Circadian clocks: an overview on its adaptive significance

Krittika, Sudhakar; Yadav, Pankaj

doi:10.1080/09291016.2019.1581480

Cited by 26 publications

(23 citation statements)

References 183 publications

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“…Nearly all living organisms have the ability to anticipate and adapt to environmental changes associated with periodic cycles such as the circadian day or the lunar month (Krittika & Yadav, 2019). Like all biological rhythms, regulation of the mammalian circalunar rhythm is regulated by environmental cues/zeitgebers (e.g., lunar illumination) that involve an internal time keeper made up of sensory receptors (e.g., photoreceptors) that communicate with a master clock/oscillator (the SCN) that triggers adaptive behavioral and metabolic responses (Hafker & Tessmar-Raible, 2020; Krittika & Yadav, 2019). How the circalunar activity rhythm is regulated by mammals in the wild remains an ecological and evolutionary enigma, but the increasing number of studies of nocturnal activity made possible by camera trap surveys is starting to provide some clues.…”

Section: Discussionmentioning

confidence: 99%

“…The primary environmental cues that change with the lunar cycle are moonlight intensity and tidal force (Andreatta & Tessmar-Raible, 2020), and these cues (or ‘zeitgebers’) act on endogenous oscillators to regulate biological processes such as mating, feeding, activity, predator avoidance, and many others (Andreatta & Tessmar-Raible, 2020). Although it has been known for 50 years that the suprachiasmatic nucleus (SCN) of the hypothalamus acts as the master circadian clock of mammals (Krittika & Yadav, 2019; Weaver, 1998), the ecological factors regulating nocturnal activity are still incompletely understood.…”

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confidence: 99%

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Does Moonlight Increase Predation Risk for Elusive Mammals in Costa Rica?

Botts

Eppert

Wiegman

et al. 2020

Tropical Conservation Science

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An increasing body of evidence indicates that moonlight influences the nocturnal activity patterns of tropical mammals, both predators and prey. One explanation is that brighter moonlight is associated with increased risk of predation (Predation Risk hypothesis), but it has also been proposed that nocturnal activity may be influenced by the sensory ecology of a species, with species that rely on visual detection of food and danger predicted to increase their activity during bright moonlight, while species relying on non-visual senses should decrease activity (Visual Acuity hypothesis). Lack of an objective measure of “visual acuity” has made this second hypothesis difficult to test, therefore we employed a novel approach to better understand the role of lunar illumination in driving activity patterns by using the tapetum lucidum as a proxy for “night vision” acuity. To test the alternative predictions, we analyzed a large dataset from our long-term camera trap study in Costa Rica using activity overlap, relative abundance, and circular statistical techniques. Mixed models explored the influence of illumination factors (moonrise/set, cloud cover, season) and night vision acuity (tapetum type) on nocturnal and lunar phase-related activity patterns. Our results support the underlying assumptions of the predation risk and visual acuity models, but indicate that neither can fully predict lunar-related activity patterns. With diurnal human “super predators” forcing a global increase in activity during the night by mammals, our findings can contribute to a better understanding of nocturnal activity patterns and the development of conservation approaches to mitigate forced temporal niche shifts.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Does Moonlight Increase Predation Risk for Elusive Mammals in Costa Rica?

Botts

Eppert

Wiegman

et al. 2020

Tropical Conservation Science

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“…Endogenous timing via circadian clocks confers adaptive advantages as it allows organisms to anticipate daily changes in the environment (see [1][2][3]). In terms of behaviour, the fitness relevance of being able to schedule locomotor activity, feeding, mating or other actions at the right time of the day is intuitive as it may help maximize success and reduce risks.…”

Section: Introductionmentioning

confidence: 99%

“…We therefore hypothesised that a "circadian dominance" with all its intuitive and likely advantages [2][3][4] may become more evident in other behaviours, especially those that serve only one particular function. Eclosion, the emergence of the adult holometabolic insect from the pupa, is arguably one of the most specific behaviours in insects, with only one dedicated function (propelling the pharate adult out of the pupal case).…”

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confidence: 99%

Natural Zeitgebers cannot compensate for the loss of a functional circadian clock in timing of a vital behaviour inDrosophila

Ruf

Mitesser

Mungwa

et al. 2019

Preprint

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The adaptive significance of adjusting behavioural activities to the right time of the day is intuitive.Laboratory studies have implicated an important role of circadian clocks in behavioural timing and rhythmicity. Yet, recent studies on clock-mutant animals questioned this importance under more naturalistic settings, as various clock mutants showed nearly normal diel activity rhythms under semi-natural Zeitgeber conditions.We here report evidence that proper timing of eclosion, a vital behaviour of the fruit fly Drosophila melanogaster, requires a functional molecular clock even under quasi-natural conditions. In contrast to wildtype flies, period 01 mutants with a defective molecular clock eclose mostly arrhythmically in a temperate environment even in the presence of a full complement of abiotic Zeitgebers. Moreover, period 01 mutants eclose during a much larger portion of the day, and peak eclosion time becomes more susceptible to variable day-to-day changes of light and temperature. Under the same conditions, flies with impaired peptidergic inter-clock signalling (pdf 01 and han 5304 mutants) stayed largely rhythmic with normal gate sizes. Our results suggest that the presence of natural Zeitgebers can mitigate a loss of peptide-mediated phasing between central clock neuron groups, but cannot substitute for the lack of a functional molecular clock under natural temperate conditions. BackgroundEndogenous timing via circadian clocks confers adaptive advantages as it allows organisms to anticipate daily changes in the environment (see [1][2][3]). In terms of behaviour, the fitness relevance of being able to schedule locomotor activity, feeding, mating or other actions at the right time of the day is intuitive as it may help maximize success and reduce risks. Many studies under constant laboratory conditions have revealed a key role of the central and peripheral clocks in timing of behaviours across taxa. However, the importance of circadian clocks in daily timing of behaviours under natural conditions or in ecological context has come under debate, as studies in the last decade have assessed the functional importance of endogenous clocks under (semi-) natural conditions in a variety of mostly vertebrate species (see [1,2,4]). One important conclusion derived from these studies is that diel activity rhythms can remarkably differ between seminatural and laboratory conditions, since the phase relationship between behavioural activity and a given Zeitgeber such as light is modulated by other abiotic Zeitgebers, particularly by temperature [5]. Furthermore, intraand interspecific interactions such as predation [6][7][8] or competition for food [9] determine ("mask") activity patterns in the wild. Most strikingly, under semi-natural conditions in an outdoor enclosure, Per2 BRDM1 mice carrying a mutation in a core clock gene showed the same activity pattern as controls, and both showed mostly diurnal feeding, although they are strongly nocturnal in laboratory conditions [10]. In the wild, chipmunks with a lesion in t...

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“…Endogenous timing via circadian clocks confers adaptive advantages as it allows organisms to anticipate daily changes in the environment ( Krittika and Yadav, 2019 ; Vaze and Sharma, 2013 ; Yerushalmi and Green, 2009 ). In terms of behavior, the fitness relevance of being able to schedule locomotor activity, feeding, mating, or other actions at the right time of the day is intuitive as it may help maximize success and reduce risks.…”

mentioning

confidence: 99%

Natural Zeitgebers Under Temperate Conditions Cannot Compensate for the Loss of a Functional Circadian Clock in Timing of a Vital Behavior in Drosophila

et al. 2021

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The adaptive significance of adjusting behavioral activities to the right time of the day seems obvious. Laboratory studies implicated an important role of circadian clocks in behavioral timing and rhythmicity. Yet, recent studies on clock-mutant animals questioned this importance under more naturalistic settings, as various clock mutants showed nearly normal diel activity rhythms under seminatural zeitgeber conditions. We here report evidence that proper timing of eclosion, a vital behavior of the fruit fly Drosophila melanogaster, requires a functional molecular clock under quasi-natural conditions. In contrast to wild-type flies, period01 mutants with a defective molecular clock showed impaired rhythmicity and gating in a temperate environment even in the presence of a full complement of abiotic zeitgebers. Although period01 mutants still eclosed during a certain time window during the day, this time window was much broader and loosely defined, and rhythmicity was lower or lost as classified by various statistical measures. Moreover, peak eclosion time became more susceptible to variable day-to-day changes of light. In contrast, flies with impaired peptidergic interclock signaling ( Pdf01 and han5304 PDF receptor mutants) eclosed mostly rhythmically with normal gate sizes, similar to wild-type controls. Our results suggest that the presence of natural zeitgebers is not sufficient, and a functional molecular clock is required to induce stable temporal eclosion patterns in flies under temperate conditions with considerable day-to-day variation in light intensity and temperature. Temperate zeitgebers are, however, sufficient to functionally rescue a loss of PDF-mediated clock-internal and -output signaling

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Circadian clocks: an overview on its adaptive significance

Cited by 26 publications

References 183 publications

Does Moonlight Increase Predation Risk for Elusive Mammals in Costa Rica?

Does Moonlight Increase Predation Risk for Elusive Mammals in Costa Rica?

Natural Zeitgebers cannot compensate for the loss of a functional circadian clock in timing of a vital behaviour inDrosophila

Natural Zeitgebers Under Temperate Conditions Cannot Compensate for the Loss of a Functional Circadian Clock in Timing of a Vital Behavior in Drosophila

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