Effects of pH on the Fertilization Response of the Medaka Egg

The effects of changing the intra- and extracellular pH on the cortical reaction and sperm penetration into eggs were examined in Oryzias latipes. When eggs were inseminated in a saline adjusted to various pH values with different buffers, fertilization took place normally over a wide range of external pH (pH₀) from about 6 to 10 with a peak at 7 to 8.5. The primary causes of the reduced fertilization were impaired motility or immobility of the spermatozoa in the acidic saline and the swelling of the chorion in the alkaline saline. A rise in the intracellular pH (pH_i) shortly after commencement of the cortical reaction was found by monitoring the color of a pH indicator micro-injected into the cytoplasm. The experimental results obtained by microinjection of various pH buffers (pH 4–12) suggest that the intracellular membrane fusion of the plasma membrane with the cortical alveolar membrane (CABD) is affected by the acidic pH_i while the propagation of the CABD and the intercellular membrane fusion between the plasma membranes of the egg and the spermatozoon are affected by the acidic pH₀.     

STUDIES ON THIAMINE TRIPHOSPHATE II. THIAMINE TRIPHOSPHATE AS PHOSPHATE DONOR

Yeast hexokinase, muscle fructokinase and glucokinase and liverhomogenate have no activity of transferring phosphate from TTPto hexose. A fraction precipitated from yeast autolysate at0.5–0.7 saturation of ammonium sulfate rendered TTP totransfer its terminal phosphoric residue to ADP to form ATP. (Received November 25, 1961; )     

The land–atmosphere water flux in the tropics

Tropical vegetation is a major source of global land surface evapotranspiration, and can thus play a major role in global hydrological cycles and global atmospheric circulation. Accurate prediction of tropical evapotranspiration is critical to our understanding of these processes under changing climate. We examined the controls on evapotranspiration in tropical vegetation at 21 pan-tropical eddy covariance sites, conducted a comprehensive and systematic evaluation of 13 evapotranspiration models at these sites, and assessed the ability to scale up model estimates of evapotranspiration for the test region of Amazonia. Net radiation was the strongest determinant of evapotranspiration (mean evaporative fraction was 0.72) and explained 87% of the variance in monthly evapotranspiration across the sites. Vapor pressure deficit was the strongest residual predictor (14%), followed by normalized difference vegetation index (9%), precipitation (6%) and wind speed (4%). The radiation-based evapotranspiration models performed best overall for three reasons: (1) the vegetation was largely decoupled from atmospheric turbulent transfer (calculated from Ω decoupling factor), especially at the wetter sites; (2) the resistance-based models were hindered by difficulty in consistently characterizing canopy (and stomatal) resistance in the highly diverse vegetation; (3) the temperature-based models inadequately captured the variability in tropical evapotranspiration. We evaluated the potential to predict regional evapotranspiration for one test region: Amazonia. We estimated an Amazonia-wide evapotranspiration of 1370 mm yr⁻¹, but this value is dependent on assumptions about energy balance closure for the tropical eddy covariance sites; a lower value (1096 mm yr⁻¹) is considered in discussion on the use of flux data to validate and interpolate models.     

Habitat differences and occurrence of native and exotic ants on Okinawa Island

Ant fauna on Mallotus japonicus, a shrub with extrafloral nectaries, was investigated in two types of habitat (the villages and the forest‐edges) on subtropical Okinawa Island, Japan. Twenty and 16 ant species were found, including 11 and 6 tramp species in the villages and in the forest‐edges, respectively. Occurrence of tramp species was higher in the villages than in the forest edges, supporting the idea that tramp species tend to dominate in disturbed habitats. Nevertheless, the richness of native ants was almost the same across the two habitat types. Consequently, the ant species diversity on M. japonicus appeared higher in the villages. However, monitoring has to be continued to determine whether the above findings represent a stable phenomenon of the community or just a temporary state.     

Culling Versus Density Effects in Management of a Deer Population

Abstract: Wildlife managers often manipulate hunting regulations to control deer populations. However, few empirical studies have examined the level of hunting effort (hunter-days) required to limit population growth and demographic effects through harvesting of females. Moreover, the relative importance of density effects on population growth has not been quantified. We reconstructed a sika deer [Cervus nippon] population over a period of 12 years (1990–2001) using age- and sex-specific harvest data. Using cohort analysis, we analyzed population dynamics, focusing on 1) the relationship between hunting effort and hunting-induced mortality rate, 2) relative contributions of hunting mortality and recruitment of yearlings to annual changes in population growth rate, and 3) annual variation in recruitment rate. Population size increased until 1998 and declined thereafter. The population growth rate changed more in response to annual changes in recruitment rate than hunting mortality rate. Temporal variation in recruitment rate was not controlled by birth rate alone; direct density dependence, intensities of hunting mortality for fawns, and for females (≥2 yr of age), which accounted for the fawn survival rate, were required as factors to explain temporal variation. Density effects on the recruitment rate were not strong enough to regulate the population within the study period; high hunting mortality, with intensive female harvesting, was necessary to prevent population growth. Hunting effort was a good predictor of the hunting mortality rate, and female harvest had a negative effect on the recruitment rate through fawn survival. We suggest that >3,500 hunter-days and prioritization of female harvesting are required to prevent increases in this deer population.     

Food web structure of the fungivorous insect community on bracket fungi in a Bornean tropical rain forest

1. If fungivorous insect diversity is maintained by host specialisation on particular fungi, it should be higher in the tropics than in temperate or boreal regions owing to high macrofungus species diversity. 2. To reveal the community and food web structure of fungivorous insects on bracket fungi, fungivorous insects were collected from 427 fruiting bodies belonging to 22 genera throughout the development and deterioration process in a 3‐ha plot of lowland dipterocarp tropical rain forest on Borneo Island. 3. Eight hundred and twenty‐nine individuals of 82 coleopteran species in 13 families from 111 fruiting bodies of 15 fungal genera were collected. Tenebrionidae and Staphylinidae were most common. Fifty‐three and 19 insect species were observed on Ganoderma and Phellinus, respectively. The numbers of insect species and individuals on a particular fungal genus were positively correlated with the abundance of that fungal genus. 4. Quantitative food web analysis revealed a high degree of specialisation at the whole‐community level. At least 65% of insect individuals were observed on Ganoderma at every stage of development and deterioration. Diverse insects coexist on one dominant fungal genus, Ganoderma, in contrast to our hypothesis. 5. The high abundance of Ganoderma fruiting bodies, which lack obvious defences against insect feeding, probably influences the bracket fungus–insect food web in this tropical rainforest.     

Receptors to Dolichos biflorus Agglutinin

Dolichos biflorus agglutinin (DBA), a lectin specific to N-acetylgalactosamine residue, identifies cell surface markers on teratocarcinoma cells. These receptors are found in very limited types of adult tissues. In the present investigation, mouse embryos collected on days 1 (2-cell) to 3 (early blastocyst) were shown to be stained with FITC-conjugated DBA. Embryos homozygous for t ^w32 were also positively stained. These results suggest that receptors for DBA on preimplantation embryos include components distinct from Forssman, F9, and SSEA-1 antigens.