Effects of Protostrongylus sp. and Pneumocystis sp. on the pulmonary tissue and the condition of mountain and brown hares from Finland

Mountain hares (Lepus timidus) and brown hares (Lepus europaeus) shot by hunters in several game management districts in southern and central Finland during the hunting season from September to the end of February 1998-2001 were examined for Protostrongylus sp. and Pneumocystis sp. Of the mountain hares, 96.5% (194/201) were infected with the lungworm Protostrongylus sp. and 16.9% (32/189) had cyst forms of the fungus Pneumocystis sp. in the lungs. The prevalence of the lungworm and fungus in brown hares was 60% (18/30) and 20.0% (6/30), respectively. The tissue changes associated with the lungworms were macroscopically and microscopically well demarcated. The majority and most severe histopathologic changes were seen at the distal part of the caudal lobes. Inflammatory cells, mainly eosinophils and macrophages, and in lesser degree neutrophils, lymphocytes, and plasma cells were typical findings in the worm-infected tissue. The condition and weight of the hare did not show any significant association with the intensity of the lungworm infection. All Pneumocystis-infected mountain hares were young, and their condition and weight correlated negatively with the intensity of the infection. The intensity of the Pneumocystis infection did not correlate with that of the lungworm infection. Within a tissue section, a slight but significant positive correlation was observed between presence of cysts and inflammatory cells.     

The lipopeptide toxins anabaenolysin A and B target biological membranes in a cholesterol-dependent manner

The two novel cyanobacterial cyclic lipopeptides, anabaenolysin (Abl) A and B permeabilised mammalian cells, leading to necrotic death. Abl A was a more potent haemolysin than other known biodetergents, including digitonin, and induced discocyte-echinocyte transformation in erythrocytes. The mitochondria of the dead cells appeared intact with regard to both ultrastructure and membrane potential. Also isolated rat liver mitochondria were resistant to Abl, judged by their ultrastructure and lack of cytochrome c release. The sparing of the mitochondria could be related to the low cholesterol content of their outer membrane. In fact, a supplement of cholesterol in liposomes sensitised them to Abl. In contrast, the prokaryote-directed cyclic lipopeptide surfactin lysed preferentially non-cholesterol-containing membranes. In silico comparison of the positions of relevant functional chemical structures revealed that Abl A matched poorly with surfactin in spite of the common cyclic lipopeptide structure. Abl A and the plant-derived glycolipid digitonin had, however, predicted overlaps of functional groups, particularly in the cholesterol-binding tail of digitonin. This may suggest independent evolution of Abl and digitonin to target eukaryotic cholesterol-containing membranes. Sub-lytic concentrations of Abl A or B allowed influx of propidium iodide into cells without interfering with their long-term cell viability. The transient permeability increase allowed the influx of enough of the cyanobacterial cyclic peptide toxin nodularin to induce apoptosis. The anabaenolysins might therefore not only act solely as lysins, but also as cofactors for the internalisation of other toxins. They represent a potent alternative to digitonin to selectively disrupt cholesterol-containing biological membranes.     

Predicting animal performance through climatic and plant phenology variables: The case of an omnivore hibernating species in Finland

Annual variation in the environment is expected to influence individual performance, e.g. measured as body condition, such as body mass or fat deposition, through its direct or indirect effects on food abundance and availability. Such environmental variation is traditionally measured by climatic observation, but recently, measures of environmental phenology obtained from satellite images have been successfully used. We examined the performance of climatic and plant phenology variables in explaining body condition of an invasive omnivore species: the raccoon dog Nyctereutes procyonoides. We collected data on fat deposition of juveniles in southern Finland from the end of June to the beginning of November. A four-parametric logistic model was fitted separately for each province to the data by non-linear regression procedure and the residuals were compared to the expected average as measure of individual performance. These values were then analysed with respect to the environmental variables. Climatic variables describing spring conditions performed better than plant phenology variables in explaining the variation in fat deposition. Harsh spring conditions negatively affected the amount of fat deposed during the growing season. Plant phenology variables, effective in explaining life history traits in herbivores, might not reflect variation in food abundance and quality for omnivore species. We propose that in Europe raccoon dogs will benefit from climate warming, because of a longer growing season, but increased spring precipitation in the form of snow at higher latitudes might compensate for the effect of greater primary productivity and outline the border of their expansion towards harsher environments.     

Penetration of fimbriate enteric bacteria through basement membranes: A hypothesis

A mechanism for penetration of basement membranes by Escherichia coli is presented. The mechanism is based on the ability of the S fimbriae of meningitis-associated E. coli to bind to vascular endothelium and choroid plexuses in brain and to basement membranes. On the other hand, the S and the type 1 fimbriae of E. coli immobilize plasminogen and tissue-type plasminogen activator; this process generates proteolytic plasmin activity on the surface of fimbriate cells. Our hypothesis is that bacterium-bound plasma activity, directed to basement membranes through fimbrial binding, promotes bacterial penetration through basement membranes.     

Competition between a toxic and a non-toxic <Emphasis Type="Italic">Microcystis</Emphasis> strain under constant and pulsed nitrogen and phosphorus supply

The toxicity of a harmful algal bloom is strongly determined by the relative abundance of non-toxic and toxic genotypes and might therefore be regulated by competition for growth-limiting resources. Here, we studied how the toxic Microcystis aeruginosa strain PCC 7806 and a non-toxic mutant compete for nitrogen and phosphorus under constant and pulsed nutrient supply. Our monoculture and competition experiments show that these closely related genotypes have distinct nutrient physiologies and that they differ in their ability to compete for nitrogen and phosphorus. The toxic wild type won the competition under nitrogen limitation, while the non-toxic mutant dominated under phosphorus limitation. Pulses of both nitrogen and phosphorus increased the dominance of the toxic genotype, which lead to an even faster competitive exclusion of the non-toxic genotype under nitrogen pulses and to coexistence of both genotypes under phosphorus pulses. Our findings indicate that the genotype level dynamics driven by resource competition can be an important factor in determining cyanobacterial bloom toxicity.     

Habitat use of the mountain hare<Emphasis Type="Italic">Lepus timidus</Emphasis> in summer: the importance of different vegetation layers

The aim of the present study was to examine how the vegetation structure of the forest, shrub and field and ground layer affect the habitat use of mountain haresLepus timidus Linnaeus, 1759 in summer (May–September) in southern Finland. The structure of each vegetation layer in woodlots throughout the entire study area of 20 km² was measured. We analysed the vegetation data using principal component analyses (PCA) that arranged the woodlots along a gradient within each vegetation layer. Data on habitat use was gathered between 1998 and 2000 from 11 radio-collared mountain hares. The core areas of the home ranges of hares were determined and the vegetation structure of these areas was compared with the mean of the entire study area (core area, periphery area and control area). A similar shrub layer gradient was identified by PCA for seven out of the 11 hares. Hares preferred thickets of willowSalix spp., downy birchBetula pubescens, and sprucePicea abies. The hares did not show a consistent preference for the forest and ground levels. The results suggest that dense understories are important in the mountain hare’s habitat use, probably because they offer both food and shelter.     

Genetic diversity in strains of the genus Anabaena isolated from planktonic and benthic habitats of the Gulf of Finland (Baltic Sea)

Late summer cyanobacterial blooms in the Baltic Sea contain Anabaena sp. together with Nodularia spumigena and Aphanizomenon flos-aquae. Although Anabaena is common especially in the Gulf of Finland, very little is known about its genetic diversity. Here we undertook a molecular phylogenetic study of 68 Anabaena strains isolated from the brackish Gulf of Finland. We sequenced the 16S rRNA genes from 54 planktonic and 14 benthic Anabaena strains, and rbcL and rpoC1 genes from a subset of these strains. Phylogenetic trees showed that Anabaena strains, from both planktonic and benthic habitats, were genetically diverse. Although the Anabaena strains were morphologically diverse, in our study only one genetically valid species was found to exist in the plankton. Evolutionary distances between benthic Anabaena strains were greater than between planktonic strains, suggesting that benthic habitats allow for the maintenance of greater genetic diversity than planktonic habitats. A number of novel lineages containing only sequences obtained in this study were compiled in the phylogenetical analyses. Thus, it seemed that novel lineages of the genus Anabaena may be present in the Baltic Sea. Our results demonstrate that the Baltic Sea Anabaena strains show surprisingly high genetic diversity.     

Diet of raccoon dogs in summer in the Finnish archipelago

The diet of raccoon dogs in summer was examined in the Finnish archipelago and compared with their diet on the mainland. Faeces were collected from latrines in the outer archipelago and the inhabited islands in May-July 1998 and 1999. Remains of waterfowl, especially those of female cider, occurred frequently in the faeces of raccoon dogs on the uninhabited islands, but less frequently on the inhabited islands and only occasionally on the mainland. Since many female eider died of disease during the summer in 1998 and 1999. and white-tailed eagles arc known to prey on brooding eider, it is probable that raccoon dogs did not themselves kill all the eider they consumed. Even if they did, they would only take a few percent of female eider population each year. It is thus improbable that raccoon dogs affect the size of the eider population in the Finnish archipelago. Frogs, reptiles, shrews and carrion occurred frequently in the diet on the mainland, but only occasionally in the outer archipelago. It is possible that raccoon dogs have decimated frog populations on small islands, as they are easy prey and occur frequently in the diet of raccoon dogs on the mainland. Small rodents are important prey for raccoon dogs on the mainland and on inhabited islands, but less important in the outer archipelago in early summer.     

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.