''Cryothenia amphitreta'' 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 found in 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 ...

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 ...

Taxonomy

''Cryothenia amphitreta'' was first formally described in 2006 by Paul A. Cziko and Chi-Hing "Christina" Cheng with the type locality given as the saltwater intake jetty of the McMurdo Station, located at 77°51.033'S, 166°39.759'W, on the eastern

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 ...

part of the

off Antarctica. It was the second species to be classified within the

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 ...

Cryothenia ''Cryothenia'' is a genus of marine ray-finned fishes, belonging to the family Nototheniidae, the notothens or cod icefishes. They are native to the Southern Ocean. Taxonomy ''Cryothenia'' was first formally described as a genus in 1981 by Rober ...

''. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

''amphitreta'' means an ‘‘an orifice with two openings,’’ an allusion to the morphology of the sensory pits between the eyes, being a feature that identifies C. amphitreta compared to '' C. peninsulae''.

Description

''Cryothenia amphitreta'' is distinguished from ''C. peninsulae'' by the shorter

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 ...

s which extend only as far as roughly halfway from the pelvic-fin base to origin of 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 ...

, and 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 ...

being inserted to the front of the

origin. It has large pores on the

lateral lines Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction *Lateral cricoarytenoid muscle *Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral cons ...

of the head. The fourth pore of the supraorbital canal opens into a central, clearly-defined, depressed pit between the eyes which is divided through its centre by a slightly raised ridge. The width of the concave interorbital area is greater than its length which does not extend farther forward than the third supraorbital canal pore. The lining of the mouth, gill cavities, and peritoneum are black. The first dorsal fin has six spines, the second dorsal fin has 38 rays and the anal fin has 35 rays. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

had a

standard 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 m ...

of suggesting that this is a larger species than ''C. peninsulae''. The living holotype was overall bronze-coloured with silver undertones and an obvious iridescence. There were a small number of vague darker blotches on the back and underneath the

pectoral 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 ...

. The first dorsal fin is blackish while the caudal fin and pectoral fins are plain and dark. The remaining fins become blackish towards their margins and the anal fin has irregular dark blotches.

Distribution, habitat and biology

''Cryothenia amphitreta'' has only being recorded in the McMurdo Sound and it is regarded as likely to be pelagic or epibenthic. This species was found to have blood which contained a high level of

antifreeze protein Antifreeze proteins (AFPs) or ice structuring proteins refer to a class of polypeptides produced by certain animals, plants, fungi and bacteria that permit their survival in temperatures below the freezing point of water. AFPs bind to small i ...

s, but this has not been tested for ''C. peninsulae''.

References

External links

Researchers Discover New Species Of Fish In Antarctic
''innovations report'', 20 December 2006. {{Taxonbar, from=Q2281769 Nototheniidae Fish of Antarctica Fish described in 2006