Extremophiles

March 27, 2013, 6:52 p.m.

 

Beetles with antifreeze blood, ants that sprint on scorching sand and spiders that live high up Mount Everest.

These incredible creatures are the extremophiles: animals that survive some of the most inhospitable conditions on Earth, and sometimes even further.

Scientists are amazed by the survival abilities of this motley crew and are currently researching their peculiar adaptations to find out whether they can be transferred to our own species.

In northern Alaska, the red flat bark beetle (Cucujus clavipes) survives arctic conditions using a cocktail of internal chemicals.

The formation of ice crystals in internal fluids is the biggest threat to its survival, but the beetle produces antifreeze proteins that stop water molecules from grouping together.

They also fortify their blood with high concentrations of glycerol, which means that the water in their bodies will not form the ice crystals that would kill other species, even at much milder temperatures.

Professor John Duman from the University of Notre Dame in Indiana, US has documented examples of larvae surviving at temperatures of -150 C, for which the antifreeze proteins alone would not be enough.

He explained that what makes these beetles unusual compared with similar species is that they deliberately dehydrate their internal tissues when temperatures fall.

"This concentrates the antifreezes several fold, such that if they're exposed to really low temperatures their body water then vitrifies [- forms a glass-like substance -] rather than freezing," Prof Duman told BBC Nature.

So why do red flat bark beetles live in these conditions?

"This is the case with any organism able to adapt to extreme environments of any sort: low temperature, high temperature, low oxygen, polluted environments," explained Prof Duman.

"Competition with other species is much reduced, because most species simply can't live in such extreme conditions."

This is the reason extremophiles thrive in hostile environments: they are exploiting an ecological niche for which they are supremely well-adapted, and face little or no competition within it.

Prof Duman said that the antifreeze proteins in red flat bark beetles are now being investigated for potential applications in cryopreservation and agriculture.

While the red flat bark beetle has adaptations to survive extreme cold, there are also species that thrive in scorching heat.

The desert ants of the Sahara are some of the most heat tolerant species in the world.

The Sahara desert ant (Cataglyphis bicolor) deliberately comes out at the hottest point in the day, when surface temperatures are around 60C and, crucially, restrict their predators' activities.

The ants scavenge for the corpses of insects which have died of heat exposure and although they are physically well developed to resist high temperatures, they could still die from heat exposure within minutes.

They survive because they only stay out for short periods. They have long legs and move quickly with as little contact with the sand as possible to stop the heat from building up in their bodies.

Finding food in an environment which does not support life is a difficulty also experienced by the Himalayan jumping spider (Euophrys omnisuperstes), which lives at heights of up to 6700m: higher than any other species.

This means there are no prey species for the spider to hunt, but the environment solves this problem: the wind blows frozen insects up the mountain for the spider to catch.While adaptation to a single harsh habitat is impressive, there are species which can survive a variety: the rarer polyextremophiles.

Tardigrades, also known as water bears, are tiny, eight legged animals which can survive extremes of heat and cold, low pressure and even high levels of radiation.

They have even survived exposure to spaceand as such are the undisputed champions of extreme environments.

Ingemar Jonsson, Associate Professor at Kristianstad University, is a specialist in tardigrade biology.

When asked what he considered their most impressive ability, he said: "Their ability to dehydrate completely when the surrounding conditions dry out, and stay in that state without any metabolism for many years or even decades, is clearly remarkable."

The way that tardigrades perform this drying-out act, however, is still a mystery.

"We know that the animal must somehow protect its basic cell structures from collapsing when water is withdrawn, and repair the damage that arises, but how this is done is unclear," Prof Jonsson.

Just like red flat bark beetles, dehydration protects tardigrades from freezing when the temperature drops, as their desiccated cells are safe from ice crystal formation.In December 2012, researchers reported observations of tardigrades able to survive being cooled to just over absolute zero, less than -270C.

They also have amazing radiation resistance: they are able to survive a thousand times more radiation than would prove fatal to humans. Again, this is due to their remarkable healing talent.

"We believe that the ability to repair damaged DNA is one of the main components of this system," said Prof Jonsson, whose recent studies have been focused on these mechanisms.

"Finding out how this works would be a breakthrough for our knowledge on tardigrades, but it would also be of considerable interest for many other fields of biology and medicine where DNA repair play a central role."

So while understanding these creatures is of interest in itself, future human benefits may also come from studies of how the extremophiles survive in the supposedly inhospitable parts of our universe.

Extremophiles feature in the BBC Four programme Insect Worlds: The Secret of their Success on Wednesday 27 March at 2030 GMT.

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