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Growth, osmoregulation and endocrine changes in wild Atlantic salmon smolts and post-smolts during marine migration

Journal article
Authors S. O. Stefansson
M. Haugland
Björn Thrandur Björnsson
S. D. McCormick
M. Holm
L. O. E. Ebbesson
J. C. Holst
T. O. Nilsen
Published in Aquaculture
Volume 362
Pages 127-136
ISSN 0044-8486
Publication year 2012
Published at Department of Biological and Environmental Sciences
Pages 127-136
Language en
Links dx.doi.org/10.1016/j.aquaculture.20...
Keywords Energetics, Growth hormone, IGF-I, Thyroid hormones, Na plus , K plus -ATPase, IGF-I receptor, transmembrane conductance regulator, alpha-subunit isoforms, salar l., smolts, coho salmon, factor-i, na+,k+,2cl(-) cotransporter, different, temperatures, seawater tolerance, northeast atlantic, thyroid-hormones, cormick sd, 1989, fish physiology and biochemistry, v6, p243, keyasu k, 1990, american journal of physiology, v259, pc619, cormick sd, 1990, general and comparative endocrinology, v78, p224, omczynski p, 1993, biotechniques, v15, p532, cormick sd, 1993, canadian journal of fisheries and aquatic sciences, v50, p656
Subject categories Biological Sciences

Abstract

We have examined physiological parameters associated with seawater adaptability, growth and energetics, as well as major endocrine regulators of these processes in wild migrating Atlantic salmon smolts and post-smolts from the river through the fjord, coastal areas and the open ocean. Muscle RNA/DNA ratio suggests that growth rate increases soon after entry into seawater and continues to increase after the post-smolts reach the offshore banks and the feeding grounds in the Norwegian Sea. Post-smolts prioritize rapid growth and protein deposition in spring and summer, and their energy intake during this period is so high that deposition of energy is possible in addition to muscle growth. An increase in thyroxine (T-4) and triiodothyronine (T-3) levels was observed, suggesting a major activation of hepatic conversion of T-4 to T-3 in post-smolts in seawater, probably related to the high metabolic activity and rapid growth and development of the post-smolts. Decreased plasma growth hormone (GH) levels were observed from the river through the fjord, with levels around 2 ng ml(-1) in rapidly growing post-smolts, concurrent with an increase in circulating insulin-like growth factor I (IGF-I). An increase in pituitary GH expression levels and hepatic GH receptor (GH-R) and local IGF-I mRNA levels suggest a physiological basis for the changes in circulating GH and IGF-I levels. Receptor expression in brain and pituitary suggests that both hormones are actively involved in the growth and differentiation of these tissues during the critical early marine phase. Gill Na+, K+-ATPase (NKA) activity increased to post-smolt levels above 20 mu mol ADP mg prot.(divided by 1) h(divided by 1), probably representing long-term NKA activity levels of Atlantic salmon in seawater. Concurrent with the changes in NKA activity the expression of the NKA alpha 1b isoform remained high in post-smolts, while the expression of the NKA alpha 1a decreased from smolts to post-smolts. Both cystic fibrosis transmembrane conductance regulator (CFTR) I and II showed a reduction in mRNA levels from smolts to post-smolts, and remained stable at low expression levels in seawater. (c) 2011 Elsevier B.V. All rights reserved.

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