Comparison of Smoltification in Atlantic Salmon (Salmo salar) from Anadromous and Landlocked Populations Under Common Garden Conditions

Abstract

We compared smolt physiology of Atlantic salmon stocks, that migrate from freshwater stream environments to a freshwater lake (Lake Saimaa, Finland), from the Neva River (Russia) to the brackish water of the Baltic Sea, and from the Teno River (Finland/ Norway) to the full-strength seawater of the Arctic Ocean. The three fish stocks were reared under common garden conditions, and ion homeostasis, seawater tolerance, activities of gill and kidney Na,K-ATPase and [ , and Mg 2+ ion concentrations of blood plasma decreased during smoltification. α1a and α1b isoforms of gill Na,KATPase decreased and increased, respectively, during smoltification. Although small differences appeared at some points in time, the seasonal pattern and magnitude of changes in smolt characteristics were generally similar in the Saimaa salmon and in the anadromous stocks of the Neva and Teno salmon. It is suggested that the strong smoltification process of the landlocked Saimaa salmon is somehow necessary for migration of the young salmon from river to lake and therefore has been retained in evolution.

Comparison of Gene Expression in the Gill of Salmon (Salmo salar) Smolts from Anadromous and Landlocked Populations

“…Whether the landlocked salmon stock includes individuals that show a weakened smoltification process and thereby is more heterogeneous than the anadromous stock might be revealed by physiological studies and an analysis of a representative subset of differential expressed genes from different functional groups (Table 2). Physiological studies of the same experimental fish, involving several parameters of smoltification, are in good agreement with the microarray data and indicate that similarity of smoltification between landlocked and anadromous salmon exists also at the functional level (Piironen et al 2013). Thus, physiological studies involving a much larger number of fish individuals strongly support the gene expression data on the genetic similarity of the smoltification process in land-locked and anadromous salmon populations and suggest that pooling the samples is not concealing inter-individual differences in gene expression.…”

“…The origin and rearing conditions of the sampled salmon populations are described in detail in Piironen et al (2013). All experiments were conducted with permission of the ethical committee of the Game and Fisheries Research Institute (permission 18/05).…”

“…1). Smolting of the fish was followed by measuring seasonal changes in the activity of gill Na,K-ATPase and the number of gill Napumps ([ 3 H]ouabain binding; for methods see Piironen et al 2013) 5 times during the 1st year of development (0+) and 4 times during the 2nd year of development (1+). In addition, developmental changes in Na,K-ATPase activity and Napump density of individual fish were followed by taking gill biopsies (6 time points) from 8-10 fish for each stock (results not shown).…”

Discovery and validation of candidate smoltification gene expression biomarkers across multiple species and ecotypes of Pacific salmonids

“…Kiilerich et al, 2007;Hecht et al, 2014), as well as the precursors to Na + /K + -ATPase (e.g. Nilsen et al, 2007;Piironen et al, 2013). In particular, the gill expression of Na + /K + -ATPase α-1 isoforms for 'a' freshwater and 'b' seawater ion regulation (c.f.…”

Physiological and biochemical basis of salmon young fishes migratory behavior

“…It has been registered that before the beginning and during migration downstream smolts' protective systems ability to keep concentration of chloride [85] and sodium [2,33,36,45,86] in blood plasma and body tissues [87,88] deteriorate at stably raised levels. Decrease of the content of these ions in blood and tissues of smolts correlated with predominance of their losses into environment [44][45][46]89].…”