bluuebunny/crossref_metadata_2025 huggingface dataset:
Black spruce somatic embryo germination and desiccation tolerance. I. Effects of abscisic acid, cold, and heat treatments on the germinability of mature black spruce somatic embryos
Authors: Beardmore Tannis , Charest Pierre J.
Published: February 2008

The effect of cold, abscisic acid (ABA), and heat treatments on the germination of mature black spruce somatic embryos (SEs) was examined. Specifically, the quality of mature black spruce SEs germinants (as assessed by the presence of hypocotyl vitrification), germination time (synchrony of root and shoot growth), and desiccation tolerance was evaluated following the treatments. Germination of black spruce SEs without any treatments was high (i.e., 89%), but 43% of germinants exhibited a vitrified hypocotyl and root growth lagged behind shoot growth. Mature SEs were exposed to cold (2 °C for 2 days), ABA (20 μM ABA for 7 days), and heat (40 °C for 10 min, 30 °C for 1 h, 25 °C for 12 h) treatments and then either germinated or exposed to fast or slow desiccation. The ABA, cold and heat treatments resulted in a slightly earlier, more uniform germination, due to increased root growth, but did not increase the quality of germinants. Sixty four percent of mature SEs were tolerant to slow desiccation, but only 18% were tolerant to fast desiccation to approximately a 20% water content (on a fresh mass basis). Tolerance to slow and fast desiccation significantly increased and the percentage of germinants with vitrified hypocotyls decreased significantly when the SEs were first exposed to the ABA and cold treatments compared with the mature SEs. None of the treatments resulted in an increase in the number of germinants compared with that of the mature SEs. These results show that the ABA and cold treatments are beneficial for increasing SE tolerance to slow and fast desiccation, decreasing germination time, and increasing the quality of germinants. The ABA treatment was superior with respect to desiccation tolerance and to the quality of germinants.
Variance reduction in Ueno's method and cylinder sampling for forest volume estimation
Authors: Lynch Thomas B.
Published: February 2008

Three basic techniques are proposed for reducing the variance of the stand volume estimate provided by cylinder sampling and Ueno's method. Ueno's method is based on critical height sampling but does not require measurement of critical heights. Instead, a count of trees whose critical heights are less than randomly generated heights is used to estimate stand volume. Cylinder sampling selects sample trees for which randomly generated heights fall within cylinders formed by tree heights and point sampling plot sizes. The methods proposed here for variance reduction in cylinder sampling and Ueno's method are antithetic variates, importance sampling, and control variates. Cylinder sampling without variance reduction was the most efficient of 12 methods compared in computer simulation that used estimated measurement times. However, cylinder sampling requires knowledge of a combined variable individual tree volume equation. Of the three variance reduction techniques applied to Ueno's method, antithetic variates performed best in computer simulation.
Using differential GPS for forest traverse surveys
Authors: Liu C.J. , (Dick) Brantigan Richard
Published: February 2008

This report documents the accuracy and efficiency of differential GPS (DGPS) when it is applied in forest environments. The report contains research results obtained from using DGPS for forest-stand boundary surveys conducted in hardwood forests in a mountainous region. Reported also is the result of a cost-effectiveness analysis that contrasts the satellite-based DGPS positioning and the conventional land-based compass-and-chain surveys. The study found that (1) both forest canopy and undulating terrain in mountainous regions would exert a definite effect on DGPS traverse surveys but neither would reduce stand area determination accuracy; (2) in general, static DGPS was more accurate but less productive than the kinematic DGPS when accuracy and cost were weighted equally; (3) inaccurate two-dimensional position determinations degraded positioning accuracy in either the kinematic or static positioning mode; and (4) kinematic DGPS traverse was a cost-effective survey technique capable of achieving closer forest stand area approximation than the compass-and-chain traverse.
Effects of magnesium deficiency on needle ultrastructure and growth of Scots pine seedlings
Authors: Palomäki Virpi
Published: February 2008

Effects of magnesium (Mg) deficiency on 3-year-old Scots pine (Pinussylvestris L.) seedlings were studied during a field experiment extending over two growth periods. Seedlings were grown in quartz sand in 7.5-L pots watered with nutrient solutions in which the Mg content was reduced to 30 and 0% of the control level (15 mg/L in the first and 3 mg/L in the second growth period). During the first growing period the Mg content of needles at the 0% Mg level was significantly lower than at the 30% level, and in the second growth period a decline was clear at both deficiency levels. Swelling of phloem cells was observed in samples taken after 4 weeks' exposure, and the frequency of swollen phloem cells increased towards autumn and through the second growth period. At the end of the first growing period a decrease in the number of thylakoids per granum and an increase in the number of plastoglobuli in chloroplasts of mesophyll cells were detected at both deficiency levels. During the second growing period the tips of needles from the previous year in the 0% Mg level group became brown, and these needles were shed in autumn from some of the seedlings. The chloroplasts in these needles were rounded and the thylakoids were abnormally organized. Structural symptoms caused by Mg deficiency were observable before visual changes and before a clear decrease in Mg content had occurred, thus showing the value of structural observations in early diagnosis of this stress.
The allowable cut effect as a policy instrument in Canadian forestry
Authors: Luckert Martin K. , Haley David
Published: February 2008

The allowable cut effect, or ACE, is defined as an immediate increase in today's allowable cut of a timber management unit that is attributable to expected future increases in yields. In Canada, the ACE has been adopted by provincial governments in an attempt to encourage voluntary, private investments in silviculture on Crown forest lands. However, such policies have been generally ineffective. Potential reasons for their failure include the presence of other public silvicultural policies that crowd out private, ACE-motivated expenditures; rent (stumpage) collection provisions that do not allow tenure holders adequate financial returns on their investments; yield control provisions that do not impose significant constraints on industrial activity; costs of compliance with regulations to secure increased harvests; and the uncertainty surrounding the future of existing tenure arrangements.
Litter production and nutrient resorption in western red cedar and western hemlock forests on northern Vancouver Island, British Columbia
Authors: Keenan Rodney J. , Prescott Cindy E. , (Hamish) Kimmins J.P.
Published: February 2008

Fine litter fall and concentrations of N and P in green foliage and foliar litter were measured in three species over 1 year in two forest types at three sites on northern Vancouver Island to explore the hypothesis that differences in nutrient use and cycling between the dominant tree species on each forest type contribute to differences in forest floor nutrient availability. Total annual aboveground fine litter fall was significantly higher in second-growth, windstorm-derived 85-year-old stands of western hemlock (Tsugaheterophylla (Raf.) Sarg.) and amabilis fir (Abiesamabilis (Dougl.) Forbes) forests (4137 kg•ha−1) than in adjacent old-growth forests of western red cedar (Thujaplicata Donn) and western hemlock (3094 kg•ha−1) occurring on similar sites. Cedar had significantly lower N concentration in green foliage (9.3 mg•g−1) and litter (4.3 mg•g−1) than the other species in each forest type. Hemlock had a higher litter N concentration in the hemlock–amabilis fir type (8.3 mg•g−1) than in the cedar–hemlock type (6.4 mg•g−1). Cedar resorbed a significantly higher percentage of N during leaf senescence (76%), than hemlock in the cedar–hemlock type (64%), hemlock in the hemlock–amabilis fir type (51%), or amabilis fir (18%). Nitrogen-use efficiency (litter-fall mass/litter N) was considerably higher in cedar (235 kg litter/kg N) than in the other species in either forest type (90–156 kg litter/kg N). These results suggest that differences within and between species in the two types in nutrient use and the amount of nutrients cycling through the litter fall and internal redistribution pathways are contributing to lower rates of nutrient cycling and forest floor nutrient availability in the cedar–hemlock type.
Effects of herbivore-induced nutrient stress on correlates of fitness and on nutrient resorption in scrub oak (Quercusilicifolia)
Authors: May Jeffrey D. , Killingbeck Keith T.
Published: February 2008

We investigated effects of defoliation by gypsy moth (Lymantriadispar L.) larvae on plant fitness and on foliar nutrient dynamics in scrub oak (Quercusilicifolia Wangenh.). Complete defoliation of treatment plants in 1986 and 1987 resulted in the production of a second flush of leaves (secondary leaves) in each of those years. Insecticide effectively protected controls from herbivory. Mean radial stem growth in 1987–1988 and acorn production in 1988–1989 in plants defoliated by L. dispar were 49% and 88% less than in controls, respectively. Defoliation had little effect on the content of nitrogen, phosphorus, copper, manganese, and zinc in green leaves. However, there was significantly less nitrogen, copper, and zinc in senesced secondary leaves of treatment plants than in the primary leaves of controls. Reduced levels of copper and zinc were also evident in senesced primary leaves of defoliated plants in 1988, when no defoliation occurred. Resorption efficiencies for copper and zinc averaged, respectively, 29% and 117% higher in defoliated plants than in controls for all three years, supporting the hypothesis that resorption may be plastic in response to changes in the magnitude of internal nutrient pools. The lack of such a response in resorption of nitrogen and phosphorus may have been due to biochemical and (or) physiological limitations that prevented increased resorption, since resorption efficiencies of these elements were already high (72% and 75%, respectively).
Ecological classification and analysis of wetland ecosystems, northern Lower Michigan, U.S.A.
Authors: Zogg Gregory P. , Barnes Burton V.
Published: February 2008

We describe an ecological, multifactor approach to wetland classification in which ecosystem types are identified on the basis of the simultaneous integration of physiography, climate, hydrology, soil, and vegetation. Aerial photographs and field reconnaissance were used to characterize the diversity of wetlands of the 4000-ha University of Michigan Biological Station, northern Lower Michigan. Twenty-eight wetland units, including nutrient-rich swamps, ombrotrophic bogs, and many intermediate types, were identified. Eight wetland ecosystems, composing 79% of the total wetland area, were sampled extensively and classified primarily on the basis of the major glacial landforms and physiographic features of the region. Canonical variates analysis was used to evaluate the distinctness of these physiographically determined units in relation to various biotic and abiotic variables. Wetland types were poorly discriminated by canonical variates analysis of overstory composition data; better separation among types was achieved using ground-flora vegetation, hydrology, or soil characteristics. To demonstrate the utility of the multifactor approach to applications in wetland ecology, vegetation–environment relationships were examined using canonical correspondence analysis. Patterns of ground-flora community composition across all ecosystems were related to substrate characteristics, primarily organic matter composition, in addition to water chemistry and light. The results suggest that a multifactor approach, within a landscape framework, is useful in distinguishing wetlands at local scales, particularly where differences in overstory vegetation among ecosystems tend to be masked by human-caused disturbance. However, the landform-mediated differences in various wetland characteristics that we observed argue for a consideration of landscape-level physiography in classification and management even at broader scales.
A comparison of crown asymmetry between Piceaabies and Betulamaximowicziana
Authors: Umeki Kiyoshi
Published: February 2008

Morphological plasticity in terms of asymmetric display of crowns was compared between Piceaabies (L.) Karst. and Betulamaximowicziana Regel. To evaluate crown asymmetry in relation to local environment, a model that predicts crown asymmetry from topography and configuration of neighbors was applied to data derived from a mixed forest in Hokkaido, northern Japan. Betulamaximowicziana had greater crown asymmetry than P. abies in absolute value. However, observed crown asymmetry of both species was determined by local environment to similar degrees. Some other differences were found between the two species. Crowns of P. abies were more influenced by neighbors than topography, while crowns of B. maximowicziana were more influenced by topography than neighbors. Crowns of P. abies were influenced mainly by larger neighbors, while crowns of B. maximowicziana were influenced by large and by relatively small neighbors.
Altitudinal effects on leaf traits and shoot growth of Betulaplatyphylla var. japonica
Authors: Kudo Gaku
Published: February 2008

Leaf demography, shoot growth, and seasonal changes of leaf size, specific leaf area, and leaf nitrogen (N) concentration of Betulaplatyphylla var. japonica Hara were compared at two altitudes (140 and 700 m above sea level). At the higher site, where the length of growing season was restricted, leaf life-span was shorter and leaf N concentration was higher throughout the growing season than at the lower site. Leaf size did not differ between sites. Production of short-lived and high N concentration leaves was considered adaptive under the condition of short growing season. At the higher site, N was translocated from senescing early leaves to late leaves in mid-September, whereas a significant increase in late leaf N concentration was not observed at the lower site. There were no differences in shoot growth, bud size, late leaf number on long shoots between sites, probably because of effective N use at the higher site.
Development of a well-behaved site index equation: jack pine in north central Ontario
Authors: Goelz J.C.G. , Burk T.E.
Published: February 2008

not available
Ecological segregation of larval black flies (Diptera: Simuliidae) in northern Saskatchewan, Canada
Authors: Ciborowski Jan J. H. , Adler Peter H.
Published: February 2008

We contrasted degree of habitat differentiation of cytospecies groupings with morphotaxon groupings of black flies collected within a small region offering extensive, spatially continuous simuliid larval habitat. Relative abundance of larvae was correlated with 16 physical and chemical attributes of 20 sites on streams near Uranium City, Saskatchewan. Chromosomal and morphological analyses demonstrated the presence of 20 species distributed among 14 morphotaxa. Principal components analysis of physical and chemical measurements distinguished five statistically independent groups of variables that were related to (i) stream size, (ii) pH, conductivity, and turbidity, (iii) oxygen saturation and substrate particle size, (iv) proximity to lake outlets, and (v) current velocity. Cytospecies belonging to species complexes tended to reach maximum relative abundances at different points along environmental gradients related to stream size and proximity to lake outlets. Cluster analysis of similarity in relative abundance of cytospecies among the 20 sites delineated seven groups. Reanalysis of sites according to morphotaxon data produced six groups. There was only partial congruence between groupings of the two analyses. Cytotaxonomic group sites were each characterized by a distinctive combination of stream size and proximity to an outlet. In contrast, sites classified as having similar morphotaxa were not environmentally distinct from river sites characterized by different morphotaxon assemblages. Thus, simuliid cytospecies represent distinct ecological entities, each adapted to particular suites of environmental variables.
Shape and focal properties of the cephalopod ocular lens
Authors: Sivak J. G.
Published: February 2008

The shape and focal properties (spherical aberration) of lenses from the eyes of three cephalopod species, the cuttlefish Rosia pacifica, the squid Loligo opalescens, and the octopus Octopus dofleini, were measured and compared with descriptions of teleost lenses. The method used involved photographing the refractive effect of lenses in solution on an array of fine parallel helium–neon laser beams. Though the cephalopod lenses approach the sphericity characteristic of teleost lenses, the equatorial lens diameter is somewhat greater (2.3–10.5% in Loligo) than the axial diameter. Spherical aberration of the lens is largely neutralized, indicating the existence of a gradient refractive index. However, the lenses show some non-monotonic variation in focal length with distance from the centre of the lens. The ability of the cephalopods to control pupil size may minimize the need to control spherical aberration.
The influence of fish predation in an experienced prey community
Authors: Wellborn Gary A. , Robinson James V.
Published: February 2008

The impact of predaceous fish on littoral macroarthropod abundances was examined during a 1-year predator density manipulation experiment in a central Texas reservoir. Six sites were selected to receive experimental units. Each site consisted of two 8-m2 plots. One plot at each site was inaccessible to fish predators, the other plot was freely accessible to fish. Fifty-four artificial substrates which simulated natural vegetation were placed in each plot to provide homogeneity in habitat structure and allow quantitative sampling of macrophyte-dwelling invertebrates. Total macroarthropod density in predator-exclusion plots exceeded densities in control plots on 10 of 12 dates examined, but this difference was significant on only 3 dates. Chironomids, the most abundant taxon in samples, were unaffected by predator manipulation. Abundances of two common species, Orthotrichia sp. (Trichoptera) and Hyalella azteca (Amphipoda), were generally enhanced by predator exclusion. Numerically minor taxa showed little or no response to the exclusion of fish. Overall, our study indicates that fish predation can reduce macroarthropod abundances, but this effect is not dramatic. Results of similar studies conducted in aquatic macroarthropod communities that have historically experienced fish predation support these findings. We suggest that experienced prey (i.e, those that naturally co-occur with fish) are likely to possess antipredator defense characteristics that greatly reduce susceptibility to predaceous fish. Therefore, removal of fish-induced mortality has a minor impact on prey survivorship.
Winter energy expenditure and the distribution of southern flying squirrels
Authors: Stapp Paul , Pekins Peter J. , Mautz William W.
Published: February 2008

The southern flying squirrel (Glaucomys volans) forms large aggregations inside nest-lined tree cavities to reduce exposure to winter temperatures. We measured oxygen consumption of individuals and grouped flying squirrels in Plexiglas and nest-box chambers in New Hampshire to determine savings provided by huddling and nest construction. Because G. volans breeds during late winter, we also measured energy expenditure of females during gestation and lactation. These data were used to construct daily energy budgets for flying squirrels during winter and to investigate the relationship between this species' cold tolerance and its current distribution. Flying squirrels had lower basal metabolism (0.95 cm3 O2∙g−1∙h−1) and rate of heat loss (0.11 cm3 O2∙g−1∙h−1∙ °C−1) than predicted according to mass. Peak reproductive costs (1 week postparturition) were 170% of nonbreeding requirements. At 9 °C, huddling in groups of three and six reduced energy expenditure by 27 and 36%, respectively. Compared with individuals without nests, nest insulation decreased heat loss by 37% for single squirrels and reduced lower critical temperature from 26.5 to 12.2 °C for groups of six. As estimated from our budget, aggregating reduces winter daily energy expenditure by 26–33%. At the northern range boundary, daily expenditure for squirrels using both aggregations and nests (2.5 times basal metabolism) and for females during peak lactation (3.9 times basal metabolism) was similar to estimates of maximal daily energy expenditure in the literature. We speculate that additional thermoregulatory costs and the decreased abundance of hard mast for winter caches prevent G. volans from occupying areas north of its current distribution.
Milk composition of Australian sea lions, Neophoca cinerea: variability in lipid content
Authors: Kretzmann Maria B. , Costa Daniel P. , Higgins Lesley V. , Needham D. J.
Published: February 2008

Thirty-eight milk samples collected over three seasons from 23 individual Australian sea lions (Neophoca cinerea) were analyzed. Mean milk composition was 25.4% lipid (± 9.3% SD), 62.4% water (± 8.1%), 10.5% protein (± 2.2%), and 0.9% ash (± 0.2%). Milk composition appeared to vary considerably among females, and occasionally between successive samples from the same individual. Milk fat content was not correlated with pup age (stage of lactation), female mass, length of the preceding foraging trip, or time onshore prior to milk collection. The relatively low lipid content of Australian sea lion milk compared with that of some other otariid seals is consistent with the hypothesis that otariid females making relatively short trips to sea produce milk with lower fat content than those species which make foraging trips of longer duration.
Glycogen depletion in juvenile rainbow trout as an experimental test of the oxygen debt hypothesis
Authors: Scarabello M. , Wood C. M. , Heigenhauser G. J. F.
Published: February 2008

Glycogen depletion was used as an experimental tool to examine the relationship between excess post-exercise oxygen consumption and lactate metabolism in 6-g rainbow trout. A 5-day starvation period reduced whole-body glycogen stores by 50% and slightly lowered resting lactate levels; resting oxygen consumption, glucose, ATP, and creatine phosphate levels were not affected. After a 5-min bout of exhaustive exercise, significantly less glycogen was utilized by the glycogen-depleted fish, 40% less lactate was accumulated, and glucose levels did not rise in comparison with the control group. Creatine phosphate recovered more quickly in the glycogen-depleted fish, whereas ATP was unaffected. Recovery from excess post-exercise oxygen consumption was not significantly different despite the large absolute differences in lactate removed and glycogen resynthesized. This experimental test demonstrates that the classical oxygen debt hypothesis does not completely explain the excess post-exercise oxygen consumption in the trout.
Kin recognition in wood frog tadpoles (Rana sylvatica): factors affecting spatial proximity to siblings
Authors: Rautio Sarah A. , Bura Elizabeth A. , Berven Keith A. , Gamboa George J.
Published: February 2008

In blind laboratory observations, we investigated three factors affecting spatial proximity to full siblings in wood frog (Rana sylvatica) tadpoles. In the first set of observations, we provided tadpoles the opportunity to associate with (i) siblings or no larvae and (ii) nonkin or no larvae. Tadpoles associated preferentially with siblings over no larvae, but showed no preference for either nonkin or no larvae. Thus tadpoles associate with siblings because they are attracted to kin rather than repulsed by nonkin. In a second set of observations, 10-day-old tadpoles failed to display sibling recognition, while 17-day-old tadpoles displayed a significant sibling preference. Furthermore, 17-day-old tadpoles spent significantly more time with siblings than did 10-day-old tadpoles. Thus, age affects sibling preference in wood frog tadpoles. When retested several days later, the former 17-day-old tadpoles again displayed a significant kin preference. However, there was no significant correlation in kin preference between a tadpole's first and second test. This and another comparison indicate that all wood frog tadpoles possess recognition ability, and that the failure of some tadpoles to manifest sibling preference is not due to a lack of recognition ability.
Chinook salmon (Oncorhynchus tschawytscha) gonadotropin IIβ subunit gene encodes multiple messenger ribonucleic acids
Authors: Xiong Fei , Hew Choy L.
Published: February 2008

We have isolated the genomic sequences encoding the β subunit of chinook salmon gonadotropin II, using a gonadotropin IIβ cDNA probe. Southern blot analysis of genomic DNA suggests that there is a single copy of the gonadotropin IIβ gene per haploid genome in salmon. The transcriptional unit is 1.0 kilobase in size and contains three exons interrupted by two introns. The location of the first exon–intron junction is within the 5′untranslated region. The second exon–intron junction is located between codons + 38 and + 39, a position that is comparatively conserved among the previously characterized glycoprotein hormone β subunits. The first intron contains an alternate 3′ splicing acceptor site, resulting in heterogeneous transcripts with 5′-untranslated sequences of 43 and 55 base pairs, respectively. Using oligonucleotide-primed reverse transcription of salmon pituitary mRNA, the start of transcription (cap site) is determined to be 30 nucleotides downstream from the authentic promoter element, Goldberg–Hogness sequence TATAA. In addition, several CAAT sequences are located between 210 and 400 base pairs upstream from the start of transcription. The nucleotide sequence of the 5′-flanking region (approximately 1.2 kilobases) is determined and compared with the corresponding regions of the tetrapod gonadotropin α and β genes. The comparison reveals several homologous regions within their 5′-flanking sequences that might be involved in either the cell-specific expression of the gonadotropin genes or their modulated expression by common regulatory factors such as sex steroids, gonadal peptides, and GnRH.
Fetal growth of northern fur seals: life-history strategy and sources of variation
Authors: Trites Andrew W.
Published: February 2008

Sex-specific growth curves are described for northern fur seal fetuses, Callorhinus ursinus. The relationships between body length, body mass, and gestational age are derived by regression analysis based on 7000 fetuses collected during 1958–1974 as part of a joint Canadian–American pelagic research effort. Male fetuses grow faster and larger than female fetuses. Length approaches an asymptote with time, but the increase in fetal mass appears exponential until parturition. The size of the fetus is influenced by the age, size, and reproductive history of the mother. Primiparous females produce smaller pups than multiparous females. This difference in fetal size is presumably due to physiological changes associated with having been previously pregnant and is not explained merely by differences in the size and age of the different parities. Older and larger females produce progressively larger fetuses until reaching their reproductive prime at about the age of 10–11 years. Adult females continue to grow beyond this age, but there is a senescent decline in the length and mass of the young they carry. There is no indication that the sex ratio differs from unity either between months, across years, or between mothers of different ages and parities.
Tree swallow diet in relation to wetland acidity
Authors: Blancher Peter J. , McNicol Donald K.
Published: February 2008

We examined 12 825 prey of tree swallows (Tachycineta bicolor) northeast of Sudbury, Ontario, to observe the importance of aquatic food and the influence of wetland pH on swallow diet during the breeding season. Items of aquatic origin constituted most of the biomass in diets of both nestlings and adults. Molluscs and Ephemeroptera (mayflies), whose distributions in the study wetlands were strongly influenced by pH, were eaten by swallows, particularly nestlings. The major change in nestling diet in relation to wetland acidity was a decrease in mayflies and a corresponding increase in aquatic Diptera at wetlands of lower pH. The number of aquatic taxa eaten by nestlings was lowest at acidic wetlands. The total biomass of emerging insects captured at acidic wetlands was not lower than at wetlands of higher pH, and in fact tended to be greater. The rate at which swallows fed their young and the amount of food fed to nestlings were not related to wetland pH or other wetland characteristics. Nevertheless, the reduced availability of calcium-rich foods at acidic wetlands and the change in types of food available may play a role in the reduced reproductive success of swallows at acidic wetlands.
Spatial distribution patterns of larval cytotypes of the Simulium venustum/verecundum complex (Diptera: Simuliidae) on the Avalon Peninsula, Newfoundland: factors associated with occurrence
Authors: McCreadie John W. , Colbo Murray H.
Published: February 2008

Larval macrodistribution of cytotypes of the Simulium venustum/verecundum complex among 60 stream sites over a limited geographic area (Avalon Peninsula, Newfoundland) was investigated. Cytotypes included EFG/C, ACD, AA AC(gb), and CC2-3 (combined CC2 and CC3). Stream sites were classified into four types: outlets, trickles, small streams, and large streams. Factors that might explain patterns of occurrence (presence or absence) were examined using correlation, frequency, and cluster analyses. The data showed that larval EFG/C and ACD dominated outlet sites. The CC2-3 and AC(gb) cytotypes were most frequent at downstream sites. In downstream locations CC2-3 was found at almost all sites, whereas AC(gb) was most frequently found in cool, canopied streams, where the bottom consisted mainly of small stones and rubble. In the spring AA was most common at outlet sites. In the summer AA was most frequently found at outlets and trickles. The summer generation(s) of AA was associated with the distribution of trailing and emergent vegetation.
Developmental changes in the blood oxygen transport system of Kemp's ridley sea turtle, Lepidochelys kempi
Authors: Davis Bonnie J.
Published: February 2008

Lepidochelys kempi is the most endangered of the seven species of sea turtles. Very little is known about the developmental rate or blood oxygen system of this diving species. Lepidochelys kempi of various ages (4 months to 10 years) were sampled for changes in hematocrit, hemoglobin concentration and components, and concentrations of organic phosphates in red blood cells as indices of the developmental rate of the oxygen delivery system. The major increase in both hematocrit and hemoglobin concentration occurs between 4 and 7 months. By 7 months all traces of an "embryonic" hemoglobin component are gone. A distinct but minor hemoglobin component appears in turtles older than 28 months. At all ages the major organic phosphate in red blood cells is adenosine triphosphate. The level is highest at 4 months, and decreases until 28 months, when it is statistically equal to that found in adult turtles. The level of 2,3-bisphosphoglycerate is highest at 4 months, then drops to the adult level by 28 months. Inositol pentaphosphate slowly increases, reaching the adult level at 19 months. It takes L. kempi approximately 2 years to acquire the blood oxygen system of an adult turtle as measured by these parameters. This developmental pattern is compared with that known for other sea turtles. The possible physiological significance of organic phosphates in sea turtle red blood cells is discussed.
A test of the condition-bias hypothesis using Brown-headed Cowbirds trapped during the breeding season
Authors: Dufour Kevin W. , Weatherhead Patrick J.
Published: February 2008

We examined trap bias relative to body condition, age, and sex using data collected from Brown-headed Cowbirds (Molothrus ater) decoy trapped during the 1987 and 1988 breeding seasons. A condition bias was evident, as decoy-trapped birds were in poor condition relative to those caught by mist net in an adjacent roost. This occurred in both sexes and independently of study year and male age. Paradoxically, however, males in better condition when first trapped were more likely to be recaptured in the same season, possibly reflecting more widespread movement, and hence fewer encounters with traps, by birds in poor condition. Hatching-year birds were more likely than adults to be recaptured in the same season. Trapped samples were strongly male biased, which probably reflects a difference in nutritional requirements, and thus foraging strategies, between males and females during the breeding season. This study indicates that biases among birds trapped by methods that rely on a feeding response are likely to be widespread and difficult to predict, suggesting that interpretation of data from such samples always requires caution.
Wolf predation risk associated with white-tailed deer movements
Authors: Nelson Michael E. , Mech L. David
Published: February 2008

The survival of 159 yearling and adult deer (Odocoileus virginianus) was monitored by telemetry during 282 spring and 219 fall individual migrations to winter deeryards in northeastern Minnesota. A disproportionate number of deer were killed by wolves (Canis lupus) during fall migration relative to the short time they spent migrating, but not during spring migration. Predation was also significantly greater for male and female yearlings and adult females outside deeryards during winter. Survival of 79 yearlings dispersing from natal ranges was high (1.00). It appears that changing climatic conditions combined with unfamiliar terrain and undetermined factors predispose migratory deer to wolf predation during fall. These findings support an earlier hypothesis that winter yarding is an antipredator strategy.
Scent deposition by cheek rubbing in the alpine marmot (Marmota marmota) in the French Alps
Authors: Bel Marie-Claude , Porteret Christelle , Coulon Jacques
Published: February 2008

The aim of this fieldwork was to provide information about the function of scent-marking behaviour in the alpine marmot (Marmota marmota). Twenty-three identified animals were observed on their home range during the season of activity, from May to September, during which the probability and rate of cheek rubbing decreased significantly. Cheek rubbing was performed more by resident adults than by 2-year-olds or yearlings. The resident adult pairs made "marking tours" during which numerous successive bouts of scent marking occurred throughout most of the home range. Scent marks were not evenly distributed within home ranges. Principal and, if present, accessory burrow systems were saturated with scent deposits, the boundaries being marked significantly more than the central area. We tested the reactions of marmots to strange odours by presenting them with two glass tubes, one clean (control) and the other covered with marks deposited by marmots belonging to other groups. The results showed that residents tended to mark the experimental tubes more frequently, or at least more intensively, than the control ones. In the alpine marmot, cheek rubbing appears to be a multipurpose activity. It is used to advertise the occupancy of burrows and, as predicted by Gosling, scent marks were also laid down where the risk of intrusion was greatest, i.e., at the boundaries, so that intruders could detect them more readily. The results of field tests support another of Gosling's predictions, that residents will tend to overmark any mark deposited by a strange animal inside their territory. Thus, in the alpine marmot, cheek rubbing can play a role in territorial defence.
Some characteristics of narwhal,Monodon monoceros, diving behaviour in Baffin Bay
Authors: Heide-JøRgensen M. P. , Dietz R.
Published: February 2008

Dive data were collected from nine narwhals, Monodon monoceros, instrumented with satellite-linked dive recorders in northwest Greenland in August–September 1993 and 1994. Data were collected for periods ranging from a few weeks to 9 months. The narwhals made daily dives to depths of more than 500 m and frequently dived to 1000 m or more. However, most of the time spent below the surface was in the water column at depths of between 8 and 52 m. For two males that were tracked from September through November the maximum dive depth increased steadily through time. There were no consistent differences in the duration of dives or the number of dives to depths > 8 m during four 6-h periods that were monitored. There were significant differences in dive rates (number of dives per hour) between the large males, the small male, and the females. More than half of the dives lasted less than 5 min and few lasted more than 20 min. These relatively short dive times suggest that narwhals do not exceed their aerobic dive limit. The average time spent in the upper 5 m of the water column was 39.3% (SD = 13.5%; n = 632) for seven whales combined. Speed of vertical movements increased significantly from 1 m∙s−1for 100-m dives to more than 2 m∙s−1for dives deeper than 900 m. A female accompanied by a calf had dive parameters and surfacing times that were identical with those of the other females.
Breeding-season frugivory by Harris' sparrows (Zonotrichia querula) and white-crowned sparrows (Zonotrichia leucophrys) in a low-arctic ecosystem
Authors: Norment Christoper J. , Fuller Martin E.
Published: February 2008

We studied breeding-season frugivory by Harris' sparrows (Zonotrichia querula) and white-crowned sparrows (Z. leucophrys) in the forest–tundra ecotone of the Northwest Territories during a 3-year period. Density of fruits produced during previous summers and preserved beneath the snow averaged between 83 and 94/m2during June. Mass of alpine bearberry (Arctostaphylos alpina) fruits collected during June was significantly greater than that of crowberry (Empetrum nigrum) or mountain cranberry (Vaccinium vitis-idaea), while the relative sugar content of mountain cranberry fruits in June was greater than that of alpine bearberry or crowberry fruits. The protein content of all fruits was relatively low (≤ 3.1%). Harris' and white-crowned sparrows maintained body mass and fat condition while feeding heavily on fruits during the early breeding season and shifted to arthropods when feeding nestlings. The results of our study, plus the widespread distribution of arctic and subarctic subshrubs that produce fleshy fruits consumed by other species, particularly ptarmigan (Lagopus spp.) and shorebirds, suggest that community-wide studies are needed to evaluate the importance of over-winter and late-summer fruits in the diets of terrestrial arctic and subarctic birds.
Fish predation, cannibalism, and larval development in the dragonfly Epitheca cynosura
Authors: Claus-Walker Debra B. , Crowley Philip H. , Johansson Frank
Published: February 2008

We manipulated the risk of fish predation and cannibalism in semi-field and laboratory experiments with larvae of the dragonfly Epitheca cynosura. Results of a 22-week semi-field experiment showed that larvae from different densities were indistinguishable in mean size by the end of the experiment, but that individuals from low densities were larger until week 12. Larvae from low densities varied less in size than did those from high densities. Larvae showed rapid convergence of densities in the absence of fish. Fish predation also generated rapid convergence of densities. The presence of fish initially reduced larval size variation. There was a significant trend for the presence of fish scent to increase larval survival at low larval densities over survival in the absence of fish. Behavioral observations in the laboratory supported the results of the semi-field study in that (i) dragonfly larvae reduced their activity under daytime conditions, (ii) the presence of large larvae caused small larvae to increase their hiding inside a refuge and inhibited their crawling while exposed, (iii) small larvae ate fewer prey in the presence of fish. The results of our study suggest that the interaction between intra- and inter-specific predation risk may prove to be important for survival and development of animals in natural systems.
Complex dynamics in the heart of the lobsterHomarus americanus
Authors: Hokkanen Jyrki E. I. , DeMont M. Edwin
Published: February 2008

Nonlinear dynamics have been shown to be important in describing a large number of complex physiological systems. This work examined the dynamics of the relatively simple neurogenic heart of the lobster Homarus americanus. A non-invasive device was used to collect continuous data of spontaneous heart beats, and time series of consecutive beat-to-beat intervals were generated from these data. This study was concerned with dynamic changes in beat-to-beat intervals that were induced by external effects including changes in both the level of activity and body temperature. Two types of temperature changes, short term (acute) and long term (chronic), were examined. In both cases, decreasing the ambient temperature increased the mean interval length as well as the variation. The regression slope of the correlation between the mean and the variation was unique for each lobster. Variation around the mean included periodic components. Not only the magnitude of the variation but also its complexity were affected by temperature. Approximate entropy increased as temperature decreased, implying temperature dependence of the regularity of the beat-to-beat intervals. We suggest that future physiological studies focus on attempts to understand changes in the complexity of physiological processes.
TORELLI ACTIONS AND SMOOTH STRUCTURES ON FOUR MANIFOLDS
Authors: CALCUT J. S.
Published: February 2008

Artin presentations are discrete equivalents of planar open book decompositions of closed, orientable three manifolds. Artin presentations characterize the fundamental groups of closed, orientable three manifolds. An Artin presentation also determines a smooth, compact, simply conected four manifold that bounds the three dimensional open book. In this way, the study of three and four manifolds may be approached purely group theoretically. In the theory of Artin presentations, elements of the Torelli subgroup act on the topology and smooth structures of the three and four manifolds. We show that the Torelli action can preserve the continuous topological type of a four manifold while changing its smooth structure. This is a new, group theoretic method of altering the smooth structure on a four manifold.
Dexamethasone Affects Inflammation but Not Trypsinogen Activation in Experimental Acute Pancreatitis
Authors: Muller C.A. , Belyaev O. , Appelros S. , Buchler M. , Uhl W. , Borgstrom A.
Published: February 2008

Background/Aims: Trypsinogen activation and inflammation are early events in acute pancreatitis. This experimental study aimed to show the effects of dexamethasone on them. Methods: Cerulein and taurocholate pancreatitis were induced in 2 groups of 12 Wistar rats each. Six animals per group were injected with dexamethasone 1 h prior to the induction of acute pancreatitis. Amylase, phospholipase A2, TNF-α, IL-6, IL-10, α2-antiplasmin in plasma and trypsinogen activation peptide (TAP) in urine were measured in healthy rats, then 0.5 and 6 h after pancreatitis induction. A severity score based on edema, necrosis and ascites was calculated at 6 h. TNF-α, IL-6 and IL-10 were measured 0.5 h after laparotomy in a control sham-operated group of 6 rats. Results: Inflammatory markers increased early in the course of both mild and severe acute pancreatitis and were significantly lowered by dexamethasone. The severity score was higher in taurocholate than in cerulein pancreatitis. It was significantly decreased by dexamethasone only in rats with mild pancreatitis. TAP remained unchanged in mild pancreatitis compared to healthy animals but increased late in the course of taurocholate pancreatitis. Trypsinogen activation was not affected by dexamethasone at all. Conclusion: Inflammation occurred earlier than the increase in urinary TAP in severe pancreatitis in rats. Dexamethasone inhibited inflammation but had no influence on TAP levels in experimental mild and severe acute pancreatitis.
Matching the Diameter of ePTFE Bypass Prosthesis with a Native Artery Improves Neoendothelialization
Authors: Cikirikcioglu M. , Pektok E. , Cikirikcioglu Y.B. , Osorio-da Cruz S. , Tille J.-C. , Kalangos A. , Walpoth B.H.
Published: February 2008

Background and Aim: The undersizing of the bypass graft diameter compared to native artery changes blood flow characteristics and velocity which may affect conduit neo-endothelialization, intimal hyperplasia reaction and patency. The aim of this study was to evaluate conduit neoendothelialization, intimal hyperplasia reaction and patency results between undersized and matched ePTFE grafts. Material and Methods: In 16 male Sprague-Dawley rats, undersized (1-mm internal diameter) and matched (2-mm internal diameter) ePTFE grafts were anastomosed end-to-end in the infrarenal abdominal aorta. Blood flow volume per minute was measured and wall shear stress was calculated for each group. After 3 weeks of follow-up, angiography was performed via the left carotid artery just before sacrifice. Conduit neoendothelialization and intimal hyperplasia reaction were measured by computer-assisted morphometry. Results: Wall shear stress was 8 times higher for the undersized group (840.56 vs. 105.07 mPa). Three weeks after implantation, conduit neoendothelialization was better in matched grafts compared to undersized grafts (441 vs. 574 µm, p = 0.008). Intimal hyperplasia reaction was similar for both groups (8.7 vs. 6.7 µm2/µm for undersized and matched grafts, respectively). Patency rate was 7/8 for undersized and 8/8 for matched ePTFE grafts. Conclusion: Although the graft patency and the intimal hyperplasia reaction were not different between the two groups after 3 weeks, matched grafts had a significantly better endothelialization compared to undersized grafts. This short-term beneficial effect may influence long-term patency results.
Effectiveness of Disinfectants Used in Cooling Towers against Legionella pneumophila
Authors: García M.T. , Pelaz C.
Published: February 2008

Background:Legionella persists in man-made aquatic installations despite preventive treatments. More information about disinfectants could improve the effectiveness of treatments. This study tests the susceptibility of Legionella pneumophila serogroup (sg) 1 against 8 disinfectants used in cooling tower treatments. Methods: We determined the minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and bactericidal effect of sodium hypochlorite (A), hydrogen peroxide with silver nitrate (B), didecyldimethylammonium chloride (C), benzalkonium chloride (D), tributyltetradecylphosphonium chloride (E), tetrahydroxymethylphosphonium sulfide (F), 2,2-dibromonitropropionamide (G) and chloromethylisothiazolone (H) against 28 L. pneumophila sg 1 isolates. Results: MIC and MBC values were equivalent. Bacteria are less susceptible to disinfectants F, B, D and A than to H, E, C and G. All disinfectants induced a bactericidal effect. The effect rate is dose dependent for G, H, F and B; the effect is fast for the rest of disinfectants at any concentration. The bactericidal activity of disinfectants A, G and F depends on the susceptibility test used. Conclusions: All disinfectants have bactericidal activity against L. pneumophila sg 1 at concentrations used in cooling tower treatments. Results depend on the assay for some products.