Natures Wonders: turtle hibernation (Introduction)

by David Turell @, Sunday, November 26, 2017, 01:55 (265 days ago) @ David Turell

They literally pick up oxygen from the water through their butts (cloaca):

https://www.livescience.com/61018-turtles-breathe-through-butt.html?utm_source=ls-newsl...

"As an ectotherm — an animal that relies on an external source of heat — a turtle's body temperature tracks that of its environment. If the pond water is 1℃, so is the turtle's body.

"But turtles have lungs and they breathe air. So, how is it possible for them to survive in a frigid pond with a lid of ice that prevents them from coming up for air? The answer lies in the relationship between body temperature and metabolism.

"A cold turtle in cold water has a slow metabolism. The colder it gets, the slower its metabolism, which translates into lower energy and oxygen demands.

"When turtles hibernate, they rely on stored energy and uptake oxygen from the pond water by moving it across body surfaces that are flush with blood vessels. In this way, they can get enough oxygen to support their minimal needs without using their lungs. Turtles have one area that is especially well vascularized — their butts.

***

"With very few exceptions (e.g., box turtles), adult turtles cannot survive freezing temperatures; they cannot survive having ice crystals in their bodies. This is why freshwater turtles hibernate in water, where their body temperatures remain relatively stable and will not go below freezing.

Water acts as a temperature buffer; it has a high specific heat, which means it takes a lot of energy to change water temperature. Pond water temperatures remain quite stable over the winter and an ectotherm sitting in that water will have a similarly stable body temperature. Air, on the other hand, has a low specific heat so its temperature fluctuates, and gets too cold for turtle survival.

"An ice-covered pond presents two problems for turtles: they can't surface to take a breath, and little new oxygen gets into the water. On top of that, there are other critters in the pond consuming the oxygen that was produced by aquatic plants during the summer.

"Over the winter, as the oxygen is used up, the pond becomes hypoxic (low oxygen content) or anoxic (depleted of oxygen). Some turtles can handle water with low oxygen content — others cannot.

"Snapping turtles and painted turtles tolerate this stressful situation by switching their metabolism to one that doesn't require oxygen. This ability is amazing, but can be dangerous, even lethal, if it goes on for too long, because acids build up in their tissues as a result of this metabolic switch.

"An ice-covered pond presents two problems for turtles: they can't surface to take a breath, and little new oxygen gets into the water. On top of that, there are other critters in the pond consuming the oxygen that was produced by aquatic plants during the summer.

"Over the winter, as the oxygen is used up, the pond becomes hypoxic (low oxygen content) or anoxic (depleted of oxygen). Some turtles can handle water with low oxygen content — others cannot.

"Snapping turtles and painted turtles tolerate this stressful situation by switching their metabolism to one that doesn't require oxygen. This ability is amazing, but can be dangerous, even lethal, if it goes on for too long, because acids build up in their tissues as a result of this metabolic switch.

***

"My research group has monitored several species of freshwater turtles during their hibernation. We attach tiny devices to the turtles' shells that measure temperature and allow us to follow them under the ice.

"We've found that all species choose to hibernate in wetland locations that hover just above freezing, that they move around under the ice, hibernate in groups and return to the same places winter after winter."

Comment: the question is how this developed and it requires a metabolic switch in some species. One cannot simply swim to the bottom and outwait winter. It is logical to say it was all developed at once, but if that is the case it requires God to arrange it.


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