Background: Human chronotypes (differences in preference for early or late rising each day) have been extensively studied in recent years, but similar studies have not been conducted in other animal species Methods: We evaluated behavioral chronotypes in 16 mammalian species along a body size gradient of five orders of magnitude (from mice to cattle) Individuals of all species were housed under a 12L:12D photoperiod in a thermoneutral environment with food and water available at all times Rhythms of locomotor activity were analyzed for onset time, acrophase, and robustness Results: None of the rhythmic parameters was significantly related to body size, but onset time and acrophase varied considerably from species to species, thus characterizing diurnal and nocturnal species Chronotype spreads ranged from less than an hour in sheep to almost 24 hours in cats, thus extending both below and above the human chronotype spread of 6 hours The variability of chronotype (as quantified by the standard deviation of group means) was much larger between species than within species and also larger between individuals of a species than within individuals on consecutive days Conclusion: These results help situate the matter of human chronotypes within the broader context of variability in the phase angle of entrainment of circadian rhythms in animals
Variability of Behavioral Chronotypes of 16 Mammalian Species Under Controlled Conditions
GIANNETTO, CLAUDIA;PICCIONE, Giuseppe
2016-01-01
Abstract
Background: Human chronotypes (differences in preference for early or late rising each day) have been extensively studied in recent years, but similar studies have not been conducted in other animal species Methods: We evaluated behavioral chronotypes in 16 mammalian species along a body size gradient of five orders of magnitude (from mice to cattle) Individuals of all species were housed under a 12L:12D photoperiod in a thermoneutral environment with food and water available at all times Rhythms of locomotor activity were analyzed for onset time, acrophase, and robustness Results: None of the rhythmic parameters was significantly related to body size, but onset time and acrophase varied considerably from species to species, thus characterizing diurnal and nocturnal species Chronotype spreads ranged from less than an hour in sheep to almost 24 hours in cats, thus extending both below and above the human chronotype spread of 6 hours The variability of chronotype (as quantified by the standard deviation of group means) was much larger between species than within species and also larger between individuals of a species than within individuals on consecutive days Conclusion: These results help situate the matter of human chronotypes within the broader context of variability in the phase angle of entrainment of circadian rhythms in animalsPubblicazioni consigliate
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