WASSMER, G.T.; HORTMAN, B.I.; FULLER, C.A.; ALPATOV, A.M.; HOBAN-HIGGINS, T.M.; Bloomsburg University of Pennsylvania; Bloomsburg University of Pennsylvania; Univ. of California, Davis; Institute for Biomedical Problems, Moscow, Russia; Univ. of California, Davis: Effects of gravity on the stability of the biological clock in the desert beetle Trigonoscelis gigas

Biological rhythms are daily fluctuations in physiology and behavior which allow organisms to predict and prepare for daily changes in the environment. These rhythms are generated by, and regulated by, a circadian timing system (CTS). Dysfunction of the CTS is associated with performance decrements, sleep and mental disorders, and jet-lag. Altered gravitation fields (microgravity, hypergravity) have been shown to affect the functioning of the CTS. Two important characteristics that are used to assess the functioning of the CTS are the period of the generated rhythms, and the stability of these rhythms. We have shown that the period of locomotor rhythm in the desert beetle Trigonoscelis gigas is affected by both light and gravity. Gravitational fields were altered by exposing the animals to microgravity (uG) aboard the MIR space station, to normal gravity (1G), and (via centrifugation)to hypergravity (2G). In microgravity and normal gravity, the period of the rhythm was longer when the animals were exposed to constant light than if they were kept in constant darkness. This difference was lost when the animals were in a hypergravitational environment. We report here that gravity and light also affect the stability of the circadian system. The rhythm was less stable in constant darkness than in constant light at both microgravity and normal gravity. Under hypergravity there was no significant difference in stability between constant light and constant darkness. These findings parallel our previous finding pertaining to the period of the rhythm and suggest that there may be a link between the period and the stability of the rhythm.