Trigger that prepares animals for the season…whatever the weather

University of Manchester scientists have helped identify the key trigger mechanism in the 'internal clocks' of animals which means they are prepared for the season whether snow comes in November or the sun shines in March. The research team, led by Dr Hugues Dardente and Professor David Hazlerigg at the University of Aberdeen and including Professor Andrew Loudon at Manchester's Faculty of Life Sciences, has pinpointed the 'switch' controlling seasonal hormone production, based on the changing daily cycle of light and darkness. Their findings, published today in Current Biology, give new insight into the link between daily and seasonal timing in mammals and suggest that an ancient mechanism has remained largely unchanged during vertebrate evolution. The extent to which such mechanisms are "hard-wired" will have a major impact on how animals cope with changing seasons in a warming world. The study, in collaboration with the universities of Manchester and Edinburgh, looked at the primitive Soay breed of sheep, which relies on strong seasonal biology to survive in the wild on the North Atlantic islands of St Kilda. The team identified the key signal to the brain controlling seasonal behaviour and physiology in a previous study in 2008. It found that a chemical known as thyroid stimulating hormone (TSH) acts in the brain to control the activation of seasonal breeding in sheep, and is regulated by day length.