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Increased metabolic cost of swimming and consequent alterations to circadian activity in rainbow trout (Oncorhynchus mykiss) exposed to dietary copper

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This study tests the hypothesis that rainbow trout (Oncorhynchus mykiss) compensate for the metabolic cost of dietary Cu exposure by reducing swimming activity at particular times during the diel cycle. Fish were exposed to excess dietary Cu for three months (726 mg Cu·kg–1 dry weight) and simultaneously oxygen consumption (MO2) and spontaneous swimming activity were measured. Rhythmicity in swimming activity was examined by videorecording fish behaviours for 48 h. Standard metabolic rate estimates (RS) of 7.2 and 8.7 mmol O2·kg–1·h–1 (15°C) were measured for control and Cu-exposed fish, respectively. MO2 was higher in Cu-exposed fish at any chosen speed compared with control Cu-exposed trout, which decreased activity (mean speed) by at least 75%, spent more time at lower speeds, and lost circadian periodicity in these parameters compared with controls. Mean growth rates were normal, although Cu-exposed fish showed a narrower range of body weights and fewer mortalities than control groups, suggesting a suppression in social behaviour in Cu-exposed fish. Overall, the increased metabolic cost of swimming in Cu-exposed fish was fully compensated by a reduction in activity, particularly at night and dawn. However, this behavioural strategy suggests that spatial and temporal aspects of ecologically important social behaviours may be compromised in Cu-exposed fish.

Nous voulons éprouver l'hypothèse selon laquelle la truite arc-en-ciel (Oncorhynchus mykiss) compense le coût métabolique d'une exposition au Cu alimentaire par une réduction de son activité de nage à des moments précis de son cycle journalier. Nous avons exposé des truites à du Cu alimentaire en excès (726 mg Cu·kg–1 de masse sèche) pendant 3 mois et mesuré leur consommation d'oxygène (MO2) et leur activité de nage spontanée. Des enregistrements vidéo de 48 h ont permis de déterminer la rythmicité du comportement de nage. Les estimations du métabolisme au repos (RS) à 15°C sont de 7,2 mmol O2·kg–1·h–1 chez les poissons témoins et de 8,7 mmol O2·kg–1·h–1 chez les poissons traités. La consommation d'oxygène est plus grande chez les poissons exposés au Cu à toutes les vitesses de nage choisies. Par comparaison aux poissons témoins, les poissons exposés au Cu diminuent leur activité (vitesse de nage) d'au moins 75 %, ils passent plus de temps aux vitesses basses et ils perdent la périodicité circadienne de ces activités. Les taux moyens de croissance sont normaux, bien que les poissons exposés au Cu affichent une gamme réduite de masses corporelles et aient une mortalité plus faible, ce qui laisse croire à une suppression des comportements sociaux. De façon générale, le coût métabolique accru de la nage chez les poissons traités est complètement compensé par une réduction de l'activité, particulièrement durant la nuit et l'aurore. Toutefois, une telle stratégie comportementale de la part des poissons exposés au Cu peut probablement compromettre des aspects spatiaux et temporels de comportements sociaux de grande importance écologique.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: 2002-05-01

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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