''Aenigmachanna gollum'', the Gollum snakehead, is a species of

aquifer An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characterist ...

-dwelling dragon snakehead fish that is

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 elsew ...

to the

Indian Indian or Indians may refer to: Peoples South Asia * Indian people, people of Indian nationality, or people who have an Indian ancestor ** Non-resident Indian, a citizen of India who has temporarily emigrated to another country * South Asia ...

state of

Kerala Kerala ( ; ) is a 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 regions of Cochin, Malabar, South ...

Description

''A. gollum'' has an elongated,

eel Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 19 families, 111 genera, and about 800 species. Eels undergo considerable development from the early larval stage to the eventual adult stage ...

-like body coloured mostly

brown Brown is a color. It can be considered a composite color, but it is mainly a darker shade of orange. In the CMYK color model used in printing or painting, brown is usually made by combining the colors orange and black. In the RGB color model used ...

and

beige Beige is variously described as a pale sandy fawn color, a grayish tan, a light-grayish yellowish brown, or a pale to grayish yellow. It takes its name from French, where the word originally meant natural wool that has been neither bleached no ...

. Its fins are long and

transparent Transparency, transparence or transparent most often refer to: * Transparency (optics), the physical property of allowing the transmission of light through a material They may also refer to: Literal uses * Transparency (photography), a still, ...

, with the

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

stretching for about three-quarters of its body length, and the

anal 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 se ...

stretching for more than half its body length. Its pectoral fin is large, while the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

is absent. Its tailfin is

ovoid An oval () is a closed curve in a plane which resembles the outline of an egg. The term is not very specific, but in some areas (projective geometry, technical drawing, etc.) it is given a more precise definition, which may include either one or ...

. Several large scales cover the top of the head. It has a reduced

swim bladder The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled Organ (anatomy), organ that contributes to the ability of many bony fish (but not cartilaginous fish) to control their buoyancy, and thus to stay at their curren ...

. Unlike many

stygofauna Stygofauna are any fauna that live in groundwater systems or aquifers, such as caves, fissures and vugs. Stygofauna and troglofauna are the two types of subterranean fauna (based on life-history). Both are associated with subterranean environments ...

- which usually have reduced colouring and have poor or no vision - ''A. gollum'' has well-developed pigmentation and normally-sized eyes. Due to its reduced swim bladder, ''A. gollum'' cannot remain buoyant in water. Like other snakehead fishes, it breathes air. It moves by undulating its fins, like an eel.

Distribution and habitat

''A. gollum'' is known only from its type locality, a paddy field in

Oorakam Oorakam is a census town in Malappuram district in the state of Kerala, India. Oorakam is located midway between Malappuram and Vengara. Oorakam is approximately 12 km from Malappuram. Demographics India census, Oorakam had a populatio ...

, Kerala, in the biodiverse Western Ghats; one other occurrence was reported in a well 250 km south of the type locality. Its habitat in subterranean

aquifers An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characterist ...

is threatened by about six million groundwater

wells Wells most commonly refers to: * Wells, Somerset, a cathedral city in Somerset, England * Well, an excavation or structure created in the ground * Wells (name) Wells may also refer to: Places Canada *Wells, British Columbia England * Wells ...

in the region, which lower the

water table The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated. T ...

Etymology

''A. gollum'' is named after the cave-dwelling character

Gollum Gollum is a fictional Tolkien's monsters, character in J. R. R. Tolkien's Middle-earth legendarium. He was introduced in the 1937 Fantasy (genre), fantasy novel ''The Hobbit'', and became important in its sequel, ''The Lord of the Rings''. Gol ...

from

J. R. R. Tolkien John Ronald Reuel Tolkien (, ; 3 January 1892 – 2 September 1973) was an English writer and philology, philologist. He was the author of the high fantasy works ''The Hobbit'' and ''The Lord of the Rings''. From 1925 to 1945, Tolkien was ...

's ''

The Hobbit ''The Hobbit, or There and Back Again'' is a children's fantasy novel by English author J. R. R. Tolkien. It was published in 1937 to wide critical acclaim, being nominated for the Carnegie Medal and awarded a prize from the '' ...

'' and ''

The Lord of the Rings ''The Lord of the Rings'' is an epic high-fantasy novel by English author and scholar J. R. R. Tolkien. Set in Middle-earth, intended to be Earth at some time in the distant past, the story began as a sequel to Tolkien's 1937 children's boo ...

'' book series, as a reference to both ''A. gollum'' and Gollum being former surface-dwellers that evolved to adapt to the caves they lived in. The genus ''Aenigmachanna'' was raised for the first time on discovery of ''A. gollum'', with ''aenigma'' meaning "

enigma Enigma may refer to: *Riddle, someone or something that is mysterious or puzzling Biology *ENIGMA, a class of gene in the LIM domain Computing and technology *Enigma (company), a New York-based data-technology startup * Enigma machine, a family o ...

" in

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

, and ''Channa'' being the generic name of Asian snakehead fishes.

Taxonomy

''A. gollum'' was the first discovered species of the genus ''

Aenigmachanna ''Aenigmachanna'' is a genus of ray-finned fish in the order 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 s ...

.'' The genus was first placed in the true snakehead fish 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 ...

. ''A. gollum'' was placed in a separate genus because of significant physiological and genetic differences between itself and the other genera in Channidae - ''

Parachanna ''Parachanna'' is a genus of snakeheads native to freshwater habitats in tropical Africa. Three recognized extant (living) species are in this genus, but a phylogenetic study from 2017 indicates that a fourth, currently undescribed species also ...

'' and ''

Channa ''Channa'' is a genus of predatory fish in the family Channidae, commonly known as snakeheads, native to freshwater habitats in Asia. This genus contains about 50 scientifically described species. The genus has a wide natural distribution extend ...

''. ''A. gollum'' has an unusually long dorsal fin, anal fin and

vertebral column The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordata, ...

compared to ''Parachanna'' and ''Channa'', and also has a more eel-like body. Unlike the other channids, it also lacks pored scales on the

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

, which normally carry the lateral-line canal, and has more

vertebrae The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

lacking

ribs The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels. The sternum, together known as the thoracic cage, is a semi- ...

. The other channids also have a longer swim bladder. In 2020, ''Aenigmachanna'' was placed in its own

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

family, the Aenigmachannidae, or the dragon snakeheads.

Discovery

''A. gollum'' was discovered as a result of the

2018 Kerala floods On 16 August 2018, severe floods affected the south Indian state Kerala, due to unusually high rainfall during the monsoon season. It was the worst flood in Kerala in nearly a century. Over 483 people died, and 15 are missing. About a milli ...

, when several individuals were washed out of their aquifer habitat and into a

paddy field A paddy field is a flooded field (agriculture), field of arable land used for growing Aquatic plant, semiaquatic crops, most notably rice and taro. It originates from the Neolithic rice-farming cultures of the Yangtze River basin in sout ...

in Oorakam, where they were found and photographed by a resident of the village, who posted the pictures on social media. The pictures were noticed by

Rajeev Raghavan Rajeev Raghavan is a fisheries scientist and aquatic conservation biologist known for his work on the freshwater fishes of the Indian subcontinent. He is currently an Assistant Professor at the Department of Fisheries Resource Management, Kerala ...

from the

Kerala University of Fisheries and Ocean Studies The Kerala University of Fisheries and Ocean Studies (KUFOS) is a university established by the Government of Kerala devoted to studies in fisheries and ocean sciences. The bill seeking to establish the university was passed by the Kerala Leg ...

, who prompted a study into the species. It was described in 2019. It is the eighth species of fish known from the Kerala aquifers, indicating the presence of a large, hidden ecosystem in the hard-to-study habitat.

References

{{Taxonbar, from=Q63676102 Fish described in 2019

gollum Gollum is a fictional Tolkien's monsters, character in J. R. R. Tolkien's Middle-earth legendarium. He was introduced in the 1937 Fantasy (genre), fantasy novel ''The Hobbit'', and became important in its sequel, ''The Lord of the Rings''. Gol ...