Autumnal equinox, moon pies, and the dark hormone

A beautiful, crisp, quarter-plus moon at Meadowcreek last night. Owls calling each other. Lovely moon shadows.

The moon is waxing, edging toward full. We have only about a week to go until the total lunar eclipse of the full harvest moon.  But  don’t focus on the eclipse just yet, we have a much more momentous celestial event occurring tonight: the equinox.  At 10:09 p.m., CDT, the center of the sun will cross Earth’s equator, marking the autumnal equinox, and the start of fall in the Northern Hemisphere.

On the equinox, night and day are nearly exactly the same length – 12 hours – all over the world. This is the reason it’s called an “equinox”, derived from Latin, meaning “equal night”.   The equinox triggers lots of hormonal changes in plants, animals and people in our neck of the woods.  Nature is telling us: get ready for winter.

Unlike many cultures, we don’t celebrate the equinox at Meadowcreek, but maybe we should.  This year, with the pending eclipse, it might be nice to have a Chinese Moon Festival–always celebrated around the time of the September equinox.  It celebrates the abundance of the summer’s harvest.  One of the main foods is the mooncake filled with lotus, sesame seeds, a duck egg or dried fruit.  Since we are in the American South, we could substitute a MoonPie instead.  Actually we already have Thanksgiving to celebrate the harvest, so I guess a Moon Festival might be overkill.  Maybe instead we could just make the last s’mores of the season since they have all the MoonPie ingredients.

black-bear-hibernation-metabolism-surprises_32353_990x742As far as I know, plants don’t have such festivals, but they do mark the change in seasons.  In high latitudes like Meadowcreek’s, trees need to know when the winter is coming.  The equinox gives them the signal.  When the night is longer than the day, get ready for the winter–go into dormancy so you can survive the low light and cold temperatures of winter.

When trees see the night is longer, their cells begin to switch from production of chlorophyll for growth, to production of sugars and amino acids, which are stores of food and act as antifreeze for the plant.  Since the green chlorophyll is responsible for the green color of the leaves, its reduction makes the yellow and orange pigments visible and we get some great fall colors.

Plants which live closer to the equator don’t have to worry about the winter, but most still respond to changes in daylength.  The poinsettia is native to Mexico and knows no freezing weather in its native land.  It flowers when the days are short and few other plants are flowering to compete with it.  So, its a great plant for Christmas, right next to the winter solstice when days are shortest.  The same is true for Christmas cactus; shorter days trigger flowering so we get beautiful flowers on the shortest days of the year.

The study of this fascinating plant phenomenon is  called photoperiodism, if you want to look up more details.  The substances which regulate response to daylight change are called hormones in both plants and animals.

In mammals, including humans, various hormones rise and fall according to the amount of daylight.  Chief among them is melatonin which is produced and regulated by the pineal gland.   The pineal gland responds to the amount of sunlight streaming through your eyes.  When the days are long, it produces less melatonin.  Melatonin increases at night.  When days get shorter, melatonin production increases.

High levels of melatonin stimulates the growth of winter coats in animals.  In reindeer and other animal species in the North, the light and dark signals that start at the equinox jumpstart the reproductive cycle.   This enables the young to arrive just when food is plentiful in the spring.

The change in ratio of night and day also stimulates melatonin in bears, leading to all sorts of physiological changes culminating in hibernation.  Melatonin concentrations during hibernation are 7.5 times greater than those during the summer in anesthetized male bears.

Melatonin, also called the dark hormone, is especially high in people afflicted with Seasonal Affective Disorder or SAD.  They just don’t want to do anything in the winter.  Maybe their bodies are just telling them to hibernate.

There are some credible reports of human hibernation. The British Medical Journal reported a 19th century  phenomenon in far Northwest Russia.  At the first fall of snow the whole family gathers round the stove, lies down, ceases to wrestle with the problems of human existence, and quietly goes to sleep. Once a day every one wakes up to eat a piece of hard bread, baked and stored in sufficient quantities the previous autumn.  When the bread has been washed down with water, everyone goes to sleep again. The members of the family take turns to watch and keep the fire alight. After winter is over the family wakes up, shakes itself, goes out to see if the grass is growing, and sets to work at summer tasks.

Travelers in this region of Russia reported whole villages appeared to sleep all winter.  The practice was called lotska in Russian.  Unfortunately, no tests of melatonin levels were made of these Russian villagers and the practice has disappeared.

Melatonin has been shown to have antioxidant qualities.  It repairs damage while you sleep.  So we try to get plenty of sleep at Meadowcreek.  Some of us at Meadowcreek are even tempted by lotska in the winter, but we don’t give in.  Instead we go out on bright winter days, let the sunlight hit our pineal glands, and enjoy winter.

Now is the time to get outside in the daylight and not let lotska or SAD take a foothold.  So any Equinox party we have should certainly be in the daytime.  MoonPies for lunch, anyone?  Happy equinox!
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Photoperiod and melatonin are means organisms use to fit into the natural adaptive cycle of rapid growth, maturation, release and reorganization. For more on the adaptive cycle, see the introduction to our free online book at this link.

For more on melatonin and hibernation in bears see this link.

For more on the pineal gland and melatonin, see this link.

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