Taxonomy & naming
Neolissochilus pnar was described by Dahanukar, Sundar, Rangad, Proudlove and Raghavan in 2023, with the formal account published in Vertebrate Zoology 73: 141–152 (6 February 2023). The type locality is Krem Um Ladaw and Krem Chympe, two caves in the Jaintia Hills district of Meghalaya, India, with drainages flowing into the Meghna River system (a major tributary of the Brahmaputra–Ganges complex).
The genus Neolissochilus belongs to the tribe Torini within the family Cyprinidae and is closely allied to the true mahseers of genus Tor. Molecular work has placed Neolissochilus pnar as sister to Tor, consistent with its placement in the broader mahseer radiation of South and Southeast Asia. The species epithet honours the Pnar people (also known as Jaintia) of East Jaintia Hills, in whose traditional territory the cave system lies.
The holotype is 13 in SL; paratypes range from 7–8 in SL, and field observations indicate adults exceeding 15.5 in SL — a size surpassing the previous record holder for subterranean fishes, the Australian blind cave eel (approximately 15 in TL).
Morphology
Neolissochilus pnar is a large, robust cyprinid that expresses the classic suite of troglobitic characters associated with prolonged isolation in lightless cave environments. The body is entirely depigmented, appearing white to pale cream in life; melanin production has been lost or suppressed across the skin and fins. The eyes are absent or reduced to vestigial, non-functional remnants beneath the skin, consistent with evolutionary regression under permanent darkness.
The species possesses long maxillary barbels, presumably enlarged relative to surface-dwelling relatives to enhance chemosensory and mechanosensory input in the absence of vision. The pectoral-fin rays are notably elongated, likely serving a tactile role in navigating cave substrates and flow gradients. Body form follows the deep, laterally compressed profile typical of large Neolissochilus and Tor — not secondarily slender as in some cave-adapted fishes — suggesting the cave colonist retained a mahseer-like body plan while losing light-associated traits.
Habitat
The entire known range of Neolissochilus pnar is within the limestone karst cave systems of the Jaintia Hills, Meghalaya, specifically Krem Um Ladaw and the adjacent Krem Chympe. These caves are part of one of the most extensive cave networks in the Indian subcontinent, carved by water percolating through Cretaceous-era limestone. The fish occupies flooded galleries and cave pools fed by percolating rainfall and groundwater — a nutrient-sparse phreatic environment in which allochthonous organic matter washed in from the surface is the primary food subsidy.
Water in Jaintia Hills cave systems is typically cool and well-oxygenated, with near-neutral to slightly alkaline chemistry reflecting dissolution of the limestone country rock. The Meghna River system, to which these caves ultimately drain, drains a high-rainfall belt of northeastern India, providing substantial hydrological input. Beyond the two known caves, the species' presence in adjacent systems has not been confirmed; its effective range may encompass a single connected aquifer.
Feeding
Like other large members of Neolissochilus and Tor on the surface, Neolissochilus pnar is presumed to be broadly omnivorous, exploiting whatever organic material is available in the resource-limited cave environment. Cave systems of the Jaintia Hills receive allochthonous inputs — bat guano, leaf litter and invertebrates washed in from surface streams — that subsidise invertebrate communities on which the fish likely preys. The elongated barbels and reduced eyes suggest a tactile and chemosensory foraging strategy rather than visual prey detection.
Given its large size, the species is capable of consuming substantial prey items and may act as an apex predator within its cave ecosystem, taking invertebrates, cave-adapted crustaceans and smaller fish if present. Formal gut-content studies have not been published in the available literature.
Mating
No direct observations of courtship or mating behaviour have been published for Neolissochilus pnar. Based on the reproductive biology of the broader mahseer and Neolissochilus clade, the species is expected to be an egg-scattering, non-guarding spawner. In surface-dwelling mahseers and large river barbs, spawning typically involves active pursuit of gravid females over gravel and rocky substrates, with eggs and milt released together without nest construction or subsequent parental involvement.
In cave environments, seasonal hydrological cycles — flood pulses driven by monsoon rainfall percolating into the karst — likely serve as the primary spawning cue in place of the photoperiod signals used by surface relatives. The elongated barbels and tactile sensory systems may play a role in locating mates in lightless conditions. No pair bond is formed, consistent with the egg-scattering reproductive mode of the family.
Breeding
Breeding details for Neolissochilus pnar in the wild remain undocumented. By analogy with other large Neolissochilus and with Tor species, spawning is expected to involve broadcast scatter of adhesive eggs over rocky or gravelly substrates within the cave, with no parental care of eggs or larvae. Adults do not guard or attend the spawn site.
The harsh, nutrient-poor cave environment may impose constraints on fecundity and growth rate typical of troglobitic fishes — slower maturation, reduced clutch sizes and longer lifespans compared with surface relatives. The species has not been established in captivity, and no aquarium-breeding data exist. Its conservation status as a cave-restricted endemic with a potentially tiny wild population makes captive research a scientific priority.
In the aquarium
Neolissochilus pnar is not available in the aquarium trade and is not suitable for private keeping. At its known adult size — exceeding 15.5 in SL — it would require a very large specialised system, and as a troglobite it has no tolerance for bright light, relying on tactile and chemosensory perception. Its entire wild population likely numbers in the hundreds or fewer individuals within a single cave network.
The species has scientific significance as the world's record-holding subterranean fish by length, and any captive holdings that may exist are in the context of conservation research rather than ornamental display. Hobbyists interested in large mahseer-clade cyprinids should look to legally sourced, surface-dwelling Neolissochilus or Tor species where applicable regulations permit.
Conservation
Neolissochilus pnar has not been formally assessed by the IUCN Red List (status: Not Evaluated, NE as of 2024). However, specialists in subterranean fish biodiversity flag it as 'Threatened with Loss of Opportunity' given its extraordinarily restricted range — a single cave system or a cluster of connected systems spanning a very limited area in East Jaintia Hills, Meghalaya.
The principal threats are those facing many cave-endemic species: groundwater extraction and depletion of the aquifer, karst quarrying and limestone mining (a significant industry in Meghalaya), water pollution from surface agriculture and coal-mining drainage entering the cave system, and disturbance from cave tourism and exploration. Because the entire known population is confined to one aquifer, any large-scale contamination, drying or physical alteration event could eliminate the species. Formal IUCN assessment and a field survey to quantify population size and clarify the extent of the connected cave network are urgent conservation needs.