''Trematomus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

es, belonging to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

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. These fishes occur 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 60th parallel south, 60° S latitude and encircling Antarctica. With a size of , it is the seco ...

Taxonomy

''Trematomus'' was first described as a genus 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, 35,800 species of fish had been described as of March 2 ...

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 ...

when he described four new species of notothen from specimens collected on the ''Southern Cross'' Expedition. In 1938 ''John Roxborough Norman'' designated ''T. newnesi'' as the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, this being the species described first in Boulenger's text. In 1982

Arkady Vladimirovich Balushkin Arkady () is a Slavic masculine given name, ultimately derived from the Greek language, Greek name Αρκάδιος, meaning “from Arcadia (region), Arcadia”. Endeared versions of the name are ''Arkasha''. The Latin equivalent is Arcadius (disa ...

created the new genus ''Pseudotrematomus'', in which he placed all the species in ''Trematomus'' other than ''T. newnesi'', but this classification has not been widely accepted. Some authorities place this genus 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 botanical subfamily names with "-oideae", and zo ...

Trematominae, but the 5th edition of ''

Fishes of the World ''Fishes of the World'' is a standard reference for the systematics of fishes. It was first written in 1976 by the American ichthyologist Joseph S. Nelson (1937–2011). Now in its fifth edition (2016), the work is a comprehensive overview of t ...

'' does not include subfamilies in the Nototheniidae. The generic name ''Trematomus'' is made up of ''trema'' which means "hole" or "opening" and "tomus" which means "cut", Boulenger explained that the "scapular fenestra being pierced in the scapula instead of between the latter and the coracoid".

Species

''Trematomus'' contains these currently recognized species: * '' Trematomus bernacchii'' Boulenger, 1902 (emerald rockcod) * '' Trematomus eulepidotus'' Regan, 1914 (blunt scalyhead) * '' Trematomus hansoni'' Boulenger, 1902 (striped rockcod) * '' Trematomus lepidorhinus'' (, 1911) (slender scalyhead) * '' Trematomus loennbergii'' Regan, 1913 (scaly rockcod) * '' Trematomus newnesi'' Boulenger, 1902 (dusky rockcod) * '' Trematomus nicolai'' (Boulenger, 1902) (spotted notothen) * '' Trematomus pennellii'' Regan, 1914 (sharp-spined notothenia) * '' Trematomus scotti'' (Boulenger, 1907) (crowned rockcod) * '' Trematomus tokarevi'' Andriashev, 1978 (bigeye notothen) * '' Trematomus vicarius'' Lönnberg, 1905 (orange notothen)

Characteristics

''Trematomus'' rockcods have oblong bodies with wide but not depressed heads. They are large mouthed with the maxilla extending towards the middle of the eye, with conical teeth arranged in one or two rows or bands, although there are sometimes a few larger teeth to the front and along the sides of the jaws. The scales are mainly ctenoid, although there are non-ctenoid scales typically in the underside and on the back near the head. The upper lateral line has tubed scales which may be reduced in extent and in the middle lateral line the tubed scales are frequently often replaced by pored scales. The

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

contains10-14 branched fin rays. The maximum length varies from a

standard length Fish measurement is the measuring of individual fish and various parts of fish anatomy, their anatomies, for data used in many areas of ichthyology, including Taxonomy (biology), taxonomy and fishery biology. Overall length Standard length (SL) is ...

of in ''T. scotti'' to a

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

of in ''T. hansoni''.

Distribution, habitat and biology

Trematomus rockcods are found all around the continent of Antarctica with two species which reach as far north as

South Georgia South Georgia is an island in the Atlantic Ocean, South Atlantic Ocean that is part of the British Overseas Territories, British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. ...

. They are benthic or epibenthic species which feed on invertebrates and smaller fishes and they are the dominant fish species on the Antarctic continental shelf. File:Trematomus bernacchii.jpg,

Emerald rockcod The emerald rockcod (''Trematomus bernacchii''), also known as the emerald notothen is a species of marine ray-finned fish belonging to the Family (biology), family Nototheniidae, the notothens or cod icefishes. It is native to the Southern Ocea ...

''(T. bernacchii)'' File:Fish8720.jpg, Blunt scalyhead ''(T. eulepidotus)'' File:Trematomus lepidorhinus.jpg, Slender scalyhead ''(T. lepidorhinus)'' File:Trematomus loennbergii.jpg, Scaly rockcod ''(T. loennbergii)'' File:Trematomus pennellii.jpg, Sharp-spined notothenia ''(T. pennellii)'' File:Trematomus scotti.jpg, Crowned rockcod ''(T. scotti)''

References

Further references

Biolib
{{Authority control Nototheniidae Perciformes genera Fish of the Southern Ocean Fish of Antarctica Taxa named by George Albert Boulenger