Whitefin dogfish
Encyclopedia
The whitefin dogfish is a species of deep-sea dogfish shark in the family Etmopteridae
. It has only been found in the northwest Pacific Ocean
off the southeastern coast of Japan
, between the latitude
s of 35°N
and 32°N
. It inhabits continental slopes and seamount
s at a depth of 320 to 1,100 m (1,050–3,610 ft). Reproduction is ovoviviparous. It is of no interest to fisheries and almost nothing is known of its biology. The specific epithet ritteri is in honor of Dr. William Emerson Ritter
of the University of California
.
The largest known example of this shark measured 43 cm (17 in) long. It has an elongated body with a broad, flattened head and a moderately long snout. The eye
s and spiracle
s are large. The mouth is broadly arched, containing many teeth with narrow cusps and lateral cusplets. There are two roughly equal-sized dorsal fin
s with grooved spines; the second spine is longer than the first and slightly curved. The pectoral fins are short and broad, not reaching the first dorsal fin base when folded back. The pelvic fins are small and placed forward of the second dorsal fin. There is no anal fin; the caudal peduncle is long, leading to an asymmetrical caudal fin.
This shark is distinctive in being the only Centroscyllium species with abrupt black markings beneath its head, trunk, and pectoral fins, with a black stripe running from under the caudal peduncle to over the pelvic fins. These markings are in fact concentrations of tiny light-emitting photophore
s. Unusually, this shark also has photophores along the underside of its upper eyelid
s. What function these structures could serve is unclear; Tchernavin
speculated that they could be used to illuminate prey or stimulate the eye. The rest of the body is gray-brown, with white fin margins. There are numerous small cone-shaped, hooked prickles over the body, except for under the snout.
Etmopteridae
Etmopteridae is a family of sharks in the order Squaliformes, commonly known as lantern sharks. Their name comes from the presence of light-producing photophores on their bodies. The members of this family are small, under long, and are found in deep waters worldwide. There are 45 species in five...
. It has only been found in the northwest 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 southeastern coast 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...
, between the latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
s of 35°N
35th parallel north
The 35th parallel north is a circle of latitude that is 35 degrees north of the Earth's equatorial plane. It crosses Africa, the Mediterranean Sea, Asia, the Pacific Ocean, North America and the Atlantic Ocean....
and 32°N
32nd parallel north
The 32nd parallel north is a circle of latitude that is 32 degrees north of the Earth's equatorial plane. It crosses Africa, Asia, the Pacific Ocean, North America and the Atlantic Ocean....
. It inhabits continental slopes and seamount
Seamount
A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface , and thus is not an island. These are typically formed from extinct volcanoes, that rise abruptly and are usually found rising from a seafloor of depth. They are defined by oceanographers as...
s at a depth of 320 to 1,100 m (1,050–3,610 ft). Reproduction is ovoviviparous. It is of no interest to fisheries and almost nothing is known of its biology. The specific epithet ritteri is in honor of Dr. William Emerson Ritter
William Emerson Ritter
William Emerson Ritter, Ph.D. was an American biologist. Ritter initiated and shaped the Marine Biological Association of San Diego and the American Society for the Dissemination of Science...
of the University of California
University of California
The University of California is a public university system in the U.S. state of California. Under the California Master Plan for Higher Education, the University of California is a part of the state's three-tier public higher education system, which also includes the California State University...
.
The largest known example of this shark measured 43 cm (17 in) long. It has an elongated body with a broad, flattened head and a moderately long snout. The eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
s and 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 are large. The mouth is broadly arched, containing many teeth with narrow cusps and lateral cusplets. There are two roughly equal-sized 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 grooved spines; the second spine is longer than the first and slightly curved. The pectoral fins are short and broad, not reaching the first dorsal fin base when folded back. The pelvic fins are small and placed forward of the second dorsal fin. There is no anal fin; the caudal peduncle is long, leading to an asymmetrical caudal fin.
This shark is distinctive in being the only Centroscyllium species with abrupt black markings beneath its head, trunk, and pectoral fins, with a black stripe running from under the caudal peduncle to over the pelvic fins. These markings are in fact concentrations of tiny light-emitting photophore
Photophore
A photophore is a light-emitting organ which appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors...
s. Unusually, this shark also has photophores along the underside of its upper eyelid
Eyelid
An eyelid is a thin fold of skin that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The levator palpebrae superioris muscle retracts the eyelid to "open" the eye. This can be either voluntarily or involuntarily...
s. What function these structures could serve is unclear; Tchernavin
Vladimir V. Tchernavin
Vladimir V. Tchernavin was a Russian-born ichthyologist who became famous as one of the first and few prisoners of the Soviet Gulag system who managed to escape abroad.-Early life:Tchernavin was born in 1887 into a noble family of modest means...
speculated that they could be used to illuminate prey or stimulate the eye. The rest of the body is gray-brown, with white fin margins. There are numerous small cone-shaped, hooked prickles over the body, except for under the snout.