The ploughfish (''Gymnodraco acuticeps'') is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

Antarctic dragonfish The Bathydraconidae, or the Antarctic dragonfishes, are a family of marine ray-finned fishes, notothenioids belonging to the Perciform suborder Notothenioidei. The family comprises four genera. These fishes are endemic to deep waters off Antarcti ...

native to the

Southern Ocean The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-small ...

around

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...

. It is found at depths of from over the

Antarctic The Antarctic ( or , American English also or ; commonly ) is a polar region around Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica, the Kerguelen Plateau and other ...

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 island ...

. This species is the only known member of its

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Taxonomy

The ploughfish was first formally described in 1902 by the Belgian-born British

ichthyologist Ichthyology is the branch of zoology devoted to the study of fish, including bony fish ( Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 33,400 species of fish had been described as of Octobe ...

George Albert Boulenger George Albert Boulenger (19 October 1858 – 23 November 1937) was a Belgian-British zoologist who described and gave scientific names to over 2,000 new animal species, chiefly fish, reptiles, and amphibians. Boulenger was also an active botani ...

with the type locality given as

Cape Adare Cape Adare is a prominent cape of black basalt forming the northern tip of the Adare Peninsula and the north-easternmost extremity of Victoria Land, East Antarctica. Description Marking the north end of Borchgrevink Coast and the west e ...

in Antarctica, Boulenger placed this species in a new monotypic genus ''Gymnodraco'', it is still the only known species in that genus. The genus name is a compound of ''gymnos'' which means "bare" or "naked", a reference to the almost complete lack of scales on the body, and ''draco'' meaning "dragon" and is a common suffix used for notothenioid fish names. The specific name ''acuticeps'' means "pointed head" an allusion to the strongly depressed head with its sharply pointed snout.

Description

The ploughfish has a naked body, the only scales being those on the two

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

s with the middle lateral line only has perforated scales, which is depressed at the head and compressed towards the tail. The head is triangular in shape with a long, pointed snout. There is a strong ridge on the operculum which forms a spine with a hooked process at its rear end and there is another spine on the soboperclulum and the preoperculum is smooth. The jaws have canine-like teeth at the

mandibular symphysis In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: ''symphysis menti'') or line of junction where the two lateral halves ...

, with bands of small, slightly decurved conical teeth behind them. The lower jaw protrudes beyond the upper with its front canine-like teeth exposed. There are 27-30 soft rays in the

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

and 23-26 in the

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

. In alcohol the overall colour of the body is dark brown, becoming paler on the underside. The head is marked with small spots and the body with dark blotches, although these may fade over time. The fins are dark brown to blackish and there is a patch of dark colour around the

anus The anus (Latin, 'ring' or 'circle') is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, the residual semi-solid waste that remains after food digestion, which, d ...

. This species attains a maximum

total length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish ...

of and a maximum weight of .

Distribution and habitat

The ploughfish is found in the Southern Ocean and has been recorded from the

Antarctic Peninsula The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martín in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctic ...

South Shetland Islands The South Shetland Islands are a group of Antarctic islands with a total area of . They lie about north of the Antarctic Peninsula, and between southwest of the nearest point of the South Orkney Islands. By the Antarctic Treaty of 195 ...

and the

of Antarctica, it probably has a circum-Antarctic range. However, as yet, it has not been recorded from West Antarctica. This is a

demersal The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of ...

species which is found at depths of , although it is rare below .

Biology

Ploughfish spawn during September off

Adelie Land Adelie or Adélie may refer to: * Adélie Land, a claimed territory on the continent of Antarctica * Adelie Land meteorite, a meteorite discovered on December 5, 1912, in Antarctica by Francis Howard Bickerton * Adélie penguin, a species of pengui ...

and hatching probably occurs in the Spring as larvae with a length of were collected in the

Bransfield Strait Bransfield Strait or Fleet Sea ( es, Estrecho de Bransfield, Mar de la Flota) is a body of water about wide extending for in a general northeast – southwest direction between the South Shetland Islands and the Antarctic Peninsula. History ...

in mid-November and juveniles have been taken as

bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

krill Krill are small crustaceans of the order Euphausiacea, and are found in all the world's oceans. The name "krill" comes from the Norwegian Norwegian, Norwayan, or Norsk may refer to: *Something of, from, or related to Norway, a country in n ...

catches in February and March. Females have around 5,000 eggs in each ovary and when ripe they have a diameter of . Studies of diet have found that off the South Shetland ISlands they ate only the krill species '' Euphasia superba'' but in

McMurdo Sound McMurdo Sound is a sound in Antarctica. It is the southernmost navigable body of water in the world, and is about from the South Pole. Captain James Clark Ross discovered the sound in February 1841, and named it after Lt. Archibald McMurdo o ...

their diet was more varied and included mostly fish, with amphipods being the next most important food type, then fish eggs and then polychaetes. The fish taken included '' Pleuragramma antarcticum'', ''

Pagothenia borchgrevinki The bald notothen (''Pagothenia borchgrevinki''), also known as the bald rockcod, is a species of marine ray-finned fish belonging to the family Nototheniidae, the notothens or cod icefishes. It is native to the Southern Ocean. Taxonomy The bald ...

'' and ''

Trematomus nicolai ''Trematomus'' is a genus of marine ray-finned fishes, belonging to the family Nototheniidae, the notothens or cod icefishes. These fishes occur in the Southern Ocean. Taxonomy ''Trematomus'' was first described as a genus in 1902 by the Belgian ...

''.

References

{{Taxonbar, from=Q2774269 Bathydraconidae Monotypic fish genera Fish of the Southern Ocean Fish of Antarctica Fish described in 1902 Taxa named by George Albert Boulenger