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First published online November 4, 2005
Journal of Experimental Biology 208, 4291-4304 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01900
Time course of osmoregulatory and metabolic changes during osmotic acclimation in Sparus auratus
1 Laboratorio de Fisioloxía Animal, Facultade de Ciencias do Mar,
Universidade de Vigo, 36310 Vigo, Spain
2 Departamento de Biología, Facultad de Ciencias del Mar y
Ambientales, Universidad de Cádiz, 11510 Puerto Real, Cádiz,
Spain
* Author for correspondence (e-mail: jsoengas{at}uvigo.es)
Accepted 26 September 2005
Changes in different osmoregulatory and metabolic parameters over time were assessed in gills, kidney, liver and brain of gilthead sea bream Sparus auratus transferred either from seawater (SW, 38 p.p.t.) to hypersaline water (HSW, 55 p.p.t.) or from SW to low salinity water (LSW, 6 p.p.t.) for 14 days. Changes displayed by osmoregulatory parameters revealed two stages during hyperosmotic and hypo-osmotic acclimation: (i) an adaptive period during the first days of acclimation (13 days), with important changes in these parameters, and (ii) a chronic regulatory period (after 3 days of transfer) where osmotic parameters reached homeostasis. From a metabolic point of view, two clear phases can also be distinguished during acclimation to hyperosmotic or hypo-osmotic conditions. The first one coincides with the adaptive period and is characterized by enhanced levels of plasma metabolites (glucose, lactate, triglycerides and protein), and use of these metabolites by different tissues in processes directly or indirectly involved in osmoregulatory work. The second stage coincides with the chronic regulatory period observed for the osmoregulatory parameters and is metabolically characterized in HSW-transferred fish by lower energy expenditure and a readjustment of metabolic parameters to levels returning to normality, indicative of reduced osmoregulatory work in this stage. In LSW-transferred fish, major changes in the second stage include: (i) decreased glycolytic potential, capacity for exporting glucose and potential for amino acid catabolism in liver; (ii) enhanced use of exogenous glucose through glycolysis, pentose phosphate and glycogenesis in gills; (iii) increased glycolytic potential in kidney; and (iv) increased glycogenolytic potential and capacity for use of exogenous glucose in brain.
Key words: gilthead sea bream, Sparus auratus, osmoregulation, energy metabolism
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