Ice Bound Life

Hiking across a glacier is not something to everyone’s taste, but to glacial geologists, it’s more than just a hobby. In 1887, one such geologist, George Wright, was walking across the Muir glacier in Alaska doing the sort of thing that glacial geologists usually do when, as the sunlight started to fade, something remarkable caught his attention.

The glacier he was hiking across began to darken - not as a result of the dimming light, but it seemed to be developing dark patches across its surface. As he watched, tiny worm like creatures were burrowing their way out of the ice and snow and wriggling about on the surface. Within a an hour, almost as far as he could see was covered in worms and they continued to cover the surface until it was almost dawn, whereupon they began to burrow back down into the ice and snow.

We now know that ice worms inhabit a wide range of the north American continent - from Alaska to Washington State and they spend their entire lives in temperatures close to or below freezing. They are curiously territorial as well, never straying far from their feeding grounds, even if nearby places are equally as chilly and feed on snow algae and pollen deposited on the surface by wind.

These tiny worms, only 15mm long and 5mm wide, appear to squeeze through tiny cracks in ice, air holes and other fissures in order to move about; some researchers have postulated that the worms secrete a lubricant from a pore on their head to help them squeeze through the ice, whilst others think that it may be some form of antifreeze that helps them melt the ice ahead of them. They also have a very narrow range of temperatures in which they can survive - below -7° and they freeze, above 5° and they literally begin to melt. It is estimated that they can reach densities of 30 - 300 worms per square metre and that these worms could easily outnumber humans if you added up their collective numbers across all their territories.

They generally follow a diurnal lifestyle during summer - emerging at sunset to feed and retreating before sunrise, although they can occasionally be found during the day in glacial streams, clinging to the ice on the surface and feeding on algae and pollen in the water. It is believed that the protection of the cold water is what keeps them from melting during the day.

They also appear in glacial ponds, where large numbers of them have been seen bundling together in groups. As they do not appear to bundle together in streams on on the surface of the ice, it is believed that this may be part of their reproductive cycle.

Little is known about the worms during the winter, where temperatures can drop as low as -40° on the surface, mostly because as likely as this temperature is lethal to the worms, it also makes life incredibly difficult for researchers. It is not really known if they remain below the surface feeding or hibernate through the winter, although specimen worms have survived being frozen in lab freezers for over a year without food.

We actually know surprisingly little about these worms and how they came to live in such a cold, harsh environment, what evolutionary path split them off from other species and what their secret is to preventing themselves from freezing at 0°.

NASA, and other researchers have taken a keen interest in the worms, with NASA even providing funding for mapping the worms genome and reverse engineering the cold tolerance that the worms possess. One of the more obvious benefits of this research is the storage and transport of organs for transplant. If it is possible to cold store organs and tissue without ice crystals forming in the cells, then long term storage of these valuable items becomes realistically possible, allowing life saving medical treatments without the rush to get a donor organ to the recipient as fast as humanly possible.

Another possible spin off of this research is the possibility of understanding how these organisms achieved their cold tolerance and what it may mean for potential life on the icy moons of the outer planets, such as Jupiter, Saturn, Uranus and Neptune. Finding ice worms or something similar in the ice of Europa and understanding how these creatures survive the intense cold would be of immense value to science and humanity.

We know of hot and highly acidic extremophile organisms that live in places where no other life could exist - hot springs, volcanic vents and undersea black smokers, but the ice worms represent a real chance at the discovery of the opposite end of that spectrum - cold. The discovery of organisms that can not only survive, but thrive in temperatures that would have ice crystals forming in our cells and blood is one step closer to understanding any evolutionary processes that may be taking place on the moons of other worlds. Mesenchytraeus solifugus may hold at least part of that key.