概年リズム、概年周期

WordNet

recurring at regular intervals (同)regular recurrence
the basic rhythmic unit in a piece of music; "the piece has a fast rhythm"; "the conductor set the beat" (同)beat, musical rhythm
the arrangement of spoken words alternating stressed and unstressed elements; "the rhythm of Frosts poetry" (同)speech rhythm

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〈U〉『律動,リズム』;韻律 / 〈C〉(特定の)リズム

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2018/04/12 13:50:45」(JST)

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A circannual cycle is a biological process that occurs in living creatures over the period of approximately one year. This cycle was first discovered by Ebo Gwinner and Canadian biologist Ted Pengelley.^[1] It is classified as an Infradian rhythm, which is biological process with a period longer than that of a circadian rhythm, less than one cycle per 28 hours. These processes continue even in artificial environments in which seasonal cues have been removed by scientists.^[2] The term circannual is Latin, circa meaning approximately and annual relating to one year. Chronobiology is the field of biology pertaining to periodic rhythms that occur in living organisms in response to external stimuli such as photoperiod.

The location of the physical circannual timer in organisms and how it works are almost entirely unknown.

Examples

In one study performed by Eberhard Gwinner, two species of birds were born in a controlled environment without ever being exposed to external stimuli. They were presented with a fixed Photoperiod of 10 hours of light and 14 hours of darkness each day. The birds were exposed to these conditions for eight years and consistently molted at the same time as they would have in the wild, indicating that this physiological cycle is innate rather than governed environmentally.^[1]

Researchers Ted Pengelley and Ken Fisher studied the circannual clock in the golden-mantled ground squirrel. They exposed the squirrels to twelve hours of light and 12 hours of darkness and at a constant temperature for three years. Despite this constant cycle, they continued to hibernate once a year with each episode preceded by an increase in body weight and food consumption. During the first year, the squirrels began hibernation in late October. They started hibernating in Mid august and early April respectively for the following two years, displaying a circannual rhythm with a period of about 10 months.^[3]

A classic example in insects is the varied carpet beetle.

Biological advantages

Generating biological rhythms internally helps organisms anticipate important changes in the environment before they occur, thus providing the organisms with time to prepare and survive.^[1] For example, some plants have a very strict time frame in regards to blooming and preparing for spring. If they begin their preparations too early or too late they risk not being pollinated, competing with different species, or other factors that might affect their survival rate. Having a circannual cycle may keep them from making this mistake if a particular geographic region experiences a false spring, where the weather becomes exceptionally warm early for a short period of time before returning to winter temperatures.

Similarly, bird plumage and mammal fur change with the approach of winter, and is triggered by the shortening photoperiod of autumn.^[4] The circannual cycle can also be useful for animals that Migrate or Hibernate. Many animals' reproductive organs change in response to changes in photoperiod. Male gonads will grow during the onset of spring to promote reproduction among the species. These enlarged gonads would be nearly impossible to keep year round and would be inefficient for the species. Many female animals will only produce eggs during certain times of the year.^[3]

Interaction with changing climate

Changing climate may unravel ecosystems in which different organisms use different internal calendars. Warming temperatures may lead to earlier blooms of flora in spring. For instance, one study performed by Menzel et al., analyzed 125,000 phenological records of 542 plant species in 21 European countries from 1971 to 2000 and found that 78% of all plants studied advanced in flowering, leafing, and fruiting while only three percent were significantly delayed. They determined that the average advance of spring and summer was 2.5 days per decade in Europe.^[5] Meanwhile, fauna may breed or migrate based on the length of day, and thus might arrive too late for critical food supplies they co-evolved with.

For example, the Parus major closely times the hatching of their chicks to the emergence of the protein-rich winter moth caterpillar, which in turn hatches to meet the budding of oaks.^[3] These birds are a single-brood bird, meaning they breed once a year with about nine chicks per brood. If the birds and caterpillars and buds all emerge at the right time, the caterpillars eat the new oak leaves and their population increases dramatically, and this hopefully will coincide with the arrival of the new chicks, allowing them to eat. But if plants, insects, and birds respond differently to the advance of spring or other phenology changes, the relationship may be altered.

As another example, studies of the Pied Flycatcher (ficedula hypoleuca) have shown that their spring migration timing is triggered by an internal circannual clock that is fine tuned to day length.^[3] These particular birds overwinter in dry tropical forest in Western Africa and breed in temperate forests in Europe, over 4,500 km away. From 1980-2000, temperatures at the time of arrival and the start of breeding have warmed significantly. They have advanced their mean laying date by ten days, but have not advanced the spring arrival on their breeding grounds because their migration behavior is triggered by photoperiod rather than temperature.^[4]

In short, even if each individual species can easily live with elevated temperatures, disruptions of phenology timing at ecosystem level may still imperil them.^[3]

Challenges for scientific study

One reason for the paucity of research on circannual cycles is the duration of required efforts. The ratio of the period length of a circannual cycle to the length of the productive life of a scientist makes this branch of chronobiology very difficult.^[3] It takes an entire year to get one data point which makes it difficult to really see how these cycles adjust in time. To put this into perspective, a two-week experiment for a circadian biologist would take fourteen years for a circannual researcher, in order to achieve the same level of data robustness for the conclusions.

References

^ ^a ^b ^c "Circannual Rhythms, Seasonal Change, Climate and Stress - Darrell Senneke". www.chelonia.org. Retrieved 2017-05-05.
^ "Circannual rhythm - Oxford Reference".
^ ^a ^b ^c ^d ^e ^f Foster RG, Kreitzman L. Seasons of life: The biological rhythms that enable living things to thrive and survive 1-303. New Haven (Connecticut): Yale University Press. ISBN 978‐0‐300‐11556‐7. 2009.
^ ^a ^b Gwinner, Eberhard (1996). "Circannual Clocks in Avian Reproduction and Migration". Ibis. Blackwell Publishing Ltd. 138: 47–63.
^ Menzel, et al., (2006). "European Phenological Response to Climate Change Matches the Warming Pattern". Global Change Biology. Blackwell Publishing Ltd. 12: 1969–1976.

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English Journal

Circadian and circannual variations in cord blood hematopoietic cell composition.

Servais S1, Baudoux E1, Brichard B2, Bron D3, Debruyn C4, De Hemptinne D5, Deneys V2, Paulus JM1, Schaaps JP1, Van Cauwenberge JR1, Seidel L1, Delforge A3, Beguin Y6.
Haematologica.Haematologica.2014 Sep 26. pii: haematol.2014.115394. [Epub ahead of print]
Several previous studies have demonstrated that cord blood unit composition is an important factor that may predict outcomes after cord blood transplantation, with higher doses of transplanted nucleated cells and hematopoietic stem and progenitor cells being associated with faster engraftment and be
PMID 25261093

The rate of spontaneous epistaxis is not linked to the lunar cycle but shows seasonal variations.

Duvdevani SI1, Migirov L, Wolf M, Yakirevitch A.
Chronobiology international.Chronobiol Int.2014 Aug;31(7):851-4. doi: 10.3109/07420528.2014.916298. Epub 2014 May 14.
Since 50-60% of the human body consists of water, the physiology of blood circulation might be affected by a full moon differently than during other days of the month. This study analyzed a potential association among lunar phases, seasonal variations, and the rate of spontaneous epistaxis. Consecut
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Morning melatonin serum values do not correlate with disease activity in rheumatoid arthritis: a cross-sectional study.

Afkhamizadeh M1, Sahebari M, Seyyed-Hoseini SR.
Rheumatology international.Rheumatol Int.2014 Aug;34(8):1145-51. doi: 10.1007/s00296-013-2930-x. Epub 2014 Feb 1.
Rheumatoid arthritis (RA), the most prevalent autoimmune arthritis worldwide, usually presents with a circannual manner and, meanwhile, follows a circadian rhythm for symptoms like morning stiffness. Therefore, association between RA and some hormones such as melatonin (MLT) and vitamin D, whose ser
PMID 24487422