Peripheral circadian rhythms and their regulatory mechanism in insects and some other arthropods: a review

Abstract

Many physiological functions of insects show a rhythmic change to adapt to daily environmental cycles. These rhythms are controlled by a multi-clock system. A principal clock located in the brain usually organizes the overall behavioral rhythms, so that it is called the "central clock". However, the rhythms observed in a variety of peripheral tissues are often driven by clocks that reside in those tissues. Such autonomous rhythms can be found in sensory organs, digestive and reproductive systems. Using Drosophila melanogaster as a model organism, researchers have revealed that the peripheral clocks are self-sustained oscillators with a molecular machinery slightly different from that of the central clock. However, individual clocks normally run in harmony with each other to keep a coordinated temporal structure within an animal. How can this be achieved? What is the molecular mechanism underlying the oscillation? Also how are the peripheral clocks entrained by light-dark cycles? There are still many questions remaining in this research field. In the last several years, molecular techniques have become available in non-model insects so that the molecular oscillatory mechanisms are comparatively investigated among different insects, which give us more hints to understand the essential regulatory mechanism of the multi-oscillatory system across insects and other arthropods. Here we review current knowledge on arthropod's peripheral clocks and discuss their physiological roles and molecular mechanisms.

Apoptosis and necrosis during the circadian cycle in the centipede midgut

“…It is composed of many periodic rhythms, e.g., seasonal, monthly, and/or circadian rhythms. The physiological reaction to the length of the day and night plays a role in regulating cell proliferation and tissue regeneration, hormone synthesis and secretion, reproduction (Lipovšek et al 2002;Dunlap et al 2003;Sankar 2011a, 2011b;Tomioka et al 2012;Park et al 2013). Myriapods, including centipedes (Chilopoda), are invertebrates whose life and behavior are synchronized with the day/night cycle (Minelli 1993).…”

Circadian rhythms affect the electroretinogram, compound eye color, striking behavior, and locomotion of the praying mantis,Hierodula patellifera(Serville)

“…For example, independent pacemakers control cuticle formation in cockroaches (Leucophaea maderae and Blaberus sp. ), sperm release in moths (Anagasta kueniella and Lymantria dispar) and steroid hormone release in Samia Cynthia, Rhodinus prolixus and Galleria mellonella (Underwood et al, 2010;Tomioka et al, 2012).…”

The involvement of the brain region containing pigment-dispersing factor-immunoreactive neurons in the photoperiodic response of the bean bugRiptortus pedestris

“…The insect circadian clock is driven by a number of circadian clock genes, which form interlocked negative feedback loops that generate rhythmicity at transcriptional and translational levels, as well as post-translational levels, such as phosphorylation (Hardin, 2005). Circadian clock genes and their protein products are expressed in a variety of tissues, but only a small number of neurons in the brain are responsible for the circadian clock regulating locomotor activity (Helfrich-Förster, 2003;Tomioka et al, 2012). While the involvement of the circadian clock genes in the photoperiodic response has been demonstrated in several insect species (Pavelka et al, 2003;Sakamoto et al, 2009;Ikeno et al, 2010;Ikeno et al, 2011b;Ikeno et al, 2011c;Ikeno et al, 2013;Bajgar et al, 2013a;Bajgar et al, 2013b), less is known about the neuronal mechanism of the circadian clock underlying photoperiodism (Shiga, 2012).…”