Influence of soil temperature on methane emission from rice paddy fields

Methane emission rates from an Italian rice paddy field showed diel and seasonal variations. The seasonal variations were not closely related to soil temperatures. However, the dieL changes of CH₄ fluxes were significantly correlated with the diel changes of the temperature in a particular soil depth. The soil depths with the best correlations between CH4 flux and temperature were shallow (1–5cm) in May and June, deep (10–15cm) in June and July, and again shallow (1–5 cm) in August. Apparent activation energies (E_a) calculated from these correlations using the Arrhenius model were relatively low (50–150 kJ mol^–1) in May and June, but increased to higher values (80–450 kJ mol^–1) in August. In the laboratory, CH₄ emission from two rice cultures incubated at temperatures between 20 and 38°C showed E . values of 41 and 53 kJ mol^–1) Methane production in anoxic paddy soil suspensions incubated between 7 and 43°C showed E values between 53 and 132 kJ mol^–1 with an average value of 85 kJ mol^–1) and in pure cultures of hydrogenotrophic methanogenic bacteria E _a values between 77 and 173 (average 126) kJ mol^–1. It is suggested that diel changes of soil properties other than temperature affect CH₄ emission rates, e.g. diel changes in root exudation or in efficiency of CH⁴ oxidation in the rhizosphere.     

Seasonal changes in the oxygen storage capacity and aerobic dive limits of the muskrat (Ondatra zibethicus)

Summary The oxygen storage capacity and partitioning of body oxygen reserves were compared in summer-and winter-acclimatized muskrats (Ondatra zibethicus). Blood volume, blood oxygen capacity, and skeletal muscle myoglobin content were higher in December than in July (P<0.02). Total lung capacity increased only slightly in winter (P>0.05). The oxygen storage capacity of a diving muskrat was calculated at 25.2 ml O₂ STPD · kg^-1 in July, compared to 35.7 ml O₂ STPD · kg^-1 in December. Blood comprised the major storage compartment in both seasons, accounting for 57% and 65% of the total oxygen stores in summer and winter, respectively. Based on available oxygen stores and previous estimates of the cost of diving, the aerobic dive limit (ADL) increased from 40.9 s in July to 57.9 s in December. Concurrent behavioral studies suggested that most voluntary diving by muskrats is aerobic. However, the proportion of dives exceeding the calculated ADL of these animals was shown to vary with the context of the dive. Only 3.5% of all dives initiated by muskrats floating in the water exceeded their estimated ADL. Provision of a dry resting site and access to a submerged food source increased this proportion to 18–61%, depending on the underwater distance that foraging muskrats were required to swim. Serial dives exceeding the estimated ADL were not accompanied by extended postdive recovery periods.Abbreviations ADL acrobic dive limit - Hb hemoglobin - Hct hematocrit - Mb myoglobin - PaO₂ arterial O₂ tension - STPD standard temperature and pressure, dry     

Zooplankton community changes in Lake Kinneret (Israel) during 1969–1985

Long-term records (1969–1985) of zooplankton density in Lake Kinneret indicated significant reduction of biomass (Copepods, Cladocera, Rotifera) and production (Copepods, Cladocera). Nauplius and adult copepod densities decreased but those of copepodites did not change. Mesocyclops was suppressed more than the smaller Thermocyclops and males of both genera became more abundant relative to the larger females. Ratios of small/large Cladocera densities became higher. Numbers of total cladocerans were stable, and therefore reduction of Cladocera grazing capacity is assumed. The abundant Keratella spp. were reduced. It is likely that intensification of fish visual-attack-predation pressure shifted the size-class structure towards smaller adult copepods and cladocerans. Reduction of Keratella spp. and copepod nauplii was probably affected by increasing pressure of fish filter-feeders. Data on fish food consumption, feeding behaviour and fisheries management suggested their direct impact on long-term changes of zooplankton in Lake Kinneret.     

Fatness and fat patterning in relation to age changes and menarche

The present study assesses changes with age in fatness and fat patterning in a cross-sectional sample of Spanish schoolgirls from 6 to 16 years of age living in an urban area (Madrid). Arm muscle area and arm fat area were derived from middle-upper arm anthropometry. Body mass index (weight/height²) and the sum of the skinfold thicknesses at three sites (triceps, subscapular and suprailiac) were computed as indices of adiposity; and two indices of subcutaneous fat distribution were also defined: the natural logarithms of subscapular/triceps and suprailiac/triceps skinfold thickness ratios. Changes with age in these variables are described, including some pattern changes found in amount of fatness as well as in fat distribution at pubescence. At this time, there is a plateau in fat deposition, and even a fat loss the average (at triceps site). Prior to pubescence, subcutaneous fat distribution changes from «pheripheral» to a more generalized pattern, but no well-defined pattern of change is found after the onset of menarche. Furthermore, the effect of the onset of puberty on all these variables is analyzed.     

Quantitative changes of the C-cell population in the rat thyroid during postnatal ontogenesis

Summary The number and distribution of C-cells in the rat thyroid gland, have been investigated during postnatal ontogenesis from birth to 120 days of age. The argyrophilic and metachromatic properties of these cells were used to identify them. In the thyroid of newborn rats the C-cells do not exhibit argyrophilia and metachromasia. These reactions appear at 10 days and can be seen at all subsequent ages. The number of C-cells shows a parallel increase with age as demonstrated by the change in the proportion of C-cellsF-cellscolloidstroma during development. A marked increase in C-cells was found at 50 days of age when the proportion of C-cells rose to 27.67% from the value of 16.78% at 30 days. At 70 days a decrease was noted (20.50%) which hardly changed until 120 days of age (22.20%). The numerical increase in C-cells occurs at the expense of the follicular epithelium and stroma.The C-cells occupy elongated islet-like region in the central part of the lobe, decreasing in number towards the periphery where no C-cells are present. The long axis of the C-cells area is parallel with the longitudinal axis of the lobe. The area of C-cells is largest at the centre of the lobe, corresponding to the territory of the peak of the Gaussian curve for the numerical distribution of C-cells.     

Host dietary changes and the hindgut fauna of cockroaches

Peregrine Pauline C. 1974. Host dietary changes and the hindgut fauna of cockroaches. International Journal for Parasitology4: 645–656. The effects of changes in the diet of Periplaneta americana on Hammerschmidtiella diesingi (Nematoda), nematode larvae, Nyctotherus ovalis (Ciliata), Endamoeba blattae (Lobosa), Lophomonas striata (Zooflagellata) and Monocercomonoides orthopterorum (Zooflagellata) have been studied. All species are found in the hindgut of the host and appear to be supported to advantage by slightly different dietary fractions thus enhancing coexistence. Interspecific competition seems to be reduced by both spatial and dietary factors although most species tend to aggregate in a ‘preferred zone’ 30–45 per cent along the length of the hindgut. Under conditions of stress, distribution often expands. Intraspecific competition also appears to be partially controlled by dietary preferences, male, female and larval nematodes responding to differing dietary fractions. Effects on H. diesingi are closely paralleled by those on Thelastoma attenuatum (Nematoda), also parasitic in the hindgut, indicating a very finely balanced system of coexistence. Some of the parameters which may be involved are discussed. Almost all parasites were adversely affected by synthetic diets.     

Seasonal changes in the prolactin cell of the pituitary gland of the freshwater stickleback,Gasterosteus aculeatus,form leiurus

Summary The relative volume of the RPD region of the pituitary gland of Gasterosteus aculeatus form leiurus was greater in animals collected in the spring than in winter. A morphometric analysis of the prolactin cells from spring animals showed only slight changes in cell ultrastructure compared with winter animals. However, in spring the prolactin cells apparently formed and released more secretory granules. Three distinct sites for the release of secretory granules are described. A preliminary study of the response of prolactin cells from spring animals to 70% sea water did not reveal any large scale changes in cell ultrastructure. The significance of this finding is discussed. It is concluded that although the freshwater stickleback cannot be regarded as physiologically hypophysectomised: with regard to prolactin secretion in the winter, it still shows a seasonal change in prolactin cell ultrastructure.This work formed part of a thesis submitted for the degree of Doctor of Philosophy in 1973 and for which the author was in receipt of an S.R.C. studentship. My thanks are due to Dr. M.P. Ireland for his support and supervision throughout the course of the work.     

Infectivity and Recovery of Tetrahymena pyriformis Strain S from Adult Female Cockroaches (Periplaneta americana)*

Hemocoelomic injection of 5,800–8,000 cells of Tetrahymena pyriformis strain S per female cockroach resulted in lethargy of the insects within 24 hr and death within 72 hr. Ciliates could be recovered 24–48 hr after injection of these amounts of ciliates. Inoculation of smaller numbers of cells resulted in no apparent ill effects to the insects and ciliates could not be recovered. After recovery from cockroaches and reestablishment in axenic culture, the ciliates were rounded and contained large numbers of lipid droplets which decreased on continued cultivation. The ciliates underwent a sequence of morphologic alterations involving a decrease in length and width to form ovoid cells, an approach to the pyriform shapes (but smaller than normal size), an elongation to an abnormal length/width ratio, and then, after 6 days in culture, a return to the normal shape with usual dimensions.     

Physical and chemical features of a vernal temporary pond in Western Canada

Temporal changes in physical and chemical features of a vernal temporary pond in western Canada are described for the 7-week duration of the pond. Average water loss through evaporation was 3 m³/day. Daily temperature ranges of 11 and 12° were frequent. Specific conductance, hardness and bicarbonate alkalinity increased progressively in proportion to the decrease in pond volume. Increase in chlorides was much less than predicted from evaporative concentration. Sulphates increased rapidly during the filling phase but then decreased steadily during the remaining weeks. The decline is attributed to uptake by meadow vegetation. Other biologically important ions examined exhibited no distinct patterns. The relative importance of evaporation, capillary creep and biological uptake processes is discussed.     

Activity of enzymes involved in lignin biosynthesis in swede root disks

The activity of nine enzymes involved in the biosynthesis of lignin precursors has been studied during the ageing of swede root disks in the presence and absence of ethylene. Peroxidase, aromatic alcohol dehydrogenase and phenylalanine transaminase show very little change in activity during ageing under either ageing condition. O-methyl transferase, shikimate dehydrogenase and ferulyl CoA reductase show only a 2–3 fold increase on ageing and are relatively insensitive to ethylene treatment. A third group (comprising phenylalanine ammonia lyase, cinnamic acid-4-hydroxylase and hydroxycinnamate CoA ligase) show 20–30 fold increase on ageing and are most sensitive to ethylene treatment. Phenylalanine ammonia lyase and cinnamic acid-4-hydroxylase behave very similarly in respect of their time course of ageing and in their responses to metabolic inhibitors such as cycloheximide, puromycin and actinomycin D. In addition the properties of the O-methyl transferase of swede root tissue are described.