Temporal and spatial instability in neutral and adaptive (MHC) genetic variation in marginal salmon populations

The role of marginal populations for the long-term maintenance of species’ genetic diversity and evolutionary potential is particularly timely in view of the range shifts caused by climate change. The Centre-Periphery hypothesis predicts that marginal populations should bear reduced genetic diversity and have low evolutionary potential. We analysed temporal stability at neutral microsatellite and adaptive MHC genetic variation over five decades in four marginal Atlantic salmon populations located at the southern limit of the species’ distribution with a complicated demographic history, which includes stocking with foreign and native salmon for at least 2 decades. We found a temporal increase in neutral genetic variation, as well as temporal instability in population structuring, highlighting the importance of temporal analyses in studies that examine the genetic diversity of peripheral populations at the margins of the species’ range, particularly in face of climate change

Baltic Salmon, Salmo salar, from Swedish River Lule Älv Is More Resistant to Furunculosis Compared to Rainbow Trout

BACKGROUND: Furunculosis, caused by Aeromonas salmonicida, continues to be a major health problem for the growing salmonid aquaculture. Despite effective vaccination programs regular outbreaks occur at the fish farms calling for repeated antibiotic treatment. We hypothesized that a difference in natural susceptibility to this disease might exist between Baltic salmon and the widely used rainbow trout. STUDY DESIGN: A cohabitation challenge model was applied to investigate the relative susceptibility to infection with A. salmonicida in rainbow trout and Baltic salmon. The course of infection was monitored daily over a 30-day period post challenge and the results were summarized in mortality curves. RESULTS: A. salmonicida was recovered from mortalities during the entire test period. At day 30 the survival was 6.2% and 34.0% for rainbow trout and Baltic salmon, respectively. Significant differences in susceptibility to A. salmonicida were demonstrated between the two salmonids and hazard ratio estimation between rainbow trout and Baltic salmon showed a 3.36 higher risk of dying from the infection in the former. CONCLUSION: The finding that Baltic salmon carries a high level of natural resistance to furunculosis might raise new possibilities for salmonid aquaculture in terms of minimizing disease outbreaks and the use of antibiotics

Impact of microbial-feeding animals on total soil activity and nitrogen dynamics - a soil microcosm experiment

Abstract in UndeterminedThe long-term impact of microbial-feeding animals on microbial populations was studied in microcosms containing pine seedlings growing in a gamma sterilized humus-sand mixture. Organism communities of diverse complexity were introduced into the microcosms. The two main experimental series contained microorganisms only and microorganisms and microorganism-feeding nematodes, respectively. After 18 months the following analyses were made: soil chemical characteristics, weight and nitrogen content of the seedlings, soil respiration, abundance, biomass, and in some cases, species composition of the different soil organism populations. During the incubation, leaching of nitrogen from the microcosms was measured continuously. The rate of nitrogen leaching from the microcosms increased during the first 6 months. During the remaining 12 months the leaching stabilized at a low rate. Initially, the series with microbial-feeding nematodes had a lower rate of nitrogen loss through leaching compared to the series with only microorganisms added. Towards the end of the experiment the situation was reversed. The pine seedlings showed a very poor growth in all series with no significant differences between the treatments. In the microcosms, bacteria appeared to be the most important microorganism group; fungi, algae and yeasts were present in low amounts. The presence of bacterial feeding nematodes reduced the number of bacteria but did not reduce the soil respiration rate. A significant correlation was obtained between the numbers of nematodes and the respiration rate of the microcosms, which is interpreted as an increased bacterial production rate due to the presence of bacterial-feeding animals

Effect of nitrogen and carbon supply on the development of soil organism populations and pine seedlings - microcosm experiment

Series of pots containing Scots pine seedlings and a humus-sand mixture were watered twice weekly for 398 d with different nutrient solutions (control treatment with complete plant nutrient solution less nitrogen; glucose addition; nitrogen addition; glucose and nitrogen addition). Analyses were made of organic and nitrogen contents in the substrate, plant weights and nitrogen contents, nitrogen fixation and respiration rates, abundance, biomass and in some cases species composition of different soil organism populations. The growth rate of pine seedlings was lowest in series supplied with glucose, which is most easily explained by a deficiency of nitrogen due to microbial immobilization. The fungi and yeast were stimulated by addition of an easily available carbon source whereas the bacteria needed both nitrogen and carbon to maintain high biomass. A positive correlation between fungal feeding soil organisms and amount of fungal mycelium was found while a more complex situation prevailed with regard to bacterial numbers and bacterial feeding nematodes. The systems are evaluated in relation to the different treatments and compared with the field situation

Effects of experimental acidification and liming on soil organisms and decomposition in a scots pine forest

Abstract in Arabic Abstract is not availabl

Immunity, biopolitics and pandemics: public and individual responses to the threat to life

This article examines discourse on immunity in general public engagements with pandemic influenza in light of critical theory on immuno-politics and bodily integrity. Interviewand focus groupdiscussions on influenzawithmembers of the general public reveal that, despite endorsement of government advice on how to avoid infection, influenza is seen as, ultimately, unavoidable. In place of prevention, members of the general public speak of immunity as the means of coping with influenza infection. Such talk on corporeal life under microbial threat is informed by self/not-self, network and ‘choice ’ immunity, and thereforemakes considerable allowance for cosmopolitan traf-fic with others, microbes, ‘dirt ’ and immune-boosting consumer products. The immuno-political orientation of members of the general public, therefore, appears to trend towards a productive cosmopolitanism that contrasts with more orthodox bioscientific and governmental approaches to pandemic influenza. We reflect on the implications of the immuno-cosmopolitanism of everyday life for the advent of global public health emergency and for biopolitical rule in general. Keyword