- Their neurons have evolved to perceive less cold than rodents that do not hibernate
In addition to holding the Catalan elections, this Thursday, at exactly 5:28 pm, will officially start the winter. Can you imagine that your body adapts naturally to feel less cold? This is what has happened to ground squirrels and golden hamsters, two of the animals that spend that season hibernating.
A study conducted by researchers at Yale University in the US reveals that the neurons of the 13- stripe ground squirrel ( Ictidomys tridecemlineatus ) and the golden or Syrian hamster ( Mesocricetus auratus ) have evolved to be less cold than other rodents that they do not have to hibernate, like rats or mice.
As detailed in the journal Cell Reports, they have discovered that their cold-sensitive neurons are less able to detect temperatures below 20 degrees than other animals. This adaptation allows the temperature of your body to fall for long periods of time without feeling stressed and they not only feel less cold when they hibernate, also when they are active.
Scientists believe, moreover, that these adaptations have occurred independently in the two species. Although all rodents have receptors in their neurons of the somatosensory system that feel the cold, in the Syrian hamster and in the ground squirrel these receptors take much longer to activate than in animals that do not hibernate.
And, unlike birds, which have the opportunity to migrate to spend the winter in warmer areas, small mammals can not travel long distances and they have no choice but to adapt their body to changes. That adaptation, says Elena Gracheva, lead author of the study, is the perfect example of how the environment can model the properties of the sensory system.
Hibernation is a strategy that many species follow to stay alive in winter, consuming few resources: “Mammals have a constant metabolism and need a lot of food so that the heat machine, its internal radiator, continues to function, as during winter there is not enough food The strategy is to stop, they store fat and spend the winter with that energy”, explains Jorge Lobo, biologist at the Museum of Natural Sciences (MNCN-CSIC), without any connection with this study.
As Elena Gracheva explains to this newspaper, the hibernation of the ground squirrels of 13 stripes (so called because their skin alternates brown and white stripes) lasts up to eight months, while that of the hamsters lasts for several weeks. “During their hibernation, these species can tolerate temperatures between two and seven degrees both internally (due to hypothermia) and externally (due to the environmental temperature).”
Experiment with heat plates
To compare the biology of all these rodent species they devised an experiment. They put the animals in two plates with controlled temperatures: a warm plate, at 30 degrees, and a colder one with variable temperatures that ranged between 20 and 0 degrees. The rodents could move freely through the two containers.
The researchers observed that mice always preferred to be warm and in all cases avoided staying on the plate when it was below 10 degrees, while hamsters and squirrels showed no special preference for the warm plate unless the cold Approximate to five degrees.
The key to these differences, according to this team, lies in the TRPM8 protein, whose activation causes the sensation of cold. In the squirrel and the hamster, the TRPM8 is less sensitive to cold than in that of the mouse. They checked it by observing how the latter increased its activity when the temperature dropped from 30 to 10 degrees, while rodents that hibernate did not modify it even if it was below 20 degrees.
Subsequently, the researchers analyzed the differences in the amino acid sequence of the TRPM8 molecules and genetically modified the TRPM8 of animals that were part of the experiment, verifying that it also changed their perception of the cold.
However, according to Jorgo Lobo, the response of a living being to low temperatures is much more complex than the mere sensation of cold, which is a warning against the damage it can cause in the body. Therefore, “practically all terrestrial organisms work better with high temperatures, with 37 or 38 degrees,” he says in a telephone conversation. “Most proteins break down, they denature, with 42 degrees,” he explains. To withstand the cold months, animals and plants have different strategies that allow them to protect their cells from freezing and that vary according to the species and climate in which they live.
According to Lobo, unlike the objective of the Yale study, the greatest interest at present is “to find out which are the adaptations that allow animals to live with more heat, that is, the mechanisms to cool down because what is coming is temperatures warmer.” The biologist believes, however, that the global increase in temperatures will also negatively affect the animals that hibernate: “Even if it seems a contradiction, the milder winters make them weaker when spring arrives because they do not become completely inactive. and they force them to spend more energy than they should.”