Endogenous circadian rhythm is a crucial tool for survival of the sand-desert tenebrionid beetle Trigonoscelis gigas Reitter

The beetle T. gigas is interesting as a successful survivor among competing species in a hostile, arid, environment (the sand-desert), and as a promis ing biological model system in laboratory experiments. Behaviour and motor activity rhythms of T. gigas were studied in the field, using autonomous mo nitors. In order to avoid extreme temperatures, this beetle developed a pec uliar behavioural strategy: narrow time windows for activity tin the mornin g and in the evening). The rest of the time it spends deep in the sand, at constant comfortable temperature and in continuous darkness, in temporal is olation. We demonstrated that there are no available Zeitgebers for the bee tle during its rest interval. Hence, a reliable circadian clock is the only way for T. gigas to implement the proper timing of its activity. It means, that the circadian timing system of this beetle is not just a source of re lative advantage, but is a crucial prerequisite of survival.