The seed of this mornings discussion in neurobiology was “Time, Love, Memory” by Jonathan Wiener. As has been the norm in past weeks we met in the on campus cafe bringing along with us four insightful questions each to keep the discussion rolling along throughout the hour. Wiener describes later in his book (p192) the three necessary components of living clocks. Living clocks are the basis of circadian rhythms and must have an input pathway so that the clock can be reset by the sunrise and sunset. A good example of why this is important is that humans actually have a twenty-five hour clock that resets itself everyday to correlate to the actual day length of twenty-four hours (23 hours, 56 minutes, and 4.1 seconds for any physicists reading this). People who are blind or people who are not exposed to the sun at all will exhibit a twenty-five hour clock, out of synchronization with the earth’s rotation.
So my question was about animals that live near the poles. How do polar bears or lynxes reset their clocks in the arctic summer when the sun doesn’t set? Some thoughts were that perhaps the living clocks are reset by magnetism but quickly realized that there is no shift of magnetism that corresponds to the length of a day. Another thought was that if it’s always light out, does it matter when the polar bear sleeps? The polar bear could have a period of activity, followed by a period of decreasing activity, and then rest and sleep. Lynxes often hunt at night and rest during the day but if it’s always light out does their clock remain synchronized with the earth’s rotation? PZ mentioned there isn’t much research pertaining to this but If anyone knows of any interesting papers that would enlighten this topic post them up.
References: Jonathan Wiener. “Time, Love, Memory.” Vintage Books, A Division of Random House, Inc. New York. 1999.