SIGNAL IN TIME: NEUROPEPTIDERGIC COUPLING OF <EM >DROSOPHILA</EM> LARVAL RHYTHMS

The diurnal fruit fly, Drosophila melanogaster, exhibits both circadian and ultradian rhythms in rest (sleep) and activity, with activity peaks at dawn and dusk. In addition to circadian feeding patterns, fruit flies display ultradian feeding bouts that vary with food availability and quality. The interaction between these circadian and ultradian rhythms remains to be elucidated. Starvation and nutrient restriction have been demonstrated to alter sleep and activity patterns, a phenomenon that is likely mediated by neuropeptides that coordinate multiscale rhythms. Our hypothesis is that neuropeptides released by clock neurons oscillate on multiple time scales, thereby integrating behavioral rhythms into a unified framework. Here, we examine the role of the ring gland in synchronizing neuropeptide release from pars intercerebralis and SEG-neurons with circadian timing. Behavioral tracking and mass spectrometry were conducted on individual larvae under various nutrient conditions (fed, 24 h & 48 h starved) and Zeitgebertimes (ZT0–ZT23). Larvae exhibited daily oscillations, peaking at dawn, dusk, midday and midnight. Foraging behaviors showed significant modulation in response to starvation, with alterations at specific times. Semiquantitative MS analysis revealed significant variations in neuropeptide abundance at different ZTs. Changes in rhythmic profiles due to starvation were observed, with alterations in both phase and amplitude. For instance, starvation induces rhythmic activity in sNPF and tachykinins. It also alters the amplitude of the rhythmic fluctuations in the concentrations of several neuropeptides, including an increase in AKH and a decrease in CAPA-PK.