Slender smooth-hound
Encyclopedia
The slender smooth-hound or gollumshark (Gollum attenuatus) is a species
of ground shark in the family
Pseudotriakidae
. It is endemic to the waters around New Zealand
, where it is usually found close to the bottom over the continental slope at depths of 300–600 m (984.3–1,968.5 ft). An extremely slim, plain brownish shark reaching 1.1 m (3.6 ft) in length, the slender smooth-hound can be identified by its broad, flattened head with a long, distinctively bell-shaped snout. Its mouth is angular with short furrows at the corners, and contains a very high number of tooth rows in both jaws. Its two dorsal fin
s are roughly equal in size.
The diet of the slender smooth-hound is diverse, but dominated by small, benthic bony fishes and decapod
crustacean
s. It exhibits a specialized form of aplacental viviparity with oophagy
: the females produce a single capsule in each uterus
that contains 30–80 ova
, of which one ovum develops into an embryo
that consumes the rest of the ova and stores the yolk material in its external yolk sac
. The growing embryo is mainly sustained by this yolk sac during gestation
, though it may be additionally supplied with histotroph ("uterine milk") produced by the mother. The typical litter size is two pups, one per uterus. The International Union for Conservation of Nature (IUCN) has assessed the slender smooth-hound as Least Concern
; it is taken as fishery
bycatch
but not in great numbers, and furthermore large portions of its range see minimal fishing activity.
on New Zealand's North Island
. It was preserved by the crew as a curiosity and given to ichthyologist Jack Garrick, who described it in a 1954 issue of the scientific journal
Transactions of the Royal Society of New Zealand. Garrick named the species Triakis
attenuata, in reference to its extremely slender ("attenuate") body.
In 1973, Leonard Compagno
proposed a separate genus for the slender smooth-hound: Gollum, after the character
in J. R. R. Tolkien
's The Lord of the Rings
, "to whom this shark bears some resemblance in form and habits." He placed Gollum with the finback catsharks (Proscylliidae), but also noted its many anatomical
similarities to the false catshark
(Pseudotriakis microdon). At the time, Compagno chose to maintain Pseudotriakis as the sole member of the family Pseudotriakidae because of its numerous unique traits
. More recently, he and other taxonomists have increasingly tended to group Gollum and Pseudotriakis together in the family Pseudotriakidae. This arrangement was corroborated by a 2006 phylogenetic study by Juan Andrés López and colleagues, which found that the two genera have a high degree of genetic similarity across four protein
-coding gene
s and form a natural clade
apart from Proscyllium
. An additional species of Gollum has now been described, and there is at least one additional species yet to be described.
, and the Wanganella Bank. This uncommon species is mainly found between 300 and 600 m (984.3 and 1,968.5 ft) deep, but has been recorded from 129 to 724 m (423.2 to 2,375.3 ft) deep. It prefers a temperature of around 10 °C (50 °F) and a salinity
of approximately 34.8‰. Generally swimming near the sea floor, this shark inhabits both soft and rocky-bottomed habitats in terrain
ranging from plateau
s to steep slopes.
.gif)
The slender smooth-hound has a very thin body and a broad, highly flattened head. The snout is long, with a distinctive bell-shaped outline when viewed from above. The eyes have an elongate horizontal oval shape, and are equipped with rudimentary nictitating membrane
s (protective third eyelids). Beneath each eye is a prominent ridge, and behind is a much smaller spiracle
. The nostrils are preceded by small, almost triangular flaps of skin. The line of the mouth forms an angle; there are very short furrows at the mouth corners. The upper and lower jaws contain 96–99 and 108–114 rows respectively of small, very closely spaced teeth; each tooth has a narrow upright central cusp flanked by smaller cusplets on both sides. The five pairs of gill slit
s are short.
The pectoral fins originate below the fourth gill slit and have gently curved margins. The pelvic fins are small and angular; the males have pointed claspers. The two dorsal fin
s are similar in size and shape, with narrowly rounded apexes and concave trailing margins. The first dorsal fin originates over rear of the pectoral fins, while the second dorsal fin originates between the pelvic and anal fins. A midline ridge is present between the dorsal fins. The anal fin is less than half as high as the first dorsal fin, and has a nearly straight trailing margin. The short and narrow caudal fin makes up about one-sixth of the total length; the lower caudal fin lobe is indistinct, while the upper lobe has a strong ventral notch near the tip. The skin is densely covered by small, overlapping dermal denticles. The crown of each denticle is mounted on a short stalk and bears three horizontal ridges leading to marginal blade-like teeth, with the central tooth particularly long. This species is plain brownish-gray above and lighter below. It grows up to 1.1 m (3.6 ft) long and 4 kg (8.8 lb) in weight, with females reaching a slightly larger size than males.
.gif)
The slender smooth-hound is likely a schooling
species. It preys on a variety of benthic fish
es and invertebrate
s, and also scavenges
; human garbage
has been reported among its stomach contents. Small bony fishes, lanternfish
es in particular, are the most important prey type, followed by decapod
crustacean
s. Cephalopod
s, gastropods, isopods, brittle star
s, dogfish sharks
, and cartilaginous fish egg capsules may also be consumed. On the Challenger Plateau, cephalopods are an important food source for juveniles under 50 cm (19.7 in) long.
Like the false catshark, the slender smooth-hound exhibits aplacental viviparity with oophagy
, in a form different from that in the mackerel sharks
. Mature females have a single functional ovary
, on the right side, and two functional uterus
es. Only one embryo
develops within each uterus at a time, resulting in litters of two (rarely one) pups. The uterus inner surface is covered by villi. Within a uterus, 30–80 ova
4–8 mm (0.15748031496063–0.31496062992126 in) across are packed into a single rigid, amber-colored capsule; of these, only one ovum is fertilized and develops into an embryo, while the remaining ova begin to break down. The embryo consumes these other ova and transfers the yolk material into its external yolk sac
, which serves as its main source of nourishment during gestation
; this oophagous process is completed by an embryonic length of 10–39 mm (0.393700787401575–1.5 in). The embryo may also receive secondary nutrition in the form of histotroph ("uterine milk") produced by the mother. When the embryo is 29–40 mm (1.1–1.6 in) long, it emerges from the capsule, which by that time has become translucent and gelatin
ous. Embryos 4–25 cm (1.6–9.8 in) long have well-developed external gill filaments. The external yolk sac is entirely absorbed when the embryo is 34–42 cm (13.4–16.5 in) long and close to being born. Males and females reach sexual maturity
at approximately 70 cm (27.6 in) long.
in bottom trawls and on bottom longlines. Much of its northern range lies in little-fished waters, and thus the International Union for Conservation of Nature (IUCN) has listed it under Least Concern
. However, this shark's very low fecundity
would render it susceptible to population depletion should fishing pressure increase in the future.
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 in 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...
Pseudotriakidae
Pseudotriakidae
Pseudotriakidae is a small family of ground sharks, order Carcharhiniformes, containing the false catsharks and gollumsharks. It contains the only ground shark species that exhibit intrauterine oophagy, in which developing fetuses are nourished by eggs produced by their mother.-Genera and...
. It is endemic to the waters around New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, where it is usually found close to the bottom over the continental slope at depths of 300–600 m (984.3–1,968.5 ft). An extremely slim, plain brownish shark reaching 1.1 m (3.6 ft) in length, the slender smooth-hound can be identified by its broad, flattened head with a long, distinctively bell-shaped snout. Its mouth is angular with short furrows at the corners, and contains a very high number of tooth rows in both jaws. Its 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 roughly equal in size.
The diet of the slender smooth-hound is diverse, but dominated by small, benthic bony fishes and decapod
Decapoda
The decapods or Decapoda are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with...
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. It exhibits a specialized form of aplacental viviparity with oophagy
Oophagy
Oophagy , literally "egg eating", is the practice of embryos feeding on eggs produced by the ovary while still inside the mother's uterus. The word oophagy is formed from the classical Greek ᾠόν and classical Greek φᾱγεῖν ....
: the females produce a single capsule in each uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
that contains 30–80 ova
Ovum
An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
, of which one ovum develops into an 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...
that consumes the rest of the ova and stores the yolk material in its external 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...
. The growing embryo is mainly sustained by this yolk sac during gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
, though it may be additionally supplied with histotroph ("uterine milk") produced by the mother. The typical litter size is two pups, one per uterus. The International Union for Conservation of Nature (IUCN) has assessed the slender smooth-hound as Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
; it is taken as fishery
Fishery
Generally, a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats,...
bycatch
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...
but not in great numbers, and furthermore large portions of its range see minimal fishing activity.
Taxonomy and phylogeny
The first known specimen of the slender smooth-hound was a 93 cm (36.6 in) long adult male collected by the trawler Maimai in December 1953, at a depth of 220 m (721.8 ft) off Cape PalliserCape Palliser
Cape Palliser is a promontory on the southern coast of New Zealand's North Island and the southernmost point of the North Island - it is in fact considerably further south than Nelson or Blenheim in the South Island....
on New Zealand's North Island
North Island
The North Island is one of the two main islands of New Zealand, separated from the much less populous South Island by Cook Strait. The island is in area, making it the world's 14th-largest island...
. It was preserved by the crew as a curiosity and given to ichthyologist Jack Garrick, who described it in a 1954 issue of the scientific journal
Scientific journal
In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. There are thousands of scientific journals in publication, and many more have been published at various points in the past...
Transactions of the Royal Society of New Zealand. Garrick named the species Triakis
Triakis
Triakis is a genus of houndshark in the family Triakidae.The name comes from the Latin word tri meaning "three", and acis meaning "sharp" or "pointed", in reference to the three-pointed teeth of these sharks.-Species:* Subgenus Cazon...
attenuata, in reference to its extremely slender ("attenuate") body.
In 1973, Leonard Compagno
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 Organization of the United Nations.-Career:*Ph.D,...
proposed a separate genus for the slender smooth-hound: Gollum, after the character
Gollum
Gollum is a fictional character from J. R. R. Tolkien's legendarium. He was introduced in the author's fantasy novel The Hobbit, and became an important supporting character in its sequel, The Lord of the Rings....
in J. R. R. Tolkien
J. R. R. Tolkien
John Ronald Reuel Tolkien, CBE was an English writer, poet, philologist, and university professor, best known as the author of the classic high fantasy works The Hobbit, The Lord of the Rings, and The Silmarillion.Tolkien was Rawlinson and Bosworth Professor of Anglo-Saxon at Pembroke College,...
's The Lord of the Rings
The Lord of the Rings
The Lord of the Rings is a high fantasy epic written by English philologist and University of Oxford professor J. R. R. Tolkien. The story began as a sequel to Tolkien's earlier, less complex children's fantasy novel The Hobbit , but eventually developed into a much larger work. It was written in...
, "to whom this shark bears some resemblance in form and habits." He placed Gollum with the finback catsharks (Proscylliidae), but also noted its many anatomical
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...
similarities to the false catshark
False catshark
The false catshark is a species of ground shark in the family Pseudotriakidae, and the sole member of its genus. It has been reported from a number of locations worldwide, usually at depths of 200-1,500 meters on the continental slopes...
(Pseudotriakis microdon). At the time, Compagno chose to maintain Pseudotriakis as the sole member of the family Pseudotriakidae because of its numerous unique traits
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...
. More recently, he and other taxonomists have increasingly tended to group Gollum and Pseudotriakis together in the family Pseudotriakidae. This arrangement was corroborated by a 2006 phylogenetic study by Juan Andrés López and colleagues, which found that the two genera have a high degree of genetic similarity across four protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
-coding gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s and form a natural 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...
apart from Proscyllium
Proscyllium
The genus Proscyllium is a small genus of fin-back catsharks in the family Proscylliidae. It currently consists of the following species:* Proscyllium habereri Hilgendorf, 1904...
. An additional species of Gollum has now been described, and there is at least one additional species yet to be described.
Distribution and habitat
The range of the slender smooth-hound is restricted to the upper and middle continental slope around New Zealand, including submarine features to the north such as the Three Kings Ridge, the Challenger PlateauChallenger Plateau
The Challenger Plateau is a large submarine plateau west of New Zealand and south of the Lord Howe Rise. It has an approximate diameter of . The plateau originated in the Gondwanan breakup and is one of the five major submerged parts of Zealandia, a largely submerged continent....
, and the Wanganella Bank. This uncommon species is mainly found between 300 and 600 m (984.3 and 1,968.5 ft) deep, but has been recorded from 129 to 724 m (423.2 to 2,375.3 ft) deep. It prefers a temperature of around 10 °C (50 °F) and a salinity
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 approximately 34.8‰. Generally swimming near the sea floor, this shark inhabits both soft and rocky-bottomed habitats in terrain
Terrain
Terrain, or land relief, is the vertical and horizontal dimension of land surface. When relief is described underwater, the term bathymetry is used...
ranging from plateau
Plateau
In geology and earth science, a plateau , also called a high plain or tableland, is an area of highland, usually consisting of relatively flat terrain. A highly eroded plateau is called a dissected plateau...
s to steep slopes.
Description
Nictitating 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 (protective third eyelids). Beneath each eye is a prominent ridge, and behind is a much smaller 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...
. The nostrils are preceded by small, almost triangular flaps of skin. The line of the mouth forms an angle; there are very short furrows at the mouth corners. The upper and lower jaws contain 96–99 and 108–114 rows respectively of small, very closely spaced teeth; each tooth has a narrow upright central cusp flanked by smaller cusplets on both sides. The five pairs of gill slit
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, rays, sawfish, and guitarfish. Most of these have five pairs, but a few species have 6 or 7 pairs...
s are short.
The pectoral fins originate below the fourth gill slit and have gently curved margins. The pelvic fins are small and angular; the males have pointed claspers. 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 similar in size and shape, with narrowly rounded apexes and concave trailing margins. The first dorsal fin originates over rear of the pectoral fins, while the second dorsal fin originates between the pelvic and anal fins. A midline ridge is present between the dorsal fins. The anal fin is less than half as high as the first dorsal fin, and has a nearly straight trailing margin. The short and narrow caudal fin makes up about one-sixth of the total length; the lower caudal fin lobe is indistinct, while the upper lobe has a strong ventral notch near the tip. The skin is densely covered by small, overlapping dermal denticles. The crown of each denticle is mounted on a short stalk and bears three horizontal ridges leading to marginal blade-like teeth, with the central tooth particularly long. This species is plain brownish-gray above and lighter below. It grows up to 1.1 m (3.6 ft) long and 4 kg (8.8 lb) in weight, with females reaching a slightly larger size than males.
Biology and ecology
Shoaling and schooling
In biology, any group of fish that stay together for social reasons are said to be shoaling , and if, in addition, the group is swimming in the same direction in a coordinated manner, they are said to be schooling . In common usage, the terms are sometimes used rather loosely...
species. It preys on a variety of benthic fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
es and 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, and also scavenges
Scavenger
Scavenging is both a carnivorous and herbivorous feeding behavior in which individual scavengers search out dead animal and dead plant biomass on which to feed. The eating of carrion from the same species is referred to as cannibalism. Scavengers play an important role in the ecosystem by...
; human garbage
Waste
Waste is unwanted or useless materials. In biology, waste is any of the many unwanted substances or toxins that are expelled from living organisms, metabolic waste; such as urea, sweat or feces. Litter is waste which has been disposed of improperly...
has been reported among its stomach contents. Small bony fishes, lanternfish
Lanternfish
Cooper Lanternfishes are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represented by 246 species in 33 genera, and are found in oceans worldwide. They are aptly named after their conspicuous use of bioluminescence...
es in particular, are the most important prey type, followed by decapod
Decapoda
The decapods or Decapoda are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with...
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. Cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s, gastropods, isopods, brittle star
Brittle star
Brittle stars or ophiuroids are echinoderms in the class Ophiuroidea closely related to starfish. They crawl across the seafloor using their flexible arms for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to in length on the largest specimens...
s, dogfish sharks
Squaliformes
Squaliformes is an order of sharks that includes about 97 species in seven families.Members of the order have two dorsal fins, which usually possess spines, no anal fin or nictitating membrane, and five gill slits. In most other respects, however, they are quite variable in form and size...
, and cartilaginous fish egg capsules may also be consumed. On the Challenger Plateau, cephalopods are an important food source for juveniles under 50 cm (19.7 in) long.
Like the false catshark, the slender smooth-hound exhibits aplacental viviparity with oophagy
Oophagy
Oophagy , literally "egg eating", is the practice of embryos feeding on eggs produced by the ovary while still inside the mother's uterus. The word oophagy is formed from the classical Greek ᾠόν and classical Greek φᾱγεῖν ....
, in a form different from that in the mackerel sharks
Lamniformes
Lamniformes is an order of sharks commonly known as mackerel sharks . It includes some of the most familiar species of sharks, such as the great white shark, as well as more unusual representatives, such as the goblin shark and the megamouth shark.Members of the order are distinguished by...
. Mature females have a single functional ovary
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
, on the right side, and two functional uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
es. Only one 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...
develops within each uterus at a time, resulting in litters of two (rarely one) pups. The uterus inner surface is covered by villi. Within a uterus, 30–80 ova
Ovum
An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
4–8 mm (0.15748031496063–0.31496062992126 in) across are packed into a single rigid, amber-colored capsule; of these, only one ovum is fertilized and develops into an embryo, while the remaining ova begin to break down. The embryo consumes these other ova and transfers the yolk material into its external 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...
, which serves as its main source of nourishment during gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
; this oophagous process is completed by an embryonic length of 10–39 mm (0.393700787401575–1.5 in). The embryo may also receive secondary nutrition in the form of histotroph ("uterine milk") produced by the mother. When the embryo is 29–40 mm (1.1–1.6 in) long, it emerges from the capsule, which by that time has become translucent and gelatin
Gelatin
Gelatin is a translucent, colorless, brittle , flavorless solid substance, derived from the collagen inside animals' skin and bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar...
ous. Embryos 4–25 cm (1.6–9.8 in) long have well-developed external gill filaments. The external yolk sac is entirely absorbed when the embryo is 34–42 cm (13.4–16.5 in) long and close to being born. Males and females 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 approximately 70 cm (27.6 in) long.
Human interactions
Harmless to humans and of no economic value, the slender smooth-hound is occasionally caught incidentallyBycatch
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...
in bottom trawls and on bottom longlines. Much of its northern range lies in little-fished waters, and thus the International Union for Conservation of Nature (IUCN) has listed it under Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
. However, this shark's very low fecundity
Fecundity
Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...
would render it susceptible to population depletion should fishing pressure increase in the future.