The planet Earth is host to an estimated 8.7 million species, with around 80 percent of all species still yet to be discovered. Needless to say, the vast richness of diversity in the life that occupies this small hunk of rock is staggering. While that does mean humans are one in 8.7 million, humankind is by no means the chart-topper across the board of species characteristics. While we rock some charts (we remain in first place for "Species that Cause Rapid Climate Change") we middle or bottom just about everywhere else. On those charts, some of the most interesting and unusual life takes the top stop -- areas like longevity, radiation tolerance, and defense mechanisms. Some of these life forms can survive conditions so extreme that they are suggested to be the subject of the search for life elsewhere in the universe. They are intriguing, they are weird, and they are here on Earth. Here are four species that will blow your mind.
1. Tardigrades (Water Bears): The toughest life on Earth?
Who knew extremophiles could be so cute?! (Source: Eye on Science)
Tardigrades are adorable microorganisms that have so far been able to withstand everything the universe has thrown at them. Some of the conditions tardigrades have been observed to survive are exposure to the vacuum of space, exposure (albeit brief) to temperatures as low as -1 degree Kelvin (-458 F!) and as high as 300 F, and high levels of radiation. The fact that these cute and tiny creatures exist is important, because it raises the possibility that similar life forms could be spread via meteors or asteroids, either between Mars and the Earth (giving some strength to the hypothesis that life in our solar system originated on Mars) or that life could exist on other planets with more extreme conditions than Earth.
2. Giant Tube Worm: Sea Vent Soldiers
A colony of giant tube worms. (Source: NOAA)
The ocean is teeming with undiscovered life-- in fact, humans have explored more of outer space than we have the ocean. While that means that far hardier/stranger/more interesting life is likely yet to be discovered, the current species we have found are redefining everything we thought we knew about the conditions in which life can survive. Giant tube worms are a prime example of this life: living, thriving, and multiplying next to hydrothermal vents (which, in addition to being near boiling temperatures, vent out a soup of chemicals that would be toxic to most life we know). These worms live around 5,000 feet below the surface and depend entirely on the vents for their life. If a geologic shift extinguishes the vent, the worms cannot survive -- but their extreme resistance to some of the hottest places on Earth is redefining the temperature limits of life.
3. Deinococcus Radiodurans: Can't Nuke This
D. Radiodurans under light microscopy. (Source: Michael Daly/Genome News Network)
Radiation exposure does not generally bode well for life. Since exposure to highly radioactive sources destroys the genome in whatever organism is harmed, cells cannot regenerate and the organism dies. In a strange, red, spherical bacterium named Deinococcus Radiodurans (a name literally meaning "strange berry that withstands radiation", the genome is still destroyed, but the organism simply repairs it -- sometimes in the span of just a few hours. This ability means that D. Radiodurans can withstand radiation levels thousands of times higher than levels survivable by humans. Once again, finding life with this ability shows that life outside of planet Earth might be easier than once thought. Radiation levels in space are far higher than levels on Earth, so for life to survive on non-Earthlike planets, asteroids, or meteors, it will have to share that defining skill with D. Radiodurans.
4. Turritopsis Dohrnii: The ageless jellyfish
The fountain of youth isn't quite what we thought... (Source: AMNH)
Humans have been seeking the fountain of youth since ancient times, and yet it took us until fairly recently to find it -- and the creature in which we found it was definitely a twist. Turritopsis Dohrnii is a species of jellyfish that never ages, because of a unique ability in which it can revert back to an earlier developmental stage as a result of tissue damage or starvation. The cell science behind it shows an extremely powerful methods of "cell recycling" where specialized adult cells can be changed into completely different specialized cells. Jellyfish with this ability have shown scientists a potential future in which doctors can rejuvenate cells damaged by disease.
