Gecko catshark
Encyclopedia
The gecko catshark is a species
of catshark
, family
Scyliorhinidae, native to the northwestern Pacific Ocean
from southern Japan
to Taiwan
, and possibly also off Vietnam
. It is a common, demersal species found at depths of 100–900 m (328.1–2,952.8 ft). Its body is slender, with a pattern of dark saddles and blotches. The dorsal
and caudal fins are edged in white, and there is a prominent crest of enlarged dermal denticles along the dorsal edge of the caudal fin. The gecko catshark is a schooling
, opportunistic predator of bony fishes, cephalopod
s, and crustacean
s. It is oviparous, with females producing two vase-shaped egg capsules at a time. This species is captured as bycatch
, but does not appear to be threatened by fishery
activities at present and has been assessed as Least Concern
by the International Union for Conservation of Nature (IUCN).
of Japan
, was presented to American ichthyologists David Starr Jordan
and John Otterbein Snyder
by Alan Owston, a shipmaster from Yokohama
. Jordan and Snyder described the species as Pristiurus eastmani in a 1904 volume of the scientific journal
Smithsonian Miscellaneous Collections. Later authors have recognized Pristiurus as a junior synonym of Galeus
. A 2005 phylogenetic analysis, based on mitochondrial
and nuclear DNA
, found that this species, G. gracilis
, and G. sauteri
form a clade
apart from G. melastomus
and G. murinus
.
and Mie Prefecture
s of Honshu
and the main islands of Shikoku
and Kyushu
, to the East China Sea
including Taiwan
. It is extremely abundant in Japanese waters. Further records from off Vietnam
may be erroneous. This species is found in water 100–900 m (328.1–2,952.8 ft) deep, on or close to the sea floor. It seems to exhibit strong spatial segregation by sex.
s (protective third eyelids) and indistinct ridges underneath. The mouth is sizable and forms a long arch; there are well-developed furrows around the corners. The teeth are small and number around 47 rows in the upper jaw and 50 rows in the lower jaw; each has a narrow central cusp and typically two pairs of smaller cusplets on the sides. The five pairs of gill slit
s are short, with the fourth pair about level with the pectoral fin origins.
The first dorsal fin
has a blunt apex and is positioned over the latter half of the pelvic fin bases. The second dorsal fin resembles the first but is slightly smaller, and is positioned over the latter third of the anal fin base. The pectoral fins are rather large and broad, with rounded corners. The pelvic fins are small with angular margins; the claspers of adult males are short and do not reach the anal fin. The anal fin base measures roughly 12% of the total length, shorter than the distance between the dorsal fins but longer than the distance between the pelvic and anal fins. The caudal peduncle is almost cylindrical, and leads to a low caudal fin with a subtle lower lobe and a ventral notch near the tip of the upper lobe. The skin is covered by small, overlapping dermal denticles; each has a leaf-shaped crown with a horizontal ridge and three marginal teeth. There is a crest of enlarged denticles along the upper edge of the caudal fin. This species is grayish above and patterned with darker, fuzzy-edged saddles and blotches along the body and tail. The underside, dorsal and caudal fin trailing margins, and interior of the mouth are white.
in nature, the gecko catshark feeds opportunistically on a wide variety of bony fishes (including lanternfish
), cephalopod
s (including sepiolid
and enoploteuthid
squid
), and crustacean
s (including isopods, amphipods, krill
, and decapod
s). The relative importance of the three prey categories varies between geographical areas and seasons, likely reflecting what is most available in the environment. This species is oviparous; adult females have a single functional ovary
, on the right, and two functional oviduct
s. A single egg matures within each oviduct at a time. Mature eggs are contained within smooth, translucent yellow, vase-shaped capsules measuring roughly 6 cm (2.4 in) long and 1.6 cm (0.62992125984252 in) across, with the top squared off and the bottom converging on a short projection. One study in Suruga Bay
recorded females with large yolked ova
inside the ovary year-round, but females in the western part of the bay were only found to carry egg cases from October to January, suggesting that the interval between egg depositions is shorter at that time. Males and females attain sexual maturity
at approximately 31 – and 36 – long respectively. However, there is a Taiwanese record of an immature male 38 cm (15 in) long.
by commercial
trawl fisheries. In Taiwan, it is occasionally brought to market and processed into fishmeal for aquacultural
use. This species' small size and oviparous mode of reproduction may make it more resilient to fishing pressure than other sharks. As the gecko catshark remains common off Japan and may be protected from fishing in the deeper parts of its range, the International Union for Conservation of Nature (IUCN) has assessed it as of Least Concern
.
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, native to 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 southern Japan
Japan
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...
to Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
, and possibly also off Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
. It is a common, demersal species found at depths of 100–900 m (328.1–2,952.8 ft). Its body is slender, with a pattern of dark saddles and blotches. The dorsal
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...
and caudal fins are edged in white, and there is a prominent crest of enlarged dermal denticles along the dorsal edge of the caudal fin. The gecko catshark is a schooling
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...
, opportunistic predator of bony fishes, 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, and 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 is oviparous, with females producing two vase-shaped egg capsules at a time. This species is captured as 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 does not appear to be threatened by 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,...
activities at present and 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).
Taxonomy and phylogeny
The first known specimen of the gecko catshark, a 35 cm (13.8 in) long female caught off the Izu PeninsulaIzu Peninsula
The is a large mountainous peninsula with deeply indented coasts to the west of Tokyo on the Pacific coast of the island of Honshū, Japan. Formerly the eponymous Izu Province, Izu peninsula is now a part of Shizuoka Prefecture...
of Japan
Japan
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...
, was presented to American ichthyologists David Starr Jordan
David Starr Jordan
David Starr Jordan, Ph.D., LL.D. was a leading eugenicist, ichthyologist, educator and peace activist. He was president of Indiana University and Stanford University.-Early life and education:...
and John Otterbein Snyder
John Otterbein Snyder
John Otterbein Snyder was an American zoologist.As a student he met David Starr Jordan who inspired him to enter zoology. He eventually became a zoology instructor at Stanford University and served there from 1899 until 1943. He went on several major collecting expeditions aboard the USS Albatross...
by Alan Owston, a shipmaster from Yokohama
Yokohama
is the capital city of Kanagawa Prefecture and the second largest city in Japan by population after Tokyo and most populous municipality of Japan. It lies on Tokyo Bay, south of Tokyo, in the Kantō region of the main island of Honshu...
. Jordan and Snyder described the species as Pristiurus eastmani in a 1904 volume 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...
Smithsonian Miscellaneous Collections. Later authors have recognized Pristiurus as a junior synonym of Galeus
Galeus
Galeus is a genus of catshark, family Scyliorhinidae, commonly known as sawtail catsharks in reference to a distinctive saw-toothed crest of enlarged dermal denticles found along the upper edges of their caudal fins. They are found in the Atlantic, the western and central Pacific, and the Gulf of...
. A 2005 phylogenetic analysis, based on mitochondrial
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
and nuclear DNA
Nuclear DNA
Nuclear DNA, nuclear deoxyribonucleic acid , is DNA contained within a nucleus of eukaryotic organisms. In mammals and vertebrates, nuclear DNA encodes more of the genome than the mitochondrial DNA and is composed of information inherited from two parents, one male, and one female, rather than...
, found that this species, G. gracilis
Slender sawtail catshark
The slender sawtail catshark is a little-known species of catshark, family Scyliorhinidae, endemic to northern Australia. It is found over the continental slope in on water...
, and G. sauteri
Blacktip sawtail catshark
The blacktip sawtail catshark is a species of catshark, family Scyliorhinidae, found off Taiwan and the Philippines. It is demersal in nature and occurs deeper than...
form a 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 G. melastomus
Blackmouth catshark
The blackmouth catshark is a species of catshark, family Scyliorhinidae, common in the northeastern Atlantic Ocean from Iceland to Senegal, including the Mediterranean Sea. It is typically found over the continental slope at depths of , on or near muddy bottoms. The youngest sharks generally...
and G. murinus
Mouse catshark
The mouse catshark is a species of catshark, family Scyliorhinidae, common in the northeastern Atlantic Ocean, from Iceland to Western Sahara. There is much taxonomic confusion regarding this species in Icelandic waters, where it may be confounded with another species of Galeus or Apristurus...
.
Distribution and habitat
The range of the gecko catshark extends from southern Japan, where it occurs off the ShizuokaShizuoka Prefecture
is a prefecture of Japan located in the Chūbu region on Honshu island. The capital is the city of Shizuoka.- History :Shizuoka prefecture was formed from the former Tōtōmi, Suruga and Izu provinces.The area was the home of the first Tokugawa Shogun...
and Mie Prefecture
Mie Prefecture
is a prefecture of Japan which is part of the Kansai regions on Honshū island. The capital is the city of Tsu.- History :Until the Meiji Restoration, Mie prefecture was known as Ise Province and Iga Province....
s of Honshu
Honshu
is the largest island of Japan. The nation's main island, it is south of Hokkaido across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyushu across the Kanmon Strait...
and the main islands of Shikoku
Shikoku
is the smallest and least populous of the four main islands of Japan, located south of Honshū and east of the island of Kyūshū. Its ancient names include Iyo-no-futana-shima , Iyo-shima , and Futana-shima...
and Kyushu
Kyushu
is the third largest island of Japan and most southwesterly of its four main islands. Its alternate ancient names include , , and . The historical regional name is referred to Kyushu and its surrounding islands....
, to the East China Sea
East China Sea
The East China Sea is a marginal sea east of China. It is a part of the Pacific Ocean and covers an area of 1,249,000 km² or 750,000 square miles.-Geography:...
including Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
. It is extremely abundant in Japanese waters. Further records from off Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
may be erroneous. This species is found in water 100–900 m (328.1–2,952.8 ft) deep, on or close to the sea floor. It seems to exhibit strong spatial segregation by sex.
Description
Attaining 40 cm (15.7 in), possibly 50 cm (19.7 in) in length, the gecko catshark has a slim, firm body and a fairly short head that comprises less than one-fifth of the total length. The snout is flattened with a blunt tip. The nostrils are large and divided by triangular flaps of skin on their anterior rims. The eyes are large and horizontally oval, 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 indistinct ridges underneath. The mouth is sizable and forms a long arch; there are well-developed furrows around the corners. The teeth are small and number around 47 rows in the upper jaw and 50 rows in the lower jaw; each has a narrow central cusp and typically two pairs of smaller cusplets on the 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, with the fourth pair about level with the pectoral fin origins.
The first 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...
has a blunt apex and is positioned over the latter half of the pelvic fin bases. The second dorsal fin resembles the first but is slightly smaller, and is positioned over the latter third of the anal fin base. The pectoral fins are rather large and broad, with rounded corners. The pelvic fins are small with angular margins; the claspers of adult males are short and do not reach the anal fin. The anal fin base measures roughly 12% of the total length, shorter than the distance between the dorsal fins but longer than the distance between the pelvic and anal fins. The caudal peduncle is almost cylindrical, and leads to a low caudal fin with a subtle lower lobe and a ventral notch near the tip of the upper lobe. The skin is covered by small, overlapping dermal denticles; each has a leaf-shaped crown with a horizontal ridge and three marginal teeth. There is a crest of enlarged denticles along the upper edge of the caudal fin. This species is grayish above and patterned with darker, fuzzy-edged saddles and blotches along the body and tail. The underside, dorsal and caudal fin trailing margins, and interior of the mouth are white.
Biology and ecology
SchoolingShoaling 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...
in nature, the gecko catshark feeds opportunistically on a wide variety of bony fishes (including 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...
), 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 (including sepiolid
Sepiolidae
Sepiolidae is a family of bobtail squid encompassing 15 genera in three or four subfamilies....
and enoploteuthid
Enoploteuthidae
Enoploteuthidea is a family of squid comprising approximately 40 species in 4 genera. Most species have a mantle length ranging from 3-13 cm. Hooks are present on all arms and tentacles...
squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
), and 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 isopods, amphipods, krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
, 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...
s). The relative importance of the three prey categories varies between geographical areas and seasons, likely reflecting what is most available in the environment. This species 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...
, on the right, 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. A single egg matures within each oviduct at a time. Mature eggs are contained within smooth, translucent yellow, vase-shaped capsules measuring roughly 6 cm (2.4 in) long and 1.6 cm (0.62992125984252 in) across, with the top squared off and the bottom converging on a short projection. One study in Suruga Bay
Suruga Bay
Suruga Bay is a bay on the Pacific coast of Honshū in Shizuoka Prefecture, Japan. It is situated north of an imaginary line joining Omaezaki Point and Irōzaki Point at the tip of the Izu Peninsula and surrounded by Honshū to the southwest and west and the Izu Peninsula to the east.-Geology:Suruga...
recorded females with large yolked 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...
inside the ovary year-round, but females in the western part of the bay were only found to carry egg cases from October to January, suggesting that the interval between egg depositions is shorter at that time. Males and females attain 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 31 – and 36 – long respectively. However, there is a Taiwanese record of an immature male 38 cm (15 in) long.
Human interactions
Uncertain numbers of gecko catsharks are 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...
by commercial
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...
trawl fisheries. In Taiwan, it is occasionally brought to market and processed into fishmeal for aquacultural
Aquaculture
Aquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the...
use. This species' small size and oviparous mode of reproduction may make it more resilient to fishing pressure than other sharks. As the gecko catshark remains common off Japan and may be protected from fishing in the deeper parts of its range, the International Union for Conservation of Nature (IUCN) has assessed it as of 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...
.