Sea urchins are a hardy mass.
The smallest of all marine mammals with the thickest fur in the animal kingdom, they can hold their breath for up to eight minutes while diving for prey like mussels and crabs, which they are known to crack open using rocks.
A lasting mystery, however, was precisely how the mustels manage to stay warm in the cool waters of their Pacific habitat, deprived of the blubber that isolates seals, whales and walruses.
The answer according to a new paper published in the journal Science on Thursday, their bodies are a unique energy conversion system, whereby their muscle tissue “leaks”
This is unlike other mammals which have to put their muscles to work through exercise or involuntary shaking to achieve the same result.
Lead author Traver Wright of Texas A&M University told AFP that while sea urchins’ dense, water-repellent fur offsets some heat loss, it is not in itself enough to cope with the cool waters off Alaska, where most of them live.
Researchers already knew that sea otters burn a lot of energy – about three times larger than predicted for mammals of their size, and to keep up with demand, they can consume up to 25 percent of their body mass in one day.
However, it was unclear which tissues used this energy and how it went towards producing heat.
To find out, Wright and colleagues took muscle samples from sea otters that had already died, or, more fortunately, had been rehabilitated by the Monterey Bay Aquarium and were being prepared for release.
They then used a device to measure oxygen consumption.
‘Making heat by being inefficient’
The main function of muscle is generally to be able to move the body, but in the otters lost much of the metabolic energy produced by the breakdown of sugar and fat, which heat instead of being used in the cells to perform work, such as drive muscle contraction.
“One of the interesting things we found out is that they are really good at making heat by being inefficient,” Wright said.
What the team observed would be considered a waste in land mammals as humans, “but if you’re an animal trying to warm up, then the” wasted “energy and heat is a good thing.”
In other words, ideal for maintaining a body temperature of 37 degrees Celsius (98.6 degrees Fahrenheit) under freezing conditions.
The team found that this “thermogenic” effect was present in sea otters from the time they were babies to adults, and there was no difference in captivity and wild animals.
Sea otters and marine mammals more broadly could have developed such traits when their terrestrial ancestors began taking to the oceans 50 million years ago, but this hypothesis will require more research to confirm.
Learning how sea urchins’ metabolic system works differently from ours could one day also help people resolve obesity, Wright added.
“If you can figure out how to increase leakage and metabolic rate, you can theoretically get people to fluctuate their metabolism and burn additional calories.”
Sea urchins, opossum and the surprising ways in which pathogens move from land to sea
T. Wright et al., “Skeletal Muscle Thermogenesis Enables Aquatic Life in at least Marine Mammals,” Science (2021). science.sciencemag.org/lookup/… 1126 / science.abf4557
© 2021 AFP
Citation: Researchers learn how odors stay warmer (2021, July 8) Retrieved July 9, 2021 from https://phys.org/news/2021-07-scientists-otters-hotter.html
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