Adult survivorship, population density, and body size in sympatric populations of Aedes triseriatus and Aedes hendersoni (Diptera: Culicidae).
Explore the source record for details and available documents.
Aedes↗
SEARCH · Search PubMed
Results for “population density”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Host population density as the major determinant of endoparasite species richness in floodplain fishes of the upper Paraná River, Brazil.
A comparative analysis of parasite species richness was performed across 53 species of fish from the floodplain of the upper Paraná River, Brazil. Values of catch per unit effort, CPUE (number of individuals of a given fish species captured per 1000 m(2) of net during 24 h) were used as a rough measure of population density for each fish species in order to test its influence on endoparasite species richness. The effects of several other host traits (body size, social behaviour, reproductive behaviour, spawning type, trophic category, feeding habits, relative position in the food web, preference for certain habitats and whether the fish species are native or exotic) on metazoan endoparasite species richness were also evaluated. The CPUE was the sole significant predictor of parasite species richness, whether controlling for the confounding influences of host phylogeny and sampling effort or not. The results suggest that in the floodplain of the upper Paraná River (with homogeneous physical characteristics and occurrence of many flood pulses), population density of different host species might be the major determinant of their parasite species richness.
Animals↗
Susceptibility to rubella infection in females at high risk. Immune protection associated to population density.
Susceptibility to rubella in 428 Mexican females of childbearing age from four sanitary areas confined to a Mexican State (Queretaro) was determined. Members of the group were residents of urban and rural communities and selected by random sampling. Anti-viral antibodies were determined by inhibition of haemagglutination. Concentration was expressed as International Units of IgG anti-rubella haemagglutinin (IU/ml). Antibody concentrations lower than 15.6 (IU/ml) were regarded as non-protective. The percentage of women immune-protected to rubella in the areas varied from 28.8 to 75.6 with an average of 61.9. The difference in percentages of immune-protected females within the areas was statistically significant (chi 2 = 48.26 and p < 0.001). Immune protection was associated to population density, with less protection in less populated areas. Our results differ from the reported values of a serosurvey performed in the same state one year before: immune protection 61.9% versus 79.96%, respectively.
Adolescent↗
Relation between population density and body size in stream communities.
The existence of a general relation between population density and body size in animal assemblages has been debated because of known biases and ambiguities in the published data and data handling. Using new comprehensive data sets from two geographically separated stream communities that encompass 448 and 260 invertebrate taxa with a wide range of body sizes, we show that an inverse proportionality between density and body size is a consistent feature in these communities. The scaling across taxa is not statistically different between the two systems, indicating a convergent pattern of communities. Variation in the regression slope among different taxonomic groups indicates that these communities are not governed universally by a single ecological or energetic rule.
Analysis of Variance↗
[Effect of the population density of the tick Ornithodoros papillipes (Argasidae) on its experimental oviposition].
It has been established under laboratory conditions that in ticks O. papillipes there exists an intrapopulation regulation of their number depending on the population density. The course of the regulation is as follows: with increasing density decreases the fecundity of females, increases the mortality of eggs and imago, increases the duration of oviposition and development of eggs.
Animals↗
Loss of cell-population-density-dependent incorporation of fucose into the lipid fraction of cultured human tumour cells.
The incorporation of radioactively labelled fucose into the lipid fraction of cultured normal human cells and several human tumour-cell lines was examined as a function of the cell population density. Normal cells exhibited a density-dependent pattern of incorporation, whereas in tumour cells the radioactivity incorporated was independent of the cell population density. An exception was found among the tumour cells, which suggests a possible correlation between the loss of this marker and the ability to produce tumours.
Cell Count↗
Fucolipid metabolism as a function of cell population density in normal and murine sarcoma virus-transformed rat cells.
The incorporation of isotopically labeled fucose into the lipids of normal and murine sarcoma virus-transformed rat cells as a function of cell population density was examined. When normal cells were seeded at low cell density, the levels of the major fucolipids, i.e., fucolipids III and IV, were substantially reduced, but then they increased as the cells approached confluency. This variation in synthesis of fucolipids III and IV appeared to be primarily related to cell density and not to cell growth. Chase experiments revealed that the reduced level of fucolipids III and IV in sparse normal cells is due to decreased synthesis rather than to increased catabolism. In contrast to the observations with normal rat cells, the high level of fucolipid III and the low level of fucolipid IV in murine sarcoma virus-transformed rat cells was shown to be independent of cell population density.
Animals↗
Temperature and population density effects on feeding activity of Stomoxys calcitrans (Diptera: Muscidae) on cattle.
The relationship of population density and temperature to feeding activity of stable flies, Stomoxys calcitrans (L.), on cattle was studied by placing cattle in constant temperature chambers with controlled fly density and temperature. The number of flies per front leg declined within hours after release but increased with fly density and temperature. The time flies spent on the host during a 5.5-h exposure period ranged from < 2.5 min at temperature < 16 degrees C to > 34 min when temperature was > 20 degrees C. Estimates of the temperature threshold for flight ranged from 10.7 to 20.1 degrees C and were influenced by density and time after release. Nearly 45% of the feeding flies were on the front legs, and this proportion was unaffected by density, temperature, and time after release. In the field, the number of flies per foreleg also was influenced by density and temperature. Estimated flight threshold was 10.7 degrees C, low enough to allow flight during 41-95% of the daylight hours from May through October in southern Alberta.
Animals↗
Sensitivity of transformation to small differences in population density during serial passage of NIH 3T3 cells.
Early passages of the NIH 3T3 mouse cell line undergo spontaneous neoplastic transformation leading to the development of transformed foci if grown to confluence in 2% (vol/vol) calf serum (CS) and left there for more than a week. Transfer of the postconfluent cultures results in the appearance of large numbers of transformed foci; many of them are larger and denser than those in the original culture. If the cells are continually kept at low population densities by frequent passages in 10% CS, they lose the capacity to undergo spontaneous transformation. If however the low-density passages are made in 2% CS or in 10% (vol/vol) fetal bovine serum, both of which support lower growth rates and saturation densities than does 10% CS, they gain the capacities to grow to high saturation densities and produce more foci when grown to confluence in 2% CS. These increases are proportional to the population densities used in the frequent passages, although the densities are all kept well below confluence. We conclude that the combined constraints of submaximal serum plus those of the limited cell contacts of the low cell densities used here elicit an adaptive response that endows the entire population with increased growth capacity. The increased growth capacity of the heterogeneous population in turn increases the capacity of a fraction of the population to initiate distinctive transformed foci. Similar studies have indicated that the capacity of cells to produce tumors and metastases in mice and rats is enhanced by prior maintenance at high density in culture. We propose the concept of progressive state selection to account for the general increase in the growth capacity of cells that is elicited by moderate constraints on their growth and metabolism.
3T3 Cells↗
The effect of food abundance on territory size and population density of juvenile steelhead trout (Oncorhynchus mykiss).
Optimal territory size models predict a decrease in territory size with increasing food abundance. However, most of these models may not be applicable to juvenile salmonids in streams, because they defend contiguous territories at high densities. The optimal size of a contiguous territory is predicted to (1) be independent of food abundance when food is rare and (2) decrease only when food abundance is high enough to induce a reduction in territory size below the contiguous optimum. To test these predictions, we raised equal densities of juvenile steelhead trout in outdoor stream channels over a 32-fold range of food abundance in the absence of emigration for 25 days. Increasing competition for scarce food resulted in increasing mortality, higher willingness to emigrate, higher variance in body mass, lower growth, lower population density and lower biomass. The size of territories decreased with increasing local population density, and increased with increasing body size. However, territory size did not change with food abundance, a result consistent with the prediction of a contiguous territory size model. On average, total salmonid biomass increased 5.7 times in response to the 32-fold increase in food abundance. Our data provide strong support for an earlier quantitative relationship between the abundance of stream salmonids and their food.
Animals↗
Local bandwidth selection for kernel estimation of population densities with line transect sampling.
Seber (1986, Biometrics 42, 267-292) suggested an approach to biological population density estimation using kernel estimates of the probability density of detection distances in line transect sampling. Chen (1996a, Applied Statistics 45, 135-150) and others have employed cross validation to choose a global bandwidth for the kernel estimator or have suggested adaptive kernel estimation (Chen, 1996b, Biometrics 52, 1283-1294). Because estimation of the density is required at only a single point, we investigate a local bandwidth selection procedure that is a modification of the method of Schucany (1995, Journal of the American Statistical Association 90, 535-540) for nonparametric regression. We report on simulation results comparing the proposed method and a local normal scale rule with cross validation and adaptive estimation. The local bandwidths and normal scale rule produce estimates with mean squares that are half the size of the others in most cases. Consistency results are also provided.
Animals↗
Changes in serum corticosterone concentration of laying hens as a response to increased population density.
The response of adrenal glands of Single Comb White Leghorn laying hens housed under different population densities was studied. The birds were reared in floor pens until they were 19 weeks of age, after which they were housed in cages. Cage size was 30.5 X 50.8 cm. Three, four, or five birds were housed per cage. Corticosterone concentrations were measured in all birds 48 and 96 hr following housing in cages and weekly thereafter for 6 weeks. Corticosterone concentrations were consistently higher in the serum of birds housed five per cage than in birds housed three or four per cage. It was concluded that in order to minimize physiological stress in cage layers, more than 387 cm2 per bird should be considered.
Adrenal Glands↗
Variations in adult body mass in roe deer: the effects of population density at birth and of habitat quality.
Body mass is a key determinant of fitness components in many organisms, and adult mass varies considerably among individuals within populations. These variations have several causes, involve temporal and spatial factors, and are not yet well understood. We use long-term data from 20 roe deer cohorts (1977-96) in a 2600 ha study area (Chizé, western France) with two habitats contrasting in quality (rich oak forest in the North versus poor beech forest in the South) to analyse the effects of both cohort and habitat quality on adult mass (i.e. median body mass between 4 and 10 years of age) of roe deer (Capreolus capreolus). Cohort strongly influenced the adult body mass of roe deer in both sexes: males born in 1994 were 5.2 kg heavier when aged between 4 and 10 years old than males born in 1986, while females born in 1995 were 4.7 kg heavier between 4 and 10 years old than females born in 1982. For a given cohort, adult males were, on average, 0.9 kg heavier in the rich oak forest than in the poor beech forest. A similar trend occurred for adult females (0.5 kg heavier in the oak forest). The effects of cohort and habitat were additive and accounted for ca. 40% of the variation observed in the adult mass of roe deer at Chizé (males: 41.2%; females: 40.2%). Population density during the spring of the birth accounted for about 35% of cohort variation, whereas rainfall in May-June had no effect. Such delayed effects of density at birth on adult body mass probably affect population dynamics, and might constitute a mechanism by which delayed density-dependence occurs in ungulate populations.
Analysis of Variance↗
Mast cell population density, blood vessel density and histamine content in normal human skin.
Mast cell population density was determined in normal skin from two regions of the arm of several healthy men and compared with blood vessel density and histamine concentration in the same sites. Mast cell and blood vessel counts were made in 1--1.5 micrometer thick plastic sections, by light microscopy and tissue-histamine concentrations were determined by automated fluorimetric analysis. Statistically significant correlations were found between mast cell counts, blood vessel counts and histamine content in skin from the upper arm but no similar correlations were obtained in the forearm. Anatomical differences between the two sites may have been the cause of this discrepancy. Wide variations in mast cell counts and blood vessel density were found in different sections from the same biopsy samples which confirms the notion that dermal mast cells are unevenly distributed. Analysis of variance of the mast cell counts showed that the variance between sections from different blocks from the same biopsy samples was greater than the variance between adjacent biopsies. There was also a marked variation in the histamine content between biopsy samples from sites only 2 cm apart in the same subject.
Adult↗
The influence of hypoxia on the population density of alveolar macrophages in the lungs of rats.
The population density of alveolar macrophages was measured in the lungs of hypoxic rats, in rats which had recovered from a period of hypoxia, and in untreated controls. Alveolar macrophages were most numerous in hypoxic animals. The recovery group contained fewer macrophages than the hypoxic group but more than the controls. In the hypoxic animals the distribution of alveolar macrophages was not homogeneous either within an individual rat or amongst the group as a whole. This suggests that the increase in their number may be stimulated by the secondary effects of hypoxia rather than by its direct interference with their metabolism.
Animals↗
[Effects of eutrophication on distribution and population density of Corbicula fluminea and Bellamya sp. in Chaohu Lake].
The investigation on the distribution an d population density of C. fluminea and Bellamya sp. in Chaohu Lake during September 2001 and September 2002 showed that in the west region of the lake where was seriously eutrophic, the density and biomass of C. fluminea were 5.1 ind. x m(-2) and 17.87 g x m(-2) in 2001, and 8.8 ind. x m(-2) and 47.29 g x m(-2) in 2002, while those of Bellamya sp. were 13.3 ind. x m(-2) and 45.45 g x m(-2) in 2001, and 3.8 ind. x m(-2) and 12.56 g x m(-2) in 2002, respectively. In the east region of the lake where was eutrophic, the density and biomass of C. fluminea were 23.8 ind. x m(-2) and 67.86 g x m(-2) in 2001, and 29.2 ind. x m(-2) and 96.18 g x m(-2) in 2002, while those of Bellamya sp. were 10.1 ind. x m(-2) and 32.00 g x m(-2) in 2001, and 9.4 ind. x m(-2) and 31.21 g x m(-2) in 2002, respectively. The density and biomass of C. fluminea and Bellamya sp. were declined with increasing eutrophication. In hypertrophic region, C. fluminea and Bellamya sp. were absent. The density and biomass of the two species were obviously higher in littoral than in pelagic region. The distribution type of C. fluminea was core-model, while that of Bellamya sp. was random. The correlation between the density and biomass of C. fluminea and Bellamya sp. and water depth was not significant (P > 0.05). The biomass of Bellamya sp. was negatively correlated with water TN (P < 0.01), NO3-N (P < 0.05), TP(P < 0.01) and PO4-P (P < 0.05), while that of C. fluminea only had a significantly negative correlation with PO4-P(P < 0.05). Compared with 1981, there was fewer C. fluminea in the lake nowadays. The effects of other environmental factors on the population distribution and growth of C. fluminea and Bellamya sp. were also discussed.
Animals↗
A critical test of the role of population density in producing transformation.
Cells of the NIH 3T3 line gain the capacity to produce neoplastically transformed foci when they are maintained at high density for more than 1 week and transferred in a standard assay for focus formation. This change in cell behavior has been variously attributed to an adaptive response to the constraint of the high population density or to a spontaneous genetic change that increases in probability for a culture with the increase in the total number of cell divisions. To distinguish between these alternatives, 200 cells of the 28H subline were seeded in many culture dishes of two size classes differing 6-fold in surface area and allowed to multiply for 1, 2, and 3 weeks. At each weekly interval, 18 dishes of each class were assayed for focus formation, and two of the original dishes were stained for focus formation. The cells in the small (S) and large (L) dishes multiplied to the same extent at 1 week and produced only a few small light foci in some of the assay dishes. At 2 weeks, cells in the S dishes had become confluent and had only one-third the number of cells as those in the nonconfluent L dishes. Upon assay, 14 of the 18 S cultures produced some foci whereas only 9 of the L cultures did so. In addition, 4 of the S cultures produced large dense foci while none of the L cultures did. By 3 weeks, the L cultures were confluent and had four times as many cells as the S cultures. When assayed at this time, both sets produced dense foci in many of the cultures and light foci in the remaining ones, indicating a narrowing of the differences between the S and L cultures between 2 and 3 weeks of incubation. There were differences in the morphology of the foci produced in parallel assays from different cultures. The results showed that transformation is a diverse graded response to the growth constraint of high population density and not a spontaneous event dependent on the number of cell divisions in a cell culture. Transformation thus is basically an epigenetic process since it represents a response to physiological restraint, but the final form of response may be modulated by genetic alterations.
3T3 Cells↗
Phylogenetic Diversity and Population Densities of Culturable Cellulolytic Soil Bacteria across an Agricultural Encatchment.
> Abstract A typical, small encatchment (catena Bölkendorf) in the moraine, northeast German agricultural landscape Schorfheide-Chorin was studied with respect to summit, midslope, and foot-slope positions at northern and southern slope exposure, respectively, including a central noncultivated kettle hole position (pot hole). Across the sequence of seven distinct sampling positions, soil organic carbon and total nitrogen contents, soil gravimetric water content, and soil microbial biomass displayed maxima at the kettle hole position. Soil pH revealed a decreasing trend at the northern exposed slope and a minimum at the kettle hole position. Against this background, the population density of total culturable bacteria clearly displayed a minimum at the kettle hole position, whereas the population density of carboxymethylcellulose decomposing bacteria was not clearly differentiated in relation to sampling positions. To study the phylogenetic diversity of culturable cellulolytic bacteria, 311 isolates were obtained from the sampling positions across the entire encatchment and examined by restriction analysis of PCR-amplified 16S rDNA. Using the restriction enzyme ScrFI, isolates were classified into 31 pattern groups. Although the ratio of actinomycetes within total isolates ranged from 0.73 to 0.94, only 16 pattern groups originated from actinomycetes, but 15 from other bacteria. At all sampling positions, a dominant pattern group was identified, containing 38 to 65% of total isolates. Two site-specific pattern groups could be identified, representing significant parts of the total population, which were highly specific for the kettle hole (19% of total isolates) and for foot- and midslope positions (15-18% of total isolates), respectively. In general, the composition of cellulolytic isolates across the encatchment displayed differences with respect to slope positions, but was not significantly affected by soil properties. Based on 16S rDNA sequence analysis, isolates of the dominant as well as the specific pattern groups could be assigned to the genus Streptomyces. Furthermore, sequencing of 16S rDNA of isolates of another three pattern groups revealed a high phylogenetic diversity among these isolates, including cellulomonads and bacilli.http://link.springer-ny.com/link/service/journals/00248/bibs/37n4p238.html
Journal Article↗