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Why don’t Arctic and Antarctic fish freeze to death? Antifreeze!

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By Valerie Clark

Many fish are cold-blooded, which means their body temperature is set by their environment. In most of the world’s oceans this works out just fine for these fish. The difficulty occurs when the water gets cold. Salt in the oceans prevents water from freezing at 32 degrees Fahrenheit like fresh water does, instead it stays liquid to 28 degrees Fahrenheit, but most fish’s blood will freeze a degree above this temperature.

But, fish are abundant in the near-freezing waters of the Arctic and Antarctic. How do they survive?

They create their own antifreeze!

These fish have adapted naturally-occurring proteins that act just like antifreeze in their blood.The amount and types of antifreeze each species of fish uses varies, but all of them prevent ice crystals from forming in their blood, which would otherwise be certain death.

Approximately 8 inches long, this translucent notothenioid fish lives under nearly 2,500 feet, almost 530 miles from the open ocean. (Photo credit: Deep-SCINI, UNL Andrill SMO team)
Approximately 8 inches long, this translucent notothenioid fish lives under nearly 2,500 feet, almost 530 miles from the open ocean. (Photo credit: Deep-SCINI, UNL Andrill SMO team)

The biochemical nature of so-called antifreeze was first discovered in Antarctic fish and published by the Journal of Biological Chemistry in 1970. Today, scientists know of more than 120 species of polar fish using this superpower. Earlier this year, scientists in Antartica with the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project were stunned to discover transparent notothenioid fish that may be a new species using antifreeze powers.

Someday, polar fish antifreeze may be adapted to create safer antifreeze solutions for human use perhaps even preventing ice cream from getting freezer burn (assuming anyone keeps ice cream instead of just eating it).

All animals are uniquely adapted to their environment, or their “niche.” The Arctic and Antarctic fish are no exception – the antifreeze in their blood allows them to thrive in the coldest waters on the planet.

Snow fleas

A close up of a snow flea. Photo credit: Daniel Tompkins
A close up of a snow flea. Photo credit: Daniel Tompkins

When ice is forming outside, can you imagine how quickly a little bug might become frozen solid? Once the ice gets in the blood stream, the prognosis turns very gloomy. But the snow flea, which is not actually a flea but a flightless insect, is adapted to life in the snow. These critters like to play on snow banks in the Arctic, but how do they survive?

Researchers from Ontario studied snow fleas and isolated a protein with a similar function as the antifreeze proteins in Arctic fish. Snow fleas have antifreeze power, too! The unique biochemistry of the antifreeze protein prevents the formation of ice inside the flea’s tiny body. Snow fleas are not alone, other examples of cold-tolerant insects include the fire colored beetle and spruce budworm caterpillar, each with its own unique antifreeze completely different than the polar fish version.

Freezing Frogs

Wood frog frozen solid. Photo credit: Evelyn Davidson / National Park Service.
Wood frog frozen solid. Photo credit: Evelyn Davidson / National Park Service.

Wood frogs also use antifreeze superpowers, but in a different way. These frogs manage to literally freeze to the point of near-death. When it gets cold, they replace the water in their cells with a concentrated sugar solution – like salt, sugar also lowers the freezing point of water. The rest of their body freezes, including their blood and even their brain. Their hearts stop beating, breathing and muscle movements cease. Protected from ice crystal damage to their cells, these near-frozen frogs hibernate until spring warmth starts to thaw the ice.

GREENLAND SHARK

Antifreeze abilities are not limited to smaller animals, the Greenland shark, one of the largest species of shark, swims in Atlantic and Arctic waters to depths beyond 7,000 feet. To stop from freezing to death, the cells of Greenland sharks possess trimethylamine oxide, an ammonia-like chemical that renders the meat of the shark toxic to humans and other animals.

The Greenland shark (Somniosus microcephalus) can grow to 24 feet and thanks to antifreeze elements in its system its meat is poisonous to humans. Photo Credit: NOAA OKEANOS Explorer Program , 2013 Northeast U. S. Canyons Expedition
The Greenland shark (Somniosus microcephalus) can grow to 24 feet and thanks to antifreeze elements in its system its meat is poisonous to humans. Photo Credit: NOAA OKEANOS Explorer Program , 2013 Northeast U. S. Canyons Expedition

Able to grow up to 24 feet long, the Greenland shark has been a consistent food source for Arctic people and their dogs for countless generations. The only way to make the poisonous meat edible is to repeatedly boil it in clean water or to allow the meat to ferment for months. Ancient methods of fermentation called for burying the meat, but in Iceland barns are often filled with huge pieces of the enormous fish hanging on hooks, similar to a traditional smokehouse minus the smoke.

In an episode of “Bizarre Foods,” noted strange food connoisseur Andrew Zimmern said the smell of the fermenting fish was “horrific” but that the meat was surprisingly edible, despite its strong smell of ammonia.

SOURCES:

http://www.oupcanada.com/catalog/9780199298112.html

http://www.planet-science.com/categories/over-11s/natural-world/2011/12/animals-with-antifreeze.aspx

http://www.eurekalert.org/multimedia/pub/3289.php

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1796811/

http://news.nationalgeographic.com/news/2007/02/070220-frog-antifreeze.html

http://www.nwf.org/news-and-magazines/national-wildlife/animals/archives/2011/animals-getting-through-winter.aspx

http://www.nytimes.com/2010/01/19/science/19creatures.html?_r=2

http://www.jbc.org/content/245/11/2909.long

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