deep notch in the trailing margin. A crescent-shaped notch is present on the

caudal peduncle 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 ...

at the upper

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 ...

origin. The caudal fin is asymmetrical, with a well-developed lower lobe and a longer upper lobe with a ventral notch near the tip. The

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 we ...

s are slightly overlapping and bear three prominent horizontal ridges leading to three or five marginal teeth. This species is greenish-yellow to greenish-gray above, sometimes with a scattering of tiny dark dots. The underside is white, which extends in a pale band onto the flanks. All the fins have sharply defined black tips, and a broad, dark midline stripe runs from the second dorsal fin base to the tip of the upper caudal fin lobe. The largest recorded specimen is long.

Distribution and habitat

PersianGulf vue satellite du golfe persique

The smoothtooth blacktip shark has only been recorded from eastern Yemen and Kuwait, some apart. These two locations differ markedly: the Gulf of Aden near Yemen is over deep with a narrow

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

and no permanent

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...

ine inputs, while the

near Kuwait is entirely shallower than and receives abundant

fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

from the

Tigris The Tigris () is the easternmost of the two great rivers that define Mesopotamia, the other being the Euphrates. The river flows south from the mountains of the Armenian Highlands through the Syrian and Arabian Deserts, and empties into the ...

Euphrates The Euphrates () is the longest and one of the most historically important rivers of Western Asia. Tigris–Euphrates river system, Together with the Tigris, it is one of the two defining rivers of Mesopotamia ( ''the land between the rivers'') ...

Karun The Karun ( fa, کارون, ) is the Iranian river with the highest water flow, and its only navigable river. It is long. It rises in the Zard Kuh mountains of the Bakhtiari people, Bakhtiari district in the Zagros Range, receiving many tribut ...

river system. The Kuwait specimens were obtained from fish markets; given the practices of Kuwaiti speedboat fishers, this shark can be supposed to inhabit shallow, coastal waters. Still, these waters encompass a range of

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

s from

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...

coral reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. Co ...

s, thus the habitat requirements of the smoothtooth blacktip shark remain largely unknown.

Biology and ecology

Considering its resemblance to the blacktip reef shark, the smoothtooth blacktip shark may play an equivalent shallow-water ecological role within its range. It is known to feed on marine catfish, and its diet probably also includes other small

es. This species is presumably

like all other ''Carcharhinus'' species, with the developing young sustained to term by a

placenta The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mater ...

l connection to the mother. Judging from the available specimens, males reach

sexual maturity Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definitio ...

at some point between long.

Human interactions

Prior to the finding of additional specimens in Kuwait, the

assessed the smoothtooth blacktip shark as

Endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inva ...

based on its presumed small range and population. Despite the discovery of a second subpopulation off Kuwait, this species likely still warrants an Endangered assessment because the waters around the

Arabian Peninsula The Arabian Peninsula, (; ar, شِبْهُ الْجَزِيرَةِ الْعَرَبِيَّة, , "Arabian Peninsula" or , , "Island of the Arabs") or Arabia, is a peninsula of Western Asia, situated northeast of Africa on the Arabian Plate ...

are subject to heavy fishing pressure and

Gillnet Gillnetting is a fishing method that uses gillnets: vertical panels of netting that hang from a line with regularly spaced floaters that hold the line on the surface of the water. The floats are sometimes called "corks" and the line with corks is ...

and other

fisheries Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

off Kuwait are known to take the smoothtooth blacktip shark 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 ...

, while intensive Yemeni and

Somalia Somalia, , Osmanya script: 𐒈𐒝𐒑𐒛𐒐𐒘𐒕𐒖; ar, الصومال, aṣ-Ṣūmāl officially the Federal Republic of SomaliaThe ''Federal Republic of Somalia'' is the country's name per Article 1 of thProvisional Constituti ...

n shark fisheries operate in the Gulf of Aden. The status of the Yemen subpopulation is uncertain because no further specimens have been recorded since the original over a century ago.

References

External links

''Carcharhinus leiodon'', Smooth tooth blacktip shark
a
FishBase

''Carcharhinus leiodon'' at www.shark-references.com
{{DEFAULTSORT:shark, blacktip, smoothtooth

smoothtooth blacktip shark The smoothtooth blacktip shark (''Carcharhinus leiodon'') is a species of requiem shark in the family Carcharhinidae. It is known only from the type specimen caught from the Gulf of Aden, off eastern Yemen, and a handful of additional specimens ...

Gulf of Aden Fish of the Persian Gulf Marine fauna of Western Asia Taxa named by Jack Garrick