Barbeled houndshark
Encyclopedia
The barbeled houndshark (Leptocharias smithii) is a species
of ground shark and the only member of the family
Leptochariidae. This demersal species is found in the coastal waters of the eastern Atlantic Ocean
from Mauritania
to Angola
, at depths of 10–75 m (32.8–246.1 ft). It favors muddy habitat
s, particularly around river mouths. The barbeled houndshark is characterized by a very slender body, nasal barbels, long furrows at the corners of the mouth, and sexually dimorphic teeth. Its maximum known length is 82 cm (32.3 in).
Likely strong-swimming and opportunistic, the barbeled houndshark has been known to ingest bony fishes, invertebrate
s, fish eggs, and even inedible objects. It is viviparous with females bearing litters of 7 young; the developing embryo
s are sustained via a unique globular placenta
l structure. The International Union for Conservation of Nature (IUCN) has assessed the barbeled houndshark as Near Threatened
, as heavy fishing pressure occurs throughout its range and it is utilized for meat and leather
.
n physician
and zoologist Andrew Smith, without any associated species, in an 1838 Magazine of Natural History article by Johannes Müller
and Friedrich Henle
. Müller and Henle added a species a year later in their Systematische Beschreibung der Plagiostomen, but adopted the name Triaenodon smithii because they regarded Leptocharias as a junior synonym
of Triaenodon. Later authors recognized the validity of Leptocharias, and shuffled it between the families Carcharhinidae and Triakidae before placing it in its own family. The type specimen is an adult male collected off Cabinda Province, Angola
.
Because of its many unique characteristics
, the evolutionary relationships of the barbeled houndshark are difficult to resolve. A morphological
study by Compagno in 1988 was inconclusive on the relationship of Leptocharias to other carcharhiniform
families. Similarly, a molecular phylogenetic study by López et al. in 2006 found that, though Leptocharias certainly belonged to a derived
clade
also containing the families Hemigaleidae
, Triakidae, Carcharhinidae and Sphyrnidae, its position within that group changed depending on the DNA sequence
and type of analysis used. Fossil
ized teeth belonging to an extinct relative, L. cretaceus, have been recovered from Late Cretaceous
(99.6–65.5 Ma) deposits in Britain
.
from Mauritania
to northern Angola, though it may range as far north as the Mediterranean Sea
. This species inhabits inshore waters 10–75 m (32.8–246.1 ft) deep, with temperatures of 20–27 °C (68–80.6 F), salinities
of 35–36 ppt, and dissolved oxygen levels of 3–4 ppm. It is typically found close to the bottom over mud, particularly around river mouths.
s. A pair of tiny spiracle
s are present behind the eyes. Each nostril
is preceded by a slender barbel. The mouth is long and strongly arched, with very long furrows at the corners extending onto both jaws. There are 46–60 upper tooth rows and 43–54 lower tooth rows; each tooth is small, with a narrow central cusp and a pair of lateral cusplets. Unusually for a shark, there is dental sexual dimorphism
with the front teeth in males being greatly enlarged. The two dorsal fin
s are small and approximately equal in size; the first is positioned between the pectoral and pelvic fins, and the second over the anal fin. The dorsal margin of the caudal fin is smooth and lacks a notch (precaudal pit) at its base; the lower caudal fin lobe is virtually absent. This shark is a plain light gray above and whitish below. Males and females grow up to 77 cm (30.3 in) and 82 cm (32.3 in) long respectively.
. It feeds on a wide variety of bottom and shore-dwelling
organisms. Crustacean
s (including crab
s, lobster
s, and shrimp
) are a favored prey item, while small bony fishes (including sardine
s, anchovies, snake eels, blennies, gobies, and flatfish
), skate
and flyingfish
eggs, octopus
, and sponges are also eaten; miscellaneous objects such as feather
s, vegetable
scraps, and flower
s have also been recovered from its stomach. Known parasites of this species include the copepod
s Eudactylina leptochariae and Thamnocephalus cerebrinoxius.
The enlarged anterior teeth of male barbeled houndsharks may function in mating behaviors. This species is viviparous; once the embryo
s exhaust their supply of yolk, they are nourished through a placenta
l connection formed from the depleted yolk sac
. Unlike any other shark, the yolk-sac placenta is globular or spherical. Off Senegal
, females bear litters of 7 pups around October, after a gestation period
of at least four months. The largest fetus
es on record measured 20 cm (7.9 in) long, which is presumably close to the birth size. Males reach sexual maturity
at 55–60 cm (21.7–23.6 in) long, and females at 52–58 cm (20.5–22.8 in) long.
region. It is caught incidentally
by artisanal
and commercial fisheries
using hook-and-line, fixed bottom gillnets
, and bottom trawls. When retained, the meat is sold fresh, smoked, or dried and salted, and leather
is made from the skin. The International Union for Conservation of Nature (IUCN) has assessed the barbeled houndshark as Near Threatened
, noting that fishing pressure is intense throughout its range. However, no specific fishery data are available.
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 ground shark and the only member of 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...
Leptochariidae. This demersal species is found in the coastal waters of the eastern Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
from Mauritania
Mauritania
Mauritania is a country in the Maghreb and West Africa. It is bordered by the Atlantic Ocean in the west, by Western Sahara in the north, by Algeria in the northeast, by Mali in the east and southeast, and by Senegal in the southwest...
to Angola
Angola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...
, at depths of 10–75 m (32.8–246.1 ft). It favors muddy habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s, particularly around river mouths. The barbeled houndshark is characterized by a very slender body, nasal barbels, long furrows at the corners of the mouth, and sexually dimorphic teeth. Its maximum known length is 82 cm (32.3 in).
Likely strong-swimming and opportunistic, the barbeled houndshark has been known to ingest bony fishes, invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s, fish eggs, and even inedible objects. It is viviparous with females bearing litters of 7 young; the developing embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
s are sustained via a unique globular placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
l structure. The International Union for Conservation of Nature (IUCN) has assessed the barbeled houndshark as Near Threatened
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
, as heavy fishing pressure occurs throughout its range and it is utilized for meat and leather
Leather
Leather is a durable and flexible material created via the tanning of putrescible animal rawhide and skin, primarily cattlehide. It can be produced through different manufacturing processes, ranging from cottage industry to heavy industry.-Forms:...
.
Taxonomy and phylogeny
The genus Leptocharias was coined by South AfricaSouth Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
n physician
Physician
A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...
and zoologist Andrew Smith, without any associated species, in an 1838 Magazine of Natural History article by Johannes Müller
Johannes Peter Müller
Johannes Peter Müller , was a German physiologist, comparative anatomist, and ichthyologist not only known for his discoveries but also for his ability to synthesize knowledge.-Early years and education:...
and Friedrich Henle
Friedrich Gustav Jakob Henle
Friedrich Gustav Jakob Henle was a German physician, pathologist and anatomist. He is credited with the discovery of the loop of Henle in the kidney. His essay "On Miasma and Contagia" was an early argument for the germ theory of disease...
. Müller and Henle added a species a year later in their Systematische Beschreibung der Plagiostomen, but adopted the name Triaenodon smithii because they regarded Leptocharias as a junior synonym
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
of Triaenodon. Later authors recognized the validity of Leptocharias, and shuffled it between the families Carcharhinidae and Triakidae before placing it in its own family. The type specimen is an adult male collected off Cabinda Province, Angola
Angola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...
.
Because of its many unique characteristics
Autapomorphy
In cladistics, an autapomorphy is a distinctive anatomical feature, known as a derived trait, that is unique to a given terminal group. That is, it is found only in one member of a clade, but not found in any others or outgroup taxa, not even those most closely related to the group...
, the evolutionary relationships of the barbeled houndshark are difficult to resolve. A morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
study by Compagno in 1988 was inconclusive on the relationship of Leptocharias to other carcharhiniform
Carcharhiniformes
The ground sharks, order Carcharhiniformes, are the largest order of sharks. With over 270 species, carcharhiniforms include a number of common types, such as the blue shark, catsharks, swellsharks, and sandbar shark....
families. Similarly, a molecular phylogenetic study by López et al. in 2006 found that, though Leptocharias certainly belonged to a derived
Derived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
also containing the families Hemigaleidae
Hemigaleidae
The weasel sharks are a family, Hemigaleidae, of ground sharks found from the eastern Atlantic Ocean to the continental Indo-Pacific. They are found in shallow coastal waters to a depth of 100 m ....
, Triakidae, Carcharhinidae and Sphyrnidae, its position within that group changed depending on the DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
and type of analysis used. Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
ized teeth belonging to an extinct relative, L. cretaceus, have been recovered from Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
(99.6–65.5 Ma) deposits in Britain
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
.
Distribution and habitat
The barbeled houndshark occurs along the western coast of AfricaAfrica
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
from Mauritania
Mauritania
Mauritania is a country in the Maghreb and West Africa. It is bordered by the Atlantic Ocean in the west, by Western Sahara in the north, by Algeria in the northeast, by Mali in the east and southeast, and by Senegal in the southwest...
to northern Angola, though it may range as far north as the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
. This species inhabits inshore waters 10–75 m (32.8–246.1 ft) deep, with temperatures of 20–27 °C (68–80.6 F), salinities
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
of 35–36 ppt, and dissolved oxygen levels of 3–4 ppm. It is typically found close to the bottom over mud, particularly around river mouths.
Description
The barbeled houndshark has an extremely slender body and horizontally oval eyes equipped with internal nictitating membraneNictitating membrane
The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Some reptiles, birds, and sharks have a full nictitating membrane; in many mammals, there is a small...
s. A pair of tiny spiracle
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...
s are present behind the eyes. Each nostril
Nostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
is preceded by a slender barbel. The mouth is long and strongly arched, with very long furrows at the corners extending onto both jaws. There are 46–60 upper tooth rows and 43–54 lower tooth rows; each tooth is small, with a narrow central cusp and a pair of lateral cusplets. Unusually for a shark, there is dental sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
with the front teeth in males being greatly enlarged. The two 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 are small and approximately equal in size; the first is positioned between the pectoral and pelvic fins, and the second over the anal fin. The dorsal margin of the caudal fin is smooth and lacks a notch (precaudal pit) at its base; the lower caudal fin lobe is virtually absent. This shark is a plain light gray above and whitish below. Males and females grow up to 77 cm (30.3 in) and 82 cm (32.3 in) long respectively.
Biology and ecology
The barbeled houndshark seems to be an active swimmer, based on its strong musculature, long tail, short trunk, and small liverLiver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
. It feeds on a wide variety of bottom and shore-dwelling
Littoral
The littoral zone is that part of a sea, lake or river that is close to the shore. In coastal environments the littoral zone extends from the high water mark, which is rarely inundated, to shoreline areas that are permanently submerged. It always includes this intertidal zone and is often used to...
organisms. Crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s (including crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s, lobster
Lobster
Clawed lobsters comprise a family of large marine crustaceans. Highly prized as seafood, lobsters are economically important, and are often one of the most profitable commodities in coastal areas they populate.Though several groups of crustaceans are known as lobsters, the clawed lobsters are most...
s, and shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
) are a favored prey item, while small bony fishes (including sardine
Sardine
Sardines, or pilchards, are several types of small, oily fish related to herrings, family Clupeidae. Sardines are named after the Mediterranean island of Sardinia, around which they were once abundant....
s, anchovies, snake eels, blennies, gobies, and flatfish
Flatfish
The flatfish are an order of ray-finned fish, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the head, one or the other migrating through and around the head during development...
), skate
Skate
Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. There are more than 200 described species in 27 genera. There are two subfamilies, Rajinae and Arhynchobatinae ....
and flyingfish
Flyingfish
Exocoetidae, is a family of marine fish in the order Beloniformes of class Actinopterygii. Fish of this family are known as flying fish. There are about 64 species grouped in seven to nine genera.- Etymology :...
eggs, octopus
Octopus
The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...
, and sponges are also eaten; miscellaneous objects such as feather
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...
s, vegetable
Vegetable
The noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....
scraps, and flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s have also been recovered from its stomach. Known parasites of this species include the copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s Eudactylina leptochariae and Thamnocephalus cerebrinoxius.
The enlarged anterior teeth of male barbeled houndsharks may function in mating behaviors. This species is viviparous; once the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
s exhaust their supply of yolk, they are nourished through a placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
l connection formed from the depleted 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...
. Unlike any other shark, the yolk-sac placenta is globular or spherical. Off Senegal
Senegal
Senegal , officially the Republic of Senegal , is a country in western Africa. It owes its name to the Sénégal River that borders it to the east and north...
, females bear litters of 7 pups around October, after a gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
of at least four months. The largest 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 on record measured 20 cm (7.9 in) long, which is presumably close to the birth size. Males reach sexual maturity
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
at 55–60 cm (21.7–23.6 in) long, and females at 52–58 cm (20.5–22.8 in) long.
Human interactions
Harmless to humans, the barbeled houndshark is relatively common and probably of some economic importance in the West AfricaWest Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
region. It is caught incidentally
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...
by artisanal
Artisan fishing
Artisan fishing is a term used to describe small scale low-technology commercial or subsistence fishing practices. The term particularly applies to coastal or island ethnic groups using traditional techniques such as rod and tackle, arrows and harpoons, throw nets and drag nets, and traditional...
and commercial fisheries
Commercial fishing
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 pursue fish far into the ocean under adverse conditions...
using hook-and-line, fixed bottom gillnets
Gillnet
Gillnetting is a common fishing method used by commercial and artisanal fishermen of all the oceans and in some freshwater and estuary areas. The gillnet also is used by fisheries scientists to monitor fish populations. Because gillnets can be so effective their use is closely monitored and...
, and bottom trawls. When retained, the meat is sold fresh, smoked, or dried and salted, and leather
Leather
Leather is a durable and flexible material created via the tanning of putrescible animal rawhide and skin, primarily cattlehide. It can be produced through different manufacturing processes, ranging from cottage industry to heavy industry.-Forms:...
is made from the skin. The International Union for Conservation of Nature (IUCN) has assessed the barbeled houndshark as Near Threatened
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
, noting that fishing pressure is intense throughout its range. However, no specific fishery data are available.