Abstract
The fruit fly Drosophila melanogaster is an established model organism in chronobiology, because genetic manipulation and breeding in the laboratory are easy. The circadian clock neuroanatomy in D. melanogaster is one of the best-known clock networks in insects and basic circadian behavior has been characterized in detail in this insect. Another model in chronobiology is the honey bee Apis mellifera, of which diurnal foraging behavior has been described already in the early twentieth century. A. mellifera hallmarks the research on the interplay between the clock and sociality and complex behaviors like sun compass navigation and time-place-learning. Nevertheless, there are aspects of clock structure and function, like for example the role of the clock in photoperiodism and diapause, which can be only insufficiently investigated in these two models. Unlike high-latitude flies such as Chymomyza costata or D. ezoana, cosmopolitan D. melanogaster flies do not display a photoperiodic diapause. Similarly, A. mellifera bees do not go into “real” diapause, but most solitary bee species exhibit an obligatory diapause. Furthermore, sociality evolved in different Hymenoptera independently, wherefore it might be misleading to study the social clock only in one social insect. Consequently, additional research on non-model insects is required to understand the circadian clock in Diptera and Hymenoptera. In this review, we introduce the two chronobiology model insects D. melanogaster and A. mellifera, compare them with other insects and show their advantages and limitations as general models for insect circadian clocks.
Highlights
THE HISTORY OF INSECT MODELS IN CHRONOBIOLOGYChronobiology is a field of biology that examines cyclic phenomena in living organisms and their adaptation to solar- and lunar-related rhythms
Rhythms are controlled by the circadian clock, which has a period of about a day, but is synchronized to a period of 24 h by the environmental rhythms (= Zeitgeber) on earth
The Pigment-Dispersing Factor (PDF) neurons in the honey bee brain project into an highly dense fiber hub in the lateral brain close to the optic lobe (Homberg et al, 1991; Helfrich-Förster et al, 1998; Závodská et al, 2003). This “communication center” of the circadian clock may be analog to the aMe in Drosophila and other insects, with a small difference in location: it seems rather less associated with the Medulla than with the Lobula (Beer et al, 2018)
Summary
Chronobiology is a field of biology that examines cyclic phenomena in living organisms and their adaptation to solar- and lunar-related rhythms These cycles are known as biological rhythms and the best known are daily, annual and lunar rhythms. Circadian clocks help individual insects and other organisms to anticipate the 24 h environmental cycles and insect populations to synchronize crucial steps in their life (such as eclosion from the pupal case or mating) at the optimal time of the day. They enable individual insects to measure time, which is important for a time memory. RNA interference has been successfully applied in different insects (Moriyama et al, 2008; Lee et al, 2009; for example: Ikeno et al, 2010; Takekata et al, 2012; Kotwica-Rolinska et al, 2017) and genome editing via CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)—Cas (CRISPR associated protein) may provide clock gene manipulation suitable for further insects (Kotwica-Rolinska et al, 2019)
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