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article imageHamsters have in-built seasonal clocks

By Tim Sandle     Sep 30, 2013 in Environment
As well as circadian rhythms (natural body cycles), many animals are thought to have seasonal clocks (including, perhaps, people). A new study has shown that such internal ‘calendars’ function in hamsters.
A study involving Siberian hamsters (or Djungarian hamsters) as shown evidence of a seasonal clock and that this clock has an ‘epigenetic component’ (this means that genes as expressed in different ways at different times). The Siberian hamster is relatively small (compared with the Syrian hamster). It has a typically thick, dark grey dorsal stripe and furry feet.
The research showed that Siberian hamsters only breed in the late spring and early summer, when days are the longest. Such hamsters avoid breeding in the fall and winter, thereby preventing births during the cold, resource-scarce winter months. The reason for this was shown to relate to triggers at the molecular level.
The molecular signals are thought to relate to the degree of exposure to sunlight. The level of sunlight appears to ‘switch on’ or ‘switch off’ a hamsters reproductive capacity, thereby affecting when it breeds and does not breed. This molecular process is known as DNA methylation.
The changes are apparent in the appearance of the hamster too. As days shorten in the fall, males lose approximately 30 per cent of their body mass, their fur moults and their testes decrease significantly in size. These changes are seen as a ‘switching off’ of the reproductive process.
The research has been published in the journal of the Proceedings of the National Academy of Sciences. The paper is titled “Reversible DNA methylation regulates seasonal photoperiodic time measurement.”
More about Hamsters, siberian hamsters, Seasonal, Circadian
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