Unique Antifreeze Protects From Extreme Cold

Biological Strategy

Darkling beetles

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Protect From Ice

Freezing temperatures can be difficult for living systems to manage. They can cause ice crystals to form in blood and tissues, which causes damage to cells and ultimately, death. Living systems can’t afford the energy required to melt ice crystals, so instead, many have strategies to prevent crystals from forming in the first place. Many amphibians, plants, and insects have chemicals that act as antifreeze to prevent icy crystal formation. Another challenge ice presents is that it creates a slick surface, requiring friction to traverse. This is why polar bears’ paws have a rough surface that grips ice.

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Protect From Temperature

Many living systems function best within specific temperature ranges. Temperatures higher or lower than that range can negatively impact a living system’s physiological or chemical processes, and damage its exterior or interior. Living systems must manage high or low temperatures using minimal energy, which often requires controlling responses along incremental temperature changes. To do so, living systems use a variety of strategies, such as avoiding high or low temperatures, removing excess heat, and holding heat in. Insulation is a well-known example of managing low temperatures by retaining heat using thick layers of hair, fur, or feathers to hold warm air next to the skin.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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A sugar-based polymer produced by an Alaskan darkling beetle keeps cell contents from freezing in extreme cold temperatures by attaching to the cell membrane.

In midwinter, temperatures at the home of an Alaskan darkling beetle (Upis ceramboides) can drop to -76 degrees F (-60 degrees C), yet this beetle species is able to keep its internal, watery cell contents from catastrophically freezing. Unlike most other extreme cold-dwelling organisms, including plants, animals, fish, fungi, and bacteria that use s as antifreeze agents, this Alaskan beetle produces a sugar-based antifreeze called xylomannan (a of alternating xylose and mannose sugars). With the help of certain oily compounds, xylomannan attaches to the outer cell membrane where it likely functions to prevent the entry of extracellular ice into the cell, keep ice from forming inside the cell, and promote membrane stability.

Last Updated August 24, 2017

References

“In the most northern climates, like the interior of Alaska, midwinter temperatures fall as low as minus 60 degrees Fahrenheit, and snow cover and subzero temperatures can last until May. At these extreme temperatures, most insects are bugsicles. The Alaskan Upis beetle, for example, freezes at around minus 19 degrees. But, remarkably, it can survive exposure to temperatures as low as about minus 100 degrees…a new kind of antifreeze was recently discovered in the Upis beetle by a team of researchers from the University of Notre Dame and the University of Alaska-Fairbanks. Unlike the protein antifreezes of other beetles, snow fleas and moths, the Upis antifreeze is a complex sugar called xylomannan that is as effective at suppressing ice growth as the most active insect protein antifreezes” (Carroll 2010).

Newspaper article

When Built-In Antifreeze Beats a Winter Coat

New York Times | 18/01/2010 | Carroll SB

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Reference

“Although all previously described TH [Thermal hysteresis]-producing biomolecules are proteins, most thermal hysteresis factors (THFs) have not yet been structurally characterized…We isolated a highly active THF from the freeze-tolerant beetle, Upis ceramboides…the THF contained little or no protein, yet it produced 3.7 ± 0.3 °C of TH at 5 mg/ml, comparable to that of the most active insect antifreeze proteins…this antifreeze contains a β-mannopyranosyl-(1->4) β-xylopyranose backbone and a fatty acid component, although the lipid may not be covalently linked to the saccharide…This xylomannan is the first TH-producing antifreeze isolated from a freeze-tolerant animal and the first in a new class of highly active THFs that contain little or no protein…We investigated…U. ceramboides, from interior Alaska because they tolerate freezing to -60 °C in midwinter.” (Walters et al. 2009:20210).

“…The fatty acid component may anchor the THF to the cell membrane. However, the mode of lipid linkage to the saccharide has not been established, and it remains possible that the lipid is not covalently linked to the saccharide constituent.” (Walters et al. 2009:20211).

“The observation that THFs were associated with the cell membrane in the [a] centipede, as also appears to be the case for THFs from U. ceramboides, suggests that these molecules may prevent the spread of extracellular ice into the cytosol (intracellular freezing is typically thought to be lethal) and/or stabilize the plasma membrane at low temperature. This study shows that a (lipo)xylomannan isolated from U. ceramboides is a highly active THF that is structurally distinct from all known AFPs and antifreeze glycoprotein (AFGPs) reported to date. In contrast to known AFGPs, which comprise ~39% peptide by mass, THFs isolated from U. ceramboides contain little to no protein. In addition, the β-Manp-(1->4) β-Xylp backbone is unrelated to the saccharide component of fish AFGPs…This xylomannan antifreeze may contribute to freeze tolerance by preventing recrystallization of extracellular ice, preventing intracellular freezing and/or stabilizing cellular membranes at low temperature.” (Walters et al. 2009:20214).

Journal article

A nonprotein thermal hysteresis-producing xylomannan antifreeze in the freeze-tolerant Alaskan beetle Upis ceramboides

Proceedings of the National Academy of Sciences | 24/11/2009 | K. R. Walters, A. S. Serianni, T. Sformo, B. M. Barnes, J. G. Duman

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