Tese Michele Fagundes.pdf - Caunesp

Abstract
Many physiological and behavioral processes expressed in live organism are
rhythmic and occur in a period of 24 hours, characterizing a circadian rhythm. In most
vertebrates, cortisol has a diel release profile, showing higher levels in the morning
which decrease up to the end of the day, related to a light-dark cycle. The aim of this
study was to evaluate the variation in blood concentrations of cortisol and glucose in
pintado (Pseudoplatystoma corruscans) along 24 hours without a stressful condition in
order to characterize their circadian profile. A total of 144 fish (mean weight 17.2 ± 5.3
g and mean length 15.7 ± 1.4 cm) were distributed into 36 aquaria (n=12) and samplings
were performed at each two hours (6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 2 and 4 hours).
There were not significant differences but the cortisol values presented a clear profile at
day and night, showing peaks at the settling of darkness and light. Blood glucose did not
present correlation to cortisol, keeping its values more stable along the day.
Key-words: Pintado, cortisol, glicemia, circadian rhythm
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