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

Abstract

We examined whether gene expression in the young salmon (Salmo salar) gill differs in relation to the salinity of their migration habitat by comparing three salmon stocks: (1) fish that migrate from a river system to Lake Saimaa, (2) fish that migrate to the brackish waters of the Baltic Sea, and (3) fish that migrate to the full-strength salinity of the Arctic Ocean. Transcripts of the gill tissue were measured at three successive developmental stages (parr, smolt and postsmolt) using the cDNA microarray in fish reared under common conditions. The changes in gene expression were qualitatively and quantitatively similar in the three stocks irrespective of the salinity of the natural growing habitat. This suggests that the parr-smolt transformation in the gill tissue of the landlocked fresh-water salmon stock is similar to the seawater migrating salmon. The transformation of the gill to a hypoosmotic organ in the freshwater salmon has been retained in evolution, possibly due to its adaptive role as a signal for migration from a relatively poor-growth environment of the river to a more productive lake habitat.

Salmonid gene expression biomarkers indicative of physiological responses to changes in salinity, temperature, but not dissolved oxygen

“…Although we detected significant differences in NKA activity in freshwater between pre-smolt and smolts, as may be expected for different degrees of smoltification (e.g. Kiilerich et al, 2007;Lemmetyinen et al, 2013;, we did not detect similar differences between smolts and desmolts. However, we can classify these freshwater individuals as pre-smolt, smolt, and de-smolt using the same biomarkers that were examined for salinity treatment (Houde et al, 2018).…”

Divergent immunity and energetic programs in the gills of migratory and resident Oncorhynchus mykiss

“…) and qualitative and quantitative similarities in gene expression in the gills of anadromous and land‐locked salmon (Lemmetyinen et al . ) suggest that it might be interesting to examine differentially expressed genes observed here more broadly within O. mykiss and also in species with greater divergence between anadromous and land‐locked populations (e.g. bull trout Salvelinus confluentus ).…”

“…; Robertson & McCormick ; Lemmetyinen et al . ). Furthermore, transcriptomic analysis of the gills of brook charr Salvelinus fontinalis identified migrant overexpression of genes involved with metabolism and development relative to residents (Boulet et al .…”

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

“…In conclusion, several studies including measurement of aerobic metabolic rate (Seppänen et al 2009), genome-wide survey of gill gene expression (Vornanen et al 2009, Lemmetyinen et al 2013) and physiology of ion regulation (the present study) strongly suggest that the landlocked salmon of Lake Saimaa has retained strong smolt characteristics similar to those of the anadromous sea-run stocks. Future studies should examine how common this type of smoltification is among different landlocked populations of the Atlantic salmon and other salmon species, and to clarify its biological significance in detail.…”

“…In contrast, the landlocked populations which do not have access to favourable growing habitats due to geographical barriers (or if the available habitats do not significantly differ in regard to food availability), may have lost some of the smolt characteristics due to negative selection pressure (Schmitz 1995). Indeed, a genome-wide microarray analysis of the gill transcripts between some anadromous and nonanadromous Atlantic salmon populations suggest that at the genetic level smoltification process can be fairly similar in sea-run and landlocked populations (Vornanen et al 2009, Lemmetyinen et al 2013.…”