Properties of the two‐peak free running circadian rhythm of locomotor activity of the sand desert beetle Trigonoscelis gigas reitt

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Abstract
Trigonoscelis gigas Reitt. (Coleoptera: Tenebrionidae) is introduced as a model system for studies of circadian rhythms as applied to ecology and space biology. Field observations are complemented with experiments on free‐running in the laboratory. In the natural environment (Kara‐Kum sand desert, Turkmenistan) the beetle population demonstrates 2 narrow (2 hr each) peaks of activity, a morning and an evening one. In DD, among 107 records, a diversity of free‐running patterns was observed. The long‐term dynamics of free‐running rhythms in DD reveals interaction between peaks, spontaneous alterations of τ, and splitting. Light and temperature pulses can change circadian phase ϕ or period τ, cause damping or re‐appearance of rhythmicity. A surprisingly strong individual variability of basic features of the circadian system of T. gigas is emphasized.