Neural Mechanism of Photoperiodism

Shiga, Sakiko

doi:10.1007/978-981-99-0726-7_14

Cited by 3 publications

(1 citation statement)

References 114 publications

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“…For seasonal adaptation, a large number of insects inhabiting temperate zones alter their physiological states for development or diapause according to photoperiod. The mechanisms underlying insect photoperiodic responses include photoreceptors, photoperiodic clocks, photoperiodic counters, and endocrine systems (Saunders, 2002;Shiga 2023;Hamanaka et al 2023).…”

Section: Introductionmentioning

confidence: 99%

Photoperiodic plasticity of pigment-dispersing factor immunoreactive fibers projecting toward prothoracicotropic hormone neurons in flesh fly Sarcophaga similis larvae

Ohe,

Hasebe,

Hamanaka

et al. 2024

Preprint

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Larvae of the flesh fly, Sarcophaga similis exhibit photoperiodic responses to control pupal diapause. Although the external coincidence model is applicable to S. similis photoperiodic responses, it remains unknown how circadian clock system integrates day-length information. To explore the mechanisms underlying the photoperiodic control of pupal diapause, we examined the neural circuitry involving circadian clock lateral neurons (LNs) and prothoracicotropic hormone (PTTH) neurons, the latter possibly controlling the ecdysteroid production. We also examined the photoperiodic effects on LN-fiber patterns in third-instar S. similis larvae. Immunohistochemistry showed that PERIOD and a neuropeptide pigment-dispersing factor (PDF) were co-localized in four cells per hemisphere, and we named these PDF-LNs of S. similis. Single-cell polymerase chain reaction of backfilled neurons from the ring gland showed that two pairs of pars lateralis neurons with contralateral axons (PL-c neurons) expressed ptth. Double labeling with immunohistochemistry and backfills revealed that PDF-immunoreactive varicose fibers projected in the proximity of fibers from PL-c neurons. However, pdf receptor was not but glutamate-gated chloride channel was expressed in most PL-c neurons. L-glutamate but not PDF acutely inhibited the spontaneous firing activity of PL-c neurons. The number of PDF-immunoreactive varicosities of PDF-LNs in the dorsal protocerebrum was significantly higher under short-day than that under long-day conditions in a time-dependent manner. These results suggest that PDF-LNs, PTTH neurons, and glutamate signaling form a potential neural circuity for the photoperiodic control of pupal diapause and that photoperiod modifies the connectivity strength between PDF-LNs and their post- or pre-neurons in the circuitry.

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Section: Introductionmentioning

confidence: 99%

Photoperiodic plasticity of pigment-dispersing factor immunoreactive fibers projecting toward prothoracicotropic hormone neurons in flesh fly Sarcophaga similis larvae

Ohe,

Hasebe,

Hamanaka

et al. 2024

Preprint

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Neural mechanism of circadian clock-based photoperiodism in insects and snails

Hamanaka,

Hasebe,

Shiga

2023

J Comp Physiol A

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The photoperiodic mechanism distinguishes between long and short days, and the circadian clock system is involved in this process. Although the necessity of circadian clock genes for photoperiodic responses has been demonstrated in many species, how the clock system contributes to photoperiodic mechanisms remains unclear. A comprehensive study, including the functional analysis of relevant genes and physiology of their expressing cells, is necessary to understand the molecular and cellular mechanisms. Since Drosophila melanogaster exhibits a shallow photoperiodism, photoperiodic mechanisms have been studied in non-model species, starting with brain microsurgery and neuroanatomy, followed by genetic manipulation in some insects. Here, we review and discuss the involvement of the circadian clock in photoperiodic mechanisms in terms of neural networks in insects. We also review recent advances in the neural mechanisms underlying photoperiodic responses in insects and snails, and additionally circadian clock systems in snails, whose involvement in photoperiodism has hardly been addressed yet. Brain neurosecretory cells, insulin-like peptide/diuretic hormone44-expressing pars intercerebralis neurones in the bean bug Riptortus pedestris and caudo-dorsal cell hormone-expressing caudo-dorsal cells in the snail Lymnaea stagnalis, both promote egg laying under long days, and their electrical excitability is attenuated under short and medium days, which reduces oviposition. The photoperiodic responses of the pars intercerebralis neurones are mediated by glutamate under the control of the clock gene period. Thus, we are now able to assess the photoperiodic response by neurosecretory cell activity to investigate the upstream mechanisms, that is, the photoperiodic clock and counter.

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Photoperiodism of Diapause Induction in the Silkworm, Bombyx mori

Shimizu

2024

Zoological Science

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Neural Mechanism of Photoperiodism

Cited by 3 publications

References 114 publications

Photoperiodic plasticity of pigment-dispersing factor immunoreactive fibers projecting toward prothoracicotropic hormone neurons in flesh fly Sarcophaga similis larvae

Photoperiodic plasticity of pigment-dispersing factor immunoreactive fibers projecting toward prothoracicotropic hormone neurons in flesh fly Sarcophaga similis larvae

Neural mechanism of circadian clock-based photoperiodism in insects and snails

Photoperiodism of Diapause Induction in the Silkworm, Bombyx mori

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