1. Are there any external resources that can be used by the damaged component?
Answer: No
2. Is there any foreign material present?
Answer: No
3. Can the repair begin without an external energy resource?
Answer: No
4. Is there a trigger event to begin the repair?
Answer: Yes
5. Does the healing change the characteristics of the system?
Answer: Yes
6. Is the trigger event related to the temperature surrounding the mechanism?
Answer: Yes
9) Wood frog, Lithobates (Rana) sylvaticus
Wood frogs can be found in the United States but are primarily found in Alaska. The temperatures can range from a minimum of -18.1 to average -6.3 degrees Celsius for around 193 consecutive days from October to May (Larson et al.). Wood frogs have the remarkable ability of freezing themselves during the winter and then unthawing during the summer months to survive.
As the temperature outside gets colder the frog will find a place to undergo its natural hibernacula. The frog will surround and cover itself with dirt and leaves to help insulate its body. Then slowly the body organs begin to shut-off, but not die so they can essentially Ôcome back to lifeÕ once the warmer weather comes back. Wood frogs have high freezing tolerances due to the presence of cryoprotectants: low molecular mass and high molecular mass xylomannan-based antifreeze glycolipid (AFGL) (Larson et al.). AFGL is present on the cell membranes and prevents the extracellular ice from crossing into the cytoplasm and killing the still living and functional cells (Larson et al.). Urea and glucose have also been found to help retain water inside the tissues so the frog will have enough liquid to live after unthawing process (Larson et al.).
Since the frogs live in a cycle where there are many stages of freezing and unthawing, the frogÕs glycogen is converted to glucose and then stored in the tissues (Larson et al.). Consecutive cycles would account for a build of glycogen in the tissues which has been found to increase the frogs tolerance of cold. This means the frog can still survive if the temperature drops below the normal low temperatures or if the winter lasts for longer than expected. As the temperatures begin to increase the frog unthaws and the unfrozen cells begin to signal for the rest of the organs to start functioning again.
Larson, Don J., Luke Middle, Henry Vu, Wenhui Zhang, Anthony S. Serianni, John Duman, and Brian M. Barnes. “Wood Frog Adaptations to Overwintering in Alaska: New Limits to Freezing Tolerance.” The Journal of Experimental Biology 217 (2014): 2193-200. The Journal of Experimental Biology. Web. 13 Jan. 2015.
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