Dive deeper: Meghalaya’s caves hold treasures we are yet to learn about

Meghalaya, often celebrated as the caving capital of India, is home to some of the most extensive and spectacular cave systems in the country. Yet despite this reputation, much of what lies beneath its lush landscapes remains shrouded in mystery.

A cave is a completely dark natural underground hollow space with constant temperature, high humidity, low pressure, low oxygen concentration, and a nutrient-limited ecosystem. Caves are formed by various geological processes such as chemical reactions of different compounds, rock dissolution, cave rock weathering, glacier melting, corrosion of rocks by water, tectonic forces, atmospheric influences, microorganisms, and anthropogenic excavation.

A study says caves represent unique ecosystems and key sites for our human history. With their unique conditions and stability, they can provide insights into their past use and an index of local climate and vegetation. In addition, caves host many of the world’s over 1,400 bat species, meaning that the ability to reconstruct past population trajectories may facilitate their conservation, as well as that of the many other often undescribed cave-dependent species.

Each year, explorers and speleologists venture into Meghalaya’s underworld, uncovering new caves and passages. However, these discoveries only scratch the surface of what truly exists. The caves of Meghalaya are more than just geological formations; they are living ecosystems teeming with unique biodiversity, historical artefacts, and geological marvels preserved for millions of years.

According to the Meghalaya tourism website: “Some narrow, some tall, and some incredibly deep, the caves of Meghalaya are carved as water meets limestone and sandstone, creating otherworldly formations and ecosystems underneath our feet, hiding magnificent formations, rare species, and fossils from millions of years ago. We are still learning about these complex cave systems and many areas have not been mapped at all. Veteran spelunkers and fully equipped adventurers have been forging into the subterranean frontiers on Meghalaya’s southern edge every year during the dry season,” the website says.

The limestone caves of Meghalaya harbour a remarkable diversity of subterranean taxa, and the state is one of the two hotspots of subterranean fish diversity, the other being the lateritic aquifers of Kerala.

The discovery of the world’s largest cavefish, Neolissochilus pnar, in Meghalaya, named after the Pnar community, turned the spotlight on the state’s caves.

Dan Harries of Grampian Speleological Group, Edinburgh, UK, who was one of the members of the expedition that discovered the largest cavefish in Meghalaya, says, “They have certainly not been fully documented—nothing even close to full documentation. Amongst available observations made in the caves, there are certainly sightings of troglobitic species yet to be described. But these observations are incomplete; if someone takes a closer look at smaller and less conspicuous animals, there are certain to be new things that have been overlooked so far. And new caves are being explored every year. We are nowhere near understanding what lives in the known caves, and there is no way of predicting what might be in the caves yet to be visited,” Harries told EastMojo.

Grampian Speleological Group is Scotland’s oldest caving club.

In fact, among all the thousands of caves, Siju Cave in Meghalaya is the best biospeleologically explored cave to date. A cave expert said, “There have not been any dedicated studies on cave flora or fauna except for Siju Cave.”

It was way back in 1922 that an attempt was made to scientifically explore, survey, and document the cave fauna. This pioneering work, the first of its kind in India, was carried out by Stanley Kemp and B. Chopra, the then Superintendent and Assistant Superintendent respectively of the Zoological Survey of India, Calcutta. Before their work, Indian caves in general, and those in Meghalaya in particular, were thought to be of limited biospeleological interest. But that perception changed following the successful documentation of the fauna of Siju Cave, which brought to the fore the myriad faunal diversity of the cave with discoveries of a good number of species that were new to science. Their historical work resulted in the documentation of 102 species from the cave that was published in several parts in the Records of the Indian Museum.

After the 1922 survey, very little work was done in Siju Cave.

A team from the Zoological Survey of India surveyed the area during the 2018-2020 period when multiple surveys were undertaken to reassess the present faunal composition of the cave. The study recorded only 36 species belonging to 11 major faunal groups, including 11 new records of the cave.

“Yes, work and research have been done in this field, but nothing is ever complete. As new caves are being discovered, so too are cave fauna. There is scope for much more research,” says famous cave explorer Brian Khapran Daly.

S. R. Hajong of North Eastern Hill University says, “Cave ecosystems are now being studied by small groups of scientists. They are unique as organisms inside the cave depend on the dead organic matter that flows through streams, and they adapt to extremely low light to almost no light and even low oxygen.”

“Cave fauna has adapted throughout millions of years of evolutionary history,” he says.

Hajong says another interesting aspect of the cave ecosystem is cave microbiology, which also needs to be studied. Except for a few papers on cave microbiology in Meghalaya, not much is known. “Cave microorganisms play an important role in the hypogean ecosystem that may contribute to the food chain of cave organisms,” Hajong says.

Cave Microbes a source of drugs?

In fact, there has been a study on cave microbes being a potential source of drug development in the modern era.

The study suggests that the world needs a novel and effective source of drug discovery.

“The world is constantly facing threats, including the emergence of new pathogens and antibiotic resistance among extant pathogens, which is a matter of concern. Therefore, the need for natural and effective sources of drugs is inevitable. The ancient and pristine ecosystems of caves contain a unique microbial world and could provide a possible source of antimicrobial metabolites. The association between humans and caves is as old as human history itself. Historically, cave environments have been used to treat patients with respiratory tract infections, referred to as speleotherapy,” the study says.

“Today, the pristine environment of caves that comprise a poorly explored microbial world is a potential source of antimicrobial and anticancer drugs. Oligotrophic conditions in caves enhance the competition among microbial communities, and unique antimicrobial agents may be used in this competition,” it says.

The study says unique characteristics of cave environments such as complete darkness, high humidity, constant low temperature, and lack of nutrients may promote the production of antimicrobial (antibiotics, antifungal, and antiviral) and anticancer compounds.

These caves are excellent habitats for fish too. A fascinating cave-dwelling fish species, Schistura sonarengaensis, has been discovered from three limestone caves in Meghalaya. The fish has been discovered by a group of scientists from Lady Kean College Shillong; Dept. of Zoology, Gauhati University; and ICAR-NBFGR, Lucknow.

The study says despite being well renowned for their distinctive underground biodiversity, Meghalaya’s caves have been very little investigated, and the description of S. sonarengaensis, among others, points to the fact that there are subterranean populations of undiscovered fish species in these caverns. “Thorough surveys will reveal the variety of this exceptional ecosystem and its remarkable fauna,” researchers say.

The Speleological Association of India (SAI) was formed to research and conserve caves, karsts, and other related ecosystems in the Indian subcontinent. “As the subject is still in its infant stage in the region, our primary focus is developing human resources towards a detailed understanding of the subterranean biome and other related systems towards their conservation through rigorous scientific investigation and advocacy,” it says.

Not only fishes but even snails have been found in the caves of Meghalaya. “There may be more species that await discovery. In Southeast Asia, where similar caves are present, more than 100 such species have been reported,” says a study by N. A. Aravind.

But sometimes the booming of tourism at caves can be a threat to snails. “The Lymput cave in East Khasi Hills has become a major threat to a new species of snail identified as Bouchetcamaena subdelibrata, which is also found at the cave,” a study said.

Also Read: Age of limestone: What researchers found in the caves of South Garo Hills