''Aenigmachanna'' 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 ...

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 ...

in the

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Ananbantiformes. It is the only genus in the family Aenigmachannidae, or dragon snakeheads. It contains two species, both of which are largely restricted to subterranean habitats in southwestern

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 ...

, namely in the Western Ghats foothills in the state of

Kerala Kerala ( , ) is a States and union territories of India, state on the Malabar Coast of India. It was formed on 1 November 1956, following the passage of the States Reorganisation Act, by combining Malayalam-speaking regions of the erstwhile ...

. Both of the species in this genus display a unique array of traits that distinguish them from their closest living relatives, the true snakeheads in the family

Channidae The snakeheads are members of the freshwater perciform fish family Channidae, native to parts of Africa and Asia. These elongated, predatory fish are distinguished by their long dorsal fins, large mouths, and shiny teeth. They breathe air with ...

. These include a much longer and more slender body, numerous scales, a very long

anal 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 o ...

, and a lack of ability to maintain

buoyancy Buoyancy (), or upthrust, is the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of t ...

. Molecular analyses indicate that they split off from Channidae around 34 or 109 MYA. This may indicate that Aenigmachannidae is a uniquely

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

n lineage, and if the higher end of estimations is correct, it may have survived the breakup of the Gondwanan supercontinent around 120 MYA. They are unique among

cavefish Cavefish or cave fish is a generic term for fresh and brackish water fish adapted to life in caves and other underground habitats. Related terms are subterranean fish, Troglomorphism, troglomorphic fish, troglobitic fish, stygobitic fish, phreat ...

for being one of the few cave-dwelling members of the large clade

Percomorpha Percomorpha () is an extremely large and diverse clade of ray-finned fish. With more than 17,000 known species (including Scombroidei, tuna, Syngnathiformes, seahorses, gobies, Cichlidae, cichlids, flatfish, Labridae, wrasse, Perciformes, perches ...

. Despite their habitat, they physically display little

troglomorphism Troglomorphism is the morphological adaptation of an animal to living in the constant darkness of caves, characterised by features such as loss of pigment, reduced eyesight or blindness, and frequently with attenuated bodies or appendages. The ter ...

aside from a slightly reduced pigmentation, indicating that they either colonized the caves relatively recently or that they are subtroglophiles that mostly live underground, but depend on aboveground habitats for some functions. Due to their restricted habitat and unique nature, both are considered relict species.

Taxonomy

Species

* '' Aenigmachanna gollum''

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 ...

, Anoop, Dahanukar and

Raghavan Raghavan is a South Indian name. It derives from the Sanskrit ''raghava'', meaning "derived from Raghu" or "descendant of Raghu" (an epithet of the Hindu god Rama, an incarnation of Vishnu), plus the Tamil-Malayalam third-person masculine singular ...

, 2019 (Gollum snakehead) * '' Aenigmachanna mahabali'' Kumar, Basheer, and

Ravi Ravi may refer to: People * Ravi (name), including a list of people and characters with the name * Ravi (composer) (1926–2012), Indian music director * Ravi (Ivar Johansen) (born 1976), Norwegian musical artist * Ravi (rapper) (born 1993), a Sou ...

, 2019 (Mahabali snakehead) The genus was initially described in early 2019 to serve as a monotypic genus for ''A. gollum'', the first species to be described in the genus. Later in the year, ''A. mahabali'' was described as a distinct species, indicating that there were indeed multiple species in the genus.

References

{{Taxonbar, from=Q64481860 Cave fish Fauna of Kerala Freshwater fish of India Endemic fauna of India Endemic fauna of the Western Ghats Taxa named by Ralf Britz Taxa named by V.K. Anoop Taxa named by Neelesh Dahanukar Taxa named by Rajeev Raghavan