Japanese bullhead shark
Encyclopedia
The Japanese bullhead shark (Heterodontus japonicus) is a species
of bullhead shark
, family
Heterodontidae, found in the northwestern Pacific Ocean
off the coasts of Japan
, Korea
, and China
. This benthic shark occurs at depths of 6–37 m (19.7–121.4 ft) over rocky bottoms or kelp beds. Measuring up to 1.2 m (3.9 ft) long, it can be identified by its short, blunt head, two high dorsal fin
s with anterior spines, and pattern of irregularly shaped, vertical brown bands and stripes. The Japanese bullhead shark is a docile, slow-swimming species that feeds mainly on shelled invertebrate
s and small bony fishes. Reproduction is oviparous, with females laying spiral-flanged eggs in communal "nests". This species is of little interest to fisheries.
, in a 1884 volume of Proceedings of the Linnean Society of New South Wales. The type specimen is a female caught off Tokyo
, Japan
. Other common name
s used for this species include bull head, cat shark, Japanese horn shark, Cestracion shark, and Port Jackson shark (which usually refers to Heterodontus portusjacksoni).
to the Korean Peninsula
, and southward along the coast of China
to Taiwan
. There is a single, apparently erroneous, record from off East Africa
. This bottom-dwelling shark inhabits the continental shelf
at a depth of 6–37 m (19.7–121.4 ft), preferring areas covered by rocks, rocky reef
s, or kelp
.
and are followed by tiny spiracle
s. Shallow supraorbital ridge
s are present above the eyes, and the space between them is slightly concave. The nostril
s are divided into incurrent and excurrent openings by long flaps of skin that reach the mouth; the incurrent opening is encircled by a groove while another groove runs from the excurrent opening to the mouth. The small mouth is positioned nearly at the tip of the snout; the front teeth are small with a sharp central cusp flanked by a pair of lateral cusplets, while the back teeth are broad and rounded. There are deep furrows at the corners of the mouth, extending onto both jaws.
The first dorsal fin
is very large and high, and is somewhat falcate (sickle-shaped); it originates over the bases of the pectoral fins. The second dorsal fin is much smaller but similar in shape, and originates over the rear tips of the pelvic fins. Both dorsal fins bear stout spines on their leading edges. The pectoral fins are large; the pelvic fins are much smaller than the first dorsal fin. The anal fin is placed well in front of the caudal fin, which is broad with a short lower lobe and a long upper lobe bearing a strong ventral notch near the tip. The dermal denticles are large and rough, particularly on the sides of the body. The coloration is light brown, with a series of diffuse-edged, darker wide bands interspersed with narrower stripes from snout to tail, numbering 11–14 in all. There is a faint lighter band on top of the head between the eyes, and a darker blotch beneath each eye.
s, molluscs, small fish
es, and sea urchin
s, often hunting for them while "walking" along the sea bottom with alternating motions of its pectoral and pelvic fins. When prey is found, it is seized with highly protrusible jaws and ground to pieces with the molar
-like rear teeth. Known parasites of this species include the copepod
Dissonus pastinum, and the haemogregarine protozoa
n Haemogregarina heterodontii.
Like other members of its family, the Japanese bullhead shark is oviparous. Females produce large egg capsules
bearing thin flanges spiraling three times around the outside and a pair of short tendrils at the tip. The eggs are deposited at a depth of 8–9 m (26.2–29.5 ft) within beds of rock or kelp. Several females may spawn communally in a single "nest", which may contain up to 15 eggs total, though the females abandon the site afterward. In Japanese waters, females lay pairs of eggs 6–12 times between March and September, with a peak in spawning activity in March and April. The eggs take about a year to hatch; the newborns measure 18 cm (7.1 in) long. Young sharks have proportionately higher dorsal fins and a similar but brighter color pattern than adults. Males attain sexual maturity
at a length of 69 cm (27.2 in).
s. The conservation status of this species has not been evaluated by the International Union for Conservation of Nature (IUCN). It has apparently disappeared from offshore waters in the Bohai Sea
, possibly as a consequence of climate change
.
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 bullhead shark
Bullhead shark
The bullhead sharks are a small order of basal modern sharks . There are nine living species in a single genus, Heterodontus, in the family Heterodontidae. All are relatively small, with the largest species being just in adult length...
, 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...
Heterodontidae, found 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...
off the coasts 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...
, 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...
, and 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...
. This benthic shark occurs at depths of 6–37 m (19.7–121.4 ft) over rocky bottoms or kelp beds. Measuring up to 1.2 m (3.9 ft) long, it can be identified by its short, blunt head, two high 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 with anterior spines, and pattern of irregularly shaped, vertical brown bands and stripes. The Japanese bullhead shark is a docile, slow-swimming species that feeds mainly on shelled 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 small bony fishes. Reproduction is oviparous, with females laying spiral-flanged eggs in communal "nests". This species is of little interest to fisheries.
Taxonomy
The Japanese bullhead shark was originally described as Cestracion japonicus by ichthyologists Nicholas Miklouho-Maclay and William John MacleayWilliam John Macleay
Sir William John Macleay . was an Australian politician, zoologist and naturalist.-Early life:Macleay was born at Wick, Caithness, Scotland, second son of Kenneth Macleay of Keiss and his wife Barbara, née Horne...
, in a 1884 volume of Proceedings of the Linnean Society of New South Wales. The type specimen is a female caught off Tokyo
Tokyo
, ; officially , is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of Japan. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family...
, 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...
. Other common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
s used for this species include bull head, cat shark, Japanese horn shark, Cestracion shark, and Port Jackson shark (which usually refers to Heterodontus portusjacksoni).
Distribution and habitat
The range of the Japanese bullhead shark extends from 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...
to the Korean Peninsula
Korean Peninsula
The Korean Peninsula is a peninsula in East Asia. It extends southwards for about 684 miles from continental Asia into the Pacific Ocean and is surrounded by the Sea of Japan to the south, and the Yellow Sea to the west, the Korea Strait connecting the first two bodies of water.Until the end of...
, and southward along the coast of 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...
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...
. There is a single, apparently erroneous, record from off East Africa
East Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
. This bottom-dwelling shark inhabits 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,...
at a depth of 6–37 m (19.7–121.4 ft), preferring areas covered by rocks, rocky reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
s, or kelp
Kelp
Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....
.
Description
A modest-sized shark reaching a maximum known length of 1.2 m (3.9 ft), the Japanese bullhead shark has a cylindrical body with the short, wide head and blunt, pig-like snout typical of the bullhead sharks. The eyes lack a 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...
and are followed by tiny spiracle
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...
s. Shallow supraorbital ridge
Supraorbital ridge
The supraorbital ridge, or brow ridge, refer to a bony ridge located above the eye sockets of all primates. In Homo sapiens sapiens the eyebrows are located on their lower margin.Other terms in use are:* supraorbital arch...
s are present above the eyes, and the space between them is slightly concave. The nostril
Nostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
s are divided into incurrent and excurrent openings by long flaps of skin that reach the mouth; the incurrent opening is encircled by a groove while another groove runs from the excurrent opening to the mouth. The small mouth is positioned nearly at the tip of the snout; the front teeth are small with a sharp central cusp flanked by a pair of lateral cusplets, while the back teeth are broad and rounded. There are deep furrows at the corners of the mouth, extending onto both jaws.
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...
is very large and high, and is somewhat falcate (sickle-shaped); it originates over the bases of the pectoral fins. The second dorsal fin is much smaller but similar in shape, and originates over the rear tips of the pelvic fins. Both dorsal fins bear stout spines on their leading edges. The pectoral fins are large; the pelvic fins are much smaller than the first dorsal fin. The anal fin is placed well in front of the caudal fin, which is broad with a short lower lobe and a long upper lobe bearing a strong ventral notch near the tip. The dermal denticles are large and rough, particularly on the sides of the body. The coloration is light brown, with a series of diffuse-edged, darker wide bands interspersed with narrower stripes from snout to tail, numbering 11–14 in all. There is a faint lighter band on top of the head between the eyes, and a darker blotch beneath each eye.
Biology and ecology
The Japanese bullhead shark is a slow-moving predator that feeds on 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, molluscs, small 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 sea urchin
Sea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...
s, often hunting for them while "walking" along the sea bottom with alternating motions of its pectoral and pelvic fins. When prey is found, it is seized with highly protrusible jaws and ground to pieces with the molar
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
-like rear teeth. Known parasites of this species include the copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
Dissonus pastinum, and the haemogregarine protozoa
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...
n Haemogregarina heterodontii.
Like other members of its family, the Japanese bullhead shark is oviparous. Females produce large egg capsules
Mermaid's purse
An egg case or egg capsule, colloquially known as a mermaid's purse or devil's purse, is a casing that surrounds the fertilized eggs of some sharks, skates, and chimaeras. They are among the common objects which are washed up by the sea. They are made of collagen protein strands...
bearing thin flanges spiraling three times around the outside and a pair of short tendrils at the tip. The eggs are deposited at a depth of 8–9 m (26.2–29.5 ft) within beds of rock or kelp. Several females may spawn communally in a single "nest", which may contain up to 15 eggs total, though the females abandon the site afterward. In Japanese waters, females lay pairs of eggs 6–12 times between March and September, with a peak in spawning activity in March and April. The eggs take about a year to hatch; the newborns measure 18 cm (7.1 in) long. Young sharks have proportionately higher dorsal fins and a similar but brighter color pattern than adults. Males 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 a length of 69 cm (27.2 in).
Human interactions
Harmless to humans, the Japanese bullhead shark can be easily hand-caught by divers. It is of only minor fisheries interest as a source of food in Japan and likely elsewhere. It is also exhibited in Japanese public aquariumPublic aquarium
A public aquarium is the aquatic counterpart of a zoo, housing living aquatic species for viewing. Most public aquariums feature tanks larger than those kept by home aquarists, as well as smaller tanks. Since the first public aquariums were built in the mid-19th century, they have become popular...
s. The conservation status of this species has not been evaluated by the International Union for Conservation of Nature (IUCN). It has apparently disappeared from offshore waters in the Bohai Sea
Bohai Sea
Bohai Sea , also known as Bohai Gulf, Bohai, or Bo Hai, is the innermost gulf of the Yellow Sea on the coast of Northeastern and North China. It is approximately 78,000 km2 Bohai Sea , also known as Bohai Gulf, Bohai, or Bo Hai, is the innermost gulf of the Yellow Sea on the coast of...
, possibly as a consequence of climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
.