Common features in diverse insect clocks

Abstract

This review describes common features among diverse biological clocks in insects, including circadian, circatidal, circalunar/circasemilunar, and circannual clocks. These clocks control various behaviors, physiological functions, and developmental events, enabling adaptation to periodic environmental changes. Circadian clocks also function in time-compensation for celestial navigation and in the measurement of day or night length for photoperiodism. Phase response curves for such clocks reported thus far exhibit close similarities; specifically, the circannual clock in Anthrenus verbasci shows striking similarity to circadian clocks in its phase response. It is suggested that diverse biological clocks share physiological properties in their phase responses irrespective of period length. Molecular and physiological mechanisms are best understood for the optic-lobe and mid-brain circadian clocks, although there is no direct evidence that these clocks are involved in rhythmic phenomena other than circadian rhythms in daily events. Circadian clocks have also been localized in peripheral tissues, and research on their role in various rhythmic phenomena has been started. Although clock genes have been identified as controllers of circadian rhythms in daily events, some of these genes have also been shown to be involved in photoperiodism and possibly in time-compensated celestial navigation. In contrast, there is no experimental evidence indicating that any known clock gene is involved in biological clocks other than circadian clocks.

The impact of artificial light at night on nocturnal insects: A review and synthesis

“…that are synchronized to daily, monthly, and yearly light cycles, respectively. Specialized photoperiodic photoreceptors use external light signals ( Zeitgebers or “time‐givers”) to entrain the internal clock to the outside environment (Numata, Miyazaki, & Ikeno, ; Numata, Shiga, & Morita, ). In nocturnal insects, daily emergence time and duration of feeding and courtship activity are dictated by internal clocks entrained by ambient light or temperature (Saunders, ; Tataroglu & Emery, ), while monthly or yearly cycles of eclosion, mating, and oviposition can be entrained by moonlight or day length cues (for a review of lunar entrainment, see Kronfeld‐Schor et al, ).…”

Neonicotinoids disrupt memory, circadian behaviour and sleep

“…The circuitry and molecular components of the mushroom body and the clock identified in Drosophila and shown to be highly conserved amongst insects 10,41,42 making it a powerful model to test the effects of neonicotinoids on memory, circadian behaviour and sleep. They are also one of the insects whose nAChRs are best characterised.…”

Circadian clock regulates photoperiodic responses governed by distinct output pathways in the bean bug,Riptortus pedestris

“…In some insect species, gene knock-down by RNA interference (RNAi) reveals causal involvement of these clock genes in photoperiodism (reviewed by Numata et al 2015). For example, RNAi directed against per, cry-m, cyc, and Clk disrupts the photoperiodic regulation of ovarian development in females of Riptortus pedestris (F.), the focal species of this study (Ikeno et al 2010(Ikeno et al , 2011(Ikeno et al , 2013.…”