S'acclimater à des salinités et températures changeantes : un focus sur la branchie chez le loup européen Dicentrarchus labrax (original) (raw)
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Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2015
a b s t r a c t 6 We investigated the impact of nutritional status on the physiological, metabolic and ion-osmoregulatory 20 performance of European sea bass (Dicentrarchus labrax) when acclimated to seawater (32 ppt), brackish 21 water (20 and 10 ppt) and hyposaline water (2.5 ppt) for 2 weeks. Following acclimation to different salinities, 22 fish were either fed or fasted (unfed for 14 days). Plasma osmolality, [Na + ], [Cl − ] and muscle water content 23 were severely altered in fasted fish acclimated to 10 and 2.5 ppt in comparison to normal seawater-acclimated 24 fish, suggesting ion regulation and acid-base balance disturbance. In contrast to feed-deprived fish, fed fish 25 were able to avoid osmotic perturbation more effectively. This was accompanied by an increase in Na + /K + -26 ATPase expression and activity, transitory activation of H + -ATPase (only at 2.5 ppt) and down-regulation of 27 Na + /K + /2Cl − gene expression. Ammonia excretion rate was inhibited to a larger extent in fasted fish acclimated 28 to low salinities while fed fish were able to excrete much more efficiently. Consequently, the build-up of 29 ammonia in the plasma of fed fish was relatively lower. Energy stores, especially glycogen and lipid, dropped 30 in the fasted fish at low salinities and progression towards the anaerobic metabolic pathway became evident 31 by an increase in plasma lactate level. Overall, the results indicate no osmotic stress in both feeding treatments 32 within the salinity range of 32 to 20 ppt. However, at lower salinities (10-2.5 ppt) feed deprivation tends to 33 reduce physiological, metabolic, ion-osmoregulatory and molecular compensatory mechanisms and thus limits 34 the fish's abilities to adapt to a hypo-osmotic environment. 35
Research Square (Research Square), 2023
The effects of increased CO 2 on the physiological responses of European sea bass (Dicentrarchus labrax) which were progressively acclimated to 32 ppt, 10 ppt and 2.5 ppt were investigated. Following acclimation to different salinities for two weeks, sh were exposed to present-day (400 µatm) and future (1000 µatm) atmospheric CO 2 for 1, 3, 7 and 21 days. Blood pH, plasma ions (Na+, K+, Cl-), branchial mRNA expression of NKA, NKCC and ammonia transporters (e.g. Rhesus glycoproteins) were examined to understand the iono-and osmoregulatory consequences of the experimental conditions. A transient but signi cant increase in the blood pH of exposed sh acclimated at 10 ppt (day 1) and 2.5 ppt (day 21) possibly due to an overshoot of the blood HCO3accumulation. However, no change was seen at 32 ppt. Additionally, plasma [Na+] of exposed sh reared at 10 ppt was signi cantly reduced at day 1 relative to control sh. Generally, Na + concentration of control sh was relatively higher at 10 ppt and lower at 2.5 ppt compared to 32 ppt control group at all sampling periods. We also found that NKA was upregulated in gill of juvenile sea bass and NKA Mrna level of control sh was relatively higher when acclimated to lower salinities compared to 32 ppt control group. Elevated expression could be due to increased activity of acid-base transporters, which rely on the Na + gradient created by the NKA enzyme. Meanwhile, a signi cant reduction of NKCC mRNA level of the exposed sh acclimated at 32 ppt (1-3 days) and 10 ppt (7-21 days) was observed which could be an adaptive response to foster ion retention during hypercapnia in sea bass acclimated at lower salinities. Furthermore, Rhesus glycoproteins were generally upregulated in the sh acclimated at lower salinities. It suggests that increased CO 2 may enhance ammonia excretion rate.
Journal of Experimental Biology, 1995
Serum osmolality and serum inorganic ion concentrations were studied in two antarctic fish species, Trematomus bernacchii and T. newnesi, during 5 weeks of acclimation to 4 ˚C and compared with control values for groups acclimated to-1.5 ˚C. Acclimation to 4 ˚C significantly decreased the serum osmolality of both species, thereby increasing their seawater-to-extracellular fluid (ECF) osmotic gradient. The decline in osmolality with acclimation to 4 ˚C was accompanied by significant and rapid losses of Na+ and Cl− during the first 14 days of acclimation and was maintained throughout the study period. At day 35 of acclimation, the lipid composition and microsomal Na+ /K+-ATPase specific activities at 4 ˚C and 37 ˚C were determined in membranes from gill, kidney, liver and muscle tissues. No warm-induced decrease in fatty acid unsaturation was found in the tissues of either species. In the gills and kidneys of both species, the Na+ /K+-ATPase activities assayed at 4 ˚C were increased a...
Mechanisms of seawater acclimation in a primitive, anadromous fish, the green sturgeon
Journal of Comparative Physiology B, 2009
Relatively little is known about salinity acclimation in the primitive groups of fishes. To test whether physiological preparative changes occur and to investigate the mechanisms of salinity acclimation, anadromous green sturgeon, Acipenser medirostris (Chondrostei) of three different ages (100, 170, and 533 dph) were acclimated for 7 weeks to three different salinities (\3, 10, and 33 ppt). Gill, kidney, pyloric caeca, and spiral intestine tissues were assayed for Na ? , K ? -ATPase activity; and gills were analyzed for mitochondria-rich cell (MRC) size, abundance, localization and Na ? , K ? -ATPase content. Kidneys were analyzed for Na ? , K ? -ATPase localization and the gastrointestinal tract (GIT) was assessed for changes in ion and base content. Na ? , K ? -ATPase activities increased in the gills and decreased in the kidneys with increasing salinity. Gill MRCs increased in size and decreased in relative abundance with fish size/age. Gill MRC Na ? , K ? -ATPase content (e.g., ion-pumping capacity) was proportional to MRC size, indicating greater abilities to regulate ions with size/age. Developmental/ontogenetic changes were seen in the rapid increases in gill MRC size and lamellar length between 100 and 170 dph. Na ? , K ? -ATPase activities increased fourfold in the pyloric caeca in 33 ppt, presumably due to increased salt and water absorption as indicated by GIT fluids, solids, and ion concentrations. In contrast to teleosts, a greater proportion of base (HCO 3 and 2CO 3 2-) was found in intestinal precipitates than fluids. Green sturgeon osmo-and ionoregulate with similar mechanisms to more-derived teleosts, indicating the importance of these mechanisms during the evolution of fishes, although salinity acclimation may be more dependent on body size.
Aquatic toxicology (Amsterdam, Netherlands), 2015
We investigated the interactive effect of ammonia toxicity, salinity challenge and nutritional status on the ecophysiological performance of European sea bass (Dicentrarchus labrax). Fish were progressively acclimated to normal seawater (32ppt), to brackish water (20ppt and 10ppt) and to hyposaline water (2.5ppt). Following acclimation to different salinities for two weeks, fish were exposed to high environmental ammonia (HEA, 20mg/L ∼1.18mM representing 50% of 96h LC50 value for ammonia) for 12h, 48h, 84h and 180h, and were either fed (2% body weight) or fasted (unfed for 7 days prior to HEA exposure). Biochemical responses such as ammonia (Jamm) and urea excretion rate, plasma ammonia, urea and lactate, plasma ions (Na(+), Cl(-) and K(+)) and osmolality, muscle water content (MWC) and liver and muscle energy budget (glycogen, lipid and protein), as well as branchial Na(+)/K(+)-ATPase (NKA) and H(+)-ATPase activity, and branchial mRNA expression of NKA and Na(+)/K(+)/2Cl(-) co-tran...