''Rakthamichthys'' 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 swamp eels that are

endemic Endemism is the state of a species being found 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 found els ...

India India, officially the Republic of India ( Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the ...

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

Northeast India , native_name_lang = mni , settlement_type = , image_skyline = , image_alt = , image_caption = , motto = , image_map = Northeast india.png , ...

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

fossorial A fossorial () animal is one adapted to digging which lives primarily, but not solely, underground. Some examples are badgers, naked mole-rats, clams, meerkats, and mole salamanders, as well as many beetles, wasps, and bees. Prehistoric e ...

lifestyle and three species (''R. digressus'', ''R. roseni'', and ''R. indicus'') being

troglobitic A troglobite (or, formally, troglobiont) is an animal species, or population of a species, strictly bound to underground habitats, such as caves. These are separate from species that mainly live in above-ground habitats but are also able to live u ...

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 speci ...

'' 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 bony "loops" present in fish, which support the gills. As gills are the primitive condition of vertebrates, all vertebrate embryos develop pharyngeal arches, though the eventual fate of these ar ...

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

Malayalam Malayalam (; , ) is a Dravidian language spoken in the Indian state of Kerala and the union territories of Lakshadweep and Puducherry ( Mahé district) by the Malayali people. It is one of 22 scheduled languages of India. Malayalam wa ...

, 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 word ''taravāri'' ( sa, तरवारि) ...

, 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 si ...

, D. Sykes,

Gower Gower ( cy, Gŵyr) or the Gower Peninsula () in southwest Wales, projects towards the Bristol Channel. It is the most westerly part of the historic county of Glamorgan. In 1956, the majority of Gower became the first area in the United Kingd ...

, & Kamei, 2018) * ''

Rakthamichthys roseni ''Rakthamichthys'' is a genus of swamp eels that are endemic to India. Three species are known from the Western Ghats and one is known from Northeast India. All species live underground, with one species (''R. rongsaw'') having a fossorial li ...

'' ( 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 {{Rayfinned-fish-stub