INFLUENCE OF SEASONALITY ON CIRCADIAN MOTOR ACTIVITY RHYTHM IN COMMON MARMOSETS DURING PUBERTY

Abstract

The effect of puberty on circadian rhythmicity in nonhuman primates has been little studied, even though it has been demonstrated that puberty-related changes in circadian activity rhythm occur in a number of species, including humans. To characterize the motor activity rhythm during puberty in common marmosets (Callithrix jacchus), six animals was continuously monitored by actimeters between their 5th and 12th months of age. The animals were housed with their families in outdoor cages under seminatural conditions. Onset of puberty was determined from fecal estrogen and progesterone levels in females and androgen levels in males. The spectral power of the circadian component stabilized later in the last two animals to enter puberty. The bimodal characteristic of the active phase in this species became progressively more apparent over the course of the months in which the mean temperature was highest, irrespective of the animal's age. Although the onset of activity advanced after entry into puberty, this parameter showed a strong correlation with sunrise, indicating that seasonality influences this variable. Neither age nor climatic factors included in the regression model influenced the differences in phase angles between sunrise and onset of activity, and between sunset and offset of activity. Total activity was the only parameter influenced by age in the regression model, showing an increase after entry into puberty. Despite the evidence of pubertal influence on both the circadian component and total activity, under seminatural conditions seasonal factors may have a more important effect on motor activity rhythm in common marmosets. (Author correspondence: E-mail: [email protected])

Keywords:

• Age
• Bimodality
• Circadian
• Common marmoset
• Motor activity
• Puberty
• Seasonality

ACKNOWLEDGMENTS

We thank Dr. Fátima Arruda and Dr. Fernando Louzada for their suggestions throughout this study; the students Christiane Silva, Guido Grimaldi, Luane Ferreira, and Bruno Gonçalves for their help in data collection and analysis; Luiz Carlos Fernandes and the employees of the Primatology Center, especially Antônio Barbosa da Silva for his technical support; and CAPES, CTinfra/Finep, and the Universidade Federal do Rio Grande do Norte for financial support.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.