Comparison of osmoregulation between Adriatic and North Sea Carcinus

In two spatially isolated species — North Sea Carcinus maenas L. and Adriatic Carcinus mediterraneus Czerniavsky —osmoconcentration in hemolymph and Na-transport were investigated. The experiments were performed on crabs which had been long-term acclimated to sea water (1190 mOsmol/l) and to 50% sea water, and on individuals immediately after transfer from sea water to 50% sea water, until new steadystate conditions had been reached. About 10 to 12 h after transfer, a new steady state of total osmoconcentration as well as of the concentrations of the most representative cations Na, K, Ca, and Mg was attained. The hemolymph contents of Na and total osmotically active substances of the North and Adriatic Sea populations are significantly different when they are long-term acclimated to sea water and to 50% sea water. Total sodium fluxes, as calculated from influx and outflux experiments, are in the range 12.1 to 15.2 M Na/g/h in both species when acclimated to sea water. In 50% sea water, sodium fluxes are retarded, especially in C. maenas (6.6 M Na/g/h). This value is significantly lower than the corresponding value in C. mediterraneus (11.4 M Na/g/h). Differences are discussed on the basis of adaptation of the populations to their different environments.     

Conductive sodium entry in gill cells of the shore crab,Carcinus maenas

Isolated posterior gills of shore crabs, Carcinus maenas, collected from the Baltic Sea, were perfused and bathed with sea water and solutions of alkali chlorides. The preparation was used to measure fluxes of sodium from the external medium across the gills into the hemolymph and to determine transepithelial potential differences (PDs). Internally negative active transport PDs resulted from perfusion and bathing the gills symmetrically with the same medium (50% sea water). Passive (asymmetry) PDs following employment of 100% sea water as internal and 50% sea water as external medium were — in contrast to symmetry PDs — insensitive to cyanide and ouabain. This result indicates that the gill recognized the desired hyperosmotic state and responded by switching off the active transport component observed under symmetry conditions. Diffusional potential differences and fluxes of Na⁺ were inhibited by the externally applied diuretic amiloride. Gradients of pure alkali chlorides between medium and blood were accompanied by cation specific PDs. These PDs and their amiloride sensitivity were inversely related to the diameter of the unhydrated cation and allowed the calculation of the permeability sequence P: Li⁺>Na⁺>K⁺>Rb⁺>Cs⁺>Cl^-. The results obtained show that the permeability of the gills to cations greatly exceeds that to anions. In addition, these findings indicate that the initial amiloride-sensitive step in Na⁺ transport across the gill is not represented by an electroneutral sodium/proton exchange but by a conductive mechanism.     

Seasonal variability of endotoxin in ambient fine particulate matter

Endotoxin is a toxic, pro-inflammatory compound that has been detected in indoor air and dust in homes and occupational settings, and also in outdoor air. Data on the outdoor sampling of endotoxin are limited. Currently, little is known about the seasonal variation and influence of temperature on outdoor endotoxin levels. In the present study, we report endotoxin levels in fine fraction particulate matter with a 50% aerodynamic cutoff diameter of 2.5 microm (PM2.5) and describe the seasonal variation of endotoxin in Munich, Germany. In 1999-2000, PM2.5 was collected at forty outdoor monitoring sites across Munich. Approximately four samples were collected at each site for a total of 158 samples. Endotoxin concentrations in the PM2.5 samples were determined using the kinetic chromogenic Limulus Amebocyte Lysate (LAL) assay. The geometric mean endotoxin concentration was 1.07 EU mg PM2.5(-1) (95% C.I.: 0.915-1.251) or 0.015 EU m(-3) of sampled air (95% C.I.: 0.013-0.018). Munich endotoxin levels were significantly related to ambient temperature (p < 0.0001) and percent relative humidity (p < 0.0001). Sampling periods with higher average temperatures yielded higher levels of endotoxin in PM2.5 (r = 0.641), whereas decreases in percent relative humidity were associated with increased endotoxin levels in PM2.5 (r = -0.388). Endotoxin levels were significantly higher during the warmer seasons of spring [means ratio (MR): 2.5-2.7] and summer (MR: 2.1-3.0) than during winter. Although temperature and relative humidity do not explain all of the variability in endotoxin levels, their effects were significant in our data set. Temperature effects and seasonal variation of endotoxin should be considered in future studies of outdoor endotoxin.     

Postgraduale Weiterbildung, Nachwuchsf?rderpreis 2005, Jahrestagung 2006 in Landau

Ohne Zusammenfassung     

Variation of stabilised,microbial and biologically active carbon and nitrogen in soil under contrasting land use and agricultural management practices

Land use and agricultural practices modify both the amounts and properties of C and N in soil organic matter. In order to evaluate land use and management-dependent modifications of stable and labile C and N soil pools, (i). organic C and total N content, (ii). microbial (C(mic)) and N (N(mic)) content and (iii). C and N mineralisation rates, termed biologically active C and N, were estimated in arable, grassland and forest soils from northern and southern Germany. The C/N-ratios were calculated for the three levels (i)-(iii) and linked to the eco-physiological quotients of biotic-fixed C and N (C(mic)/C(org), N(mic)/N(t)) and biomass-specific C and N mineralisation rate (qCO(2), qN(min)). Correlations could mainly be determined between organic C, total N, C(mic), N(mic) and C mineralisation for the broader data set of the land use systems. Generally, the mineralisation activity rate at 22 degrees C was highly variable and ranged between 0.11 and 17.67 microg CO(2)-C g(-1) soil h(-1) and -0.12 and 3.81 microg (deltaNH(4)(+)+deltaNO(3)(-))-N g(-1) soil h(-1). Negative N data may be derived from both N immobilisation and N volatilisation during the experiments. The ratio between C and N mineralisation rate differed significantly between the soils ranging from 5 to 37, and was not correlated to the soil C/N ratio and C(mic)/N(mic) ratio. The C/N ratio in the 'biologically active' pool was significantly smaller in soils under conventional farming than those under organic farming systems. In a beech forest, it increased from the L, Of to the Ah horizon. The biologically active C and N pools refer to the current microbial eco-physiology and are related to the need for being C and N use efficient as indicated by metabolic qCO(2) and qN(min) quotients.     

Behavioral diversification in a young species flock of pupfish (<Emphasis Type="Italic">Cyprionodon</Emphasis> spp.): shoaling and aggressive behavior

Increasing empirical and theoretical evidence supports the idea that sympatric speciation is operating, for example, in species flocks comprising several closely related fish species within one lake. Divergent natural selection (promoting spatial and food niche partitioning) and sexual selection (assortative mating) have been identified as key selection factors in intralacustric adaptive radiations. However, the evolution of social behaviors accompanying such adaptive radiations is less well understood. Using a phylogenetically young species flock of pupfish (Cyprinodon spp.) as a model, we examined differences among six sympatric species and compared their shoaling, aggressive, and territorial behaviors with that of a sister species (C. artifrons). Despite an estimated age of the species flock of less than 8,000 years, pronounced behavioral differentiation was found. C. simus, the smallest species in the flock, shoaled more than the other species and was less aggressive and less territorial than C. beltrani. F₁-hybrids between C. simus males and C. beltrani females showed an intermediate expression of shoaling and aggressive behavior. Niche partitioning among the members of this species flock appears to be accompanied by rapid divergent evolution of social behaviors. We discuss the potential role of phenotypic plasticity and within-species variation of social behaviors for such rapid behavioral diversifications in sympatric speciation processes.     

Recovery agenda for sustainable development post COVID-19 at the country level: developing a fuzzy action priority surface

Environment, Development and Sustainability - As a response to the urgent call for recovery actions against the COVID-19 crisis, this research aims to identify action priority areas...