Metabolic effects of swimming velocity and water temperature in the muskrat (Ondatra zibethicus)

Metabolic rates, VO2, were studied in four muskrats (Ondatra zibethicus) swimming in a water channel at velocities of 0.2 to 0.75 m/s in water at temperatures of 25 and 30 degrees C. At both water temperatures, VO2 increased linearly with increasing swimming velocity. The VO2 was higher for muskrats swimming in water at 25 than 30 degrees C. The metabolic performance of swimming appears to be influenced by the interaction of swimming velocity and water temperature.     

Rare and infrequent southern African grasses: assessing their conservation status and understanding their biology

The taxonomic treatment for the grasses of southern Africa was one of the first to be based on computerised data and the DELTA system. These data, based on over 70,000 herbarium records, are amenable for analysis of species parameters including abundance, frequency and distribution. This information is suitable for the allocation of species into the seven categories of rarity proposed by Rabinowitz using a combination of habitat specificity (“Narrow” or “Broad”), population structure (“Sparse” or “Abundant”) and distribution (“Restricted” or “Widespread”). We compare the species lists obtained for each combination of these three aspects to published Red Data Lists (RDLs) for southern and South Africa. Ninety-three species are placed in the most sensitive or potentially threatened category (Narrow habitat, Sparse populations and Restricted distributions; RSN). This is substantially more than the number of species listed in current RDLs for the region. Chi-square tests indicate a statistically significant bias in taxa from the Fynbos Biome for three of the categories (RSN, RAN and WSN), from the Savanna Biome for the WAN category and from the arid Succulent Karoo and Desert Biomes for the RAB category. Analyses of habitat requirements indicate that many grasses listed (especially those associated with a “Narrow” habitat) are found in some form of wetlands (ephemeral or permanent), especially those at higher altitudes (montane). Despite concerns about the subjective nature in determining the boundaries between the categories, this method is shown to provide a meaningful and valuable list of taxa that require prioritisation for more detailed assessment according to the IUCN criteria.     

Protective properties of Vi-antigen preparations as dependent on their adhesin content

Adhesins contained in the preparation of Vi-antigen have been found to enhance its immunogenic and protective properties. In the preparations of Vi-antigen obtained from Salmonella typhi and Citrobacter freundii the presence of two antigenic determinants has been revealed. One of them is associated with the Vi-receptor and the other determinant, with adhesin. Both determinants take part in the protection of mice from Salmonella infection.