Isolation of a novel fish thymidylate kinase gene, upregulated in Atlantic salmon (Salmo salar L.) following infection with the monogenean parasite Gyrodactylus salaris

Analysis of differential gene expression in salmon (Salmo salar) blood following infection with the monogenean parasite Gyrodactylus salaris, resulted in the isolation of a thymidylate kinase gene not previously described from fish and which showed similarity to an LPS-inducible thymidylate kinase gene isolated from mouse macrophages. This salmon TYKi-like gene may play a role in an innate generalised response to pathogen infection as it was upregulated in salmon following infection with the parasite, and also in response to injection with the immunostimulants LPS and Poly I:C, used to emulate bacterial and viral infections, respectively. The possible role of this gene in the biosynthesis of mitochondrial DNA in activated macrophages, in response to G. salaris infection is discussed.     

Can variation in standard metabolic rate explain context‐dependent performance of farmed Atlantic salmon offspring?

Escaped farmed Atlantic salmon interbreed with wild Atlantic salmon, leaving offspring that often have lower success in nature than pure wild salmon. On top of this, presence of farmed salmon descendants can impair production of wild‐type recruits. We hypothesize that both these effects connect with farmed salmon having acquired higher standard metabolic rates (SMR, the energetic cost of self‐maintenance) during domestication. Fitness‐related advantages of phenotypic traits associated with both high SMR and farmed salmon (e.g., social dominance) depend on environmental conditions, such as food availability. We hypothesize that farmed offspring have an advantage at high food availability due to, for example, dominance behavior but suffer increased risks of starvation when food is scarce because this behavior is energy‐demanding. To test these hypotheses, we first compare embryo SMR of pure farmed, farmed‐wild hybrids and pure wild offspring. Next, we test early‐life performance (in terms of survival and growth) of hybrids relative to that of their wild half‐siblings, as well as their competitive abilities, in semi‐natural conditions of high and low food availability. Finally, we test how SMR affects early‐life performance at high and low food availability. We find inconclusive support for the hypothesis that domestication has induced increased SMR. Further, wild and hybrid juveniles had similar survival and growth in the semi‐natural streams. Yet, the presence of hybrids led to decreased survival of their wild half‐siblings. Contrary to our hypothesis about context‐dependency, these effects were not modified by food availability. However, wild juveniles with high SMR had decreased survival when food was scarce, but there was no such effect at high food availability. This study provides further proof that farmed salmon introgression may compromise the viability of wild salmon populations. We cannot, however, conclude that this is connected to alterations in the metabolic phenotype of farmed salmon.     

Host-dependent genetic variation in freshwater pearl mussel (Margaritifera margaritifera L.)

Freshwater fishes are vulnerable to changes in water quality, physical habitat and connectivity resulting from drought, particularly in regulated rivers. When adequate river flows return, the recovery of populations might depend on the duration and consequences of drought. Rivers of the highly regulated Murray–Darling Basin in south-eastern Australia terminate at two large, shallow lakes that are separated from the estuary by tidal barrages. Over-abstraction of water and widespread prolonged drought (1997–2010) placed the lakes under severe environmental stress, culminating in critical water level recession from 2007 to 2010. Concurrently, most freshwater fish populations collapsed. We investigate shifts in fish assemblages resulting from habitat inundation in the lakes following the drought. The inundation and re-connection of the lakes and fringing habitats led to a substantial reduction of salinity throughout the region, and aquatic vegetation shifted from salt-tolerant to freshwater species. Fish assemblages became increasingly characterized by common freshwater taxa (ecological generalists), including high proportions of alien species. There were no indications of population recovery for three threatened species. The findings emphasize that short-lived fishes with specialized habitat requirements are vulnerable to severe population declines during prolonged drought in regulated rivers, which might restrict their recovery when adequate flows return.     

Spatial and temporal genetic structure of a river‐resident Atlantic salmon (Salmo salar) after millennia of isolation

The river‐resident Salmo salar (“småblank”) has been isolated from other Atlantic salmon populations for 9,500 years in upper River Namsen, Norway. This is the only European Atlantic salmon population accomplishing its entire life cycle in a river. Hydropower development during the last six decades has introduced movement barriers and changed more than 50% of the river habitat to lentic conditions. Based on microsatellites and SNPs, genetic variation within småblank was only about 50% of that in the anadromous Atlantic salmon within the same river. The genetic differentiation (F_ST) between småblank and the anadromous population was 0.24. This is similar to the differentiation between anadromous Atlantic salmon in Europe and North America. Microsatellite analyses identified three genetic subpopulations within småblank, each with an effective population size N_e of a few hundred individuals. There was no evidence of reduced heterozygosity and allelic richness in contemporary samples (2005–2008) compared with historical samples (1955–56 and 1978–79). However, there was a reduction in genetic differentiation between sampling localities over time. SNP data supported the differentiation of småblank into subpopulations and revealed downstream asymmetric gene flow between subpopulations. In spite of this, genetic variation was not higher in the lower than in the upper areas. The meta‐population structure of småblank probably maintains genetic variation better than one panmictic population would do, as long as gene flow among subpopulations is maintained. Småblank is a unique endemic island population of Atlantic salmon. It is in a precarious situation due to a variety of anthropogenic impacts on its restricted habitat area. Thus, maintaining population size and avoiding further habitat fragmentation are important.     

Regulation of FynT function by dual domain docking on PAG/Cbp

In resting T-cells, the transmembrane adaptor protein PAG (phosphoprotein associated with glycosphingolipid-enriched microdomains) is constitutively tyrosine-phosphorylated, a state maintained by the Src family kinase FynT. PAG has a role in negative regulation of Src family kinases in T-cells by recruitment of Csk (C-terminal Src kinase) to the membrane via binding to PAG phosphotyrosine 317. The interaction between FynT and PAG is essential for PAG function; however, so far the FynT binding mode has been unknown. Here, we demonstrate that the FynT-PAG complex formation is a dual domain docking process, involving SH2 domain binding to PAG phosphotyrosines as well as an SH3 domain interaction with the first proline-rich region of PAG. This binding mode affects FynT kinase activity, PAG phosphorylation, and recruitment of FynT and Csk, demonstrated in Jurkat TAg cells after antibody stimulation of the T cell receptor. Furthermore, we show that TCR-induced tyrosine phosphorylation is regulated by SH3 domain modulation of the FynT-PAG interaction in human primary T-cells. Although FynT SH3 domain association is shown to be crucial for efficiently initiating PAG phosphorylation, we suggest that engagement of the SH2 domain on PAG renders FynT insensitive to Csk negative regulation. Thus, in T-cells, PAG is involved in positive as well as negative regulation of FynT activity.     

A tool for analyzing information from data storage tags: the continuous wavelet transform (CWT)

Electronic Data Storage Tags (DSTs) have the potential of providing long term, high-resolution observation data of individual fish in the ecosystem. However, traditional time series analysis methods are limited in extracting the required information from DSTs. The continuous wavelet transform (CWT) is a tool for decomposing a time series into instantaneous frequency versus time characteristics. This allows data signals, which are restricted to specific frequencies (localized frequencies), or frequency components, which are restricted to specific time intervals (time localized) to be extracted and displayed in a highly intuitive way. The aim of this short communication is to present the CWT as a tool for extracting information from DST data. In the first case, synthetically generated data is used to demonstrate how the methodology captures different time–frequency dependent patterns in the time series data. The relevance of the methodology to real field data is demonstrated by an analysis of DST depth data from tagged Barents Sea coastal cod. This work has also enjoyed partial funding from the EU-FP5-Q5RS200200813 CODYSSEY project.     

Regulatory T cells in colorectal cancer patients suppress anti-tumor immune activity in a COX-2 dependent manner

Objective Naturally occurring regulatory T (T_R) cells suppress autoreactive T cells whereas adaptive T_R cells, induced in the periphery, play an important role in chronic viral diseases and cancer. Several studies indicate that cyclooxygenase (COX) inhibitors prevent cancer development of colon adenomas and delay disease progression in patients with colorectal cancer (CRC). We have shown that adaptive T_R cells express COX-2 and produce PGE₂ that suppress effector T cells in a manner that is reversed by COX-inhibitors. Methods and results Here we demonstrate that CRC patients have elevated levels of PGE₂ in peripheral blood, and CRC tissue samples and draining lymph nodes display increased numbers of FOXP3+ T_R cells. Depletion of T_R cells from PBMC enhanced anti-tumor T-cell responses to peptides from carcinoembryonic antigen. Furthermore, the COX inhibitor indomethacin and the PKA type I antagonist Rp-8-Br-cAMPS significantly improved the anti-tumor immune activity. Conclusion We suggest that adaptive T_R cells contribute to an immunosuppressive microenvironment in CRC and inhibit effector T cells by a COX-2–PGE₂-dependent mechanism and thereby facilitate tumor growth. Therapeutic strategies targeting T_R cells and the PGE₂–cAMP pathway may be interesting to pursue to enhance anti-tumor immune activity in CRC patients.     

Brown trout (Salmo trutta) metallothioneins as biomarkers for metal exposure in two Norwegian rivers

The potential use of the metal binding protein metallothionein (MT) as a biomarker for trace metal exposure has been evaluated in brown trout (Salmo trutta)     

Relative size predicts competitive outcome through 2 million years

Competition is an important biotic interaction that influences survival and reproduction. While competition on ecological timescales has received great attention, little is known about competition on evolutionary timescales. Do competitive abilities change over hundreds of thousands to millions of years? Can we predict competitive outcomes using phenotypic traits? How much do traits that confer competitive advantage and competitive outcomes change? Here we show, using communities of encrusting marine bryozoans spanning more than 2 million years, that size is a significant determinant of overgrowth outcomes: colonies with larger zooids tend to overgrow colonies with smaller zooids. We also detected temporally coordinated changes in average zooid sizes, suggesting that different species responded to a common external driver. Although species‐specific average zooid sizes change over evolutionary timescales, species‐specific competitive abilities seem relatively stable, suggesting that traits other than zooid size also control overgrowth outcomes and/or that evolutionary constraints are involved.