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Auteur Viblanc, V.A.; Saraux, C.; Malosse, N.; Groscolas, R.
Titre Energetic adjustments in freely breeding-fasting king penguins: does colony density matter? Type Article scientifique
Année 2014 Publication Revue Abrégée Functional Ecology
Volume Numéro Pages
Mots-Clés body temperature; energy expenditure; fasting; heart rate; physical activity; Seabird; social density; Stress
Résumé * For seabirds that forage at sea but breed while fasting on land, successful reproduction depends on the effective management of energy stores. Additionally, breeding often means aggregating in dense colonies where social stress may affect energy budgets. * Male king penguins (Aptenodytes patagonicus) fast for remarkably long periods (up to 1·5 months) while courting and incubating ashore. Although their fasting capacities have been well investigated in captivity, we still know very little about the energetics of freely breeding birds. * We monitored heart rate (HR, a proxy to energy expenditure), body temperature and physical activity of male king penguins during their courtship and first incubation shift in a colony of some 24 000 freely breeding pairs. Males were breeding either under low but increasing colony density (early breeders) or at high and stable density (late breeders). * In early breeders, daily mean and resting HR decreased during courtship but increased again 3 days before egg laying and during incubation. In late breeders, HR remained stable throughout this same breeding period. Interestingly, the daily increase in resting HR we observed in early breeders was strongly associated with a marked increase in colony density over time. This finding remained significant even after controlling for climate effects. * In both early and late breeders, courtship and incubation were associated with a progressive decrease in physical activity, whereas core body temperature remained unchanged. * We discuss the roles of decreased physical activity and thermoregulatory strategies in sustaining the long courtship–incubation fast of male king penguins. We also draw attention to a potential role of conspecific density in affecting the energetics of breeding-fasting seabirds, that is, a potential energy cost to coloniality.
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ISSN 1365-2435 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 320
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Auteur McKenzie, D.J.; Skov, P.V.; Taylor, E.W.T.; Wang, T.; Steffensen, J.F.
Titre Abolition of reflex bradycardia by cardiac vagotomy has no effect on the regulation of oxygen uptake by Atlantic cod in progressive hypoxia Type Article scientifique
Année 2009 Publication Revue Abrégée Comp. Biochem. Physiol. A-Mol. Integr. Physiol.
Volume 153 Numéro 3 Pages 332-338
Mots-Clés Cranial nerve X; Gas exchange; Heart rate; Hypoxia; Sodium cyanide; Vagus; blood; channel catfish; dogfish scyliorhinus-canicula; fish; fish hearts; gadus-morhua; performance; pressure; rainbow-trout; respiration; responses; ventilation
Résumé The functional significance of chemoreflexive hypoxic bradycardia was explored in Atlantic cod Gadus morhua L. (mean mass similar to 800 g, acclimated to a seawater temperature of 11 degrees C) by investigating responses to progressive hypoxia following section of the cardiac branches of cranial nerve X Cardiac denervation had no effect on oxygen uptake rate (M(O2)), gill ventilation rate (f(G)) or opercular pressure amplitude (P(OP)) under normoxic conditions, but caused a significant increase in heart rate (f(H)), to 50 +/- 1 beats min(-1) by comparison to 40 +/- 2 beats min(-1) in sham-operated cod (mean +/- s.e.m., n=9). Sham-operated cod exhibited transient profound bradycardia following oxygen chemoreceptor stimulation by bolus injection of sodium cyanide into the buccal cavity (2 mg in 2 ml seawater), but this cardiac chemoreflex was abolished in denervated cod. Both groups, however, exhibited similar marked transient chemoreflexive hyperventilation following NaCN. When exposed from normoxia (PO(2)similar to 18 kPa) to progressive hypoxia at nominal water PO(2)'S of 8, 6, 5, 4 and 3 kPa, both groups exhibited the same pattern of homeostatic regulation of M(O2), with no significant difference in their mean critical PO(2) (P(crit)) values, which were 7.40 +/- 0.81 kPa and 8.73 +/- 0.71 kPa, respectively (n=9). Both groups exhibited significant bradycardia during progressive hypoxia, although denervated fish always had higher mean f(H). The incipient threshold for bradycardia coincided with P(crit) in sham-operated cod whereas, in denervates, the threshold was below their P(crit) and bradycardia presumably reflected direct effects of hypoxia on the myocardium. The sham-operated group displayed a significantly more pronounced ventilatory response than denervates in hypoxia, in particular for P(OP). In sham-operated cod, peak ventilatory responses occurred in deep hypoxia below P(crit) whereas, in denervates, more modest peak responses coincided with Pit and, in deep hypoxia, they exhibited a significant decline in f(G) below their normoxic rate. Only a minority of shams lost equilibrium in hypoxia whereas a majority of denervates did, some of which failed to recover. The results indicate that chemoreflexive bradycardia plays no role in the homeostatic regulation of oxygen uptake by cod in hypoxia, but does contribute to maintenance of overall functional integrity below P(crit). (C) 2009 Elsevier Inc. All rights reserved.
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Langue English Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
Volume de collection Numéro de collection Edition
ISSN 1095-6433 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 431
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Auteur Blasco, F.R.; McKenzie, D.J.; Taylor, E.W.; Rantin, F.T.
Titre The role of the autonomic nervous system in control of cardiac and air-breathing responses to sustained aerobic exercise in the African sharptooth catfish Clarias gariepinus Type Article scientifique
Année 2017 Publication Revue Abrégée Comp. Biochem. Physiol. A-Mol. Integr. Physiol.
Volume 203 Numéro Pages 273-280
Mots-Clés Adrenergic tone; bass dicentrarchus-labrax; cardiorespiratory interactions; Cholinergic tone; Fishes; Heart rate; heart-rate; hoplerythrinus-unitaeniatus; Hypoxia; oxygen-tensions; rainbow-trout; salmo-gairdneri; Swimming; synbranchus-marmoratus
Résumé Clarias gariepinus is a facultative air-breathing catfish that exhibits changes in heart rate (f(H)) associated with air breaths (AB). A transient bradycardia prior to the AB is followed by sustained tachycardia during breath-hold. This study evaluated air-breathing and cardiac responses to sustained aerobic exercise in juveniles (total length similar to 20 cm), and how exercise influenced variations in f(H) associated with AB. In particular, it investigated the role of adrenergic and cholinergic control in cardiac responses, and effects of pharmacological abolition of this control on air-breathing responses. Sustained exercise at 15, 30 and 45 cm s(-1) in a swim tunnel caused significant increases in f(AB) and f(H), from approximately 5 breaths h(-1) and 60 heartbeats min(-1) at the lowest speed, to over 60 breaths h(-1) and 100 beats min(-1) at the highest, respectively. There was a progressive decline in the degree of variation in f(H), around each AB, as f(AB) increased with exercise intensity. Total autonomic blockade abolished all variation in fH during exercise, and around each AB, but f(AB) responses were the same as in untreated animals. Cardiac responses were exclusively due to modulation of inhibitory cholinergic tone, which varied from >100% at the lowest speed to <10% at the highest. Cholinergic blockade had no effect on f(AB) compared to untreated fish. Excitatory beta-adrenergic tone was approximately 20% and did not vary with swimming speed, but its blockade increased f(AB) at all speeds, compared to untreated animals. This reveals complex effects of autonomic control on air-breathing during exercise in C. gariepinus, which deserve further investigation. (C) 2016 Elsevier Inc. All rights reserved.
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Langue English Langue du Résumé Titre Original
Éditeur de collection Titre de collection Titre de collection Abrégé
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ISSN 1095-6433 ISBN Médium
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Numéro d'Appel MARBEC @ alain.herve @ collection 1714
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