Entrainment of eclosion and preliminary ontogeny of circadian clock gene expression in the flesh fly, Sarcophaga crassipalpis

Abstract

Timing of circadian activities is controlled by rhythmic expression of clock genes in pacemaker neurons in the insect brain. Circadian behavior and clock gene expression can entrain to both thermoperiod and photoperiod but the availability of such cues, the organization of the brain, and the need for circadian behavior change dramatically during the course of insect metamorphosis. We asked whether photoperiod or thermoperiod entrains the clock during pupal and pharate adult stages by exposing flies to different combinations of thermoperiod and photoperiod and observing the effect on the timing of adult eclosion. This study used qRT-PCR to examine how entrainment and expression of circadian clock genes change during the course of development in the flesh fly, Sarcophaga crassipalpis. Thermoperiod entrains expression of period and controls the timing of adult eclosion, suggesting that the clock gene period may be upstream of the eclosion pathway. Rhythmic clock gene expression is evident in larvae, appears to cease during the early pharate adult stage, and resumes again by the time of adult eclosion. Our results indicate that both patterns of clock gene expression and the cues to which the clock entrains are dynamic and respond to different environmental signals at different developmental stages in S. crassipalpis.

Expanding the view of Clock and cycle gene evolution in Diptera

“…Most of the knowledge about Brachycera flies comes from D. melanogaster , which is used as a model for insect clocks. In addition, mRNA expression data are available for both genes in Musca domestica (Diptera, Muscidae) (Codd et al ., ) and Sarcophaga crassipalpis (Diptera, Sarcophagidae) (Goto & Denlinger, ; Short et al ., ), which corroborate the patterns found in D. melanogaster . A more comprehensive investigation of nonmodel species would help explain when the loss of the BCTR domain in CYC occurred, which is thus far attributed only to the drosophilid lineage (Allada et al ., ; Rutila et al ., ), making Drosophila an exception.…”

Cues for cavity nesters: investigating relevant zeitgebers for emerging leafcutting bees, Megachile rotundata

“…For example, photoperiod may not be the best cue for synchronizing with the environment if an insect develops in a lightrestricted environment. Some data support this hypothesis in insects that pupate below ground, where thermoperiod cues were shown to regulate emergence (Zdarek and Denlinger, 1995;Short et al, 2016;Miyazaki et al, 2011;Watari and Tanaka, 2014;Greenberg et al, 2006). Insects that pupate in other types of light-restricted habitats such as nests, natural or artificial cavities, and brood cells may also rely on thermoperiod cues.…”

“…To determine whether photoperiod or thermoperiod was dominant, cues were decoupled (Pittendrigh and Minis, 1964), which is generally referred to as a conflicting zeitgeber experiment (Watari and Tanaka, 2010;Short et al, 2016). Bees were exposed to a Δ4°C thermoperiod, although the lights were turned on during the cryophase and turned off during the thermophase.…”

“…A well-known phenomenon controlled by circadian rhythms in many insect species is the timing of eclosion, which is the emergence of the adult from the pupal cuticle (Miyazaki et al, 2016;Short et al, 2016;Kikukawa et al, 2013;Dolezel et al, 2008). Many studies have identified photoperiod as the critical cue in synchronizing eclosion (Pittendrigh et al, 1959;Pittendrigh and Minis, 1964;Smith, 1985;Kumar et al, 2007;Umadevi et al, 2009;Guo and Qin, 2010;Thöming and Saucke, 2011;Wu et al, 2014;Yadav et al, 2014).…”

A Precise and Autonomous System for the Detection of Insect Emergence Patterns

“…Analyzing data for presence of synchronization can be done by calculating "parameter R," a scalar statistic that identifies if emergence is rhythmic or arrhythmic 10,11,12 . This is done by calculating the highest number of emerging adults in an 8-hour window, dividing this number by the number of adults emerging outside the 8-hour window, then multiplying by 100.…”