Variation in salinity tolerance, gill Na+/K+-ATPase,Na+/K+/2Cl– cotransporter and mitochondria-rich cell distribution in three salmonids Salvelinus namaycush, Salvelinus fontinalis and Salmo salar

Abstract

SUMMARY We compared seawater tolerance, gill Na+/K+-ATPase and Na+/K+/2Cl– cotransporter (NKCC)abundance, and mitochondria-rich cell (MRC) morphology of three salmonids,lake trout Salvelinus namaycush, brook trout Salvelinus fontinalis and Atlantic salmon Salmo salar. They were transferred directly from 0 p.p.t. (parts per thousand; freshwater) to 30 p.p.t. seawater, or transferred gradually from 0 to 10, 20 and 30 p.p.t. at 1-week intervals and kept in 30 p.p.t. for 3 weeks. The survival rates of lake trout, brook trout and Atlantic salmon were 80%, 50% and 100% following direct transfer, and 80%, 100% and 100% during gradual transfer, respectively. Plasma Na+, K+ and Cl– concentrations in surviving lake trout increased rapidly and remained at high levels in 30 p.p.t. of both direct and gradual transfer, whereas those in brook trout showed a transient increase following direct transfer but did not change significantly during gradual transfer. Only minor changes in plasma ions were observed in Atlantic salmon smolts in both direct and gradual transfer. These results suggest that lake trout retains some degree of euryhalinity and that brook trout possesses intermediate euryhalinity between lake trout and Atlantic salmon smolts. Gill Na+/K+-ATPase activity of lake trout and brook trout increased in seawater, whereas that of Atlantic salmon smolts was already upregulated in freshwater and remained high after seawater exposure. NKCC abundance was upregulated in parallel with gill Na+/K+-ATPase activity in each species. Immunocytochemistry with anti-Na+/K+-ATPaseα-subunit and anti-NKCC revealed that the two ion transporters were colocalized on the basolateral membrane of gill MRCs. Immunopositive MRCs were distributed on both primary filaments and secondary lamellae in all three species kept in freshwater; following transfer to seawater this pattern did not change in lake trout and brook trout but lamellar MRCs disappeared in Atlantic salmon. Previous studies on several teleost species have suggested that filament and lamellar MRCs would be involved in seawater and freshwater acclimation, respectively. However, our results in lake trout and brook trout suggest that lamellar MRCs could be also functional during seawater acclimation.

Transcriptomics of salinity tolerance capacity in Arctic charr (Salvelinus alpinus): a comparison of gene expression profiles between divergent QTL genotypes

“…Lines in boldface are instances where the mean intergenic distance (IGD) of genes differentially expressed in Arctic charr is significantly less than the mean IGD of the corresponding stickleback chromosome. man), which is consistent with previous findings and expectations (7,22,30,37,46,47,51,52,55,57,65). It is also possible that changes in the transcription rates of these genes were missed due to the experimental design, as sampling occurred at a single time-point, rather than at multiple-time points spanning pre-and postseawater exposure.…”

Short‐term low‐salinity tolerance by the longhorn sculpin, Myoxocephalus octodecimspinosus

“…With the anti-NKCC1 antibody, we found two bands of $200 and $130 kDa in the longhorn sculpin gill. Because we found only single (CFTR, NKA) or double bands (NKCC1) with our western blots, and these findings mirror those from other teleosts (Tipsmark et al, 2002;Hiroi and McCormick, 2007), we quantified protein differences with dot blots (total protein, not proteins separated by molecular weight).…”

“…Studies in euryhaline fishes, such as the killifish (Fundulus heteroclitus), or anadromous fishes such as the rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), or Atlantic salmon (S. salar) have explored the effects of changes in environmental salinity on gill ion transporter density (e.g. Mancera and McCormick, 2000;Seidelin et al, 2000;Pelis et al, 2001;Marshall et al, 2002;Singer et al, 2002;Scott et al, 2004;Hiroi and McCormick, 2007). In general, when these fishes move from FW/brackish water to marine waters, there is a rapid increase in plasma [Na…”

Lack of hormonal stimulation prevents the landlocked Biwa salmon (Oncorhynchus masousubspecies) from adapting to seawater

“…Diluted seawater was used for the experiment because a previous study showed that Biwa salmon was intolerant to full-strength seawater (11). When juvenile salmon are transferred from freshwater to seawater, a typical response is transitional increases in blood sodium and chloride ion concentrations within 24 h followed by a reduction to the levels comparable to those in freshwater (7,15). In the present study, the sham-treated Biwa salmon showed increases in both sodium and chloride ion concentrations within 24 h, and it stayed high for additional 2 days.…”