The cloudy catshark (''Scyliorhinus torazame'') is a common

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

catshark Catshark may refer to: * Scyliorhinidae, a family of ground sharks, many species of which are commonly referred to as "catshark". * Pentanchidae, a family of ground sharks with the overall name deepwater catsharks, but many species are referred ...

, belonging to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Scyliorhinidae Scyliorhinidae is a Family (biology), family of sharks, one of a few families whose members share the common name catsharks, belonging to the Order (biology), order Carcharhiniformes, the ground sharks. Although they are generally known as cats ...

. It is a bottom-dweller that inhabits rocky

reef A reef is a ridge or shoal of rock, coral, or similar relatively stable material lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic component, abiotic (non-living) processes such as deposition (geol ...

s in the northwestern

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

, from the shore to a depth of . Growing up to 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

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s, and

bony fish Osteichthyes ( ; ), also known as osteichthyans or commonly referred to as the bony fish, is a Biodiversity, diverse clade of vertebrate animals that have endoskeletons primarily composed of bone tissue. They can be contrasted with the Chondricht ...

es. It is

oviparous Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings kno ...

, with females laying encapsulated eggs two at a time in nursery areas. The

clasper In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating. Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's ...

s of the male bear numerous hooks that likely serve to facilitate

copulation Sexual intercourse (also coitus or copulation) is a sexual activity typically involving the insertion of the erect male penis inside the female vagina and followed by thrusting motions for sexual pleasure, reproduction, or both.Sexual inte ...

. This harmless shark can be readily maintained in captivity and is used as a

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 model organism will provide insight into the workings of other organisms. Mo ...

for biological research. It is caught incidentally, and generally discarded, by

commercial fisheries Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often p ...

. These activities do not appear to have negatively affected its population, leading it to be listed under

Least Concern A least-concern species is a species that has been evaluated and categorized by the International Union for Conservation of Nature (IUCN) as not being a focus of wildlife conservation because the specific species is still plentiful in the wil ...

by the

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...

(IUCN).

Taxonomy

The original description of the cloudy catshark was published in 1908 by

Shigeho Tanaka was a Japanese ichthyologist and professor of zoology at the Imperial University of Tokyo. He published numerous works on fishes and sharks and co-authored a book on Japanese fish with famous American scientist David Starr Jordan David Starr Jo ...

in the ''Journal of the Faculty of Science, University of Tokyo''. He gave it the

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

''torazame'', which is its Japanese name (虎鮫, literally "tiger shark"), and assigned it to the genus ''Catulus''. The

type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...

was a long adult male caught off Misaki, Kanagawa,

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

. Subsequent authors have synonymized ''Catulus'' with ''Scyliorhinus''.

Description

The cloudy catshark reaches 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 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. Most ...

s (protective third eyelids), and followed by moderate spiracles. 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 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 c ...

s are short, with the fourth pair over the

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

origins. The two

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

s are placed towards the back of the body, with the first originating over the rear of the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

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

s. The origin of the

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

lies approximately between the dorsal fins. The

caudal peduncle Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

is about as deep as the body, and leads to a low

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

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 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 scale (zoology), scales, which can also provide effective Underwater camouflage, camouflage through the us ...

s, 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.

Distribution and habitat

The cloudy catshark is common in the northwestern Pacific off

Korea Korea is a peninsular region in East Asia consisting of the Korean Peninsula, Jeju Island, and smaller islands. Since the end of World War II in 1945, it has been politically Division of Korea, divided at or near the 38th parallel north, 3 ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

, and possibly the

Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...

Bottom-dwelling The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

in nature, this species can be found from the shore out to a depth of on the

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 islan ...

and upper

continental slope A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margi ...

. It favors rocky reefs and does not appear to be migratory.

Biology and ecology

The cloudy catshark feeds primarily on

s, followed by

s and

es. A

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

of both this shark and its egg cases is the blotchy swell shark (''Cephaloscyllium umbratile''). A known

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

of this species is the myxosporidian ''Chloromyxum scyliorhinum''. Reproduction is

; adult females have a single functional

ovary The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/ oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are end ...

and two functional

oviduct The oviduct in vertebrates is the passageway from an ovary. In human females, this is more usually known as the fallopian tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, or will dege ...

s. As a prelude to

mating In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. '' Copulation'' is the union of the sex organs of two sexually repr ...

, 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 A cloaca ( ), : cloacae ( or ), or vent, is the rear orifice that serves as the only opening for the digestive (rectum), reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles, birds, cartilagin ...

Copulation Sexual intercourse (also coitus or copulation) is a sexual activity typically involving the insertion of the erect male penis inside the female vagina and followed by thrusting motions for sexual pleasure, reproduction, or both.Sexual inte ...

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 (: sperm or sperms) is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm ...

within her

nidamental gland Nidamental glands are internal organs found in some elasmobranchs and certain molluscs, including cephalopods (specifically Decapodiformes and nautiluses) and gastropod Gastropods (), commonly known as slugs and snails, belong to a large Ta ...

(an organ that secretes egg cases) for many months. Females produce two mature

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...

s at a time, one per oviduct. The eggs are enclosed in smooth, translucent yellow, vase-shaped capsules measuring across and 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 off

Hakodate is a Cities of Japan, city and seaports of Japan, port located in Oshima Subprefecture, Hokkaido, Japan. It is the capital city of Oshima Subprefecture. As of January 31, 2024, the city had an estimated population of 239,813 with 138,807 househol ...

. When the

embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...

is long, it has external gills, undeveloped fins, and no pigmentation. At an embryonic length of , the external gills have all but disappeared, and a covering of small denticles is present. By a length of , the embryo has well-developed fins and pigmentation, and generally resembles the adult. The eggs take 15 months to hatch at , and 7–9 months to hatch at . The newly hatched shark measures long or more. Maturation size tends to increase with decreasing water temperature: Off northerly Hakodate, both sexes mature at over long, while some females remain immature even at long. By contrast, off southerly Tsushima Island both sexes mature at around long. The

maximum lifespan Maximum life span (or, for humans, maximum reported age at death) is a measure of the maximum amount of time one or more members of a population have been observed to survive between birth and death. The term can also denote an estimate of the m ...

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

physiology Physiology (; ) is the science, scientific study of function (biology), functions and mechanism (biology), mechanisms in a life, living system. As a branches of science, subdiscipline of biology, physiology focuses on how organisms, organ syst ...

research. On September 25, 1995, Masuda Motoyashi and colleagues used this species to perform the first successful

artificial insemination Artificial insemination is the deliberate introduction of sperm into a female's cervix or uterine cavity for the purpose of achieving a pregnancy through in vivo fertilization by means other than sexual intercourse. It is a fertility treatment ...

of a shark or ray. The cloudy catshark is caught incidentally by

with bottom

fishing net A fishing net or fish net is a net (device), net used for fishing. Fishing nets work by serving as an improvised fish trap, and some are indeed rigged as traps (e.g. #Fyke nets, fyke nets). They are usually wide open when deployed (e.g. by cast ...

s including

trawl Trawling is an industrial method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch di ...

s 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 ...

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 is a Prefectures of Japan, prefecture of Japan located in the Chūgoku region of Honshu. Yamaguchi Prefecture has a population of 1,377,631 (1 February 2018) and has a geographic area of 6,112 Square kilometre, km2 (2,359 Square mile, sq mi). ...

fisheries are of this species. The bottom trawl fishery operating off

Fukushima Prefecture is a Prefectures of Japan, prefecture of Japan located in the Tōhoku region of Honshu. Fukushima Prefecture has a population of 1,771,100 () and has a geographic area of . Fukushima Prefecture borders Miyagi Prefecture and Yamagata 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

by the

(IUCN). Cloudy catsharks from a number of locations off Japan have been found to be contaminated with

polychlorinated biphenyl Polychlorinated biphenyls (PCBs) are organochlorine compounds with the formula Carbon, C12Hydrogen, H10−''x''Chloride, Cl''x''; they were once widely used in the manufacture of carbonless copy paper, as heat transfer fluids, and as dielectri ...

s (PCBs) and

dichlorodiphenyldichloroethylene Dichlorodiphenyldichloroethylene (DDE) is a chemical compound formed by the loss of hydrogen chloride (dehydrohalogenation) from DDT, of which it is one of the more common breakdown products. Due to DDT's massive prevalence in society and agricul ...

(DDEs), which they acquire from their food. One likely source of these

pollutant A pollutant or novel entity is a substance or energy introduced into the environment that has undesired effect, or adversely affects the usefulness of a resource. These can be both naturally forming (i.e. minerals or extracted compounds like oi ...

s is the use of the

pesticide Pesticides are substances that are used to control pests. They include herbicides, insecticides, nematicides, fungicides, and many others (see table). The most common of these are herbicides, which account for approximately 50% of all p ...

DDT Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmental impacts. ...

developing nation A developing country is a sovereign state with a less-developed industrial base and a lower Human Development Index (HDI) relative to developed countries. However, this definition is not universally agreed upon. There is also no clear agreeme ...

s in southern Asia.

References

{{DEFAULTSORT:catshark, cloudy

cloudy catshark The cloudy catshark (''Scyliorhinus torazame'') is a common species of Scyliorhinidae, catshark, belonging to the family (biology), family Scyliorhinidae. It is a benthic fish, bottom-dweller that inhabits rocky reefs in the northwestern Pacific ...

Marine fauna of East Asia