Ritmo biolÃgico da temperatura corporal em preguiÃas (Bradypus variegatus)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Sloths are heterothermal mammals showing a mean Body Temperature (BT) of around 33ÂC, and behavioral responses possibly related with the light-dark cycle (LD) and ambient temperature. Reports on studies regarding BT rhythmicity during the 24h period are inconclusive. The aim of the present study was to characterize the biological rhythm of BT in Bradypus variegatus sloths under different lighting conditions. A temperature sensor (iButton DS 1921G-F5), with a sample rate of 30 min, was implanted subcutaneously in the abdominal wall of 7 adult sloths, 6 males and 1 female (3,63Â0,55Kg). Simultaneous to BT data collection, motivating, activity and resting behavior was observed, every 30min. The animals were kept in an experimental room with acoustical and thermal isolation (24ÂC) and artificial lighting, and submitted to a protocol of 15 days under: light-dark cycle (LD â 12:12h, lights on at 6:00h), constant light (LL) and constant darkness (DD), 5 days under each condition. The rhythmometric parameters were determined by the COSINOR technique (p<0,05), and the period was determined by the Sokolove-Bushell periodogram. BT showed statistically significant circadian rhythmicity, with MESOR (XÂDP) of 32,81Â0,19ÂC, amplitude of 0,28Â0,13oC, and acrophase occurring approximately at 23:00h. The BT period (t) was 21:52hÂ59 min, in LL and 23:18hÂ36 min, in DD. BT showed statistically significant increase during feeding (FD) and dislocation (DS) behavior. The BT of the Bradypus variegatus sloths under constant ambient temperature, shows circadian rhythmicity, with acrophase occurring at the dark phase of LD cycle. The animals with the biggest body weight, had the highest BT amplitudes. The BT circadian rhythm is endogenous and does not depend on FD and DS behavior. The rise of t, with LL, and reduction, in DD, prove that the sloth is a nocturnal animal

ASSUNTO(S)

body temperature circadian rhythm ritmo circadiano temperatura corporal sloths preguiÃas fisiologia

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