Deep underground, where sunlight never reaches, animals can develop unusual traits to survive in complete darkness. A new study has identified a rare freshwater snail in a high-altitude cave in China, revealing another example of how life can adapt to extreme environments.
The newly discovered species, named Erhaia dijiang, was found in a limestone cave in Yuxi City, Yunnan province. The discovery is particularly significant because freshwater cave snails were not previously documented in China, leaving scientists with limited information about the country’s underground aquatic biodiversity.
The snail has several physical characteristics that distinguish it from species living in environments exposed to sunlight.
It has completely lost its eyes, has a cone-shaped shell that is nearly transparent and has a pale body without pigmentation.
Its long, slender tentacles also contribute to its unusual appearance. These characteristics are associated with life in dark environments, where vision and pigmentation may provide less benefit.
Researchers named the species after Di Jiang, a faceless mythical creature described in the ancient Chinese text “Classic of Mountains and Seas.” The name reflects the snail’s eyeless appearance and its sensitivity to light.
During laboratory observations, researchers found that the snails retreated into dark spaces beneath rocks when exposed to illumination.
The discovery site was also notable for its elevation. Researchers found the snail at approximately 2,062 meters above sea level, making it the highest-altitude cave snail recorded within the family Erhaiidae.
The animals lived in shallow water among submerged gravel and broken rocks. The cave’s water temperature remained close to 20 degrees Celsius, providing a relatively stable environment.
Scientists also investigated what the snails eat. During laboratory observations, the animals fed on diatoms, microscopic algae that grow on rock surfaces. They also consumed fish food provided by researchers, offering preliminary insight into their dietary habits.
Despite the discovery, researchers are concerned about the species’ survival. During their first field investigation in August 2025, they found only three living adult snails and one empty shell.
No juveniles were observed, raising questions about the population’s size and ability to reproduce. Because the species appears restricted to a small habitat, environmental changes could pose a serious threat.
The findings highlight how much remains unknown about underground ecosystems. By identifying E. dijiang, researchers have expanded scientific knowledge of cave-dwelling animals and emphasized the need to investigate and protect these fragile habitats before rare species disappear.
