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Arctic creepy-crawlies part I: the ice worms

The views expressed are those of the author and are not necessarily those of Scientific American.


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Following my previous post on wildlife diseases, I’ve been in a fairly multicellular mood. Rather than try and turn my mind back to bacteria I decided to get it out of my system by finishing the month with a two part mini-series on creepy-crawlies that survive in some of the harshest conditions on earth; the frozen arctic.

Ice ridges in the Beaufort Sea off the northern coast of Alaska. Photo by Rear Admiral Harley D. Nygren, NOAA Corps from the U.S. National Oceanic and Atmospheric Administration

Part I: the ice worms

Related to common earthworms, these annelids spend their entire lives in glaciers. They are the largest multicellular eukaryotes that require below-freezing temperatures to survive. First discovered in Alaska, ice worms are found across the northern United States [edit: and Canada]; in Alaska, Washington, Oregon and British Columbia. They haven’t been found in any other parts of the world, even those with glaciers.

Ice worm on snow image from wikimedia commons by Southwick3

The ice-worms live inside glaciers, although it is uncertain whether they are able to tunnel through the ice by releasing some form of antifreeze or just take advantage of natural breaks in the ice. They feed on snow algae, and come to the surface of the glaciers during the morning and evening to feed, spending the rest of the day safely tucked inside their icy home. Ice worms are so well adapted to the freezing conditions that they cannot live anywhere else. Exposing them to even 5 degrees above freezing and their internal membranes start to fall apart causing the whole worm to liquefy and essentially melt.

There are some fascinating biochemical changes that allow the ice worms to survive below zero (and are responsible for their rather gruesome death if they get too hot). One example is tubulin – the protein that forms little networks inside the cell to aid with structure and transport. These networks are formed by subunits of the tubulin all joining together, and in most species tubulin breaks apart at low temperatures. The ice worms have tweaked the protein structure of their tubulin to form more stabilising contacts between subunits in a way that is distinct from other cold-adapted organisms.

Mendenhall Glacier in Juneau, Alaska. Public domain image from wikimedia commons.

Another adaptation the ice worms have made is to adjust their levels of ATP, the molecule that is used as energy currency inside the cell. In most temperate organisms ATP production decreases in the cold, leading to animals becoming lethargic and sluggish. In the ice worms ATP is kept at very high levels within the cell, and production increases as temperatures drop.

They might not sound, or look, like the most romantic creatures but to my surprise I’ve found they feature in the odd love poem, including this sweet little one by the English poet Robert William Service written in 1910:

“In the land of the pale blue snow
Where it’s ninety-nine below,
And the polar bears are dancing on the plain,
In the shadow of the pole
Oh, my Heart, my Life, my Soul,
I will meet thee when the ice-worms nest again.”

Tartaglia LJ, Shain DH. Cold-adapted tubulins in the glacier ice worm, Mesenchytraeus solifugus, Gene. 2008 Nov 1;423(2):135-41.

Napolitano MJ, Nagele RG, Shain DH. The ice worm, Mesenchytraeus solifugus, elevates adenylate levels at low physiological temperature. Comp Biochem Physiol A Mol Integr Physiol. 2004 Jan;137(1):227-35.

S.E. Gould About the Author: A biochemist with a love of microbiology, the Lab Rat enjoys exploring, reading about and writing about bacteria. Having finally managed to tear herself away from university, she now works for a small company in Cambridge where she turns data into manageable words and awesome graphs. Follow on Twitter @labratting.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Lacota 11:38 am 06/28/2014

    “First discovered in Alaska, ice worms are found across the northern United States; in Alaska, Washington, Oregon and British Columbia.” Hate to break it to you but British Columbia is Canada not the United States. Perhaps you meant to say North America instead of The United States though I am sure many “Americans” wouldn’t appreciate the difference.

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  2. 2. S.E. Gould in reply to S.E. Gould 4:09 am 06/29/2014

    Ooops, I was so concerned with getting the multicellular biology correct I messed up the Geography! Many thanks for letting me know.

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