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We compared smolt physiology of Atlantic salmon stocks, that migrate from freshwater stream environments to a freshwater lake (Lake Saimaa, Finland), from the Neva River (Russia) to the brackish water of the Baltic Sea, and from the Teno River (Finland/ Norway) to the full-strength seawater of the Arctic Ocean. The three fish stocks were reared under common garden conditions, and ion homeostasis, seawater tolerance, activities of gill and kidney Na,K-ATPase and [3H]ouabain binding of gill and kidney tissues were determined at different phases of smoltification. Activity of gill Na,K-ATPase and number of gill [3H]ouabain binding sites reached peak values in May and were strongly suppressed in July. Osmolality and Na, Cl-, and Mg2 ion concentrations of blood plasma decreased during smoltification. αla and αlb isoforms of gill Na,K-ATPase decreased and increased, respectively, during smoltification. Although small differences appeared at some points in time, the seasonal pattern and magnitude of changes in smolt characteristics were generally similar in the Saimaa salmon and in the anadromous stocks of the Neva and Teno salmon. It is suggested that the strong smoltification process of the landlocked Saimaa salmon is somehow necessary for migration of the young salmon from river to lake and therefore has been retained in evolution.
We examined whether gene expression in the young salmon (Salmo salar) gill differs in relation to the salinity of their migration habitat by comparing three salmon stocks: (1) fish that migrate from a river system to Lake Saimaa, (2) fish that migrate to the brackish waters of the Baltic Sea, and (3) fish that migrate to the full-strength salinity of the Arctic Ocean. Transcripts of the gill tissue were measured at three successive developmental stages (parr, smolt and postsmolt) using the cDNA microarray in fish reared under common conditions. The changes in gene expression were qualitatively and quantitatively similar in the three stocks irrespective of the salinity of the natural growing habitat. This suggests that the parr—smolt transformation in the gill tissue of the landlocked fresh-water salmon stock is similar to the seawater migrating salmon. The transformation of the gill to a hypoosmotic organ in the freshwater salmon has been retained in evolution, possibly due to its adaptive role as a signal for migration from a relatively poor-growth environment of the river to a more productive lake habitat.
We conducted an analysis of relationships between results of survey on breeding community of birds, including species richness, abundance of individual species and ecological groups of birds, and habitat features of 91 isolated reed patches in southwestern Poland. The approach to the reedbed habitat involves environmental differentiation at the patch level, landscape context and isolation, including the impact of man-made structures as potential constraints to the occurrence of birds. Generalized linear models have shown that 12 out of 14 analyzed environmental predictors had a statistically significant effect on birds. The results from individual species (sedge warbler, great reed warbler, bluethroat, Savi's warbler, water rail, moorhen and coot) models revealed that the number of territories was affected from two to four predictors. The number of reedbed specialists was affected positively by reed edge, water area and proportion of reed habitat within a 100-m radius, and negatively by railway. The number of water birds was affected positively by reedbed area, internal reed edge, treebelt, distance to reedbed > 1 ha and a proportion of reed habitat within a 100-m radius, and negatively by external reed edge. The proportion of reed habitat within a 100-m radius and internal reed edge were the predictors which positively affected richness of bird species. Our results showed that, apart from the habitat features measured within a reedbed, i.e. area of a reed patch, length of external edge or presence of trees, some other factors measured in larger landscape context, i.e. isolation (expressed mainly as the proportion of reed habitat within a 100-m radius) and the presence of man-made structures are important predictors in explaining the abundance of birds. The area sensitivity of birds nesting in reedbeds in terrestrial habitat was considerably lower than in reed islands located in lakes and wetlands of southern Europe.
The applicability of simple PCR-based approaches for sex discrimination in the three European Phalacrocoracidae species was tested, using 93 individuals of known sex and two sets of primers (1237L/1272R and 2550F/2718R) for the amplification of the avian sex-specific chromo-helicase-DNA-binding protein gene. We evaluated the accuracy of each set of primers in providing the correct sex for each individual. The first primer set did not produce reliable results. The second provided a band pattern for each sex, easily distinguishable with agarose gel electrophoresis, which correctly identified all the individuals, even in samples of low DNA yield. The amplification products were sequenced and aligned revealing important nucleotide diversity among Phalacrocoracidae species. Compared with morphometric discriminant analysis and DNA-fingerprinting techniques previously applied, the PCR-based sexing with the 2550F/2718R primers is more accurate, less invasive and widely applicable to both adults and chicks, using a variety of DNA sources such as blood, tissue, feathers, egg shells and others.
Acorn barnacles were assumed to have a self-thinning exponent close to -3/2 widely acknowledged for plant populations. However, space and food competition mechanisms would lead to a different exponent. Different recruit densities between tidal levels should result in different geometry of space occupation with adult individuals morphologically different and a different biomass-density relationship. Using Tetraclita squamosa, an intertidal barnacle, we investigated the biomass-density relationship along an intertidal gradient to study self-thinning. The self-thinning slope was steeper than the -3/2 power and did not differ among lower tidal levels with an intercept significantly higher in the low intertidal than in the mid-intertidal, whereas there was no significant relationship in the high intertidal. Growth in height of crowded barnacles along with the weaker effect of competition for food may retard mortality and result in a self-thinning slope steeper than -3/2. Our results suggested that self-thinning exponent in barnacles is steeper than -3/2 found for plant populations and allometric growth may not be the only factor causing this deviation from the “self-thinning law”. As one progresses higher in the intertidal, self-thinning processes disappear owing to reduced competition.
Adult birds are frequently observed consuming nestling feces. However, fecal sac ingestion has received little attention, including a lack of experimental tests to understand such behavior. Traditionally, it has been explained by the “parental nutrition hypothesis” (parents acquire nutrients and energy) or the “economic disposal hypothesis” (parents save time to do other tasks). Here, we propose a third explanation, the “nest predation hypothesis”: parents ingest fecal sacs to reduce nest detectability in the presence of a nest predator. We experimentally manipulated the nest-predation risk perceived by adult common blackbirds (Turdus merula). We detected an effect of brood size in the removed and ingested feces while our experiment did not increase fecal sac comsumption. However, we found other evidences supporting that nest predation could play a more subtle role in this parental care behavior: (1) both sexes contributed equally to fecal ingestion; (2) adults ingested more feces in the population with the highest nest-predation risk; and (3) parents that ate fecal sacs increased their permanence at the nest.
Voles are the main prey item for many mammalian and avian predators. Changes in vole abundance affect predator density directly and influence small game species indirectly. To test the hypothesis that intensive management of boreal forests increases vole population density, we surveyed small mammals twice during 2006–2010 in forests representing four succession stages in Taivalkoski, northern Finland. We focused on the bank vole (Myodes glareolus) and the field vole (Microtus agrestis) and found that bank voles were more numerous in all stages of succession while densities of both species were lowest in young (24–30-year-old) forest stands. We also found that field voles increased after clear-cutting. Based on this study, current forestry practice in Finland has a clear impact on the abundance of these voles.
Biogeochemical markers in ecology are useful for indicating geographic origin and movement patterns of species on various temporal and spatial scales. By assessing these markers in a tissue that is chemically inert once formed (e.g., claws) and is grown incrementally (i.e., deposited in layers), changes in an individual's foraging environment would be captured in the chemical signatures in these tissues. To determine whether trace elements can be used as a marker to track movement in terrestrial carnivores, we resolved multi-elemental data at a fine spatial scale in the claw keratin of a model species (Taxidea taxus) using high resolution laser ablation inductively coupled plasma mass spectrometry (LA ICP-MS). The unique chemical signatures we detected in claws suggested that these chemical variations were, in part, a reflection of the chemical environment and were not be attributable to sex or random deposition. Neighbouring claw samples were not more chemically related than distant ones, which suggests that local differences in chemical composition (e.g., habitat type) may have a stronger influence on claw chemistry than large-scale patterns in trace element variation associated with underlying geology. Our findings illustrated that temporallyexplicit chemical profiles in the blade horn keratin of mammalian claws may be used to examine endogenous uptake of trace element signatures from the local environment and serve as tool to assist in reconstructing animal movement pathways.
Sex differences in foraging ecology have been found in a variety of taxa. We tested the hypothesis that breeding female wolverines (Gulo gulo), probably due to their smaller home ranges and higher energy demands because of gestation and lactation, are forced to rely more on food caches and carrion than other wolverines. The diet composition, as the percentage occurrence, was estimated for four breeding females and six males and non-breeding females by analyzing scat samples, all collected in eastern Finland. The most important food source for breeding female wolverines was human- and wolfkilled moose (55%), while the diet also comprised mountain hare (13%), domestic pig (13%) and grouse (11%). Mountain hare (52%) was the most utilized food source for males and non-breeding females. Moose (22%) and grouse (15%) were also important components of the diet. Our study highlights the importance of human- and wolf-killed carrion for breeding female wolverines in areas where the density of medium-sized ungulates is low.
Limited data exist on ecology of European hedgehog (Erinaceus europaeus) at the northern edge of the species’ range. In our study, spatial analysis using radio-tracking data from Finland showed that sex and season had significant effects on the homerange size of hedgehogs. Although males were heavier than females, body weight had no effect on home-range size. Total home ranges (male 98, female 55 ha) were larger than those in southern areas. Thus, male home ranges were larger than those of females during the mating (male 72, female 21 ha) and post-mating seasons (male 48, female 20 ha), but the differences were small and reversed before hibernation (male 17, female 29 ha). Home ranges of individuals of both sexes overlapped, but females shared core areas with other females only during the mating season. Our results imply possible differences in hedgehog ecology probably due to a less productive and harsh northern habitat.