''Trematomus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

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 h ...

es, belonging to the

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

Nototheniidae, 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 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-smal ...

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, 33,400 species of fish had been described as of October ...

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 botan ...

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 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 species that contains the biological type specimen( ...

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

Arkady Vladimirovich Balushkin Arkady (russian: Арка́дий, Arkadiy) is a Slavic masculine given name, ultimately derived from the Greek name Αρκάδιος, meaning “from Arcadia”. The Latin equivalent is Arcadius. Notable people with the name include: People: * ...

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 Trematominae, but the 5th edition of ''

Fishes of the World ''Fishes of the World'' by the American Ichthyology, 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 classificat ...

'' 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 Boulenger is a surname. Notable people with the surname include: * Benjamin Boulenger (born 1990), French footballer * Edward George Boulenger (1888–1946), British zoologist, director of aquarium at London Zoo * George Albert Boulenger (1858–1 ...

, 1902 (emerald rockcod) * '' Trematomus eulepidotus''

Regan The family name Regan, along with its cognates O'Regan, O Regan, Reagan, and O'Reagan, is an Anglicized form of the Irish surname Ó Riagáin or Ó Ríogáin, from Ua Riagáin. The meaning is likely to have originated in ancient Gaelic ''ri' ...

, 1914 (blunt scalyhead) * '' Trematomus hansoni'' Boulenger, 1902 (striped rockcod) * ''

Trematomus lepidorhinus ''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 Belgia ...

'' (, 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 A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as w ...

, 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 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 s ...

contains10-14 branched fin rays. The maximum length varies from a standard length of in ''T. scotti'' to a

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 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 ( es, Isla San Pedro) is an island in the South Atlantic Ocean that is part of the British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. Stretching in the east ...

. 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 ''(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
{{Taxonbar, from=Q2580443 Nototheniidae Perciformes genera Fish of the Southern Ocean Fish of Antarctica Taxa named by George Albert Boulenger