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Two cases of Eurasian lynx Lynx lynx (Linnaeus, 175S) caching prey (roe deer Capreolus capreolus) jn trees were documented: in southeastern Polami in February 1996 and in southwestern Czech Republic in November 19911. Both carcasses were
The influence of turbulence (turbulent kinetic energy dissipation) on predator-prey interactions in zooplankton is discussed with respect to the combined effect of the choice of the turbulent length scale, and size and velocity of predator and prey concentration on the encounter rate. The significance of correct scaling to the turbulent encounter velocity is demonstrated, with three different definitions being considered: the average prey separation, the Kolmogorov scale, and the predator's reactive distance. Numerical investigations using these different definitions of scale were carried out to find the convergence conditions and the behaviour of the scale values for 5-10 mm fish larvae which feed off copepod nauplii in the 10⁴-10⁵ m⁻³ concentration range. The choice of the turbulent length scale is not important for small predator body sizes <5mm and high prey concentrations in the 10⁷-10⁸ m⁻³ range, which are reasonable prey densities for a 1-3 mm copepod (i.e. algae and protozoans). Also in the quasi-laminar regime of water flow (l=2πη) and high prey concentrations, the choice of correct scaling is not important. Predators of any body size will forage in such a regime immovably (swimming velocity v ≈0). However, for large larval lengths >10 mm and prey concentrations <10⁶ m⁻³, the scale can be defined as the average prey separation or as the predator's reactive distance. The effect of turbulence on the encounter rate decreases with the increasing size and velocity of the predator and with prey concentration. A simple one-dimensional prey-predator ecosystem model in the upper mixed layer is presented, which examines the relative importance of turbulence to growth in planktonic consumers. This effect is less for low prey densities <10⁴ m⁻³, when the initial predator biomass and constant growth rate term have a decisive influence. However, the effect of turbulence on the characteristics investigated increases with rising prey density, in which case the controlling factor is encounter rate and in the case of prey concentration, diurnal migration.
The invasive Asiatic freshwater bivalve Corbicula fluminea is regarded as a pest in several countries including Brazil. Two water birds native to South America, the limpkin Aramus guarauna and the common gallinule Gallinula galeata, are herein recorded preying on C. fluminea in a pond of an urban park in South-eastern Brazil. The exotic clam is becoming increasingly common in the diet of both these water birds. This trend is likely due to its increasing population and the consequent rarity of the habitual prey (apple snails and native clams) for the mollusc-specialised limpkin, besides being an accessible animal protein source for the omnivorous gallinule.
Eighteen species of birds of prey in the Netherlands were examined for helminth parasites: Accipitriformes - Accipiter gentilis (15 birds), A. nisus (9), Aquila pomarina (1), Buteo buteo (56), B. lagopus (4), Circaetus gallicus (2), Circus aeruginosa B (2), C. cyaneus (3), Pernis apivorus (5); Falconiformes - Falco coluinbarius (2), F. peregrinus (2), F. subbuteo (6), F. tinnunculus (31); Strigiformes — Asio flammeus (3), A. otus (35), Athene noctua (12), Strix aluco (19) and Tyto alba (15). Sixteen nematode species were found: Baruscapillaria falconis, Capillaria tenuissima, Eucoleus dispar, Pterothominx caudinflata, Cyathostoma americana, Porrocaecum angusticolle, P. depressum, P. spiralae, Physaloptera alata, P. apivori, Procyrnea leptoptera, P. seurati, P. spinosa, Spirocerca lupi, Synhimantus laticeps and Diplotriaena henryi. All species of birds were infected with nematodes with the exception of F. peregrinus. Eleven trematode species were present: Brachylaeme fuscatus, Echinostoma revolutum, Echinoparyphium agnatum, Strigea falconis, S. strigis, Parastrigea flexilis, Neodiplostomim spathoides, N. attenuation, Ichthyocotylurus platycephalus and Prosthogonimus cuneatus. Trematode infections were found in all birds except A. nisus, C. cyaneus, P. apivorus, F. columbarius, F peregrinus and A. flammeus. Centrorhynchus aluconis was the only identifiable acanthocephalan. Acanthocephalan infections were seen in A. nisus, B. buteo, C. gallicus, C. aeruginosus and S. aluco. Cestode infections were seen in 8 bird species. The cestodes could not be identified to the genus, because they were poorly preserved. Most findings are new host records for the Netherlands.
Though newts are exclusively carnivorous predators, non-prey items (silt, plants, skin sloughs) also have been found in their stomachs. There are no previous studies on this topic apart from casual reports. We conducted a dietary study of Alpine newts (Mesotriton alpestris) at two localities in the Czech Republic, focusing on the influence of sex, locality, month, and weight of digested prey on consumption of non-prey items. Localities were two fishless ponds (surface area <40 m2, depth <1 m) at an elevation of about 450 m. Both ponds were isolated from other water bodies and inhabited also by Smooth newts (Lissotriton vulgaris L.) and Common frogs (Rana temporaria L.). Newts were captured by net from the shores and stomach contents were extracted using a stomach flushing technique. We sampled 190 individuals. At least one non-prey item (i.e. silt, plants, skin sloughs) was found in 44% of newts’ stomachs. The most numerous items were plant fragments. The weight of consumed prey did not affect the presence of non-prey items in stomachs of newts. Locality (probably relating to prey availability) affected frequency of newts with plants and silt in their digestive tracts, but skin sloughs were consumed at both localities with the same frequencies. All non-prey items were consumed mainly at the beginning of the breeding season (year 1997) and with no difference in frequencies between males and females.
In the past 30 years, Daphnia has become a model organism in aquatic ecology. I review the changing concepts and paradigms in plankton ecology as reflected in the work on Daphnia. The availability of radiotracers favoured a new physiological approach that resulted in better energetic models and more reliable estimates of filtering rates. This led to deeper insights into the role of herbivore grazing on phytoplankton and microbial communities, and nutrient recycling. It provided a conceptual basis for general hypotheses on predictable seasonal successions (e.g. the PEG model). On the other hand, increasing knowledge about selective predation on zooplankton triggered population dynamic models and gave explanations for changing community structures. The Size-Efficiency-Hypothesis generated a framework for studies on trade-offs between competitive ability and susceptibility to predation. Daphnia was now in the centre of interaction-based concepts, being predator and prey at the same time. It was the backbone of practical applications of the theory in food-web manipulations. When ultimate factors came into the focus, Daphnia played an important role in explaining striking phenomena like diel vertical migration and cyclomorphosis. Its central position in food-webs, the unique propagation mode, easy cultivation and accessibility by molecular genetic methods made it a favourite object for studies in evolutionary ecology, concerning local ad a ptation, evolution of defences and life histories, induced phenotypic change, and genetic diversity. The large advantage of Daphnia over other biological model organisms is that its importance in pelagic freshwater systems is undoubtedly known. Hence there is a direct way of applying the results to ecological systems.
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