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Scientists have described a new species of cave snail, an eyeless, almost transparent mollusc that avoids light. Named Erhaia dijiang, it is the first documented freshwater cave snail discovered in China, according to a study published in the journal Subterranean Biology.

The snail was found in a high-altitude limestone cave at an elevation of 2,062 metres, making it the highest-altitude member of its family recorded to date. Adaptation to life in perpetual darkness has left the mollusc without eyes, while its shell is almost transparent. In the cave environment, vision and protective pigmentation offer little apparent advantage.

The species inhabits shallow water less than one metre deep, with a temperature of around 20°C.

During an initial survey in August 2025, researchers found just three living adult snails and one empty shell. No juveniles were observed. All the living specimens were located within two metres of the cave entrance, while nearby streams yielded no specimens.

In laboratory conditions, the snails fed on diatoms and fish food provided by the researchers.

The species belongs to a group known as troglobionts — organisms fully adapted to life underground. Such animals offer insights into how evolution shapes organisms in extreme but relatively stable environments without sunlight. The loss of eyesight and pigmentation can be an adaptation that reduces the allocation of resources to traits with little benefit in permanent darkness.

However, the species’ survival prospects are a concern. Its population appears extremely small and confined to a limited area near the entrance of a single cave. The researchers described its conservation outlook as far from optimistic, warning that disturbances such as water pollution and tourism could threaten its survival.

The discovery expands scientific knowledge of cave biodiversity in China and raises the possibility that similar, previously undocumented species may inhabit other limestone caves in the region.