INTRA- AND INTERSPECIFIC VARIATIONS IN CALCIUM CONTENT OF FRESHWATER MOLLUSCA IN RELATION TO CALCIUM CONTENT OF THE WATER

Analyses of calcium content of molluscs collected from 53 freshwaterhabitats on a naturally occurring calcium gradient between theCanadian Shield and limestone formations in southern Ontarioshowed both intraspecific and interspecific variations in relationto pH, total alkalinity, total hardness and calcium hardnessof the water. The calcium content of individuals is relatedto the calcium concentration of the water for only about halfof the species analysed. Two species (Sphaerium rhomboideumand Sphaerium simile) showed negative correlations, while six(Cincinnatia cincinnatiensis, Pisidium casertanum, Pisidiumcompressum, Sphaerium striatinum, Anodonta grandis grandis,and Elliptio complanata showed positive correlations beteencalcium content of individuals and environmental calcium content.In general, species associated with the sediments (e.g. bivalves)showed better calcium concentrations than did species associatedwith macrophytes (e.g. gastropods). (Received 12 July 1982;     

PRIMARY AND SECONDARY EFFECTS OF WATER CONTENT ON THE SPECTRAL REFLECTANCE OF LEAVES

Leaves of six species selected to represent a broad range in internal structure were collected in the field and studied in the laboratory to determine primary and secondary effects of water content on leaf spectral reflectance. Primary effects were those that resulted solely from the radiative properties of water. Secondary effects were those that could not be explained solely by these properties. Decreased leaf water content generally increased reflectance throughout the 400-2,500-nm wavelength range. For the aquatics Eichhornia crassippes and Nuphar luteum, the broadleaved trees Liquidambar styraciflua and Magnolia grandiflora, the cane-grass Arundinaria tecta, and the needle-leaved Pinus taeda, the sensitivity of reflectance to water content was greatest in the water absorption bands near 1,450, 1,940, and 2,500 nm. Sensitivity maxima occurred also between 400 and 720 nm, indicating secondary effects that resulted from decreased absorption by pigments. Secondary effects of water content on reflectance that were largely wavelength-independent, together with any wavelength-independent effects of leaf internal structure, were far less significant than primary and secondary effects resulting from decreased absorption by water and pigments, respectively.     

A NOTE ON THE THERMODURIC BACTERIAL CONTENT OF FARM WATER SUPPLIES

SUMMARY: Significantly higher thermoduric colony counts were obtained when 5 ml. of water were laboratory pasteurized in 5 ml. of sterile milk or 2 ml. of water were pasteurized in 8 ml. of sterile milk, than when 10 ml. of water were directly pasteurized; 86% of the water samples had higher thermoduric counts after pasteurization in milk. Large differences were not common, only 19% of the ratios being over 5 and 5% over 10. Aerobic sporing rods were dominant in the thermoduric microflora irrespective of the method of pasteurization.     

WATER CONTENT OF SLUGS (GASTROPODA:PULMONATA) IN NATURAL HABITATS, AND THE INFLUENCE OF CULTURE CONDITIONS ON WATER CONTENT STABILITY IN ARION ATER (LINNE)

10 species of slug were collected from a variety of habitats.Within species, water contents were relatively constant, andit was concluded that they were maintained by water uptake,mainly through the integument, together with appropriate cryptozoicbehaviour. Weights of A. ater individuals held outdoors didnot show large daily fluctuations. ^*Present address: Department of Zoology, East Mailing ResearchStation, Maidstone, Kent ME19 6BJ (Received 15 June 1982;     

METHODS OF ASSESSING THE SPORICIDAL EFFICIENCY OF AN ULTRA-HIGH-TEMPERATURE MILK STERILIZING PLANT I. EXPERIMENTS WITH SUSPENSIONS OF SPORES IN WATER

SUMMARY: A method of assessing the sporicidal efficiency of a UHT milk sterilizing plant operating on water is described. Water heavily contaminated with spores of a strain of Bacillus subtilis was filtered, after treatment in the plant, through membrane filters and the surviving spores estimated by incubation of the membranes in nutrient agar. With this plant a temperature of c . 135° caused a 99·99999% kill of B. subtilis spores. Confirmation of the lethal effects of temperatures above 135° was obtained by passing treated water into 10 gal churns containing sterile concentrated nutrient broth and incubating the churns.