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Cause of animals’ internal body clocks discovered

Manchester and Edinburgh researchers identify specialist cells responsible for seasonal adaptations in mammals

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Researchers have discovered the cells responsible for driving the annual body clock in animals that enable them to adapt their bodies to the different seasons.

The team, made up of scientists from the universities of Manchester and Edinburgh, have identified a specific group of cells in the pituitary gland as being accountable for the changes that many animals go through depending on the time of year.

These so-called “calendar cells” are found in the ‘pars tuberalis’ part of the gland’s anterior lobe and respond according to how many hours of daylight there are. This provides the animal with an internal genetic clock.

The behaviour of many animals varies drastically throughout the year, which can now be explained by the fact that these cells produce different proteins in the summer and winter months.

This switching of proteins repeats itself over the course of the year and enables many mammals to adapt accordingly.

The study was led by Professor Andrew Loudon of The University of Manchester’s Faculty of Life Sciences.

Professor Loudon said: “Scientists have long puzzled over how many animals seem to change their physiology according to the seasons.

“Animals need to change their physiology to predict the changing environment and increase their chances for survival.

“For example, some animals hibernate through the winter and others, including sheep, will time mating to the winter so they can give birth in the spring—when more food is available.

“Now we have a much stronger understanding about how the body’s so-called circannual clock regulates this process.”

The study, which was published in the journal Current Biology, focused on the seasonal behavioural patterns of sheep and was conducted over the course of three years.

In addition to enhancing our knowledge of animal physiology and behaviour, the study could also prove beneficial in explaining how humans respond to different environments and seasons.

Even though humans do not demonstrate any adaptions as dramatic as hibernation, it is believed that internally, there are still multiple changes taking place.

Dr. Shona Wood, a Research Associate at the University of Manchester, said: “A similar structure can be found in most animals—including humans.

“Scientists once believed that humans did not show seasonal adaptations, but more recent research has found that this may not be the case and in fact there is seasonal variation in protection against infectious disease.

“Our study gives more increases our understanding of how this may work.”

Professor Dave Burt of the University of Edinburgh’s Roslin Institute added: “The seasonal clock found in sheep is likely to be the same in all vertebrates, or at least, contains the same parts list.

“The next step is to understand how our cells record the passage of time.”