Tese Michele Fagundes.pdf - Caunesp

Abstract
Few studies have been evaluating the effect of photoperiod on stress of native
fish. The aim of this study was to assess physiological responses of pintado
(Pseudoplatystoma corruscans) submited to continuous light (24L:0D) and darkness
(0L:24D) during 24 h. A total of 66 juvenile fish (70.15 ± 18.2 g and 25.28 ± 2.18 cm)
were distributed in 33 boxes (n=6). Samplings were performed at the completion of the
24h photoperiod exposure (zero hour), 24, 48, 72 horas and one week after. Blood
cortisol did not differ statistically but in fish submitted to continuous light values were
numerically higher compared to those of fish submitted to darkness and both compared
to control. Blood glucose did not show statiscal diference but lower levels had been
seen in fish under darkness. No osmorregulatory disturbance was seen. Hematocrit,
number of red cells and hemoglobin showed the same profile trending to be higher in
fish exposed to continuous light. Results suggest that pintado, nocturnal species,
presents moderate responses to the photoperiod changes.
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