Time measurement in insect photoperiodism: external and internal coincidence

Saunders, David S.

doi:10.1007/s00359-023-01648-4

Cited by 8 publications

(2 citation statements)

References 56 publications

(97 reference statements)

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“…This indicates that different circadian oscillators may regulate the different behaviours: activity and diapause. It is important to recognise that our data can be explained by an external coincidence timing model, but they do not exclude the possible existence of more complex internal coincidence timing that requires two oscillators (Saunders 2023 , this issue). In fact, the observation that Nasonia measures a mixture of both day length and night length can be viewed as evidence that an internal coincidence timing model with two oscillators is at play.…”

Section: Discussionmentioning

confidence: 84%

Variation in photoperiod response corresponds to differences in circadian light sensitivity in northern and southern Nasonia vitripennis lines

Floessner,

Benetta,

Beersma

et al. 2023

J Comp Physiol A

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The circadian clock times physiological and behavioural processes and resets on a daily basis to synchronize with the environment. The involvement of the circadian clock in photoperiodic time measurement synchronising annual rhythms is still under debate and different models have been proposed explaining their integration. Insects overcome unfavourable conditions in diapause, a form of dormancy. A latitudinal cline in diapause induction in the parasitoid wasp Nasonia vitripennis as well as a difference in circadian light sensitivity between north and south provide us with additional evidence that the circadian system of Nasonia is involved in photoperiodic time measurement and that latitude-specific seasonality drives adaptive evolution in photoperiodism partly through adaptation responses in the circadian system. We tested diapause induction in a range of T-cycles and photoperiods and found diapause induction in short photoperiods in all T-cycles in the northern line but in the southern line, diapause only occurred in T-cycles close to 24 h. Due to a lower light sensitivity in the southern line, a wider distribution of phase angles of entrainment can be expected at a specific T-cycle duration, while the range of entrainment will decrease. Taking these oscillator properties into account, our data can be explained by an external coincidence model involving a single oscillator with a light-sensitive phase that drives annual timing of diapause in Nasonia vitripennis.

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Section: Discussionmentioning

confidence: 84%

Variation in photoperiod response corresponds to differences in circadian light sensitivity in northern and southern Nasonia vitripennis lines

Floessner,

Benetta,

Beersma

et al. 2023

J Comp Physiol A

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“…Whatever form of seasonal adaptation we see in an organism, this is achieved by the coordinated work of multiple players including the circadian system. Two of the most applicable models originally explaining photoperiodic regulation in plants (Davis 2002 ) and insects (Saunders 2023 ; Pittendrigh 1972 ) suggest coincidence detection between either light and a circadian oscillation (external coincidence) or between two endogenous clocks (internal coincidence). While these models have been very helpful directing research, the exact mechanisms of photoperiodic time measurement and the role of circadian clocks still need more work.…”

mentioning

confidence: 99%

One seasonal clock fits all?

Michel,

Kervezee

2023

J Comp Physiol A

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Adaptation of physiology and behavior to seasonal changes in the environment are for many organisms essential for survival. Most of our knowledge about the underlying mechanisms comes from research on photoperiodic regulation of reproduction in plants, insects and mammals. However, even humans, who mostly live in environments with minimal seasonal influences, show annual rhythms in physiology (e.g., immune activity, brain function), behavior (e.g., sleep–wake cycles) and disease prevalence (e.g., infectious diseases). As seasonal variations in environmental conditions may be drastically altered due to climate change, the understanding of the mechanisms underlying seasonal adaptation of physiology and behavior becomes even more relevant. While many species have developed specific solutions for dedicated tasks of photoperiodic regulation, we find a number of common principles and mechanisms when comparing insect and mammalian systems: (1) the circadian system contributes to photoperiodic regulation; (2) similar signaling molecules (VIP and PDF) are used for transferring information from the circadian system to the neuroendocrine system controlling the photoperiodic response; (3) the hormone melatonin participates in seasonal adaptation in insects as well as mammals; and (4) changes in photoperiod affect neurotransmitter function in both animal groups. The few examples of overlap elaborated in this perspective article, as well as the discussion on relevance for humans, should be seen as encouragement to unravel the machinery of seasonal adaptation in a multitude of organisms.

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The circadian and photoperiodic clock of the pea aphid

2023

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The pea aphid, Acyrthosiphon pisum, is a paradigmatic photoperiodic species that exhibits a remarkable annual life cycle, which is tightly coupled to the seasonal changes in day length. During spring and summer, characterised by longer days, aphid populations consist exclusively of viviparous females that reproduce parthenogenetically. When autumn comes and the days shorten, aphids switch their reproductive mode and generate males and oviparous sexual females, which mate and produce cold-resistant eggs that overwinter and survive the unfavourable season. While the photoperiodic responses have been well described, the nature of the timing mechanisms which underlie day length discrimination are still not completely understood. Experiments from the 1960’s suggested that aphids rely on an ‘hourglass’ clock measuring the elapsed time during the dark night by accumulating a biochemical factor, which reaches a critical threshold at a certain night length and triggers the switch in reproduction mode. However, the photoperiodic responses of aphids can also be attributed to a strongly dampened circadian clock. Recent studies have uncovered the molecular components and the location of the circadian clock in the brain of the pea aphid and revealed that it is well connected to the neurohormonal system controlling aphid reproduction. We provide an overview of the putative mechanisms of photoperiodic control in aphids, from the photoreceptors involved in this process to the circadian clock and the neuroendocrine system.

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Time measurement in insect photoperiodism: external and internal coincidence

Cited by 8 publications

References 56 publications

Variation in photoperiod response corresponds to differences in circadian light sensitivity in northern and southern Nasonia vitripennis lines

Variation in photoperiod response corresponds to differences in circadian light sensitivity in northern and southern Nasonia vitripennis lines

One seasonal clock fits all?

The circadian and photoperiodic clock of the pea aphid

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