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Stony Brook University\u2019s Department of Ecology & Evolution, located in the Life Sciences Building. Researchers from the department have teamed up with European institutes and universities to study the Eurasian common shrew.\u00a0ZOIE MASTRIANO\/THE STATESMAN<\/p>\n
The Eurasian common shrew has a biological superpower \u2014 this small rodent is able to shrink itself during winter and regrow during spring. Uncovering the peculiar way this shrew saves its energy during the winter may help advance research for treatments of neurodegenerative disorders in humans.<\/p>\n
Researchers from Stony Brook University and other institutes and universities\u00a0in Germany and Denmark published two studies that examined the Eurasian common shrew to understand the inner workings of Dehnel\u2019s phenomenon<\/a>, a rare adaptation where animals shrink their body mass, skulls and organs during winter and regrow them during spring.<\/p>\n Both studies were conducted in collaboration with researchers from John Jay College of Criminal Justice, the Max Planck Institute of Animal Behavior, Aalborg University and Universitat Aut\u00f2noma de Barcelona.<\/p>\n William Thomas, the lead author on both papers and a former postdoctoral research associate in the Department of Ecology and Evolution\u00a0explained that the Eurasian common shrew can reshape essential organs ranging from the liver to the brain.<\/p>\n \u201cIt\u2019s hypothesized to be this energy-saving mechanism,\u201d he said in an interview with The Statesman. \u201cDuring winter, you\u2019re spending less energy on maintaining this tissue and then you can regrow it during the time of spring when you have more energy.\u201d<\/p>\n Wild Eurasian common shrews\u2019 lifespans are approximately a year,<\/a> which means they\u2019re likely to experience Dehnel\u2019s phenomenon only once.\u00a0<\/p>\n If juvenile shrews are born in the spring and summer, then Dehnel\u2019s phenomenon starts in autumn and completes in winter. As next spring arrives, they start growing back to normal size and finish growing in the summer. During spring, the shrews reach maturity and can breed.<\/p>\n Thomas clarified that the overall goal behind this project is to understand how the shrews change their brain mass in hopes of furthering research into treatments for certain disorders.<\/p>\n \u201cCan we mimic what the shrews are doing to shrink and regrow their brains and help humans [who are undergoing neurodegenerative processes] do the same thing?\u201d Thomas said.<\/p>\n The two studies touch on different aspects of the overall research into Dehnel\u2019s phenomenon. The first, published in Genome Research<\/a>, looks at the metabolic and molecular changes that occur during the shrew\u2019s shrinkage and regrowth. The second, published in Molecular Biology and Evolution<\/a>, looks into the genetic basis of the phenomenon, including a new sequenced genome for the Eurasian common shrew.<\/p>\n \u201cOne was done about 10 or 15 years ago that wasn\u2019t as contiguous of a genome,\u201d Thomas said. \u201cWe now have this kind of chromosomal reference for the shrew, which is not only important for our understanding of the seasonal size change, but can also be used as a resource for other scientists.\u201d<\/p>\n He explained that although other organisms such as certain species of weasels, stoats and other types of shrews exhibit Dehnel\u2019s phenomenon, the Eurasian common shrew, which is also the most abundant species of shrew, was studied due to how pronounced its seasonal changes are.<\/p>\n Liliana M. D\u00e1valos, the principal investigator of both papers and a professor in the Department of Ecology and Evolution, quantified the change in size that occurs during Dehnel\u2019s phenomenon.<\/p>\n \u201cIt is a very extreme change \u2014 if your head shrank by 25%, everyone around you would notice it right away,\u201d she said.<\/p>\n Dehnel\u2019s phenomenon shares many similarities with hibernation. They\u2019re both methods of conserving energy so animals can survive the food scarcity winter brings. The major difference is that animals in hibernation remain in a dormant state, while animals that undergo Dehnel\u2019s phenomenon stay active.<\/p>\n \u201cWhat we hypothesize is that [Eurasian common shrews] don\u2019t hibernate because they have such a high metabolic rate,\u201d Thomas said. \u201cIf you\u2019re only alive for a year and you\u2019re going to sleep for a quarter of your life, it might not make too much sense.\u201d<\/p>\n Researchers trapped wild shrews during these five stages of development: juveniles before shrinkage, during shrinkage, after shrinkage, then adults during regrowth and after regrowth.<\/p>\n Jeremy Searle, a professor at Cornell University\u2019s Department of Ecology and Evolutionary Biology and whose lab focuses on the evolutionary biology of small mammals, explained why wild shrews were used for this project.<\/p>\n \u201cCommon shrews are not easy to breed in the laboratory, and that hinders some types of research,\u201d he said. \u201cHowever, with care, shrews can be maintained in captivity, and they can be studied in nature. For many of the sophisticated methods recently developed in biology, there is no need to have laboratory animals.\u201d<\/p>\n Researchers collected blood samples from these shrews and removed and weighed their livers to confirm if Dehnel\u2019s phenomenon was occurring. These samples were also used for further testing.<\/p>\n The analysis showed that during their shrinkage, the shrews showed regulatory changes in oxidative phosphorylation. That\u2019s the last step in cellular respiration, a process where cells produce adenosine triphosphate, a high-energy molecule that powers our cells and our body as a whole.\u00a0\u00a0<\/p>\n It also increased the shrews\u2019 fatty acid metabolism, which is a process where fatty acids are broken down to provide more adenosine triphosphate.<\/p>\n The researchers found that during autumn and early winter, the shrews show the highest rate of gluconeogenesis, a process where an organism produces glucose from inside its body. It\u2019s what helps organisms survive starvation, which is prevalent during winter.<\/p>\n One of the more significant biological mechanisms researchers discovered behind the phenomenon is Forkhead box protein O1 or FOXO1 signaling. This signaling is the information the FOXO1 protein sends to activate certain cellular responses.\u00a0<\/p>\n \u201cThis signaling is involved in metabolism, energy balance and it\u2019s also involved in body size,\u201d D\u00e1valos said. \u201cSo in fall, as the [Eurasian common shrews shrink], they are increasing this signaling \u2014 it\u2019s at a peak, but then in the spring, they have to grow back and this signaling drops.\u201d<\/p>\n