''Rakthamichthys'' 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 ...

swamp eel The swamp eels (also written "swamp-eels") are a family (biology), family (Synbranchidae) of freshwater eel-like fishes of the tropics and subtropics. Most species are able to breathe air and typically live in marshes, ponds and damp places, som ...

s that are

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

. Three species are known from the Western Ghats and one is known from

Northeast India Northeast India, officially the North Eastern Region (NER), is the easternmost region of India representing both a geographic and political Administrative divisions of India, administrative division of the country. It comprises eight States and ...

. All species live underground, with one species (''R. rongsaw'') having a

fossorial A fossorial animal () is one that is adapted to digging and which lives primarily (but not solely) underground. Examples of fossorial vertebrates are Mole (animal), moles, badgers, naked mole-rats, meerkats, armadillos, wombats, and mole salamand ...

lifestyle and three species (''R. digressus'', ''R. roseni'', and ''R. indicus'') being troglobitic in nature. All species display adaptations to this lifestyle, including a bright red coloration and highly reduced eyes.

Taxonomy

All four species were formerly classified in the genus ''

Monopterus ''Monopterus'' is a genus of swamp eels native to Asia. They live in various freshwater habitats and some have a fossorial lifestyle.Britz, R., Doherty-Bone, T.M., Kouete, M.T., Sykes, D. & Gower, D.J. (2016)''Monopterus luticolus'', a new specie ...

'' until a 2020 study found significant genetic and osteological differences between them and the rest of ''Monopterus'', including unique and highly divergent characteristics in the

gill arch Branchial arches or gill arches are a series of paired bony/ cartilaginous "loops" behind the throat ( pharyngeal cavity) of fish, which support the fish gills. As chordates, all vertebrate embryos develop pharyngeal arches, though the event ...

skeleton. This led to the species being classified in a new genus ''Rakthamichthys'', with "raktham" meaning "blood-red" in

Malayalam Malayalam (; , ) is a Dravidian languages, Dravidian language spoken in the Indian state of Kerala and the union territories of Lakshadweep and Puducherry (union territory), Puducherry (Mahé district) by the Malayali people. It is one of ...

, as a reference to their distinctive coloration.

Species

* '' Rakthamichthys digressus'' (K. C. Gopi, 2002) (blind eel) * '' Rakthamichthys indicus'' ( Eapen, 1963) (Malabar blind swamp eel) (='' Monopterus eapeni''

Talwar The talwar (), also spelled talwaar and tulwar, is a type of curved sword or sabre from the Indian subcontinent. Etymology and classification The word ''talwar'' originated from the Sanskrit Language, Sanskrit word ''taravāri'' () which means ...

, 1991) * '' Rakthamichthys mumba'' (Jayasimhan, Thackeray, Mohapatra & Kumar, 2021) * '' Rakthamichthys rongsaw'' (

Britz Britz () is a German locality (''Ortsteil'') within the Berlin borough (''Bezirk'') of Neukölln. History The village of ''Britzig'' was first mentioned in 1273. It was incorporated by the 1920 Greater Berlin Act. It is known for being the sit ...

, D. Sykes,

Gower The Gower Peninsula (), or simply Gower (), is a peninsula in the south-west of Wales. It is the most westerly part of the historic county of Glamorgan, and is now within the City and County of Swansea. It projects towards the Bristol Channel ...

, & Kamei, 2018) * '' Rakthamichthys roseni'' ( R. M. Bailey & Gans, 1998)

References

Cave fish Freshwater fish genera Synbranchidae Freshwater fish of India Taxa named by Ralf Britz Taxa named by Neelesh Dahanukar Taxa named by Rajeev Raghavan {{Synbranchiformes-stub