CIRCADIAN-RHYTHM OF ACTIVITY IN TRIGONOSC ELIS-GIGAS (COLEOPTERA, TENEBRIONIDAE) AND ITS ADAPTIVE SIGNIFICANCE

The paper deals with the results of the field st;dy of circadian rhyth m in Trigonoscelis gigas. This beetle is one of the most promising bio logical objects for chronobiological studies in spaceships. Active ima gines occur on the surface from early spring till late autumn despite the pronounced daily and seasonal contrasts of temperature in the Kara -Kum desert (Turkmenistan). It became possible due to pronounced circa dian rhythm of activity. This rhythm is controlled by the mechanism of circadian ''gates'': the beetles are active only within morning (6 to 10 AM) and evening (4 to 8 PM) independently from weather and season. We could not stimulate the activity in other hours by the means of ar tificial lighting or heating in the field experiments performed with b eetles placed into enclosures. The temperature of sand surface and the level of illumination may cause some shift of the circadian phases, b ut only within the relevant time gate. In the natural environment, bot h gates keep about 12 hrs apart throughout all seasons. Beetles someti mes can skip some gates and stay under sand, if conditions on the surf ace are unfavorable. We conclude, that T. gigas unlike many other dese rt animals has a peculiar survival strategy: its activity is related n ot to the optimal weather conditions, but to rigid time intervals, whe n the weather over seasons is usually favorable or, at least, never is dangerous.