Seasonal activity patterns and movements of the raccoon dog, a vector of diseases and parasites, in southern Finland

Activity patterns and movements of raccoon dogs (Nyctereutes procyonoides) were studied in Virolahti, southeast Finland, in 2000–2003. Activity data were compared to those collected from Evo, south-central Finland, in 1990–1993. Activity in winter was compared to weather (temperature and snow depth), day length and moon. Also circadian activity rhythm was studied in Evo. Raccoon dogs moved fastest in late winter after winter dormancy and slowest in autumn before settling in their winter dens. In March, males were moving more often than females. Raccoon dogs stayed usually in their dens in mid-winter (December–February) but were sometimes wandering around also during the harshest months of the year and changed their winter den on average three times. Both day length and weather affected the activity of raccoon dogs in winter. Animals usually stayed in their dens, when temperature was below –10 °C, snow depth >35 cm and day length <7 h and were moving around, when temperature was >0 °C, there was no snow and day length was >10 h. Day length and snow depth together predicted rather well the probability of animals being active during winter. Although raccoon dogs were more often active at night than during the light hours, they also showed rather much diurnal activity.     

Direct evidence for production of microcystins by Anabaena strains from the Baltic Sea

Anabaena is a filamentous, N(2)-fixing, and morphologically diverse genus of cyanobacteria found in freshwater and brackish water environments worldwide. It contributes to the formation of toxic blooms in freshwater bodies through the production of a range of hepatotoxins or neurotoxins. In the Baltic Sea, Anabaena spp. form late summer blooms, together with Nodularia spumigena and Aphanizomenon flos-aquae. It has been long suspected that Baltic Sea Anabaena may produce microcystins. The presence of microcystins has been reported for the coastal regions of the Baltic proper, and a recent report also indicated the presence of the toxin in the open Gulf of Finland. However, at present there is no direct evidence linking Baltic Sea Anabaena spp. to microcystin production. Here we report on the isolation of microcystin-producing strains of the genus Anabaena in the open Gulf of Finland. The dominant microcystin variants produced by these strains included the highly toxic MCYST-LR as well as [d-Asp(3)]MCYST-LR, [d-Asp(3)]MCYST-HtyR, MCYST-HtyR, [d-Asp(3),Dha(7)]MCYST-HtyR, and [Dha(7)]MCYST-HtyR variants. Toxic strains were isolated from the coastal Gulf of Finland as well as from the easternmost open-sea sampling station, where there were lower salinities than at other stations. This result suggests that lower salinity may favor microcystin-producing Anabaena strains. Furthermore, we sequenced 16S rRNA genes and found evidence for pronounced genetic heterogeneity of the microcystin-producing Anabaena strains. Future studies should take into account the potential presence of microcystin-producing Anabaena sp. in the Gulf of Finland.     

Sources of Listeria monocytogenes Contamination in a Cold-Smoked Rainbow Trout Processing Plant Detected by Pulsed-Field Gel Electrophoresis Typing

Sites of Listeria monocytogenes contamination in a cold-smoked rainbow trout (Oncorhynchus mykiss) processing plant were detected by sampling the production line, environment, and fish at different production stages. Two lots were monitored. The frequency of raw fish samples containing L. monocytogenes was low. During processing, the frequency of fish contaminated with L. monocytogenes clearly rose after brining, and the most contaminated sites of the processing plant were the brining and postbrining areas. A total of 303 isolates from the raw fish, product, and the environment were characterized by pulsed-field gel electrophoresis (PFGE). PFGE yielded nine pulsotypes, which formed four clusters. The predominating L. monocytogenes pulsotypes of the final product were associated with brining and slicing, whereas contaminants of raw fish were not detected in the final product. Air-mediated contamination in the plant could not be proved. In accordance with these results, an L. monocytogenes eradication program was planned. The use of hot steam, hot air, and hot water seemed to be useful in eliminating L. monocytogenes. None of the control samples taken in the 5 months after the eradication program was implemented contained L. monocytogenes.     

Genotypic variation in growth and resistance to insect herbivory in silver birch (<Emphasis Type="Italic">Betula pendula</Emphasis>) seedlings

If herbivory is unevenly distributed among different types of plants, or if individual plants differ in their response to herbivory, herbivores may affect seedling growth and survival, and consequently plant population structure. In this study we examined variation in resistance to insect herbivory and in growth responses to feeding among 20 silver birch (Betula pendula Roth) genotypes representing variation within a natural population. Birch seedlings were grown in dense stands in random arrangement so that seedlings of different genotypes competed with each other. On insect exposure plots natural colonization of insects was allowed, and insect removal plots were sprayed with insecticide. Resistance to insect herbivory was measured as the inverse of leaf damage, and growth responses of seedlings to feeding were determined as the change in seedling height relative to the amount of damage. Resistance varied significantly among genotypes, but growth responses to feeding did not. In fertilized seedlings, resistance correlated negatively with height, indicating a trade-off between resistance and growth. The absence of such a correlation in non-fertilized seedlings is a sign of environmental effects on the cost of resistance. Growth responses to feeding did not correlate with either resistance or growth. Nevertheless, different effects of the actual damage on height increase changed the positions of the genotypes in the size hierarchy of the experimental populations. Thus, even moderate levels of insect herbivory can change the outcome of competitive interactions between birch genotypes.Due to an error in the citation line, this revised PDF (published in December 2003) deviates from the printed version, and is the correct and authoritative version of the paper.     

Pediastrum algae from the classic late glacial Bølling Sø site, Denmark: Response of aquatic biota to climate change

The late glacial and the early Holocene sediments of the classic site Bølling Sø in Denmark are being reinvestigated by multi-proxy analyses. We present here the record of Pediastrum species and discuss the climate-mediated changes in the aquatic ecosystem, as reflected by aquatic proxies (e.g. aquatic plants and mosses, cladocerans, ostracods, bryozoan statoblasts), as well as a number of other proxies (organic content, biogenic silica, carbonates, terrestrial plant macrofossils). Climate had warmed to such an extent at c. 12,500 ¹⁴C yrs BP that aquatic life could begin. Productivity was low and only very scarce indication of a warmer interval predating the Allerød chronozone was found. At the beginning of the Allerød chronozone climate ameliorated and productivity clearly increased. The cool climate of the Younger Dryas chronozone (YD) was more clearly reflected in the terrestrial ecosystem than in the aquatic ecosystem, where productivity appeared to remain rather high. The lake was very shallow and non-stratified during the YD, indicating low effective moisture. Probably it warmed throughout early in the open-water season and in that way enabled higher productivity, even if summer temperatures were rather low. It is also possible that the difference in July temperatures between the late part of the Allerød chronozone and the YD was not large in central Jutland. The amelioration of climate at the beginning of the Holocene is clearly reflected in all proxies. There is also evidence that the lake level rose. The lake probably remained alkaline during all of its history but some evidence suggests that pH was somewhat lowered during the YD chronozone. Pediastrum species appear to be relatively good indicators of environmental conditions; similarly, the concentrations may reflect productivity variations during changing climatic conditions.     

Consequences of Increasing Hypoxic Disturbance on Benthic Communities and Ecosystem Functioning

Disturbance-mediated species loss has prompted research considering how ecosystem functions are changed when biota is impaired. However, there is still limited empirical evidence from natural environments evaluating the direct and indirect (i.e. via biota) effects of disturbance on ecosystem functioning. Oxygen deficiency is a widespread threat to coastal and estuarine communities. While the negative impacts of hypoxia on benthic communities are well known, few studies have assessed in situ how benthic communities subjected to different degrees of hypoxic stress alter their contribution to ecosystem functioning. We studied changes in sediment ecosystem function (i.e. oxygen and nutrient fluxes across the sediment water-interface) by artificially inducing hypoxia of different durations (0, 3, 7 and 48 days) in a subtidal sandy habitat. Benthic chamber incubations were used for measuring responses in sediment oxygen and nutrient fluxes. Changes in benthic species richness, structure and traits were quantified, while stress-induced behavioral changes were documented by observing bivalve reburial rates. The initial change in faunal behavior was followed by non-linear degradation in benthic parameters (abundance, biomass, bioturbation potential), gradually impairing the structural and functional composition of the benthic community. In terms of ecosystem function, the increasing duration of hypoxia altered sediment oxygen consumption and enhanced sediment effluxes of NH₄ ⁺ and dissolved Si. Although effluxes of PO₄ ³⁻ were not altered significantly, changes were observed in sediment PO₄ ³⁻ sorption capability. The duration of hypoxia (i.e. number of days of stress) explained a minor part of the changes in ecosystem function. Instead, the benthic community and disturbance-driven changes within the benthos explained a larger proportion of the variability in sediment oxygen- and nutrient fluxes. Our results emphasize that the level of stress to the benthic habitat matters, and that the link between biodiversity and ecosystem function is likely to be affected by a range of factors in complex, natural environments.     

Analysis of an inactive cyanobactin biosynthetic gene cluster leads to discovery of new natural products from strains of the genus microcystis

Cyanobactins are cyclic peptides assembled through the cleavage and modification of short precursor proteins. An inactive cyanobactin gene cluster has been described from the genome Microcystis aeruginosa NIES843. Here we report the discovery of active counterparts in strains of the genus Microcystis guided by this silent cyanobactin gene cluster. The end products of the gene clusters were structurally diverse cyclic peptides, which we named piricyclamides. Some of the piricyclamides consisted solely of proteinogenic amino acids while others contained disulfide bridges and some were prenylated or geranylated. The piricyclamide gene clusters encoded between 1 and 4 precursor genes. They encoded highly diverse core peptides ranging in length from 7-17 amino acids with just a single conserved amino acid. Heterologous expression of the pir gene cluster from Microcystis aeruginosa PCC7005 in Escherichia coli confirmed that this gene cluster is responsible for the biosynthesis of piricyclamides. Chemical analysis demonstrated that Microcystis strains could produce an array of piricyclamides some of which are geranylated or prenylated. The genetic diversity of piricyclamides in a bloom sample was explored and 19 different piricyclamide precursor genes were found. This study provides evidence for a stunning array of piricyclamides in Microcystis, a worldwide occurring bloom forming cyanobacteria.     

Effect of cold exposure on cortical microtubules of rye (Secale cereale) as observed by immunocytochemistry

The responses of cortical microtubules to sub-zero temperatures were examined in non-acclimated (NA) and cold-acclimated (CA) rye ( Secale cereale L. cv. Voima) leaf and root cells, and in protoplasts isolated enzymatically from leaves. Responses of leaf and root cells to hypertonic solutions equivalent to the dehydration response of freezing (P. L. Steponkus and D. V. Lynch 1989. J. Bioenerg. Biomembr. 21: 21–41) were also examined. At the respective growth temperatures both NA and CA leaf and root cells had typical organization and abundance of cortical microtubules as observed by indirect immunofluorescence (IIF) staining. Unchanged microtubule arrays were still present in CA leaf cells after -4°C treatment, while in leaf cells of NA plants and in the root cells of both NA and CA plants microtubules were shorter and less abundant. After -10°C treatment the cortical microtubules were almost totally depolymerized in both types of root cells and in leaf cells of NA plants, while CA leaf cells still had abundant cortical microtubule arrays. Semiquantitative analyses of cortical microtubules (MTs) of protoplasts confirmed the findings with intact leaf cells. Hypertonic treatment of NA and CA leaf cells gave similar effects as exposure of cells to sub-zero temperatures. However, after the hypertonic treatment, more microtubules remained present in the CA root cells than in the NA root cells, suggesting that also in root cells cold acclimation increases the dehydration stability of MTs. In conclusion, cold acclimation induces both greater frost stability and greater osmotic tolerance in the cortical microtubules of the leaf cells, and greater osmotic tolerance in the microtubules of the root cells in winter rye.     

Intramembrane particles and filipin labelling on the membranes of autophagic vacuoles and lysosomes in mouse liver

Summary Morphologically detectable protein (intramembrane particles) and cholesterol (filipin labelling) in the membranes of autophagic vacuoles and lysosomes were studied in mouse hepatocytes using thin-section and freeze-fracture electron microscopy. Both isolated autophagic vacuoles and lysosomes, and intact tissue blocks were used due to the facts (i) that lysosomes are difficult to recognize in freeze-fracture replicas of intact hepatocytes, and (i) that filipin penetration into the tissue blocks is unsatisfactory. Intramembrane particle density was low in the membranes of early autophagic vacuoles (defined as round-shaped vacuoles in which an inner membrane parallel with the outer limiting membrane was clearly visible). The lysosomal membranes contained considerably more intramembrane particles. Particle-rich lysosomes or other vesicles were observed to fuse with the early autophagic vacuoles. The membranes of nascent autophagic vacuoles with morphologically intact contents were usually not labelled by filipin, whereas the membranes of all other autophagic vacuoles and lysosomes were heavily labelled. The increased cholesterol in the membranes of slightly older autophagic vacuoles is presumably derived from cholesterol-rich lysosomes or other vesicles fusing with the vacuoles and from the degrading organelles inside the autophagic vacuoles.