Prolonged deprivation of sleep-like rest raises metabolic rate in the Pacific beetle cockroach, Diploptera punctata (Eschscholtz)

Abstract

SUMMARY Rats respond to sustained sleep deprivation with increased mortality preceded by a rise in resting metabolic rate that may or may not be attributed to dysfunction of the thermoregulatory system. The present study was designed to test the hypothesis that deprivation of sleep-like rest will lead to increased metabolic rate in an ectothermic insect, the Pacific beetle cockroach. A mild alerting stimulus consisting of a brief <1% pulse of CO2 and simultaneous 2 s rotation (1 cm motion) of the animal chamber consistently prevented the adoption of a sleep-like resting posture in cockroaches. Two groups of 15 male adult cockroaches were studied; a group targeted for deprivation of sleep-like rest (SD) was presented with one stimulus per minute continuously, and a group of stimulus controls (SC) was given the same number of stimuli per day but scheduled such that the animals received a 3 h interval without stimuli four times per day. This protocol led to significantly increased mortality in the SD group beginning on day 17(averaging 0.57 deaths per day thereafter), but not in the SC group (averaging 0.17 deaths per day throughout). Oxygen consumption(V̇O2) increased significantly after 4 weeks in the SD group but not the SC group. V̇O2 was 82% above pre-deprivation baseline after 35 days in the SD group (P=0.009). Body mass was unchanged throughout. We conclude that sleep-like rest is essential for long-term viability in insects and that prolonged vigilance leads to an increase in whole-animal metabolic rate in this ectothermic species.