If you were to ask what creatures on the planet have the most tenacious vitality, many people would first think of tardigrades. This small animal, in many extremely harsh environments, can survive unscathed.
Some researchers have tested the vitality of tardigrades at extreme temperatures of 150 ° C and -200 ° C, and found that they are not killed immediately, and can be miraculously "resurrected" after being put into a normal temperature environment! Even at a terrifying pressure of 600 megapascals, equivalent to 6 times the water pressure of the Mariana Trench, the tardigrades were not crushed to death. Even the powerful radiation that an atomic bomb can produce is not enough to take the life of the tardigrade. Even without oxygen and water, they can hibernate!
Other researchers went even further, shooting tardigrades like cannonballs and finding that some tardigrades survived. They hope to be able to verify whether the tardigrades that crashed on the lunar surface in 2019 with Israel's Genesis probe can survive there.
Unexpectedly, human beings are so space, and these slow-moving animals can easily go to the moon.
In fact, for tardigrades, large-scale movement is indeed not an easy task. They are usually between 50 microns and 1.4 millimeters long, and they move very slowly indeed, and it seems that the name tardigrades is indeed worthy of the name. However, they do not seem to accept their fate, because these tardigrades have found their own way of moving, that is, "free riding".
Recently, researchers published a new paper in Science Reports, and they found that these tardigrades are indeed very smart, finding their own way to move widely. However, hitchhiking also has the elegance of hitchhiking, compared to some animals will be attached to large animals or directly wait for the "wind blowing", tardigrades have their own preferred "means of transport", that is, snails.
For us, snails have always been synonymous with dullness, but like the story of "ponies crossing the river", for tardigrades, snails are simply a "sports car".
In fact, tardigrades are not completely dependent on nature's air currents to move, and previous studies have shown that sometimes they may even be blown 1,000 kilometers (621 miles) away by high winds, after all, their tiny sizes are difficult to resist strong winds. The researchers pointed out that this is not necessarily the trip that tardigrades expect, because the direction of the wind is not fixed, and the tardigrades will fall into some harsh environments. Although the tardigrades are tenacious, they don't want to use this skill...
In contrast, snails are much more reliable because they themselves do not travel to extreme environments and are likely to travel to specific microhabitabs.
It should be noted that the researchers did not actually observe the tardigrades using snails to hitchhike, but made such a guess. They found that there was a relatively large overlap in the habitats of tardigrades and snails, which is unlikely to be accidental, so they made this reasonable conjecture.
To test this conjecture, they conducted experiments using silicone Petri dishes. There is only water in one part of the Petri dish, and there are snails in the other part of the Petri dish. It turned out that only the tardigrades in the Petri dish where the snails were present were able to escape the petri dish, and the tardigrades in the water, despite swimming, were always bound here.
They speculated that the tardigrades would use snails as their saddles and hide here to travel. When the snails defecate, the tardigrades will escape and start a new life – it seems that this is really a "poop" car...
"If tardigrades (or tardigrades' eggs) travel with snails, these passengers (probably) will (possibly) get off at a stop in a suitable environment," the researchers noted. ”
Despite the convenience provided, snails also pose some threat to tardigrades, and that is their mucus. This mucus is harmful to tardigrades and can even endanger the lives of tardigrades, starting with the viability of tardigrades themselves.
Why do tardigrades have such a strong vitality? Scientists have found that these tardigrades can enter a special state in harsh environments, which scientists call "cryptobiosis." Faced with different harsh environments, tardigrades have four different cryptoecosis, namely low-humidity cryptosystems , Cryobiosis , Osmobiosis and Anoxybiosis.
Among them, low-humidity cryptogenes are also known as "tun state". In this state, tardigrades can dehydrate in large quantities, greatly reducing the metabolism in the body, almost equivalent to pressing the pause button for almost the entire life. When metabolism is stopped, the tissues or organs of living organisms are not easily destroyed, thereby greatly improving the probability of survival.
It is precisely because of the various hidden ecology that the tardigrade has become a well-known "immortal body", and can not even be killed in space.
When the surrounding environment improves, or when the hidden water bears are transferred to the right environment under the influence of external forces, they can absorb the water around them and reawaken as if they had never encountered an extreme environment. To put it graphically, it is actually similar to the method of the three-body people in "The Three-Body Problem" to survive the harsh environment through dehydration.
Therefore, when traveling long distances with snails, tardigrades will face new embarrassments: the main component of snail mucus is water, and the tardigrades that originally lived in the snail's internal organs through the bucket state will accidentally contact the snail's mucus when they are ready to sleep peacefully, and are forced to absorb water, thus leaving the tub state.
On the other hand, this mucus dries very quickly, which causes tardigrades to have difficulty adapting to this rapid change and failing to transition into a vat state in time, threatening their lives.
The researchers found that only about 34 percent of the tardigrades that were exposed to snail mucus survived. In contrast, if there is no exposure to snail mucus, 98% of tardigrades can spend their journey safely.
I have to say that this is really a dangerous trip...