Meeting Abstract
Almost all physiological processes within the organism, including immune parameters and hormones, follow a circadian rhythm. These 24h-day fluctuations are often observed in free-living organisms. However, in anurans, little is known regarding hormonal and immune daily variations, particularly under captive bred conditions. The aim of this study was investigating the immune and hormonal circadian rhythms in captive bred Bullfrogs (Lithobates catesbeianus), a species often used as anuran model in laboratory studies. We measured plasma bacterial killing ability (BKA), blood phagocytosis (PP), neutrophil/lymphocyte ratio (NL), plasma corticosterone (CORT), testosterone (T) and melatonin (MEL) levels. Bullfrogs were kept individually in plastic containers in a controlled room (12:12 LD photoperiod [lights on 7am] and 21 ± 2°C) for 7 days. Animals were randomly sampled by cardiac puncture every 3h (5 animals at each time, 40 individuals total). BKA, CORT, T and MEL levels were determined from plasma. Our results show 24h-day rhythms for BKA, CORT, T and MEL, with increased values during the nighttime when compared with daytime for all those variables. Moreover, increased MEL levels were observed only late night (6h after lights turn off; ~ 1am). These results show captive bred Bullfrogs, under artificial conditions, exhibit immune and hormonal circadian rhythms with increased values associated with nighttime. PP and NL were performed from blood leukocytes, and are still being analyzed.
