Razorback scabbardfish
Encyclopedia
The razorback scabbardfish, Assurger anzac, is a rare species of cutlassfish
, family Trichiuridae, and the only member of its genus. It has been caught from scattered locations worldwide: in the Atlantic Ocean
it is known from off Puerto Rico
, Uruguay
, and the Walvis Ridge, in the Indian Ocean
it is known from off western Australia
, and in the Pacific Ocean
it is known from off New Guinea
, southern Japan
, Midway Island, California
, and the Nazca and Sala y Gomez Ridges. Adults are thought to be benthopelagic, occurring at a depth of 150-400 meters (490-1,300 ft), while juveniles are found near the surface or in midwater.
This fish has a very long and thin body, measuring 25 to 28 times as long as deep and 12 to 14 times as long as the head. The dorsal profile of the head is straight or slightly convex, with a prominent sagittal crest. The eye
diameter is about one-eighth the head length. The lower jaw juts out past the upper, and both jaws are tipped with a short dermal process. There are three pairs of fangs at the front of the jaws. The dorsal fin
is very long, containing a few weak spines at the front followed by 116-123 soft rays. The origin of the anal fin lies beneath the 42nd to 44th dorsal fin ray; the anal fin contains 74-87 elements but only 14-17 have external rays, led by 2 small spines. The pelvic fins are reduced to only 1 scale-like spine and 1 soft ray, placed beneath the 8th or 9th dorsal fin ray. A tiny forked caudal fin is present. The coloration is silver, with the front of the dorsal fin membrane black until the 3rd or 4th soft ray.
The razorback scabbardfish attains a maximum length of 2.5 meters (8.2 ft). Its diet consists of fish
es, such as the Californian anchovy (Engraulis mordax) and the North Pacific hake
(Merluccius productus), and squid
. The only known parasite of the razorback scabbardfish is the copepod
Avitocaligus assurgericola. Reproduction is presumably oviparous with pelagic eggs
and larvae as with other members of the family, though eggs and newly hatched larvae
have not been described. Flexion (the bending of the notochord
as part of caudal fin formation) occurs at around a length of 14 mm (0.55 in). Post-flexion larvae have slender bodies and pointed heads, with the pelvic and first dorsal spines elongated. They can be distinguished by the presence of pigment on the top of the head, snout, and opercles. This species is not targeted by fisheries; it is sometimes hooked or netted, or found washed ashore.
Cutlassfish
The cutlassfishes are about 40 species of predatory fish in the family Trichiuridae found in seas throughout the world. Fish of this family are long, slender, and generally steely blue or silver in colour, giving rise to their name...
, family Trichiuridae, and the only member of its genus. It has been caught from scattered locations worldwide: in the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
it is known from off Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
, Uruguay
Uruguay
Uruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...
, and the Walvis Ridge, in the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
it is known from off western Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, and in the 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...
it is known from off New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
, 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...
, Midway Island, California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, and the Nazca and Sala y Gomez Ridges. Adults are thought to be benthopelagic, occurring at a depth of 150-400 meters (490-1,300 ft), while juveniles are found near the surface or in midwater.
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...
diameter is about one-eighth the head length. The lower jaw juts out past the upper, and both jaws are tipped with a short dermal process. There are three pairs of fangs at the front of the jaws. The 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 long, containing a few weak spines at the front followed by 116-123 soft rays. The origin of the anal fin lies beneath the 42nd to 44th dorsal fin ray; the anal fin contains 74-87 elements but only 14-17 have external rays, led by 2 small spines. The pelvic fins are reduced to only 1 scale-like spine and 1 soft ray, placed beneath the 8th or 9th dorsal fin ray. A tiny forked caudal fin is present. The coloration is silver, with the front of the dorsal fin membrane black until the 3rd or 4th soft ray.
The razorback scabbardfish attains a maximum length of 2.5 meters (8.2 ft). Its diet consists of 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, such as the Californian anchovy (Engraulis mordax) and the North Pacific hake
North Pacific hake
The North Pacific hake, Pacific hake, or Pacific whiting, Merluccius productus, is a merluccid hake of the genus Merluccius, found in the north east Pacific Ocean from northern Vancouver Island to the northern part of the Gulf of California....
(Merluccius productus), and 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...
. The only known parasite of the razorback scabbardfish is 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,...
Avitocaligus assurgericola. Reproduction is presumably oviparous with pelagic eggs
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...
and larvae as with other members of the family, though eggs and newly hatched larvae
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...
have not been described. Flexion (the bending of the notochord
Notochord
The notochord is a flexible, rod-shaped body found in embryos of all chordates. It is composed of cells derived from the mesoderm and defines the primitive axis of the embryo. In some chordates, it persists throughout life as the main axial support of the body, while in most vertebrates it becomes...
as part of caudal fin formation) occurs at around a length of 14 mm (0.55 in). Post-flexion larvae have slender bodies and pointed heads, with the pelvic and first dorsal spines elongated. They can be distinguished by the presence of pigment on the top of the head, snout, and opercles. This species is not targeted by fisheries; it is sometimes hooked or netted, or found washed ashore.