One is a small record and the other seems to be decorating his house with feces

Armed with items including a sieve and a bucket of water, scientists in limestone caves in Vietnam and Laos have discovered two remarkable species of snail.

Who’s Sheet Contributions to zoology Open the door and check out the latest additions to the world of microsnails, you may not be affected right away. Because at first glance, the two new species presented by the international team of researchers – including some from the Dutch – are very similar to snails we find in parks and gardens. But appearances are deceptive, as the scale number in the photos reveals. Because these snails are small. One is even recorded in books as the smallest land snail described by researchers so far.

smallest
smallest sample – Angstopella Bassamion It is called – it has a snail shell, the size of which is about 0.5 millimeters. says Mino Schilthuizen, one of the discoverers and evolutionary biologist associated with Natural Biodiversity Center Initiate.

only home
Remarkably, Schilthuizen and his colleagues could only guess at the appearance of this tiny shell’s inhabitant. “We only found houses,” says the biologist. Scientias. nl. “This is often the case with small snails and has something to do with the way we discover these snails. We scrape some soil or – as in this case – some gravel from a crevice in a limestone cave, take it off and then throw the sieve into a bucket of water and see what floats. Because unmanned snail shells are filled with air bubbles, they float and so do we a. psammion finds.” After discovering this new species, the scientists also cleaned the cave walls, hoping to find a living specimen. But without result. “We think they live underground.” The recovered snail shells may have washed away – along with the sediments – It eventually ended up in the cleft of the limestone cave in which the researchers found it.

Unanswered questions
Obviously, the fact that the researchers found only the home of microsnails does not prevent them from describing and introducing the new species. “It is very common with terrestrial snails to do this on the basis of snail shells,” explains Schilthuizen. “In snail science the whole classification is in fact based on the houses rather than the creatures themselves. Sometimes it is a little strange to outsiders, like this science which depends entirely on a secretion product, but in snail science it is an imitation. It is also possible to describe species The new ones are based on the house alone, because homes often have many distinct species characteristics.” On the other hand, it means that many questions remain unanswered. “We know very little about what the animal looks like,” admits Schildhuizen. “We don’t know, for example, whether the animal also has color patterns or what the genitals look like.”

the little one is beautiful
What researchers do know is that an animal has to be small to fit into its tiny home. Such a small size undoubtedly has evolutionary advantages. For example, it enables small snails to crawl into spaces that are only inaccessible or much larger. Because of its small size, it creates a place where it can thrive. But miniaturization – the shrinkage process that eventually led to… a. psammion – He knows the limits. This means that the snail cannot continue to contract. It stops for a while. “If you get too small, you have physiological problems,” says Schilthuizen. In the case of snails, drought is likely one of them. With snails, moisture evaporates across the surface. The smaller the snails, the larger the surface relative to the content and the greater the chance of dehydration. This is also why we know very small snails, but not small slugs; Without a protective shell, the young snail is doomed to dehydration.” Thus, there are more physiological constraints that prevent the snails from getting smaller and smaller. “They also have to be able to produce an egg – and this happens in the upper house – and these have to be The egg is also able to come out afterwards. And because that egg already has the beginning of a snail shell, that egg can’t get any smaller either. This automatically leads us to the fascinating question of whether there are still Earth snails much smaller than a. psammion to be present. “Of course, that cannot be completely ruled out.” What is striking, however, is that many of the recently discovered small nails differ in size from them a. psammion cling to. It is cautiously suggested that when it comes to terrestrial snails at least, we are gradually approaching the limits of miniaturization.

Land snails may be small; They are clearly fine. Perhaps this is not a rare species. we’ve got a. psammion It is found in large numbers in our samples. This suggests that – although we don’t see them – they are very common.”

Another new comer
next one a. psammion Schilthuizen and colleagues introduced another new little nail in their research article: Angustopila coprologues. “It looks almost the same, but it’s a bit bigger. Besides, a. coprologos All the sharp spurs in his house are adorned with grains.” These grains are bound to their shell by a snail in a regular pattern. “And it appears to be excrement. Nobody knows why a. coprologos This does. And more snails have been known to cover their homes with trash. “And they seem to be doing this to camouflage themselves.” So who knows, that’s why too. a. coprologos The house was carefully covered with droppings.

Angustopila coprologos decorates his house with cereals; Maybe feces. Image: Contributions to Zoology 2022; 10.1163/18759866-bja10025.

With the discovery of the two new species, the stock of the young nail expanded again. “It still feels great,” says Schilthuizen, who has already discovered more snail species. “This way you can fill in the gaps in the civil registry for biodiversity.” Schilthuizen is convinced that there are still many holes. “I think globally we don’t even know half of microsnails. That’s of course also because the bugs move slowly and therefore barely move. There are species that are only found in an area of ​​a few square meters and they evolved there right away. Before we went to all those places, we spent many years “.