There are still new species to be discovered on Earth, not only in deep ocean trenches and dense jungles, but also in the world of the microscopic. Scientists have now found a total of 42 new species of microsnails in Southeast Asian caves, mostly in northern Vietnam. On average, these tiny creatures are just 0.89 millimeters in size, making them smaller than many a grain of sand. They are among the smallest land snails on our planet.
Angustopila psammion – this is the name of the smallest known land snail in the world. Its housing is only around 0.48 millimeters high and 0.6 millimeters long. As small as a grain of sand and barely visible to the human eye. However, it is reasonable to think that we are far from knowing all the tiny land snails that can be found in the world. Twelve sibling species of Angustopila psammion are known to date, but how closely related is the tiny one actually?
Over 200 caves “riddled”
In search of new microsnail species, an international research team led by Barna Páll-Gergely from the Center for Agricultural Research in Budapest combed a total of 223 caves in China, Laos, Myanmar, Thailand and Vietnam. The collected soil samples were sieved through a large metal screen and nylon stocking. The researchers then sorted the dried samples under the stereo microscope to find the tiny snail shells. In a few cases, they were also able to collect living snails on site by carefully picking them up with fine tweezers.
The tedious search was worth it: “In our extensive work, five times more species were discovered than we had expected,” reports Páll-Gergely’s colleague Adrienne Jochum. Overall, the researchers succeeded in describing 42 new species from the Angustopila snail genus. They are therefore close relatives of the previously known micro-land snails. The analyzes also led to some corrections in the naming and classification of the previously known species. All in all, the genus Angustopila now includes 53 species of microsnails instead of the previously known 13 species.
Hotspot in North Vietnam
“The smallest of the 42 species we newly described are Angustopila maasseni and Angustopila somasaki with a shell height of only 0.62 to 0.67 millimeters. The ‘largest’ species, Angustopila majuscula sp. nov., has a shell height of 1.31 millimeters. On average, the 53 species reach a size of 0.89 millimeters,” reports Jochum. This means that the animals are smaller than many a grain of sand and certainly live up to their rank as the smallest land snail species in the world. As far as their appearance is concerned, the animals differ not only in their size, but also in the shape of their shell openings. According to scientists, some shell openings resemble a pear, while others are more like a kidney or an egg.
Due to their small size, it is not surprising that most of these microsnails only have a small distribution area or even only occur in a single cavity. Nevertheless, there are also some “outliers”, as Jochum explains. Three species are distributed over several hundred kilometers and occur in many different caves. Three others are known from two locations up to 500 kilometers apart. However, the micro snails seem to feel most comfortable in the north of Vietnam. At this hotspot, the researchers were able to count up to seven different species in a single cave. But also in northern Laos, Myanmar and in the Chinese province of Guangxi, the micro snail diversity is above average.
Source: Senckenberg Research Institute and Natural History Museums; Specialist article: ZooKeys, doi: 10.3897/zookeys.1147.93824