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- Hulthén, Kaj, et al.
(author)
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Timing and synchrony of migration in a freshwater fish : Consequences for survival
- 2022
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In: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 91:10, s. 2103-2112
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Journal article (peer-reviewed)abstract
- Animal migration is one of the most spectacular and visible behavioural phenomena in nature with profound implications for a range of ecological and evolutionary processes. Successful migration hinges on the ability to exploit temporary resources (e.g. food) and evade threats (e.g. predators) as they arise, and thus the timing of migration is often regarded as a dominant predictor of individual migratory success. However, with the exception of intensively studied taxa (mainly birds), relatively few studies have investigated inter-individual annual and seasonal variation in migratory timing and performance, or tested predictions on how migration across high and low predation-risk habitats may exert selection on migratory timing. In particular, studies that assess the survival consequences of variation in migratory timing remain rare, which is most likely due to the logistical challenges associated with monitoring survival success and population-level characteristics simultaneously. Here, we address the above-mentioned questions using roach Rutilus rutilus, a fish that migrates from lakes characterised by high predation risk into low-risk streams during winter. Specifically, we used individual-based tracking of roach in two European lake systems over multiple migration periods (9 and 7 years respectively), to obtain highly detailed (year-round scheduling, repeat journeys and the fate of individuals) data on the variability/synchrony of migratory timing in spring and autumn respectively. We report seasonal differences in the variability of migratory timing, with lower variance and higher migration synchrony in spring lake arrival timing as compared to autumn lake departure timing. Furthermore, the timing of autumn migration is more variable across years than the timing of spring migration. Second, we find that later arrival to the lake habitat is positively associated with apparent survival from 1 year to the next, whereas we found no effect of lake departure timing on survival probability. These findings represent rare evidence showing how intraspecific variation in timing in migratory fish differs across years and seasons, and how variation in timing can translate into survival consequences for prey in systems characterised by high predation risk.
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- Kanchugal P, Sandesh
(author)
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Antibiotic Resistance and the Cellular Currency S-adenosyl-methionine : Modification of aminoglycosides and nucleic acids
- 2020
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Doctoral thesis (other academic/artistic)abstract
- Streptomycin and spectinomycin are antibiotics that bind to ribosomes and inhibit protein synthesis. Common resistance mechanisms involve enzymatic modification of the two drugs by aminoglycoside nucleotidyltransferases (ANTs). The first part of this thesis covers the structural mechanism of two ANT enzymes. The first is the dual-specificity AadA, belonging to the ANT(3")(9) family, which modifies the 3" position of streptomycin and position 9 of spectinomycin. The second is ANT(9) that only modifies spectinomycin at position 9.We solved crystal structures of both enzymes, AadA in complex with ATP and streptomycin and ANT(9) with ATP and spectinomycin. The two enzymes show overall structural similarity and both consist of an N-terminal nucleotidyltransferase domain and a C-terminal helical domain. The binding of ATP between the two domains induces a conformational change that allows the drug to bind. The modified hydroxyl groups of both drugs align at similar positions in the active site, even though the drugs are chemically distinct. Comparison of the ANT(9) and AadA structures shows that spectinomycin specificity is explained by the straight α5 helix followed by a short loop in ANT(9) that would clash with larger drug streptomycin. These findings allowed us to explain the substrate recognition of these enzymes and propose a catalytic mechanism.In the second and third parts of this thesis, I studied two enzymes that use S-adenosyl-methionine (SAM), RlmF in site-specific methylation of ribosomal RNA (rRNA) and Svi3-3 in SAM degradation. SAM is an essential molecule for normal cellular function in all-living cells and termed as a ‘cellular currency’. Knowledge is lacking about the substrate recognition of rRNA methyltransferases and the role of the modifications that they add during ribosome assembly. Here, we identify the residues of RlmF that are critical for binding of the cofactor SAM and the lithium chloride core particle substrate that mimics a 50S ribosome assembly intermediate.In the third part, I present structural and ligand-binding studies of a newly discovered SAM degrading enzyme Svi3-3 from bacteriophage.
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- Nilsson, P. A., et al.
(author)
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First-season growth and food of YOY pike (Esox lucius) are habitat specific within a lake
- 2023
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In: Fisheries Research. - : Elsevier BV. - 0165-7836. ; 259
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Journal article (peer-reviewed)abstract
- Piscivorous fish are important predators in aquatic systems and as such they can have far-reaching effects on ecosystem composition and function. These effects depend on piscivore predation rates and behaviour, and recruitment of young-of-the-year fish into piscivory can hereby govern ecosystem properties. Growth and recruitment can differ between water bodies due to e.g. general productivity, but information on variation in juvenile growth and body condition between habitats within water bodies is scant. We here evaluate growth, body condition, food occurrence and stomach contents of an important piscivore, pike (Esox lucius), over the first growth season in two contrasting and spatially separated homogenous habitat types (emergent and submerged vegetation separated by 50 m of open sand) within the same lake. Individual size and body condition in pike were higher in the submerged vegetation early in the season, whereas by the end of their first summer pike were larger and in higher body condition in the emergent vegetation, in spite of occurrence of zooplankton, macroinvertebrates and fish prey being overall higher in the submerged vegetation. Pike showed habitat-specific patterns of macroinvertebrate consumption (higher in the submerged vegetation) and date-specific patterns of zooplankton (higher early in the season), macroinvertebrate (lower late in the season) and fish (higher later in the season) consumption that were not a result of occurrence of food types, as occurrence and consumption patterns did not match. We conclude that pike that hatched in the emergent vegetation habitat were larger towards the end of the season and, hence, these pike should have a higher survival probability and possibly contribute more to pike population density and predation at older ages, but also that submerged vegetation provides an alternative and added recruitment environment for pike in shallow lake ecosystems.
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- Skov, Christian, et al.
(author)
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A field evaluation of long-term effects of PIT tagging
- 2020
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In: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 96:4, s. 1055-1059
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Journal article (peer-reviewed)abstract
- Passive integrated transponder (PIT)-tagging is commonly used in behavioural studies of fish, although long-term evaluations of effects from tagging under natural conditions are scarce. We PIT-tagged common bream Abramis brama, European perch Perca fluviatilis, pike Esox lucius and roach Rutilus rutilus, released them in their lakes of origin and recaptured them after 103–3269 days. Overall, tagged fish did not differ in condition from non-tagged fish, except for small R. rutilus that had a lower length-specific body mass in one lake in 1 year. We conclude that PIT-tagging in general has negligible long-term effects on fish condition.
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