World's Tiniest Snail Discovered in Southern China

The world's smallest snail, Angustopila dominikae, measures 0.88 millimiters across. Dr. Barna Páll-Gergely

Seven species of extremely tiny snails, including the world's smallest specimen, have been discovered in southern China.

When researchers first found the smallest snail, which has been named Angustopila dominikae, they thought it might be a juvenile. But further inquiry showed that it was an adult, says Adrienne Jochum, a researcher at Switzerland's University of Bern and Bern Natural History Museum.

This species has a shell that at its widest measures 0.88 millimeters across (0.03 inches), making it small enough to fit through the head of a needle, and much smaller than the head of a match, as noted in a study describing the find published September 28 in the journal Zookeys. The researchers found only shells of the species, in a sample of soil at the base of a limestone cliff in Guangxi, just north of Vietnam, so many of the details of their life history remain a mystery, Jochum says.

The world's smallest snail yet described, Angustopila dominikae, can fit inside the head of a needle. Dr. Barna Páll-Gergely and Nikolett Szpisjak

That said, it's quite likely that they have a similar diet and lifestyle compared with small nails that live in caves, because there are only so many tiny sources of food, Jochum adds. These cave snails feed on microorganisms like bacteria and fungal filaments. Jochum hypothesizes that the round shape of the shells of these new species may enable them to wedge themselves into tiny cracks in rocks. It could also allow them to trap air bubbles in their shell and float in water if they become dislodged by rain, and also probably enables them to survive being eaten by a bird, she adds.

Being so small is a huge evolutionary advantage. It allows the sails "to survive anything," Jochum says, from wind, floods and changes in climate to predation—most creatures bypass the snails in their hunt for larger prey.

Like other similar snails, these species are likely hermaphroditic, changing sex based on the season and what other snails are around, she says.

The world's smallest snail is much smaller than the head of a match. Adrienne Jochum

The snails need limestone to provide calcium for their shells, which are made of calcium carbonate. The tiny cave snails that Jochum studies have often been found with bits of stone in their microscopic guts.

Eike Neubert, a researcher at Bern's Natural History Museum who wasn't involved in the paper, says that "this is a superb study on usually overlooked species of snails. People are not aware that the world is full of microscopic life beyond the level of bacteria or unicellular organisms." Neubert estimates that more than 75 percent of snails are actually quite small, at less than 5 millimeters in length, and thus "beyond the magic boundary of public awareness."

"The world is full of small snails," he says, "on land as well as in the seas or in the freshwater."