QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online October 7, 2005
Journal of Experimental Biology 208, 3859-3871 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01853

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Nebel, C. Articles by Charmantier, G. Search for Related Content PubMed PubMed Citation Articles by Nebel, C. Articles by Charmantier, G.

Differential freshwater adaptation in juvenile sea-bass Dicentrarchus labrax: involvement of gills and urinary system

Catherine Nebel^*, Bernard Romestand, Geneviève Nègre-Sadargues, Evelyse Grousset, Fabien Aujoulat, Julien Bacal, François Bonhomme and Guy Charmantier

Laboratoire Génome, Populations, Interactions, Adaptation, UMR 5171, Université Montpellier II, Place E. Bataillon, 34095 Montpellier, Cedex 05, France

^* Author for correspondence (e-mail: nebelcatherine{at}yahoo.fr)

Accepted 17 August 2005

The effects of long-term freshwater acclimatization were investigated in juvenile sea-bass Dicentrarchus labrax to determine whether all sea-bass juveniles are able to live in freshwater and to investigate the physiological basis of a successful adaptation to freshwater. This study particularly focused on the ability of sea-bass to maintain their hydromineral balance in freshwater and on their ion (re)absorbing abilities through the gills and kidneys. Two different responses were recorded after a long-term freshwater acclimatization. (1) Successfully adapted sea-bass displayed standard behavior; their blood osmolality was maintained almost constant after the freshwater challenge, attesting to their efficient hyperosmoregulation. Their branchial and renal Na⁺/K⁺-ATPase abundance and activity were high compared to seawater fish due to a high number of branchial ionocytes and to the involvement of the urinary system in active ion reabsorption, producing hypotonic urine. (2) Sea-bass that had not successfully adapted to freshwater were recognized by abnormal schooling behavior. Their blood osmolality was low (30% lower than in the successfully adapted sea-bass), which is a sign of acute osmoregulatory failure. High branchial Na⁺/K⁺-ATPase abundance and activity compared to successfully adapted fish were coupled to a proliferation of gill chloride cells, whose ultrastructure did not display pathological signs. The large surface used by the gill chloride cells might negatively interfere with respiratory gas exchanges. In their urinary system, enzyme abundance and activity were low, in accordance with the observed lower density of the kidney tubules. Urine was isotonic to blood in unsuccessfully adapted fish, ruling out any participation of the kidney in hyperosmoregulation. The kidney failure seems to generate a compensatory ion absorption through increased gill activity, but net ion loss through urine seems higher than ion absorption by the gills, leading to lower hyper-osmoregulatory performance and to death.

Key words: teleost, osmoregulation, gills, kidney, Na⁺/K⁺-ATPase, sea-bass, Dicentrarchus labrax

This article has been cited by other articles:

				H. Chasiotis and S. P. Kelly Occludin immunolocalization and protein expression in goldfish J. Exp. Biol., May 15, 2008; 211(10): 1524 - 1534. [Abstract] [Full Text] [PDF]

				C. Lorin-Nebel, V. Boulo, C. Bodinier, and G. Charmantier The Na+/K+/2Cl- cotransporter in the sea bass Dicentrarchus labrax during ontogeny: involvement in osmoregulation J. Exp. Biol., December 15, 2006; 209(24): 4908 - 4922. [Abstract] [Full Text] [PDF]