Small mammals with high metabolic rates exhibit a seasonal adaptation known as the Denely phenomenon: with the onset of winter, they can reduce the volume of their brains, skulls, and other organs by as much as 30% to radically decrease energy expenditure in conditions of cold and food scarcity.
A new study of the common shrew (Sorex araneus), combining comparative genomics and gene expression analysis, has revealed the molecular mechanisms underlying this reversible plasticity, which is also observed in European moles and some weasels.
Genes related to energy homeostasis and calcium signaling play a key role in this process. They help cells restructure and manage energy expenditure, as well as genes responsible for the integrity of the blood-brain barrier, which protects the brain during structural changes.
Scientists suggest that the reduction in volume occurs not due to neuronal death, but likely through controlled changes in the hydrobalance and hydration levels of brain tissues. This allows for the complete restoration of its size and functions in the spring.
Studying this natural phenomenon of "reversible change without catastrophe" is of great interest to biomedicine, as it may point to new mechanisms of resilience and recovery of nervous tissue, potentially relevant for research on neurodegenerative diseases.
Thus, the survival strategy of the tiny shrew serves as a vivid example of how flexibility and the ability to undergo temporary "reduction" can be evolutionarily more advantageous than the constant maintenance of resource-intensive systems in harsh and variable environmental conditions.
