''Thymallus'', commonly known as graylings, 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 freshwater ray-finned fish and the only genus within 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 ...

Thymallinae of the family Salmonidae. Although all ''Thymallus'' species can be generically called graylings, without specific qualification the term "grayling" typically refers to 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 ...

'' Thymallus thymallus'', the European grayling.

Name

The name of the genus ''Thymallus'' first given to grayling (''T. thymallus'') described in the 1758 edition of ''Systema Naturae'' by Swedish zoologist

Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

originates from the faint smell of the herb

thyme Thyme () is a culinary herb consisting of the dried aerial parts of some members of the genus ''Thymus (plant), Thymus'' of flowering plants in the mint family Lamiaceae. Thymes are native to Eurasia and north Africa. Thymes have culinary, medici ...

, which emanates from the flesh. ''Thymallus'' derives from the Greek θύμαλλος, "thyme smell".

Species

According to FishBase, 14 species are placed in this genus. However, views differ on their taxonomic rank. * '' Thymallus arcticus'' ( Pallas, 1776) - Arctic grayling * '' Thymallus baicalensis'' Dybowski, 1874 - Baikal black grayling * '' Thymallus brevipinnis'' Svetovidov ( ru), 1931 - Baikal white grayling * '' Thymallus brevirostris'' Kessler, 1879 - Mongolian grayling * '' Thymallus burejensis'' Antonov, 2004 - Bureya grayling * '' Thymallus flavomaculatus'' Knizhin, Antonov & Weiss, 2006 - yellow-spotted grayling * '' Thymallus grubii'' Dybowski, 1869 - Amur grayling *'' Thymallus mertensii'' Valenciennes, 1848 - Kamchatka grayling * '' Thymallus nigrescens'' Dorogostaisky, 1923 - Kosogol grayling * '' Thymallus pallasii'' Valenciennes, 1848 - East Siberian grayling * '' Thymallus svetovidovi'' Knizhin & Weiss, 2009 - Upper Yenisei grayling * '' Thymallus thymallus'' (

Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

, 1758) - European grayling (

) * '' Thymallus tugarinae'' Knizhin, Antonov, Safronov & Weiss, 2007 - Lower Amur grayling * '' Thymallus yaluensis'' T. Mori, 1928 - Yalu grayling Modern reviewsWeiss, S. J., D. V. Gonçalves, G. Secci-Petretto, G. K. Englmaier, A. Gomes-Dos-Santos, G. P. J. Denys, H. Persat, A. Antonov, C. Hahn, E. B. Taylor and E. Froufe (2021) Global systematic diversity, range distributions, conservation and taxonomic assessments of graylings (Teleostei: Salmonidae; ''Thymallus'' spp.). ''Organisms Diversity & Evolution'': -18 (published online 25 Nov. 2020) and the '' Catalog of Fishes'' also list additional species including '' Thymallus nikolskyi'' , '' Thymallus baicalolenensis'' and '' Thymallus ligericus'' . An old controversy exists over the status of Baikal black vs white graylings, ''T. baicalensis'' and ''T. brevipinnis''. Modern research supports the view that they are not separate taxa, but alternative ecological forms of ''T. baicalensis''.

Distribution

The fishes of this genus are native to the northern parts of the

Palearctic The Palearctic or Palaearctic is a biogeographic realm of the Earth, the largest of eight. Confined almost entirely to the Eastern Hemisphere, it stretches across Europe and Asia, north of the foothills of the Himalayas, and North Africa. Th ...

and Nearctic realms, ranging from the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

and northern

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

across

Eurasia Eurasia ( , ) is a continental area on Earth, comprising all of Europe and Asia. According to some geographers, Physical geography, physiographically, Eurasia is a single supercontinent. The concept of Europe and Asia as distinct continents d ...

to Siberia, as well as northern

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

. ''T. thymallus'', the grayling, is widespread in Europe, and ''T. arcticus,'' the Arctic grayling, is widespread throughout Eurasia east of the Ural Mountains and in the Nearctic. The other species have more localized ranges in northern Asia.

Appearance

''Thymallus'' species are distinguished from other members of the salmonid family by their larger scales, their small mouths with teeth on the maxillary bone, and most striking of all, their showy, sail-like dorsal fins. This fin is longer in males and highly colourful, with spots of red, orange, purple or green. The body is also colourful; the dorsal surface is a dark purplish to bluish black or gray, grading to dark blue or silver gray on the flanks and gray or white on the belly. The body is further decorated with a smattering of small dark spots; these are much more numerous in juveniles. The longest of the graylings is the Arctic grayling, ''T. arcticus'', at a maximum length of and a maximum weight of . ''T. thymallus,'' while somewhat shorter - - may weigh significantly more, . The fishes of this genus may live for 18 years or more.

Ecology and reproduction

These fishes require cool, well-oxygenated water, preferably with a swift current; they are found in large, sandy- or gravel-bottomed rivers and lakes, but ''T. thymallus'' may occasionally be found in brackish conditions. Generally omnivorous, they feed primarily on

crustaceans Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of Arthropod, arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquat ...

, insects, and zooplankton. The grayling species, typically for salmonids, spawn in rivers and do not guard their brood, although they do conceal their eggs in silt. The spawning behavior of the Arctic grayling may be typical for the genus ''Thymallus''. As they are highly sensitive to changes in water quality, ''Thymallus'' fishes may be considered indicator species; ''T. arcticus'' has largely disappeared from the Great Lakes Basin.

Human use

Due to their agreeable taste and attractive form, the grayling species are valued as food and game fishes, and they are occasionally seen in public aquaria. The most economically important of these fishes, for which fisheries and aquaculture operations exist, are the grayling (''T. thymallus'') and the Arctic grayling (''T. arcticus'').

References

{{Authority control Extant Pleistocene first appearances Ray-finned fish genera Fauna of the Holarctic realm