Caracterization of the Motor Activity Rhythm in a Common Marmoset Family

*Corresponding author e-mail: biopaula21@yahoo.com.br Introduction: Most studies about the ontogeny of biological rhythmicity are based on the idea that the circadian periodicity is installed during infancy and remains the same until the beginning of the senescence. Although some studies have exploited the circadian rhythmicity in the transition phase between the infancy and adult stages, they not explored the peculiarities of this development phase that prepares a subject to the adult stage. The diurnal rodent Octodon degus shows a phase delay in activity onset in the puberty that remains until adult stage. Methods: In order to compare the phase relation of the motor activity rhythm between juveniles marmosets and parents, two juveniles and their parents were maintained under artificial light conditions (light-dark cycle: 12:12h) and the activity was monitored by Actiwatch (MiniMitter) during twenty days. Results and conclusion: The activity onset occurred earlier and activity offset occurred later in adults than in juveniles (Tukey, p <0.05). Consequently, phase active duration was higher in the adults in relation to juveniles. If the activity onset advance observed in pubertal animals (preliminary data observed in our laboratory) and in adults compared to pre-pubertal animals is confirmed in more animals, it is possible to suggest that this advance begins in the puberty and remains until the adult stage. The phase angle of activity onset and offset was smaller in adults than in juveniles (Tukey, p <0.05). Since the activity total was smaller in adults than in juveniles, this result may be consequence of the play behavior that involves juvenile displacement increase. In relation to 24h and 8 h components of motor activity rhythm, there was no difference between adults and juveniles, possibly because the circadian component becomes stable near five months age. Although the evidence that motor activity rhythm showed difference between adults and juveniles, the evaluation of more animals is necessary to confirm this hypothesis. Publication History Article published online: 16 June 2026 © 2009. Brazilian Sleep Academy. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/) Thieme Revinter Publicações Ltda. Rua Rego Freitas, 175, loja 1, República, São Paulo, SP, CEP 01220-010, Brazil