It is from total darkness that wildlife photographer Dhritiman Mukherjee found the light. When he set out to explore the deepest known shaft cave in India—Krem Umladaw, nestled in Meghalaya—he came across an entirely unique subterranean ecosystem, filled with blind fish, small shrimp, rare fossils, and more. Today, they have rare video documentation of this hidden habitat and its creatures.

Caves in India, home to mysterious micro-ecosystems, have not been documented extensively. But these subterranean spaces now hold interest for biologists, anthropologists, geologists and hydrologists. Take, for instance, “Caving in the Abode of the Clouds”, an ongoing project to systematically explore the caves of Meghalaya. It’s a partnership between Indian, European, Middle Eastern and American universities and independent researchers, with over 519km of cave passages having been surveyed since 1992. It was on one research trip in 2019, led by Daniel Harries, a biologist from the Heriot-Watt University in Scotland, that a nearly-blind species of fish was discovered. Experts, who specialise in studying cave life, think it is possibly related to the chocolate mahseer. This has turned out to be the world’s biggest subterranean fish.

Though there has been photographic evidence and post-expedition analysis of this species, it is only now that rare video documentation of this blind fish is available. This came about when an expedition organised in February 2021 by RoundGlass Sustain, which tells stories related to India’s wildlife and nature, set out to explore the worlds that lie beneath Meghalaya’s green valleys. The expedition included Mukherjee, a crew from Biont, a Kolkata-based collective of film-makers, and writer Divya Candade from RoundGlass Sustain. The aim was to document the deep caves—named and unnamed—and visually record the world’s largest troglobitic blind fish.

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After a challenging journey, the team returned last December, completing the first video documentation not only of this rare species but also of the habitat in Krem Umladaw, Krem Chympe and other caves. The resulting three films on the cave ecosystems of Meghalaya have been released recently on the RoundGlass Sustain website and its YouTube channel.

The blind fish in Krem Umladaw

Mukherjee has, in his career, visited caves across India, from the laterite caves in Goa to the limestone ones in the Andaman islands. “But Meghalaya is unique, for it has a network of caves unlike other regions. I have never seen such long and deep caves. The diversity of life and cave formations are more than in any other area in India,” he says.

There are numerous factors that make these caves unique—a hilly plateau with elevations of over 1,000m, a landscape rich in limestone, and an abundance of rain, to name a few.

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The caves that the team visited have hidden their secrets in complete darkness. To uncover some of these mysteries, Mukherjee and the team had to carry multiple lights. He calls them the lifeline for any caving expedition, essential to survival. “But that also means you cannot truly experience the cave system the way it is. The creatures live in the dark but we can’t see anything at all. When we entered the cave, we felt we were in a terrible, vast darkness. Our torches could only light up small patches,” he says. In time, Mukherjee’s eyes adjusted to the blackness. His other senses became sharper and every sound seemed to stand out. It offered a tiny inkling of the process that has shaped the abilities of the creatures that dwell within these caves.

“We were very careful and mindful about the fact that the species that thrive in this darkness are sensitive to light, and hence used our lights minimally. We kept them pointed to the ground or walls to avoid stunning any cave creatures as far as possible,” says Mukherjee. Even when the team had to shoot and needed larger lights to brighten up the far reaches of the cave chamber, or underwater lights for the river, it used them sparingly. There were moments when they would turn off all the lights to immerse themselves in the total darkness and silence. “It was an eerie feeling, and, after a short while, the mind started to play tricks,” he adds.

The team settled on specific caves such as Krem Chympe and Umladaw for their significant features. The former, for instance,is one of the six longest caves in Meghalaya and happens to be a river cave. Both Chympe and Umladaw are inaccessible during the monsoon.

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“Umladaw is shrouded in mystery. It is a vertical and deep shaft cave. Entering it requires technical skill, training and endurance. Its inaccessibility raises so many questions about its ecosystem. There is practically next to no research about it,” notes Mukherjee. Any documentation, such as this one, helps pierce some of the ignorance. It also gives rise to new questions and theories on how creatures survive in these habitats.

Expeditions to caves in Meghalaya are extremely dependent on sound technical equipment. You need climbing and diving gear, logistical support for camping, 4×4 vehicles to reach remote locations, and even kayaks to explore river caves like Krem Chympe. While Mukherjee had his own gear, organisations such as the Meghalaya Adventure Association, Chiborlang Wahlang and Wallambok Lyngdoh provided support and information.

Mukherjee visited Umladaw twice in 2021. In December, the team came across a species of frog, possibly new to science. “According to experts, since this population is geographically closest to the Bangladesh one, it could be Leptobrachium sylheticum. However, further research will be needed to understand the ecology and behaviour of a population that lives inside a cave,” he says. The team saw shrimps, some of them blind, small fish, crustaceans, fungi and several species of spider.

Interestingly, they came across some land reptiles, such as the Pope’s pit viper, during the visits to Umladaw. “We all know how difficult it is for these creatures to survive in these dark habitats with limited energy and food. However, these creatures we saw were healthy, so this documentation is triggering questions in the minds of researchers and biologists,” explains Mukherjee.

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After the trip, he shared the documentation with scientists such as Abhijit Das, Varad Giri, Sandeep Das and Pratyush Mahapatra, seeking their assistance in identifying the species. All the documentation can be accessed freely by scientists, researchers and students on RoundGlass Sustain.

The rare video documentation of the blind cave fish sheds light on the environment in which they thrive. You can see the amount of debris at the bottom of the cave, the quality of water, and other aquatic species in the pools. “We also noticed that while some of the fish are indeed blind, others seem to have an eye-like black dot. So, there is a difference in appearance. There is also the question of how they sense presence and navigate towards these pools. During the second expedition, the number of fish in the pool seemed to have increased,” he says.

The expedition has left Mukherjee with a lot of questions, from the nature of fossils on the cave walls to the undocumented life forms in these subterranean ecosystems. In Umladaw, he came across an underground stream that disappeared some way along. “Where does this stream go and what is its origin? Are there other cave habitats with these blind fish? Are the land frog species breeding here? If so, how are they surviving? I wonder about the habitat itself. Since Umladaw is located within a valley, does the cave fill up with water? If that happens, does the water overflow and come to the surface? Do the fish come to the surface too?” he wonders. Further expeditions and consistent research, Mukherjee hopes, will yield answers to some of these questions.