Cloudy catshark
Encyclopedia
The cloudy catshark is a common species
of catshark
, family
Scyliorhinidae. It is a bottom-dweller that inhabits rocky reef
s in the northwestern Pacific Ocean
, from the shore to a depth of 320 m (1,049.9 ft). Growing up to 50 cm (19.7 in) long, this small, slim shark has a narrow head with a short blunt snout, no grooves between the nostrils and mouth, and furrows on the lower but not the upper jaw. It is also characterized by extremely rough skin and coloration consisting of a series of dark brown saddles along its back and tail, along with various darker and lighter spots in larger individuals.
The diet of the cloudy catshark consists of molluscs, crustacean
s, and bony fishes. It is oviparous, with females laying encapsulated eggs two at a time in nursery areas. The claspers of the male bear numerous hooks that likely serve to facilitate copulation. This harmless shark can be readily maintained in captivity and is used as a model organism
for biological research. It is caught incidentally
, and generally discarded, by commercial fisheries. These activities do not appear to have negatively affected its population, leading it to be listed under Least Concern
by the International Union for Conservation of Nature (IUCN).
. Subsequent authors have synonymized
Catulus with Scyliorhinus.
, Korea
, China
, and possibly the Philippines
. Bottom-dwelling in nature, this species can be found from the shore out to a depth of 320 m (1,049.9 ft) on the continental shelf
and upper continental slope. It favors rocky reefs and does not appear to be migratory
.
s (protective third eyelids), and followed by moderate spiracle
s. There are no grooves between the nostrils and the mouth. There are furrows extending from the corners of the mouth over the lower jaw only. The small teeth have a long central cusp typically flanked by two pairs of cusplets. The five pairs of gill slit
s are short, with the fourth pair over the pectoral fin origins.
The two dorsal fin
s are placed towards the back of the body, with the first originating over the rear of the pelvic fin bases. The first dorsal fin has a rounded apex and is larger than the second dorsal fin, which has a more angular shape. The pectoral and pelvic fins are moderate in size. In males, the inner margins of the pelvic fins are merged to form an "apron" over the long, cylindrical claspers. The origin of the anal fin lies approximately between the dorsal fins. The caudal peduncle is about as deep as the body, and leads to a low caudal fin with an indistinct lower lobe and a ventral notch near the tip of the upper lobe. The skin is thick and very rough due to the dermal denticles, which are large and upright with three backward-pointing teeth. This species is brown on the back and sides, with 6–10 indistinct darker dorsal saddles, and plain yellowish on its ventral side. Larger sharks also have many large, irregularly-shaped light and dark spots.
s and bony fishes. A predator of both this shark and its egg cases is the blotchy swell shark
(Cephaloscyllium umbratile). A known parasite of this species is the myxosporidian Chloromyxum scyliorhinum. Reproduction is oviparous; adult females have a single functional ovary
and two functional oviduct
s. As a prelude to mating
, the male bites at the female's pectoral fin, side, and gill region. Once he has a grip, he wraps his body around hers and inserts one of his claspers into her cloaca
. Copulation may last between 15 seconds and 4 minutes. The claspers of the male are unusual in that each has a row of around a hundred hooks running along the inner margin. These hooks likely serve to anchor the male to the female during copulation. The female is capable of storing sperm
within her nidamental gland
(an organ that secretes egg cases) for many months.
Females produce two mature egg
s at a time, one per oviduct. The eggs are enclosed in smooth, translucent yellow, vase-shaped capsules measuring 1.9 cm (0.748031496062992 in) across and 5.5 cm (2.2 in) long. There are long tendrils at the four corners of the capsule. The eggs are laid in defined nursery areas: One such area is located at a depth of 100 m (328.1 ft) off Hakodate. When the embryo
is 3.6 cm (1.4 in) long, it has external gills, undeveloped fins, and no pigmentation. At an embryonic length of 5.8 cm (2.3 in), the external gills have all but disappeared, and a covering of small denticles is present. By a length of 7.9 cm (3.1 in), the embryo has well-developed fins and pigmentation, and generally resembles the adult. The eggs take 15 months to hatch at 11.3 °C (52.3 °F), and 7–9 months to hatch at 14.5 °C (58.1 °F). The newly hatched shark measures 8 cm (3.1 in) long or more. Maturation size tends to increase with decreasing water temperature: Off northerly Hakodate, both sexes mature at over 38 cm (15 in) long, while some females remain immature even at 47 cm (18.5 in) long. By contrast, off southerly Tsushima Island
both sexes mature at around 33 cm (13 in) long. The maximum lifespan is at least 12 years.
in physiology
research. On September 25, 1995, Masuda Motoyashi and colleagues used this species to perform the first successful artificial insemination
of a shark or ray
. The cloudy catshark is caught incidentally
by commercial fisheries with bottom fishing net
s including trawls and gillnet
s, as well as on bottom longlines. Captured individuals are typically discarded, possibly with a high survival rate due to their hardiness. Some 40% of the fish discarded in Yamaguchi Prefecture
fisheries are of this species. The bottom trawl fishery operating off Fukushima Prefecture
may catch over a ton of cloudy catsharks annually, which are also discarded.
Despite heavy fishing pressure within its range, the cloudy catshark remains common, perhaps because it may be more biologically productive
than most other sharks. As a result, it has been assessed as Least Concern
by the International Union for Conservation of Nature (IUCN). Cloudy catsharks from a number of locations off Japan have been found to be contaminated with polychlorinated biphenyl
s (PCBs) and dichlorodiphenyldichloroethylene
(DDEs), which they acquire from their food
. One likely source of these pollutant
s is the use of the pesticide
DDT
by developing nations in southern Asia.
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 catshark
Catshark
Catsharks are ground sharks of the family Scyliorhinidae, with over 150 known species. While they are generally known as catsharks, many species are commonly called dogfish....
, 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...
Scyliorhinidae. It is a bottom-dweller that inhabits rocky reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
s in the northwestern Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
, from the shore to a depth of 320 m (1,049.9 ft). Growing up to 50 cm (19.7 in) long, this small, slim shark has a narrow head with a short blunt snout, no grooves between the nostrils and mouth, and furrows on the lower but not the upper jaw. It is also characterized by extremely rough skin and coloration consisting of a series of dark brown saddles along its back and tail, along with various darker and lighter spots in larger individuals.
The diet of the cloudy catshark consists of molluscs, 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, and bony fishes. It is oviparous, with females laying encapsulated eggs two at a time in nursery areas. The claspers of the male bear numerous hooks that likely serve to facilitate copulation. This harmless shark can be readily maintained in captivity and is used as a model organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
for biological research. 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...
, and generally discarded, by commercial fisheries. These activities do not appear to have negatively affected its population, leading it to be listed 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...
by the International Union for Conservation of Nature (IUCN).
Taxonomy
The original description of the cloudy catshark was published in 1908 by Shigeho Tanaka in the Journal of the Faculty of Science, University of Tokyo. He gave it the specific epithet torazame, which is its Japanese name (虎鮫, literally "tiger shark"), and assigned it to the genus Catulus. The type specimen was a 45 cm (17.7 in) long adult male caught off Misaki, Kanagawa, JapanJapan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
. Subsequent authors have synonymized
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...
Catulus with Scyliorhinus.
Distribution and habitat
The cloudy catshark is common in the northwestern Pacific off JapanJapan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, Korea
Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, and possibly the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
. Bottom-dwelling in nature, this species can be found from the shore out to a depth of 320 m (1,049.9 ft) on the continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
and upper continental slope. It favors rocky reefs and does not appear to be migratory
Fish migration
Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...
.
Description
The cloudy catshark reaches 50 cm (19.7 in) long and has a thin, deep, and firm body. The narrow head makes up slightly under one-sixth of the total length, and is two-thirds as wide as it is long. The snout is short and rounded. The large nostrils are preceded by small, triangular flaps of skin that do not reach the wide mouth. The medium-sized eyes are horizontally oval, equipped with rudimentary 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 (protective third eyelids), and followed by moderate 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. There are no grooves between the nostrils and the mouth. There are furrows extending from the corners of the mouth over the lower jaw only. The small teeth have a long central cusp typically flanked by two pairs of cusplets. 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, with the fourth pair over the pectoral fin origins.
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 placed towards the back of the body, with the first originating over the rear of the pelvic fin bases. The first dorsal fin has a rounded apex and is larger than the second dorsal fin, which has a more angular shape. The pectoral and pelvic fins are moderate in size. In males, the inner margins of the pelvic fins are merged to form an "apron" over the long, cylindrical claspers. The origin of the anal fin lies approximately between the dorsal fins. The caudal peduncle is about as deep as the body, and leads to a low caudal fin with an indistinct lower lobe and a ventral notch near the tip of the upper lobe. The skin is thick and very rough due to the dermal denticles, which are large and upright with three backward-pointing teeth. This species is brown on the back and sides, with 6–10 indistinct darker dorsal saddles, and plain yellowish on its ventral side. Larger sharks also have many large, irregularly-shaped light and dark spots.
Biology and ecology
The cloudy catshark feeds primarily on molluscs, followed by crustaceanCrustacean
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 and bony fishes. A predator of both this shark and its egg cases is the blotchy swell shark
Blotchy swell shark
The blotchy swell shark or Japanese swellshark is a common species of catshark, family Scyliorhinidae, found at depths of in the northwestern Pacific Ocean from Japan to Taiwan. It is benthic in nature and favors rocky reefs...
(Cephaloscyllium umbratile). A known parasite of this species is the myxosporidian Chloromyxum scyliorhinum. Reproduction is oviparous; adult 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...
and two functional oviduct
Oviduct
In non-mammalian vertebrates, the passageway from the ovaries to the outside of the body is known as the oviduct. The eggs travel along the oviduct. These eggs will either be fertilized by sperm to become a zygote, or will degenerate in the body...
s. As a prelude to mating
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...
, the male bites at the female's pectoral fin, side, and gill region. Once he has a grip, he wraps his body around hers and inserts one of his claspers into her cloaca
Cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...
. Copulation may last between 15 seconds and 4 minutes. The claspers of the male are unusual in that each has a row of around a hundred hooks running along the inner margin. These hooks likely serve to anchor the male to the female during copulation. The female is capable of storing sperm
Sperm
The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...
within her nidamental gland
Nidamental gland
The nidamental gland is an internal organ found in some elasmobranchs and certain molluscs, including cephalopods and gastropods....
(an organ that secretes egg cases) for many months.
Females produce two mature egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
s at a time, one per oviduct. The eggs are enclosed in smooth, translucent yellow, vase-shaped capsules measuring 1.9 cm (0.748031496062992 in) across and 5.5 cm (2.2 in) long. There are long tendrils at the four corners of the capsule. The eggs are laid in defined nursery areas: One such area is located at a depth of 100 m (328.1 ft) off Hakodate. When 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...
is 3.6 cm (1.4 in) long, it has external gills, undeveloped fins, and no pigmentation. At an embryonic length of 5.8 cm (2.3 in), the external gills have all but disappeared, and a covering of small denticles is present. By a length of 7.9 cm (3.1 in), the embryo has well-developed fins and pigmentation, and generally resembles the adult. The eggs take 15 months to hatch at 11.3 °C (52.3 °F), and 7–9 months to hatch at 14.5 °C (58.1 °F). The newly hatched shark measures 8 cm (3.1 in) long or more. Maturation size tends to increase with decreasing water temperature: Off northerly Hakodate, both sexes mature at over 38 cm (15 in) long, while some females remain immature even at 47 cm (18.5 in) long. By contrast, off southerly Tsushima Island
Tsushima Island
Tsushima Island is an island of the Japanese Archipelago situated in the middle of the Tsushima Strait at 34°25'N and 129°20'E. The main island of Tsushima was once a single island, but the island was divided into two in 1671 by the Ōfunakosiseto canal and into three in 1900 by the Manzekiseto canal...
both sexes mature at around 33 cm (13 in) long. The maximum lifespan is at least 12 years.
Human interactions
Harmless to humans, the cloudy catshark adapts well to captivity and has reproduced in the aquarium. It is often used as a model organismModel organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
in physiology
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
research. On September 25, 1995, Masuda Motoyashi and colleagues used this species to perform the first successful artificial insemination
Artificial insemination
Artificial insemination, or AI, is the process by which sperm is placed into the reproductive tract of a female for the purpose of impregnating the female by using means other than sexual intercourse or natural insemination...
of a shark or ray
Elasmobranchii
Elasmobranchii is a subclass of Chondrichthyes or cartilaginous fish, that includes the sharks and the rays and skates .-Evolution:...
. The cloudy catshark 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 commercial fisheries with bottom fishing net
Fishing net
A fishing net or fishnet is a net that is used for fishing. Fishing nets are meshes usually formed by knotting a relatively thin thread. Modern nets are usually made of artificial polyamides like nylon, although nets of organic polyamides such as wool or silk thread were common until recently and...
s including trawls and gillnet
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...
s, as well as on bottom longlines. Captured individuals are typically discarded, possibly with a high survival rate due to their hardiness. Some 40% of the fish discarded in Yamaguchi Prefecture
Yamaguchi Prefecture
is a prefecture of Japan in the Chūgoku region on Honshū island. The capital is the city of Yamaguchi, in the center of the prefecture. The largest city, however, is Shimonoseki.- History :...
fisheries are of this species. The bottom trawl fishery operating off Fukushima Prefecture
Fukushima Prefecture
is a prefecture of Japan located in the Tōhoku region on the island of Honshu. The capital is the city of Fukushima.-History:Until the Meiji Restoration, the area of Fukushima prefecture was known as Mutsu Province....
may catch over a ton of cloudy catsharks annually, which are also discarded.
Despite heavy fishing pressure within its range, the cloudy catshark remains common, perhaps because it may be more biologically productive
Productivity (ecology)
In ecology, productivity or production refers to the rate of generation of biomass in an ecosystem. It is usually expressed in units of mass per unit surface per unit time, for instance grams per square metre per day. The mass unit may relate to dry matter or to the mass of carbon generated...
than most other sharks. As a result, it has been assessed 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...
by the International Union for Conservation of Nature (IUCN). Cloudy catsharks from a number of locations off Japan have been found to be contaminated with polychlorinated biphenyl
Polychlorinated biphenyl
Polychlorinated biphenyls are a class of organic compounds with 2 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings. The chemical formula for PCBs is C12H10-xClx...
s (PCBs) and dichlorodiphenyldichloroethylene
Dichlorodiphenyldichloroethylene
Dichlorodiphenyldichloroethylene is a chemical compound formed by the loss of hydrogen chloride from DDT, of which it is one of the more common breakdown products. DDE is fat soluble which tends to build up in the fat of animals. Due to its stability in fat, DDE is rarely excreted from the body,...
(DDEs), which they acquire from their food
Bioaccumulation
Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...
. One likely source of these pollutant
Pollutant
A pollutant is a waste material that pollutes air, water or soil, and is the cause of pollution.Three factors determine the severity of a pollutant: its chemical nature, its concentration and its persistence. Some pollutants are biodegradable and therefore will not persist in the environment in the...
s is the use of the pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...
DDT
DDT
DDT is one of the most well-known synthetic insecticides. It is a chemical with a long, unique, and controversial history....
by developing nations in southern Asia.