Navigation Links
Alaska frogs reach record lows in extreme temperature survival

Freezing and thawing might not be good for the average steak, but it seems to help wood frogs each fall as they prepare to survive Alaska's winter cold.

"Alaska wood frogs spend more time freezing and thawing outside than a steak does in your freezer and the frog comes back to life in the spring in better shape than the steak," said Don Larson, University of Alaska Fairbanks graduate student and lead author on a recent paper demonstrating that freeze tolerance in Alaska wood frogs is more extreme than previously thought.

Although wood frogs are well-studied freeze-tolerant amphibians, Larson's research is believed to be the first to examine the frogs under natural conditions.

In subarctic Interior Alaska, wood frogs overwinter in the ground covered by duff and leaf litter, creating a hibernacula, where temperatures can remain below freezing for more than six months with minimum temperatures of minus four (minus 20 Celsius).

Tracking wood frogs to their natural hibernacula, and using a fenced hibernacula in the Biological Reserve north of the UAF campus, Larson and co-author Brian Barnes, director of the UAF Institute of Arctic Biology and an expert in cold-climate physiology, wanted to know how cold and how long Alaska's wood frogs could survive in their natural habitat.

"Imagine what happens when you suck on a freeze pop," said Larson. "After you've sucked out all the sweet stuff, you're left with just ice. That's what happens to cells when they freeze. As ice formation pulls the water out of cells, the cells desiccate or dry out and eventually die."

Frogs prevent this freeze-pop effect by packing their cells with glucose (a kind of sugar) that reduces drying and stabilizes cells, a process scientists call cryoprotection.

"Concentrating sugar inside the cell helps balance the concentration of salts outside the cell that occurs as ice forms," said Barnes. "Less water leaves the cell than if sugar was not present and sugar and other cryoprotectants are thought to "hold" water inside the cell."

The curious thing Larson discovered is that when wood frogs are outside in their natural environment they accumulate much higher concentrations of glucose in their tissues than do frogs frozen in the lab.

Glucose concentrations in the outside frogs were 13-fold higher in muscle tissue, 10-fold higher in heart tissue and 3.3-fold higher in liver tissue compared to lab-frozen frogs, as described in their paper published in the Journal of Experimental Biology.

This extra protection enabled frogs to survive colder temperatures for a longer time than scientists previously thought, but Larson and Barnes wondered how they accumulated so much glucose?

Larson thinks the process that creates freezer burn on a frozen steak gives frogs the ability to survive being frozen at minimum temperatures below zero (minus 18 Celsius) for up to 218 days with 100 percent survival.

Frogs collected from sites in the Eastern U.S. and Canada have previously been shown to only survive being frozen for a few weeks and to no lower than about 19 degrees (minus 7.2 Celsius).

"In the field in early Autumn it's freezing during the night, thawing slightly during the day, and these repeated freezing episodes stimulate the frogs to release more and more glucose," Larson said. "It's not warm enough for long enough for the frog to reclaim much of that glucose and over time it accumulates giving the frog more protection against cell damage."

Lab-frozen frogs are held at a constant temperature and without the freeze-thaw cycles Larson observed in the wild and so the frogs made glucose only when they initially froze and that was that.

"Whether the extremes in freezing tolerance in Alaska frogs as compared to more southern populations are due to patterns of temperature change during freezing or are due to genetic differences, and thereby represent evolutionary change, awaits further study," said Barnes.

The feats of freezing frogs are more than just a curiosity and may one day have application in the science of human organ transplantation.

"If science can figure out how to freeze human organs without damage it would allow more time to reach people in need of organs," said Larson.


Contact: Marie Thoms
University of Alaska Fairbanks

Related biology news :

1. New technology tracks sparrow migration for first time from California to Alaska
2. Funny River Fire, Alaska
3. Update on Funny River Fire, southern Alaska
4. Alaska neuroscientist receives national mentor award
5. Athletic frogs have faster-changing genomes
6. Richer parasite diversity leads to healthier frogs, says University of Colorado study
7. Preserved frogs hold clues to deadly pathogen
8. Genetic matchmaking saves endangered frogs
9. What do American bullfrogs eat when theyre away from home? Practically everything!
10. New scientific studies reveal Midwestern frogs decline, mammal populations altered by invasive plant
11. Croaking chorus of Cuban frogs make noisy new neighbors
Post Your Comments:
Related Image:
Alaska frogs reach record lows in extreme temperature survival
(Date:10/29/2015)... , Oct. 29, 2015  The J. Craig Venter ... titled, "DNA Synthesis and Biosecurity: Lessons Learned and Options ... of Health and Human Services guidance for synthetic biology ... --> --> ... has the potential to pose unique biosecurity threats. It ...
(Date:10/29/2015)... -- Connected health pioneer, Joseph C. Kvedar , MD, ... and wellness, and the business opportunities that arise from ... of Healthy Things . Long before health and ... Kvedar, vice president, Connected Health, Partners HealthCare, was creating ... from the hospital or doctor,s office into the day-to-day ...
(Date:10/27/2015)... , Oct. 27, 2015 In the present ... of concern for various industry verticals such as banking, ... to the growing demand for secure & simplified access ... ,sectors, such as hacking of bank accounts, misuse of ... equipment such as PC,s, laptops, and smartphones are expected ...
Breaking Biology News(10 mins):
(Date:11/24/2015)... DIEGO , Nov. 24, 2015 Halozyme Therapeutics, Inc. ... Healthcare Conference in New York on Wednesday, ... Helen Torley , president and CEO, will provide a corporate ... New York at 1:00 p.m. ET/10:00 a.m. PT ... and investor relations, will provide a corporate overview. --> ...
(Date:11/24/2015)... Inc., a worldwide provider of clinical research services headquartered in ... has set a new quarterly earnings record in Q3 of 2015.  ... Q3 of 2014 to Q3 of 2015.   ... the establishment of an Asia-Pacific office to ... and Mexico , with the establishment ...
(Date:11/24/2015)... , November 24, 2015 ... market research report released by Transparency Market Research, the ... at a CAGR of 17.5% during the period between ... Market - Global Industry Analysis, Size, Volume, Share, Growth, ... non-invasive prenatal testing market to reach a valuation of ...
(Date:11/24/2015)... ... November 24, 2015 , ... InSphero AG, the leading supplier of ... has promoted Melanie Aregger to serve as Chief Operating Officer. , Having ... management team and was promoted to Head of InSphero Diagnostics in 2014. ...
Breaking Biology Technology: