Entrainment properties of the circadian system changing with reproductive state and molt in the canary.
Changes in entrainment properties of the circadian pacemaking system with respect to changes in reproductive state and molt were investigated in the male domestic canary (Serinus canaria). In two experiments canaries were subjected to three and two similar sequences of light regimens, respectively, during 1 year. Locomotor activity, feeding, and vocalization were simultaneously recorded. Only birds showing complete postnuptial wing feather molt and related changes in behavior (vocalization) expressed differences in the ability of their circadian system to entrain to low-amplitude light/dark (LD) cycles with periods (T) > 24 h. It is suggested that changes in the organization of the circadian system, including differences in entrainment properties, are associated with the state of photorefractoriness and related functions (testicular regression, postnuptial molt). Regardless of the molt status, over 90% of the birds that were arrhythmic in constant light (LL) entrained to low-amplitude LD cycles with T 25.5 h (Experiment 1) or T 25.0 h (Experiment 2). Birds that did not entrain or were relatively entrained with the respective light regimes were (with one exception) rhythmic in LL. It is therefore likely that the occurrence of arrhythmia in LL facilitates entrainment to low-amplitude light cycles.
Max-Planck-Institut für Verhaltensphysiologie, Andechs, Germany.
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D000818:Animals; D002171:Canaries / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D005247:Feeding Behavior / Q000502:physiology; D012739:Gonadal Steroid Hormones / Q000502:physiology*; D008027:Light; D008297:Male; D009043:Motor Activity / Q000502:physiology; D012621:Seasons; D012726:Sexual Behavior, Animal / Q000502:physiology*; D014828:Vocalization, Animal / Q000502:physiology
D012739:Gonadal Steroid Hormones