The animals that lives for 10,000 years( By Zaria Gorvett - 17 December 2015 - BBC News )One creature can survive for millennia in the so-called 'Sea of Death'They fell out of the sky and landed on the pale blue planet with a splash. Many of the crew missed the whole thing. Deep inside the spacecraft, arranged in neat stacks, were rows and rows of sleeping astronauts. Each was curled up inside their own pod, where they could have stayed for 10,000 years.These were no ordinary space travellers. In the following weeks, they burst from their shells and developed into full-blown aquatic monsters: they are salmon-pink, with three eyes and eleven pairs of thrashing legs.This really happened. The year was 1972 and the slumbering passengers were brine shrimp, otherwise known as "sea monkeys", returning from the Apollo 16 moon mission. They had been taken into space to test the impacts of cosmic radiation on astronauts.This treacherous experiment required a near-indestructible guinea pig. Enter the brine shrimp, whose survival skills defy belief.You can safely dry them out, set them on fire, dissolve them in alcohol, deprive them of oxygen, zap them with ultraviolet light, boil them at 105 °C or chill them to temperatures approaching absolute zero: the point at which atoms stop moving. They can also survive extremes of pH that would dissolve human flesh, water that is 50% salt, or a bath of insecticides. They are happy in the vacuum of space or at the crushing pressures found under 6,000 metres (20,000 feet) of ocean.We are now starting to understand how they do it. Apollo 16 commander John Young on the Moon (Credit: B.A.E. Inc/Alamy Stock Photo)Space is drenched in high-energy particles called cosmic rays, which easily rip through cells, tissues and the aluminium walls of a spacecraft. The Moon was the perfect place to study their effects.The "Biostack I" experiment involved stacking brine shrimp embryos, along with plant seeds and bacterial spores, between layers of radiation-sensitive materials. Any rays that passed through the stack would end up on the detection layer, so the NASA scientists knew exactly which passengers had been hit.Of 110 brine shrimp embryos that took a galactic bullet, many hatched – albeit with deformities – and a few went on to live full shrimp lives.A follow-up experiment called Biostack II was taken to the Moon by Apollo 17 later the same year. It achieved similar results.The strange thing is, brine shrimp look rather fragile, with their wafting legs and long antennae. What is their secret? Great Salt Lake in Utah is home to brine shrimp (Credit: John McLean/Alamy Stock Photo)Despite their brand name, sea monkeys do not live in the open ocean. They have been splashing around in salty pools and lakes, from the Great Salt Lake in Utah to the Caspian Sea, for over 100 million years.Brine shrimp are also not shrimp, but they do belong to the same group, the crustaceans. They are tiny, just 15mm long. They eat algae, which they filter out of the water. They swim upside-down and breathe through their legs, and females do not need a male to reproduce.Crucially, they have a unique affinity for salt. They can tolerate concentrations up to 50%. Such water is far saltier than the ocean, which is only about 3.5% salt, and the salt will be on the verge of precipitating out as a solid. The brine shrimp are fine with this.But there is a catch: if you live in a pond, there is always a risk that it will dry out. The pools and lakes brine shrimp inhabit frequently disappear for months, years or decades. This should be a gigantic problem, but the brine shrimp simply dry out. Male brine shrimp have claspers for holding onto females (Credit: Nature Picture Library/Alamy Stock Photo)When conditions are favourable, female brine shrimp produce thin-shelled eggs that hatch immediately. But when food is scarce or salt levels are rising, they resort to plan B. They produce hard-shelled "cysts", each of which contains a near-fully-developed larva.These cysts are able to withstand near-total dehydration, losing more than 97% of their water content. All their life processes stop and they enter a state of suspended animation called anhydrobiosis, a bizarre stopover between life and death.As anyone who has kept sea monkeys as pets will know, to resurrect the embryos you just add water. The cysts take on 1.4 times their weight in less than 24 hours, before hatching into larvae the size of the full stop at the end of this sentence. When they first hatch they have just one primitive eye, though they add two more sophisticated eyes later.It is an aggressive strategy for an aggressive environment, and it works. In the 1990s, oil exploration crews were drilling near the Great Salt Lake when they dredged up a mat of cysts between two layers of salt. Wondering whether they would hatch, they put some in water and reportedly a few did. Radiocarbon dating estimated they had been lying there for 10,000
đang được dịch, vui lòng đợi..