Circadian activity rhythms in colonies of ‘blind’ Molerats, <i>Cryptomys damarensis</i> (Bathyergidae)

Abstract

Various activity rhythms (general, feeding, and toilet) were measured under controlled laboratory conditions in two colonies of the Damara molerai Cryptomys damarensis, for 140 consecutive days (following a 30 day test period) under various photoperiod regimes (16:8 LD, 12:12 LD, and constant dark DD). As a general rule, all activities showed a significant diurnal rhythm with a period of 24 h under LD photoperiods. However, under a 16 : 8 LD photoperiod a very prominent activity component during the first part of the subjective night was observed, especially following a shift in photoperiod. The molerats responded rapidly to LD phase shifts. In constant dark, all activities had free-running periods of τ = 24,1-24,2 h, thus indicating that light can synchronize and entrain endogenous circadian rhythms in these molerats.