Erhaia dijiang lives in shallow water inside a high-altitude karst cave. Its traits mirror cave animals in Kentucky and Texas, and its tiny population worries researchers.

A snail smaller than a grain of rice, with no eyes, no body color, and a nearly transparent shell, has been described as the first freshwater cave-dwelling snail ever documented in China. Researchers found it in a cave near Yuxi City in southwest China's Yunnan Province at about 6,765 feet (2,062 meters) above sea level, a record altitude for its snail family, according to a study in the open-access journal Subterranean Biology.

The finding comes with a warning. During an August 2025 field survey, the team found just three living adults, one empty shell and no young, and described the species' survival status as "far from optimistic," according to a release from publisher Pensoft shared by ScienceDaily.

The snail is a clear example — tiny but telling — of how animals change after generations in total darkness, a pattern also seen in caves under Kentucky and Texas.

A Snail Built for Darkness

The research team, led by scientists at Yuxi Agriculture Vocational-Technical College with a co-author from Nanchang University, confirmed the species by comparing shell features and DNA with related snails. Because the paper is published open access under a Creative Commons license, its photos of the snail and cave habitat can be reused with credit to He et al., 2026.

The new species, Erhaia dijiang, is named for Di Jiang, a faceless mountain god from the ancient Chinese text Classic of Mountains and Seas. The name fits. The structures associated with vision have fully degenerated, and the body has no pigment.

The shell is cone-shaped and translucent, about 2 millimeters (0.08 inches) long and 1 millimeter wide, according to the paper. The snails have long, slender tentacles and, in lab observations, crawled under rocks whenever exposed to light. They fed on diatoms scraped from rock surfaces and on fish food the researchers supplied.

The species lives among submerged gravel and broken rock in water less than about 3 feet (1 meter) deep, at roughly 68°F (20°C). Heavy rains sometimes wash a few snails out of the cave's outlet, but none has been found in nearby surface streams, and all stay within about 6 feet (2 meters) of the entrance.

Why Cave Animals Lose Eyes and Color

Scientists call animals that spend their whole lives underground troglobites. "Troglobites spend their entire life cycle in caves," the National Park Service explains at Mammoth Cave National Park in Kentucky, where cave animals show depigmentation, reduced or lost eyesight and slow metabolisms.

In total darkness, eyes and pigment offer little benefit, so over many generations those traits fade. Slow metabolisms help animals survive where food is scarce and arrives mostly by water from the surface. Mammoth Cave's northern cavefish shows the same pattern. "Complete darkness has caused them to evolve without eyes and without pigment," the park says, adding that the fish may live 30 to 40 years, according to its cavefish page.

The United States has its own fragile examples. Mammoth Cave's endangered Kentucky cave shrimp and the Texas blind salamander of the Edwards Aquifer beneath San Marcos are both pale, eyeless animals protected under federal law, and the U.S. Fish and Wildlife Service has worked with regional partners to protect the Texas species and its groundwater.

A High-Altitude Cave and a Tiny Population

Most known cave snails in this family come from lower elevations. The researchers said the new find shows freshwater cave snails can live in karst caves above about 6,560 feet (2,000 meters), a habitat that has received little survey attention.

The bigger concern is numbers. "The population density of this newly discovered species was found to be extremely low, and no juveniles were observed," the authors wrote. With so few animals collected, the team could not dissect specimens to study internal anatomy.

Evidence check: the species was confirmed using shell features and DNA from a gene called COI, but the description rests on three live adults and one shell from a single site. The population estimate comes from one survey season, and the paper does not name specific threats. Cave animals that live in one site are generally vulnerable to water pollution, groundwater changes, and disturbance, but those risks have not been measured at this cave. Lab observations of feeding and light avoidance also come from only a handful of animals and may not reflect behavior in the wild.

Protecting Life Most People Never See

The researchers called for broader cave surveys across China and quick conservation measures for Yunnan's endemic mollusks. Because troglobites usually live in a single cave system, losing one site can mean losing a species entirely.

The same principle applies at home. Groundwater that feeds cave streams also supplies wells and springs, so pollution entering sinkholes can reach both cave animals and drinking water. Residents in karst regions, from central Kentucky to Texas Hill Country and Florida, can help by keeping trash and chemicals out of sinkholes and following local well and septic guidance.

Cave visitors should stay on marked routes, avoid touching cave water or animals, and follow park rules on cleaning shoes and gear between caves. The bottom line is that a nearly invisible snail adds a new altitude record and a new species to science, and its survival now depends on protecting one small stream inside one cave.

What Readers Want to Know

What is Erhaia dijiang?

A newly described freshwater cave snail from Yunnan, China, with no eyes, no body pigment, and a nearly transparent shell about 2 millimeters long.

Why is it notable?

It is the first freshwater cave snail documented in China and the highest-altitude cave snail recorded in its family, at 2,062 meters.

Why do cave animals lose their eyes?

In total darkness, eyes and pigment offer little benefit, so over generations cave animals often lose them while slowing their metabolisms.

Is the snail endangered?

It has no formal listing yet, but researchers found only three living adults and no juveniles and called its outlook far from optimistic.

Are there similar animals in the United States?

Yes. Kentucky's Mammoth Cave and Texas's Edwards Aquifer host eyeless, pale animals such as the Kentucky cave shrimp and Texas blind salamander.

How can people protect cave life?

Keep pollutants out of sinkholes, follow cave rules on gear cleaning, and avoid disturbing cave water and animals.