Scientists have discovered China’s first known freshwater cave snail, an eyeless species so rare that only three living adults have been found.
Deep inside a mountain cave in southwestern China, scientists found an animal that appears built for a world where sunlight never reaches. The tiny freshwater snail has no eyes, almost no color, and a translucent shell that reveals its delicate body beneath.
The newly identified species, Erhaia dijiang, is the first freshwater cave snail ever documented in China. It was discovered in Hongta District of Yuxi City, Yunnan Province, and formally described in the journal Subterranean Biology. The finding fills a notable gap in the study of East Asia’s underground freshwater ecosystems, which remain far less explored than many habitats at the surface.
Erhaia dijiang is a troglobiont, meaning it is specialized for life entirely within caves. Its eyes and related structures have disappeared through evolution, while its body lacks the pigmentation that protects many surface animals from sunlight. These traits are common among organisms that spend countless generations in permanent darkness, where vision and protective coloring offer little advantage.
A Faceless Snail Built for Darkness
The snail’s appearance inspired its unusual name. Researchers named it after “Di Jiang,” a mountain god described in the ancient Chinese text Classic of Mountains and Seas as a faceless creature. The connection goes beyond looks. In laboratory observations, the snails strongly avoided light and crawled into narrow spaces beneath rocks whenever they were exposed.
The discovery also pushes the known limits of where these snails can live. The cave lies 2,062 meters (6,765 feet) above sea level, the highest elevation recorded for a cave-dwelling member of the family Erhaiidae. Its presence shows that freshwater cave snails can survive in high-altitude karst systems more than 2,000 meters (6,562 feet) above sea level.
Karst landscapes form when water slowly dissolves soluble rock, often creating networks of caves, underground streams, and isolated pools. Such habitats can act like biological islands. Populations may remain separated from the outside world and from one another for long periods, allowing highly specialized species to evolve within a single cave or water system.
Life Inside a High-Altitude Karst Cave
Erhaia dijiang lives among gravel and broken stone in shallow cave water less than one meter (3.3 feet) deep. The water remains close to 20°C (68°F), providing a relatively stable environment despite the cave’s elevation. The snails graze on diatoms growing across submerged rocks and will also eat fish food under laboratory conditions.
Heavy rain occasionally sends fast water through the cave, washing a few snails toward its outlet. Even then, researchers found no individuals in nearby surface streams. The animals stayed inside the cave and within two meters (6.6 feet) of the entrance, suggesting that even brief exposure to the outside environment may be unsuitable for them.
That extreme specialization also makes the species vulnerable. During a survey in August 2025, scientists found only three living adults and one empty shell. They saw no juveniles, raising concerns about whether the population is successfully reproducing. The researchers described its survival outlook as “far from optimistic.”
An Extremely Rare Species at Risk
The low number of observed animals, combined with their highly restricted habitat, gives them little protection against pollution, changes in water flow, cave disturbance, or other local threats.
The researchers are calling for wider surveys of China’s caves, both to determine whether Erhaia dijiang exists elsewhere and to search for other overlooked species. They also recommend developing conservation measures quickly. For animals confined to a single underground habitat, damage to one cave can threaten an entire species.
Reference: “A new eyeless species in Erhaiidae (Gastropoda, Truncatelloidea) from a cave in Yuxi City, Yunnan, China” by Yue-Ming He, Hong-Quan Xiang, Jin-Mei Yang, Hui Zheng, Suo-Zhu Yang, Yu-Feng Zhou and Jian Zheng, 29 May 2026, Subterranean Biology.
DOI: 10.3897/subtbiol.56.188075
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