''Lycodichthys'' is a

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 ...

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 ...

Zoarcidae, the

eelpout The eelpouts are the ray-finned fish family Zoarcidae. As the common name suggests, they are somewhat eel-like in appearance. All of the roughly 300 species are marine and mostly bottom-dwelling, some at great depths. Eelpouts are predominantly ...

s. They are found in 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 ...

Taxonomy

''Lycodichthys'' was first proposed as a

monospecific genus In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

in 1911 by the German

zoologist Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the Animal, animal kingdom, including the anatomy, structure, embryology, evolution, Biological clas ...

when he described ''L. antarcticus'' giving its type locality as the Gauss winter station on the coast of

Kaiser Wilhelm II Land Kaiser Wilhelm II Land is a part of Antarctica lying between Cape Penck at 87° 43'E and Cape Filchner at 91° 54'E. Princess Elizabeth Land is located to the west, and Queen Mary Land to the east. The area is claimed by Australia as ...

in Antarctica. The American ichthyologist Hugh Hamilton DeWitt described ''Rhigophila dearbornii'' in 1962 but in 1988 this taxon was reviewed by the South African based American ichthyologist

M. Eric Anderson ( ; ; pl. ; ; 1512, from Middle French , literally "my lord") is an honorific title that was used to refer to or address the eldest living brother of the king in the French royal court. It has now become the customary French title of respec ...

and reclassified as the second species in ''Lycodichthys'', making ''Rhigophila'' as

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

of ''Lycodichthys''. This genus is classified 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 ...

Lycodinae, one of four subfamilies in the family Zoarcidae, the eelpouts.

Etymology

''Lycodichthys'' combines the name of the Northern genus ''

Lycodes ''Lycodes'' is a genus of Zoarcidae, zoarcid fish in the subfamily (biology), subfamily Lycodinae. It is the most species-rich genus in its family (biology), taxonomic family as well as in the Arctic Ocean and adjacent waters. They occupy both sh ...

'' with ''ichthys'', meaning "fish", as this genus closely resembles ''Lycodes'' in the shape of the body and fins.

Species

''Lycodichthys'' contains the following species:

Characteristics

''Lycodichthys'' eelpouts have robust bodies which have a depth which is equal to 8.4% to 12.7% of their

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 ...

. They have firm, thick skin and both scales and the

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 ...

are present. Pelvic fins can be either present or absent. There are five suborbital bones and five pores on the head. The gill slit does not typically extend as far as the lower edge of the base of the pectoral fin. There are no vomerine or palatine teeth. Both species within ''Lycodichthys'' are similar in size with maximum published of for ''L. antarcticus'' and for ''L. dearbornii''. The evolution of the antifreeze protein in ''L. dearborni'' provides a prime example of neofunctionalization after

gene duplication Gene duplication (or chromosomal duplication or gene amplification) is a major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene. ...

. In the case of the Antarctic zoarcid fish type III antifreeze protein gene (AFPIII; ) diverged from a paralogous copy of sialic acid synthase (SAS) gene. The ancestral SAS gene was found to have both sialic acid synthase and rudimentary ice-binding functionalities. After duplication one of the paralogs began to accumulate mutations that led to the replacement of SAS domains of the gene allowing for further development and optimization of the antifreeze functionality. The new gene is now capable of noncolligative freezing-point depression, and thus is neofunctionalized. This specialization allows Antarctic zoarcid fish to survive in the frigid temperatures of the Antarctic Seas.

Distribution and habitat

Lycodichthys are endemic to the waters of the Southern Ocean off Antarctica, ''L. antarcticus'' occurs from the northern tip of the Antarctic Peninsula east as far as

Wilkes Land Wilkes Land is a large district of land in eastern Antarctica, formally claimed by Australia as part of the Australian Antarctic Territory, though the validity of this claim has been placed for the period of the operation of the Antarctic Treaty, ...

being found at depths between while ''L. dearborni'' has only been recorded from the Ross Sea at depths between ,

References

{{Taxonbar, from=Q2345426 Lycodinae Ray-finned fish genera