Effects of long-distance migration on circulating lipids of sockeye salmon (Oncorhynchus nerka)

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Abstract:

Lipids circulate as nonesterified fatty acids (NEFAs) or as triacylglycerol (TAG) associated with phospholipids (PLs), the two main components of lipoproteins. Changes in plasma lipid levels of migrating salmon were anticipated in response to the combined demands of exercise and osmoregulation. Circulating NEFAs, TAG, and PLs were measured in sockeye salmon (Oncorhynchus nerka) at different stages of their 500 km migration up the Fraser River (British Columbia, Canada). We found that NEFAs represent <7% of total plasma fatty acids (FAs) and show only a minor decrease during migration. In contrast, lipoproteins account for >93% of all the energy of circulating lipids, and concentrations of their main constituents show 27-fold (TAG) and 6-fold (PLs) decreases. The most pronounced change in FA composition of plasma lipids was found in the sample immediately after freshwater transition, with an increase in TAG eicosapentaenoic acid (20:5) and a decrease in TAG palmitic acid (16:0). Lipoproteins are therefore involved in key physiological processes necessary for successful spawning. Previous investigations of lipid metabolism in swimming salmon have focused on plasma NEFAs, but this study shows that shifting attention to lipoproteins should prove more fruitful for future studies of migration energetics.

Les lipides circulent comme acides gras non estérifiés (« NEFAs ») ou comme triacylglycérol (TAG) associé aux phospholipides (PLs), les deux composantes principales des lipoprotéines. Chez les saumons migrateurs, la combinaison des besoins en exercice et en osmorégulation laissent prévoir des changements dans les concentrations des lipides plasmatiques. Nous avons dosé les NEFAs, TAG et PLs chez des saumons rouges (Oncorhynchus nerka) à différentes étapes de leur migration de 500 km vers l'amont dans le Fraser (Colombie-Britannique, Canada). Les NEFAs représentent <7 % des acides gras plasmatiques totaux et ils ne déclinent que légèrement durant la migration. En revanche, les lipoprotéines constituent >93 % de toute l'énergie des lipides en circulation et leurs composantes accusent des déclins respectivement de 27 fois (TAG) et de 6 fois (PLs). Les changements les plus importants dans la composition en acides gras (« FAs ») des lipides plasmatiques se retrouvent dans l'échantillon prélevé immédiatement après la transition en eau douce, avec une augmentation de l'acide eicosapentaénoïque (20 : 5) de TAG et une diminution de l'acide palmitique (16 : 0) de TAG. Les lipoprotéines sont donc impliquées dans les processus physiologiques essentiels nécessaires pour réussir la fraye. Les études antérieures du métabolisme des lipides chez les saumons en nage se sont concentrées sur les NEFAs du plasma, mais notre étude montre qu'une attention particulière aux lipoprotéines pourrait s'avérer plus productive dans les travaux futurs sur l'énergétique de la migration.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: August 1, 2006

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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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