Srologicxl Rhythm Research, 1994, Vol.25, No. 2. pp. | 53- | 67 0929- 1016/94/2502-0153$6.00 @ Swets & Zeitlinger of an activity inducing antempeoture rhythmJ elrl mice:The effect of biology of agidg:Tem- | 299-309. )f ageon the circadian r-E6. Undet Temporal Isola. n sleep-wake andtem- Le environmental ligh!- Properties of the Two-peak Free Running Circadian Rhythm of Locomotor Activity of the SandDesert Beetle Trigonoscelis gigas Reitt. A.M. Alpato',1, W.J. Rietveld2., L.B. Oryntaeva3 and A.A. Putilova ABSTRACT Trigonoscelis gigasReitt, (Coleoptera: Tenebrionidae) is introduced asa model system forstudies of circadian rhythmsas appliedto ecologyand space biology. Field observations are complemented v/ith experiments on flee-running in the laboratory. In the naturalenvironment (Kara-Kumsand dcscrt, Turkmcnistan) tho beetle population demonstntes 2 narow (2 hr each) peaks of activity, a nloroingand an evening one. ln DD, among 107 records, a diversityof free-running patterns was observed. The long-term dynamics offrce-running rhythms in DD rcveals interaction between peaks, spon- raneous alterations oft, and splitting. Light andtempelature pulses canchange circadian phase 0 or pcriod t, cause damping or re-appearance ofrhythmicity. A surprisingly strong individualvariability of basicfcatures ofthe circadian system of ?1 glgal is emphasizcd. Abstracting keywords: Circadian rhythms, motor activity, free-run, splitting, phaseresetting, ColeoDtera. Tenebrionidae. iNTRODUCTION The desert beetle was selectedas a model system for experiments in spaceflight, bccause it pedectly fits for long-term maintenance and activity monitoring in a small closed volume, and is very convenient in handling (Tchernyshev, 1984). Being adapted to survive in an extremely arid environment, this animal is used to prolonged fasting and doesnot require any wat€r.So it is possible to record from desert beetles for several months without (external) interferenca, wheras chronobiological experiments with other insects usually last no longer than l-2 weeks. I Institute of Biomedical Problems, 123007 Moscow, Khoroshevskoye shosse 76-4,Russia. l Department ofPhysiology, University of Leiden, POBox 9604, 2333 AL Leiden, The Netherlands*. rDepartment of Biology, University of Alma'Ata, Kazakhstan. { Institure of Physiology, Novosibirsk, Russia. . Correspondence