Guwahati: Many more cave-dwelling fish fauna are waiting to be discovered in the deep caves of Meghalaya, and many may become extinct even before they are discovered, according to L Kosygin Singh of the Zoological Survey of India.
Scientists at the Zoological Survey of India have documented, for the first time, a list of four true troglobiont species found only in the caves of Meghalaya, namely, Schistura ijuensis, Schistura papulifera, Schistura larketensis and Neolissochilus pnar. The Maan Ki Baat episode provided the insights to document the cave fishes of Meghalaya which will provide awareness to the stakeholders and local communities to conserve the cave fauna and their unique habitat.
The study done by L Kosygin Singh, Boni Amin Laskar and Dimos Khynriam has been published in the Records of Zoological Survey of India journal.
Troglobiont are true cave dwellers that are characterised by the absence of pigmentation, loss of eyesight and development of sensors suited to live in the absence of light.
In the 23rd February 2020 episode of Mann Ki Baat, Prime Minister Narendra Modi shared amazing facts about a rare fish species found by biologists in the cave of Meghalaya and remarked that it is the biggest among the cave-dwelling species. It exists in deep underground caves where even light cannot reach easily, and scientists are puzzled at the ability of this large fish to survive in such deep caves, thereby lending a new facet to India’s biodiversity. Dahanukar et al. (2023) further studied the genetic analysis of the species from fresh specimens and formally described the world’s largest cavefish as Neolissochilus pnar.
Meghalaya is home to more than 1000 caves, including India’s longest and deepest caves and ranks among the top 10 caving destinations in the world. These caves spread along the state’s southern boundary from West Garo Hills, West and East Khasi Hills and Jaintia Hills. The abundance of caves in Meghalaya is due to the prevailing conditions of high-quality limestone, abundant rainfall, and high elevation.
The Siju cave in Southern Garo Hills was first explored in 1875 by Mr Sanderson, the then Superintendent of the Government Kheddans or elephant catching operations in Garo Hills, followed by Mr T.D. La Touche of the Geological Survey of India in 1881. The first collection of cave fauna was made by Mr R. Friel, the then Deputy Commissioner of the Garo Hills, who visited the cave in 1919. Subsequently, in 1922, Kemp and Chopra of the Indian Museum explored the faunal resources of the cave up to 3900 ft inside from the entrance. They discovered 102 species, including eight species of fish.
Among the four troglobiotic fish species, three species belong to the family Nemacheilidae, and one is under Cyprinidae.
Schistura larketensis was described from Krem Khung, about 1.5 km from Larket village, EastJaintia Hills District of Meghalaya in 2017 by Choudhury and others. The species can be immediately distinguished from all other species of Schistura from the Brahmaputra River and neighbouring basins by the complete absence (or only vestigial presence) of eyes. The conservation status of the species is yet to be evaluated.
Schistura sijuensis was described by Menon in 1987 from the Siju cave of Garo Hills. The species is only recorded from the Siju cave in the Garo Hills, Meghalaya, and is categorized as endangered (EN) in the IUCN Red List. The main threats to this species are quarrying and mining for limestone. Deforestation is also reducing habitat quality as it produces siltation and habitat disturbance. No specific conservation measures are in place. It is endemic to Meghalaya.
Schistura papulifera is currently known with certainty only from the Krem Synrang Pamiang system in the Jaintia Hills, eastern Meghalaya. Synrang Pamiang is an extensive system with over 14 km of mapped cave passages and five known entrances. The species is considered to be Critically Endangered (CR) as it is known from a single location with a highly restricted extent of occurrence and area of occupancy with threats from mining and quarrying resulting in habitat loss and a decline in habitat quality.
Neolissochilus pnar was discovered in the cave Krem Um Ladaw of Meghalaya. The species also occurs in another adjacent cave, Krem Chympe. The species is regarded as the world’s largest cavefish species. The species is yet to be evaluated in IUCN Red List. Neolissochilus pnar grows to over 400 mm (1.3 feet) and occurs only in the limestone caves of Meghalaya and is endemic to Meghalaya.
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“The caves fauna in Meghalaya is vulnerable due to anthropogenic activities such as mining, quarrying and dumping of wastes, which ultimately lead to high siltation, pollution and acidification of the water bodies. It is the right time to save these cave fauna in general and endemic cavefish in particular. Some of the critical conservation strategies required for conserving the cave fish fauna of Meghalaya are checking illegal mining and quarrying for limestone, afforestation programmes, controlling acid mine drainage inside the cave, and awareness programmes should be conducted at different levels of stakeholders, including the local communities. The local communities should be encouraged to participate in the conservation activities” L Kosygin Singh told EastMojo.
He said cave-dwelling fauna are a focus of immense interest worldwide due to the endemism, extraordinary adaptation, and risk of extinction. Our knowledge of the hidden subterranean fish fauna is limited due to its fragile and inaccessible habitats. “Many more endemic Troglobiont fish species may be waiting for their discovery in the deep caves of Meghalaya, and many may become extinct even before they are discovered. Therefore, scientific investigations and explorations of the cavefish fauna must be conducted and documented to know their status and conserve their diversity” he said.
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