The increased population of the Wild Boar (Sus scrofa L.) in Europe

In this paper the recent population changes of the Wild Boar in different European countries is analysed through the study of hunting statistics. A simultaneous increase in numbers is observed throughout the whole area during the period 1965–1975. From 1975 onwards the population stabilizes itself apart from in peripheral areas like Finland. Potentially favourable factors which play a part in this process are discussed and certain reproductive and dispersive characteristics which favour its invasive behaviour are discussed.     

Study of thymocytes resistance to ionising irradiation in vitro

The influence of ionising irradiation with doses of 0.5, 1, 2 Gy upon the suspension of mice thymocytes was studied. The state of the system of lipid peroxidation-antioxidation activity and structural and functional state of cell membrane was studied. It was found that, 15 minutes' after irradiation POL processes are within the norm. But the content of vitamins A and E decreases (the former after 0.5 Gy, the latter after 1 Gy). Changes in structural and functional state of thymocyte membranes can be observed by using fluorescent probes. Particularly, it turned out that after irradiation accessibility of incorporated proteins increases, the polarity of lipids increases and the lipophility of membrane lipids decreases. These changes can lead to short-time increase in specific functional activity of cells, but they can cause rapid death of cells as well.     

Filtering Impacts of an Introduced Bivalve (Dreissena polymorpha) in a Shallow Lake: Application of a Hydrodynamic Model

Nonindigenous species may exert strong effects on ecosystem structure and function. The zebra mussel (Dreissena polymorpha) has been attributed with profound changes in invaded ecosystems across eastern North America. We explored vertical profiles of water flow velocity and chlorophyll a concentration in western Lake Erie, over rocky substrates encrusted with Dreissena, to assess the extent to which mussels influence coupling between benthic and pelagic regions of the lake. Flow velocity was always low at surveyed sites (less than or equal to 2.9 cm s^-1) and declined in direct proximity to the lakebed. Mean chlorophyll a concentration was also low (less than 5μg L^-1) at all sites and depths. Chlorophyll a concentration was positively correlated with distance above lakebed and was lowest (0.3μg L^-1) directly adjacent to the lakebed. Spatial patterns of zooplankton grazers could not explain observed vertical gradients in chlorophyll concentration. Hydrodynamic modeling revealed that filtering effects of Dreissena in a nonstratified, shallow basin depend mainly on upstream chlorophyll concentration, intensity of turbulent diffusion, feeding efficiency of the mussel colony, and the distance downstream from the leading edge of the mussel colony. In contrast to widespread perceptions that molluscs reduce phytoplankton concentration only adjacent to the lakebed, modeling scenarios indicated that depletion occurs throughout the water column. Depletion was, however, inversely proportional to distance above the lakebed. Simulation results are consistent with field-based observations made in shallow water habitats populated by large Dreissena populations in the Great Lakes and elsewhere. Results from this study indicate that zebra mussels strongly enhance coupling between pelagic and benthic regions in shallow lakes. Enhanced coupling between these regions explains, in part, high population densities of Dreissena and of many benthic invertebrates in ecosystems invaded by zebra mussels. Received 14 July 1998; accepted 25 March 1999.