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Seasonal body clocks are controlled by 'calendar cells': Scientists identify proteins that determine when mammals mate

Experts found cells in the 'pars tuberalis' structure respond to daylight
These so-called 'calendar cells' change dramatically as seasons change
This is said to be what drives the seasonal cycle and body clock of animals
For example, they make sure sheep mate in winter so they give birth in spring when there is more food available

Published: 11:26 EST, 24 September 2015 | Updated: 12:35 EST, 24 September 2015

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Many animals go through physiological changes as the seasons shift, and now scientists have discovered how these changes occur.

By studying the genes of sheep, experts found cells in a structure called the 'pars tuberalis' respond according to how much daylight there is.

These so-called 'calendar cells' change dramatically over the year and this is what drives the seasonal reproductive cycle, for example, in mammals.

By studying the genes of sheep, experts found cells in a structure called the 'pars tuberalis' respond according to how much daylight there is. These so-called 'calendar cells' change dramatically over the year and this is what drives the seasonal reproductive cycle, for example, in the mammals

The cell structure is situated in the pituitary gland.

By monitoring how much daylight there is, the cells are able to release different level of proteins depending on whether its winter or summer.

ANIMAL SEASONAL BODY CLOCKS

The research was carried out by the biotechnology and biological sciences research council team at the Universities of Manchester and Edinburgh and is published in the journal Current Biology.

By studying the genes of sheep, experts found cells in a structure called the 'pars tuberalis' respond according to how much daylight there is.

These so-called 'calendar cells' change dramatically over the year and this is what drives the seasonal reproductive cycle, for example, in mammals.

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.

These proteins then kickstart a chain reaction which ultimately sees reproductive hormones being released in winter to make sure the sheep give birth in spring when there is more food.

The research was carried out by the biotechnology and biological sciences research council team at the Universities of Manchester and Edinburgh and is published in the journal Current Biology.

Lead author Professor Andrew Loudon from the University of Manchester 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 took three years to complete and involved analysis of how sheep respond to seasonal changes in day length.

The cell structure is situated in the pituitary gland. By monitoring how much daylight there is, the cells are able to release different level of proteins such as prolactin (pictured) depending on whether its winter or summer

The researchers also said that 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,' said Dr Shona Wood, research associate from the university.

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

The next step, the researchers added, is to understand how our cells record the passage of time.