Age Determination of Frogs and Toads (Amphibia, Anura) from North-western Europe

Age was determined in three anuran species inhabiting a temperate oceanic climate ( Rana temporaria, Bufo calamita and Bufo bufo ) by means of the histological structure of the phalanges. Narrow, haematoxylinophilic lines were visible in these, and evidence from the examination of subadults and frog ( R. temporaria ) recaptures showed the lines to be annual. The validity of using the lines as age indicators was tested most extensively on natural frog populations and the effects of endosteal resorption were not found to be significant. The evidence for this conclusion was provided directly by recapture data and indirectly by an analysis of histological measurements made on the phalanges.     

Variants of Myxococcus virescens Exhibiting Dispersed Growth. Growth and Production of Extracellular Enzymes and Slime

The growth of two strains of Myxococcus virescens exhibiting dispersed growth was followed in casamino acids (N III-C) media and casitone media. The changes in optical density, pH, pigmentation as well as the secretion of bacteriolytic and proteolytic enzymes, DNA and polysaccharides during growth were recorded. In both media the bacteria grew exponentially with a generation time of 4 (casitone) and 20 hours (N III-C) respectively. The maximal cell mass was about 4 times higher in casitone than in casamino acids media. The amounts of bacteriolytic enzymes produced by the two strains in N III-C medium were different but in casitone medium they were about equal and considerably higher. The maximal values of proteolytic enzymes were about the same in both media and always occurred later than the bacteriolytic maxima. Both activity peaks appeared before the phase of decline. The polysaccharide production reached a maximum during the stationary growth phase in both media. A higher value was reached during growth in casitone medium than in N III-C medium. During the phase of decline a second increase of polysaccharide in the medium appeared. No DNA could be detected in the cell-free solutions until the beginning of the phase of decline.     

A Note on a Selective Isolation Medium for the Thermophilic Actinomycete Thermomonospora chromogena

Thermomonospora chromogena was isolated from mushroom compost by spreading diluted suspensions on an agar medium containing kanamycin at 25 µg/ml. The antibiotic prevented the growth of other thermophilic actinomycetes on media incubated at 50°C and significantly reduced the growth of associated bacteria.