A newly identified freshwater cave snail in China is offering scientists a rare glimpse into the little-known aquatic ecosystems hidden beneath East Asia. Published in the journal Subterranean Biology, the discovery represents an important step forward in understanding the region’s underground wildlife. Until now, no freshwater cave snails had been documented in China, and the country’s subterranean freshwater mollusks had received relatively little scientific attention.
The newly discovered species, Erhaia dijiang, has evolved remarkable features that allow it to live in complete darkness. As a true cave-dwelling animal, it has entirely lost its eyes, with the structures normally associated with vision having fully degenerated. The tiny snail also has a cone-shaped, nearly transparent shell, a delicate body without pigmentation, and long, slender tentacles.
Its unusual appearance inspired a name drawn from ancient Chinese mythology. Researchers chose dijiang in honor of “Di Jiang,” a mountain patron god portrayed as a faceless beast in the ancient text Classic of Mountains and Seas (山海经). The connection is particularly fitting because the snail is extremely sensitive to light. During laboratory observations, individuals consistently retreated into dark spaces beneath rocks whenever they were exposed to illumination.
The location of the discovery is just as remarkable as the animal itself. Scientists found Erhaia dijiang at an elevation of 2,062 meters, making it the highest-altitude cave snail yet recorded within the family Erhaiidae. The finding demonstrates that freshwater cave snails can inhabit limestone cave systems at elevations above 2,000 meters.
Life in the Dark Waters of a Mountain Cave
Within its underground habitat, Erhaia dijiang lives among submerged gravel and broken rock in water less than one meter deep. The cave’s water temperature stays close to 20°C, providing a relatively stable environment for the tiny mollusks.
Even when heavy seasonal rains increase the flow of water and occasionally wash a few snails out through the cave opening, they have not been observed in nearby streams. Researchers found that the animals remain confined to the cave environment, staying within two meters of its entrance.
Laboratory observations also provided clues about what these elusive creatures eat. The snails were seen feeding on diatoms, microscopic algae that grow on rock surfaces, and they also consumed fish food supplied by the researchers.
Only Three Living Snails Found, Raising Conservation Concerns
Although the discovery sheds new light on China’s largely unexplored underground aquatic biodiversity, researchers are concerned about the species’ future. They describe its conservation outlook as “far from optimistic.”
During the first field investigation in August 2025, the team encountered an exceptionally small number of snails. Despite searching the shallow cave waters, researchers located only three living adults and one empty shell. They found no juveniles, suggesting that the known population is extremely sparse.
The scientists are now urging more comprehensive investigations of cave ecosystems throughout China to uncover additional species and better understand these fragile underground habitats. They also emphasize the need to develop conservation protections quickly for these vulnerable mollusks, which are native to highly restricted environments and could face serious threats before their populations are fully understood.
