Circadian pattern of hepatosomatic index, liver glycogen and lipid content, plasma non-esterified fatty acid, glucose, T3, T4, growth hormone and cortisol concentrations in Oncorhynchus mykiss held under different photoperiod regimes and fed using demand-feeders

Abstract

The circadian patterns of several tissue and plasma metabolites, and several plasma hormone concentrations are described in rainbow trout (Oncorhynchus mykiss) that were held in groups under three different photoperiod regimes, and given free access to a demand-feeder. Regardless of photoperiod regime, all the measured parameters showed significant diel rhythms that appeared to be synchronized by dawn; dawn was represented by the concomitant onset of both light and feeding. The diel increases in hepatic glycogen content, and plasma T4 and cortisol concentrations were in phase with the main period of feeding activity, whereas the peaks in plasma T3 and glucose concentrations that may also be triggered by feeding activity, were delayed by several hours. The peaks in hepatosomatic index, plasma non-esterified fatty acids and plasma growth hormone concentrations were 180° out of phase with the main period of feeding activity, and associated with periods of hypophagia and low activity.

Effect of Illuminance Transition Rate on Survival of Juvenile Pacific Bluefin Tuna, Thunnus orientalis

“…Direct correlations between behavioral rhythms and endocrinological rhythms are still unclear. Nevertheless, the diel rhythm of plasma cortisol concentration that peaked during the dawn period in this study is similar to that observed by Boujard and Leatherland (), suggesting that responses to photophase are associated with feeding times. Plasma cortisol concentration peaked at the transition between scotophase and photophase, and pre‐feeding diving behaviors caused mortality in the limited space of the rearing tank.…”

Effect of Illuminance Transition Rate on Survival of Juvenile Pacific Bluefin Tuna, Thunnus orientalis

“…Direct correlations between behavioral rhythms and endocrinological rhythms are still unclear. Nevertheless, the diel rhythm of plasma cortisol concentration that peaked during the dawn period in this study is similar to that observed by Boujard and Leatherland (), suggesting that responses to photophase are associated with feeding times. Plasma cortisol concentration peaked at the transition between scotophase and photophase, and pre‐feeding diving behaviors caused mortality in the limited space of the rearing tank.…”

Glucosensing capacity in liver of rainbow trout displays day-night variations possibly related to melatonin action

“…Several parameters assessed in controls (for instance, GK activity in liver or PK activity in hypothalamus and hindbrain) displayed clear day-night differences, which in some cases agree with those described for the same species in the literature (Boujard and Leatherland, 1992;Reddy and Leatherland, 1994;Polakof et al, 2007c;Polakof et al, 2007d), allowing us to postulate the existence of daily rhythms. Treatment with glucose during the day induced hyperglycemia, which is in agreement with similar studies carried out previously in the same fish species (Polakof et al, 2007a;CondeSieira et al, 2010a).…”

Does the time of feeding affect the diurnal rhythms of plasma hormone and glucose concentration and hepatic glycogen content of rainbow trout?

“…This observation is in agreement with the reports from other workers (Eales et al 1981;Cook and Eales 1987;Boujard and Leatherland 1992c;Boujard et al 1993). It is noteworthy that the plasma T 4 concentrations were higher at the time of feeding in the post-dawn and midday fed groups, but there was a significant decrease in the levels following feeding.…”

Effect of Illuminance Transition Rate on Survival of Juvenile Pacific Bluefin Tuna, Thunnus orientalis

“…Direct correlations between behavioral rhythms and endocrinological rhythms are still unclear. Nevertheless, the diel rhythm of plasma cortisol concentration that peaked during the dawn period in this study is similar to that observed by Boujard and Leatherland (), suggesting that responses to photophase are associated with feeding times. Plasma cortisol concentration peaked at the transition between scotophase and photophase, and pre‐feeding diving behaviors caused mortality in the limited space of the rearing tank.…”

Glucosensing capacity in liver of rainbow trout displays day-night variations possibly related to melatonin action

“…Several parameters assessed in controls (for instance, GK activity in liver or PK activity in hypothalamus and hindbrain) displayed clear day-night differences, which in some cases agree with those described for the same species in the literature (Boujard and Leatherland, 1992;Reddy and Leatherland, 1994;Polakof et al, 2007c;Polakof et al, 2007d), allowing us to postulate the existence of daily rhythms. Treatment with glucose during the day induced hyperglycemia, which is in agreement with similar studies carried out previously in the same fish species (Polakof et al, 2007a;CondeSieira et al, 2010a).…”

Does the time of feeding affect the diurnal rhythms of plasma hormone and glucose concentration and hepatic glycogen content of rainbow trout?

“…This observation is in agreement with the reports from other workers (Eales et al 1981;Cook and Eales 1987;Boujard and Leatherland 1992c;Boujard et al 1993). It is noteworthy that the plasma T 4 concentrations were higher at the time of feeding in the post-dawn and midday fed groups, but there was a significant decrease in the levels following feeding.…”

Effect of Illuminance Transition Rate on Survival of Juvenile Pacific Bluefin Tuna, Thunnus orientalis

“…Direct correlations between behavioral rhythms and endocrinological rhythms are still unclear. Nevertheless, the diel rhythm of plasma cortisol concentration that peaked during the dawn period in this study is similar to that observed by Boujard and Leatherland (), suggesting that responses to photophase are associated with feeding times. Plasma cortisol concentration peaked at the transition between scotophase and photophase, and pre‐feeding diving behaviors caused mortality in the limited space of the rearing tank.…”

Glucosensing capacity in liver of rainbow trout displays day-night variations possibly related to melatonin action

“…Several parameters assessed in controls (for instance, GK activity in liver or PK activity in hypothalamus and hindbrain) displayed clear day-night differences, which in some cases agree with those described for the same species in the literature (Boujard and Leatherland, 1992;Reddy and Leatherland, 1994;Polakof et al, 2007c;Polakof et al, 2007d), allowing us to postulate the existence of daily rhythms. Treatment with glucose during the day induced hyperglycemia, which is in agreement with similar studies carried out previously in the same fish species (Polakof et al, 2007a;CondeSieira et al, 2010a).…”

Does the time of feeding affect the diurnal rhythms of plasma hormone and glucose concentration and hepatic glycogen content of rainbow trout?

“…This observation is in agreement with the reports from other workers (Eales et al 1981;Cook and Eales 1987;Boujard and Leatherland 1992c;Boujard et al 1993). It is noteworthy that the plasma T 4 concentrations were higher at the time of feeding in the post-dawn and midday fed groups, but there was a significant decrease in the levels following feeding.…”