The longfin icedevil (''Aethotaxis mitopteryx''), also known as the threadfin pinhead, 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 ...

of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

belonging to the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Nototheniidae : ''In some scientific literature, the term "cod icefish" is used to identify members of this family. This should not be confused with the term "icefish," which refers to the "white-blooded" fishes of the family Channichthyidae. See Icefish (disam ...

, the notothens or cod icefishes. It is 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 ...

where it can be found at depths down to . This species grows to a length of TL. 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 ...

and is of no interest to

commercial fisheries 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 ...

Taxonomy

The longfin icedevil was first formally described in 1962 by the American

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 ...

Hugh H. DeWitt with the type locality given as off

Pram Point Hut Point Peninsula () is a long, narrow peninsula from wide and long, projecting south-west from the slopes of Mount Erebus on Ross Island, Antarctica. McMurdo Station (US) and Scott Base (NZ) are Antarctic research stations located on the ...

Ross Island Ross Island is an island formed by four volcanoes in the Ross Sea near the continent of Antarctica, off the coast of Victoria Land in McMurdo Sound. Ross Island lies within the boundaries of Ross Dependency, an area of Antarctica claimed by New ...

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 ...

, Antarctica at 77°53'S, 166°44'E, the type being picked up dead at the surface. Dewitt placed the new species in the monotypic genus ''Aethotaxis'' in which it is still the only species. The species is sometimes split into 2 subspecies, with ''A.m. pawsoni'' proposed as a subspecies in the

Weddell Sea The Weddell Sea is part of the Southern Ocean and contains the Weddell Gyre. Its land boundaries are defined by the bay formed from the coasts of Coats Land and the Antarctic Peninsula. The easternmost point is Cape Norvegia at Princess Martha ...

and the

Scotia Sea The Scotia Sea is a sea located at the northern edge of the Southern Ocean at its boundary with the South Atlantic Ocean. It is bounded on the west by the Drake Passage and on the north, east, and south by the Scotia Arc, an undersea ridge and i ...

but this requires more evidence. Some authorities place this taxon in the

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...

Pleuragrammatinae, but the 5th edition of ''

Fishes of the World ''Fishes of the World'' by the American ichthyologist Joseph S. Nelson (1937–2011) is a standard reference for fish systematics. Now in its fifth edition (2016), the work is a comprehensive overview of the diversity and classification of the ...

'' does not include subfamilies in the Nototheniidae. The genus name ''Aethotaxis'' is a compound of ''ethes'', which means "unusual" or "strange", and ''taxis'' meaning "line" an allusion to the unusual

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 ...

system in which the upper lateral line curves up nearly vertically for a short distance beneath the forward rays of the second

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 ...

before suddenly turning towards the

caudal 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 ...

. The specific name ''mitopteryx'' compounds ''mitos'' meaning "thread" or "string" with "pteryx" meaning "fin" a reference to the filaments extending out from the first dorsal and

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

Description

The longfin icedevil has an elongated, moderately compressed body with a flattened head with a long snout. The large mouth is oblique with a projecting lower jaw, both jaws are equipped with a thin band of villiform teeth. The sensory canals on the head are enlarged, their pores are large holes or pits. They have an upper lateral line made up of tubed scales which curves steeply upward below forward rays of the second dorsal fin, then turns sharply towards the rear running close to the base of the second dorsal fin and extending to just underneath the rearmost rays of that fin. They also have a middle and lower lateral line. There are no scales on the snout, in fronmt of the eyes or on the top of the head. The first dorsal fin contains 7 rays, the first two of which are extended into long filaments. The second dorsal fin has 34 soft rays and 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 ...

has 30. The uppermost ray of each pelvic fin are also elongated into filaments. The caudal fin is rounded. This species attains a maximum total length of . They are grey in colour with a violet tint, paler below with a metallic sheen.

Distribution and habitat

The longfin icedevil is found in the Southern Ocean where it has been recorded from the islands of the Scotia Sea, Weddell Sea,

Prydz Bay Prydz Bay is a deep embayment of Antarctica between the Lars Christensen Coast and Ingrid Christensen Coast. The Bay is at the downstream end of a giant glacial drainage system that originates in the East Antarctic interior. The Lambert Glacie ...

and the

Ross Sea The Ross Sea is a deep bay of the Southern Ocean in Antarctica, between Victoria Land and Marie Byrd Land and within the Ross Embayment, and is the southernmost sea on Earth. It derives its name from the British explorer James Clark Ross who vi ...

. It is a

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...

fish which is found af depths down to .

Biology

The longfin icedevil stores

lipids Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...

in their

adipose Adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular ...

tissue and have reduced

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...

in their bones to help their buoyancy. This species is thought to be pelagic but some studies have suggested that it is a

benthopelagic 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 ...

sit and wait predator which will venture into the pelagic zone. It does not uses its pectoral fins to rest on the bottom as the rays are too soft but uses them for swimming rather than the caudal fin. Larval fish are more abundany in different areas from the adults suggesting that a

spawning Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of releasing the eggs and sperm, and the act of both sexes is called spawning. Most aquatic animals, except for aquati ...

migration is undertaken. Their characteristics of their blood suggest that they have a slow growth and rather slow lifestyle, adapted to reduce the fish's energy requirements. These fishes have a high reproductive rate and reach early sexual maturity but have a long lifespan.

References

{{Taxonbar, from=Q10402021 Nototheniidae Fish described in 1962 Fish of the Southern Ocean Monotypic fish genera Taxa named by H. H. DeWitt