Spatial and temporal variations in parasite communities of freshwater fish in the subarctic

The papers of this thesis are not available in Munin.Paper I. Parasite communities of two three-spined stickleback populations in subarctic Norway— effects of a small spatial-scale host introduction. Jesper A. Kuhn, Roar Kristoffersen, Rune Knudsen, Jonas Jakobsen, David J. Marcogliese, Sean A. Locke, Raul Primicerio and Per-Arne Amundsen. Available in Parasitology Research, April 2015, Volume 114, Issue 4, pp. 1327-1339Paper II. Effects of fish species composition on Diphyllobothrium spp. infections in subarctic brown trout - is three-spined stickleback a key species? Jesper A. Kuhn, André Frainer, Rune Knudsen, Roar Kristoffersen and Per-Arne Amundsen. (Manuscript)Paper III. Temporal changes and structural variation in the intestinal parasite community of Arctic charr in a subarctic lake. Jesper A. Kuhn, Rune Knudsen, Roar Kristoffersen, Raul Primicerio and Per-Arne Amundsen. (Manuscript)Parasite communities are complicated systems believed to be affected by multiple ecological and environmental factors, both in time and space. These communities might be disrupted by anthropogenic host introductions which unfortunately appear to be a common practice e.g. in freshwater fish management. By addressing parasite occurrences in three of the most common freshwater fish species in subarctic lakes of Northern Europe; brown trout (Salmo trutta), Arctic charr (Salvelinus alpinus) and three-spined stickleback (Gasterosteus aculeatus), we sought to increase the knowledge regarding how these complicated systems vary and how they might be affected by a possible host introduction. The main aim of this PhD thesis was therefore to study the spatial and temporal differences and changes in parasite occurrences in freshwater fish from northern Norway, and also to explore the importance of three-spined stickleback as a tentative transmission host for salmonid fishes. By comparing the parasite community of an introduced three-spined stickleback population in comparison with the nearby source population, an overall high similarity was observed between the two systems. This suggests that parasite occurrences can be expected to be similar in locally separated ecosystems, as long as important environmental variables are similar. Additionally, a high degree of successful parasite introductions and establishment suggests that concomitant parasite introductions should be anticipated when new host species are introduced into an ecosystem on a small spatial scale. In addition to introducing new parasite species, introduction of a host species may also create additional host links in the food web of the recipient ecosystem which possibly aid other parasite species, such as trophically transmitted generalist parasites, to increase in occurrence. An introduced host species might additionally function as a new prey item with potential importance to the parasite infra- and component populations of piscivorous fish species in the recipient ecosystem. By analyzing the importance of available prey fish for the transmission of Diphyllobothrium spp. to piscivorous brown trout, it was observed that the Diphyllobothrium infections increased in trout when sympatric fish species were present. Particularly high infections occurred when brown trout had the opportunity to prey on threespined stickleback. These findings indicate that by introducing a prey fish, which feeds extensively on the first intermediate host of a trophically transmitted parasite species, into an ecosystem with a piscivorous fish population, in which there is almost absent utilization of that intermediate host, underused transmission links in the food web can be bypassed. Consequently, parasite transmission may flow through the newly introduced trophical node (the fish prey) causing an increase in parasite host links and in the occurrence of the parasite species. Investigating within-ecosystem variation in the parasite infracommunity composition of a host species further helped to understand the impact that host introduction and manipulation might have on an ecosystem. Overall stability was observed when exploring long-term temporal and spatial variation in the intestinal parasite infracommunities of an Arctic charr population. Long-term temporal variation was absent, indicating that the infracommunities were in an overall steady state, and spatial stability was present in the form of similar infracommunity composition between individual charr. Helminth endoparasite communities of freshwater fish are considered inherently unstable, as no regulating factors are usually identified. Observed stability likely comes from environmentally stable biotic and abiotic factors. An unregulated parasite community would likely experience large changes following a perturbation such as the introduction of a new host species and associated parasites. This again stress the severity of a host introduction.Even though parasite communities are complex ecological entities, the present study demonstrate that a great degree of similarity, predictability and stability can be observed in parasite communities of freshwater fish in northern Norway. In addition, three-spined stickleback was found as expected to play an important role in the occurrences of various parasite species emphasizing the ecological importance of this fish species. Its high impact on the structure and functionality of ecological food webs and parasite communities therefore strongly advises to discourage the practice of introducing this host species

Open Source Software Acquisition: Beyond the Business Case

Lately we have seen a growing interest from both public and private organisations to adopt Open Source Software (OSS), not only for a few, specific applications but also on a more general level throughout the organisation. As a consequence, the organisations’ decisions on adoption of OSS are becoming increasingly more important and complex. We present three perspectives organisations can employ in their decisions: seeing OSS acquisition as a business case, as COTS acquisition, and as architectural change within a governance framework. We present case studies of decisions on OSS adoption, and categorise the decision criteria we have found. Our results indicate that for large-scale adoption of OSS, focus will be on architectural considerations: enterprise-wide architectures will at first be a barrier, but in the long term OSS’s support of open standards can be a major enabler for OSS adoption. In contrast, in smaller organisations and in small-scale adoption of OSS, the cheap price of OSS is a major enabler, as it provides a good opportunity for experiments and short-term economic benefits. For small organisations these experiments can lead to development of a common IT-architecture, and in larger organisations OSS can be adopted in niche-areas, without significantly violating an existing IT-architecture

Indirect measurement of the magnetocaloric effect using a novel differential scanning calorimeter with magnetic field

Curli are bacterial appendages involved in the adhesion of cells to surfaces; their synthesis is regulated by many genes such as <i>csgD</i> and <i>ompR</i>. The expression of the two curli subunits (CsgA and CsgB) in <i>Escherichia coli</i> (<i>E. coli</i>) is regulated by CsgD; at the same time, <i>csgD</i> transcription is under the control of OmpR. Therefore, both genes are involved in the control of curli production. In this work, we elucidated the role of these genes in the nanomechanical and adhesive properties of <i>E. coli</i> MG1655 (a laboratory strain not expressing significant amount of curli) and its curli-producing mutants overexpressing OmpR and CsgD, employing atomic force microscopy (AFM). Nanomechanical analysis revealed that the expression of these genes gave origin to cells with a lower Young’s modulus (<i>E</i>) and turgidity (<i>P</i>₀), whereas the adhesion forces were unaffected when genes involved in curli formation were expressed. AFM was also employed to study the primary structure of the curli expressed through the freely jointed chain (FJC) model for polymers. CsgD increased the number of curli on the surface more than OmpR did, and the overexpression of both genes did not result in a greater number of curli. Neither of the genes had an impact on the structure (total length of the polymer and number and length of Kuhn segments) of the curli. Our results further suggest that, despite the widely assumed role of curli in cell adhesion, cell adhesion force is also dictated by surface properties because no relation between the number of curli expressed on the surface and cell adhesion was found

Development of 14 microsatellite markers for zoonotic tapeworm dibothriocephalus dendriticus (Cestoda: Diphyllobothriidea)

Dibothriocephalus dendriticus is one of the causative agents of the fish-borne zoonosis diphyllobothriosis. Polymorphic microsatellite markers were originally developed for future genetic studies using microsatellite library screening and next-generation sequencing (NGS). Out of 128 microsatellite candidates selected after NGS analysis, 126 yielded PCR products of the expected size. A declared repetitive motif was confirmed in 92 loci by Sanger sequencing. The level of polymorphism was tested by fragment analysis. Statistical tests for observed and expected heterozygosities and deviations from Hardy–Weinberg equilibrium revealed 14 polymorphic microsatellite loci suitable for studies on the finer genetic structure of global populations of D. dendriticus

Polychromatic neutron phase contrast imaging of weakly absorbing samples enabled by phase retrieval

We demonstrate the use of a phase retrieval technique for propagation-based phase contrast neutron imaging with a polychromatic beam. This enables imaging samples with low absorption contrast and/or improving the signal-to-noise ratio to facilitate e.g. time resolved measurements. A metal sample, designed to be close to a pure phase object, and a bone sample with canals partially filled with D2O were used for demonstrating the technique. These samples were imaged with a polychromatic neutron beam followed by phase retrieval. For both samples the signal-to-noise ratio were significantly improved and in case of the bone sample, the phase retrieval allowed for separation of bone and D2O, which is important for example for in situ flow experiments. The use of deuteration-contrast avoids the use of chemical contrast enhancement and makes neutron imaging an interesting complementary method to X-ray imaging of bone

A baseline study of the occurrence of non-indigenous species in Danish harbours

Project Manager/Main Author Jesper H. AndersenWe report the first ever nation-wide study of the occurrence of non-indigenous species in Danish harbours. The sampling was car-ried out using both conventional and biomolecular methods (eDNA). In total, 16 harbours were covered – Esbjerg and Aarhus, the two largest harbours in Denmark, with intensive sampling and 14 harbours with a reduced programme. 26 non-indigenous species were recorded using conventional sampling and 13 species were recorded using eDNA-based methods. Excluding overlapping rec-ords, we have recorded a total of 34 non-indigenous species in the 16 harbours studied. Based on the results, we conclude the following: 1) more non-indigenous species are found in the western parts of Denmark (North Sea region) then in the eastern parts (Baltic Sea), and 2) a few species previously unseen in Danish marine waters were recorded, i.e. the two bristle worms Eteone het-eropoda (fam. Phyllodocidae) and Streblospio benedicti (fam. Spionidae). Further, we provide a proof-of-concept regarding the overarching objectives of the MONIS 1-3 projects and the eDNA-based test systems developed. The results constitute a baseline for future studies in Danish ports and other hotspot areas.publishedVersio