The Virtually Indestructible Water Bear
Want to be a superhero? Then you may want to pick up some skills from the segmented microscopic Tardigrades (slow steppers). Popularly known as water bears or moss piglets because of their slow gait, these tiny creatures can survive anything - From boiling to sub-zero temperatures, radiation, and even the vacuum of outer space. It is no wonder that this virtually indestructible animal has had the scientific community buzzing with excitement, for years.
The 1,150 known species of the micro-animals that measure between 0.5mm to 1.2 mm long, can be found almost anywhere, from mountaintops to the bottom of the deep sea, from tropical rainforests to the Antarctic. However, their favorite habitat seems to be in ordinary places like the film of water on lichens and mosses, deep inside sand dunes or soil and even, leaf litter - Any place they can find plentiful plant and animal cells and be cool enough to avoid sun desiccation.
Though they were first discovered in 1773 by Italian scientist, Lazarro Sapallanzani, the barrel-shaped animals that sport four pairs of stubby legs, are ancient creatures that have been inhabiting earth for at least 530 million years! This is not surprising given that the animals which have been subjected to all kind of tests on earth and space, are very hard to kill. Turns out, that it is because they possess a 'super power' like none other that has ever been encountered.
When subjected to any kind of extreme conditions, water bears have the ability to suspend themselves in a state called cryptobiosis - this brings their basic metabolic functions to almost a halt and reduces their body water content to between 1-3% of normal. This means that the animals are in a suspended state - neither completely alive nor dead. While in cryptobiosis, water bears can survive some of the most extreme conditions imaginable. Scientist have exposed them to temperatures ranging from 1° Kelvin or -458° F, something that can only be achieved in a laboratory to dousing them in 300° F water. In each case, they emerged unscathed.
And if that is not enough to impress you, how about this? They can withstand hundreds of times the levels of radiation that would kill humans, survive pressure six-times that of the deepest ocean and live through ten days in the airless vacuum of space. Oh, and after being boiled, frozen, irradiated, or sent to space, the water bear might still have a lifespan of 200 years or more. What's even more astonishing is that they can survive in this suspended state for a century and come back to life when the environment turns favorable again. So what can kill the water bears? So far, it appears to be only old age, which for them means at least two centuries.
The questions that have confounded most scientists is how and why these creatures have evolved to be so resilient, especially given the fact that their preferred habitat seems to be in normal environments like backyards or sandy beaches.
Bob Goldstein, a biology professor at the University of North Carolina who has been studying these amazing creatures since 1999, has still not found an answer to the 'why'. He does however have a theory on the 'how'. He thinks that water bears are able to survive in cryptobiosis because of their ability to produce a sugar-based substitute for water, called trehalose. This he believes, prevents some of the damage that is caused by desiccation. But again, not all species of water bears have this ability, so these crafty animals obviously have another trick up their sleeve, that they have not revealed yet.
One of the biggest challenges scientists have had in studying these animals is that they are very difficult to raise in a laboratory. However, they finally seemed to have cracked the code and are using them in lieu of the fruit fly as test subjects in a range of experiments that will help solve everyday issues like keeping vaccines stable at room temperatures. In case you are curious to see what these superheroes look like, they are readily available in any garden moss and can be viewed using the simplest of microscopes. So be sure to check them out!
Resources: wired.com, wikipedia.org, serc.carelton.edu, space.com
Reading Comprehension (3 questions)
- How many species of water bears are there? Where do they live?
- What are the many ways scientists have tried to kill them?
Critical Thinking Challenge
Why would it be harder for humans to achieve a state of 'cryptobiosis'...