bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Haemobaphes cyclopterina and H. intermedius (Copepoda) on Arctic cod (Boreogadus saida) and tidepool sculpins (Oligocottus maculosus), respectively
Authors: Khan R. A. , Ryan K. , Lawson J. W. , Munehara H.
Published: April 2008

A study was conducted to determine the prevalence and effects of two species of blood-feeding copepods on their definitive fish hosts, viz. Haemobaphes cyclopterina parasitizing Arctic cod (Boreogadus saida) and H. intermedius infecting tidepool sculpins (Oligocottus maculosus). Infected and uninfected Arctic cod and tidepool sculpins were captured by SCUBA and dip net in the northwest Atlantic and northeast Pacific, respectively. Biological variables such as condition factor, hepatic somatic index, gonadal somatic index, and haematocrit were compared between the two groups of Arctic cod of both sexes, whereas only condition factor was compared in the two groups of sculpins of both sexes. Prevalence of H. cyclopterina (8%) was considerably lower than that of H. intermedius (46%). This difference is probably associated with the hosts' behaviour, as the Arctic cod is pelagic whereas the tidepool sculpin is restricted to the littoral zone, where infections are probably acquired. Infected Arctic cod of both sexes had significantly lower condition factor, hepatic and gonadal somatic indices, and haematocrit than non-parasitized fish. Only females harboured large numbers of the parasite and showed even more dramatic changes than the corresponding groups. The growth period of H. cyclopterina on Arctic cod from the time of infection to the fully developed egg sac stage is probably about 6 months. In tidepool sculpins, condition factor was significantly lower in infected than in uninfected fish. These results, especially for the Arctic cod, parallel those reported for gadoid fish following infection with haematophagous species of Lernaeocera that impair growth and reproduction.
Variation in assimilation efficiency and digestive efficiency of captive harp seals (Phoca groenlandica) on different diets
Authors: Lawson John W. , Miller Edward H. , Noseworthy Elizabeth
Published: April 2008

Digestive efficiency (DE) is influenced by many factors including food type or quality. Assimilation efficiency (AE) and DE of 12 captive harp seals (Phoca groenlandica) were estimated for five prey types in large outdoor seawater tanks. In trials of > 9 days' duration, the seals were fed Atlantic cod (Gadus morhua), Arctic cod (Boreogadus saida), Greenland halibut (Reinhardtius hippoglossoides), Atlantic herring (Clupea harengus), and capelin (Mallotus villosus). Fish were marked with inert tracers so that faecal samples could be matched to individual animals. AE (digestibility of dry matter) was estimated from the relative concentration of Mn2+in food and faeces. DE (digestible energy) was estimated from the relative concentrations of both Mn2+and energy in food and faeces. AE and DE values were high, but varied among the fish species (DE: Atlantic cod 93.5%; Arctic cod 93.5%; halibut 94.7%; capelin 95.7%; herring 96.6%). Both estimates of digestive efficiency were positively correlated with prey energy density. For most prey, AE and DE were not correlated with meal size, number of prey in a meal, size of prey, or seal body mass. However, digestive efficiency was greater in seals fed smaller Atlantic cod, or meals of greater mass. Quantifying estimates of digestive efficiency is important for formulating energy-based population consumption models, and so should be improved. It is recommended that more pinniped species be studied in captivity, that experiments last longer, and that the number of individuals studied be increased so that individual differences can be investigated.
Lifetime reproduction of giant transgenic mice: the energy stress paradigm
Authors: Rollo C. D. , Rintoul J. , Kajiura L. J.
Published: April 2008

Lifetime reproduction of female transgenic rat growth hormone (TRrGH) mice and their normal siblings was evaluated on a high-protein (38%) diet, a standard diet (23% protein), and the standard diet supplemented with sucrose cubes. Compared with those on the standard diet, normal mice fed the high-protein diet showed significant increases in litter size, number of litters, and lifetime fecundity. Number of litters and lifetime fecundity were also enhanced in normal mice fed sucrose. TRrGH mice showed no significant improvements in reproduction on the high-protein diet, but they were significantly smaller. Sucrose dramatically improved reproduction of TRrGH mice, with no reduction in mature mass. The percentage of fertile TRrGH mice increased from 45% on standard chow to 71% with sucrose. The number and size of litters of TRrGH mice also significantly increased with sucrose, mean lifetime fecundity doubling from 9 pups on standard food to 18 pups on sucrose. However, TRrGH mice did not attain the reproductive success of normal mice on any diet. These results suggest that TRrGH mice are energetically stressed by enforced channelling of energy into growth. An immense literature addresses infertility due to energy limitation and stress generally. We synthesize these aspects with growth hormone transgenesis to derive an integrated view of neuroendocrine energy regulation relevant to restoring fertility of transgenic GH animals.
Experimental transmission of Otostrongylus circumlitus (Railliet, 1899) (Metastrongyloidea: Crenosomatidae), a lungworm of seals in eastern arctic Canada
Authors: Bergeron Emmanuelle , Huot Jean , Measures Lena N.
Published: April 2008

The transmission of few metastrongyloids infesting marine mammals is known. The results of experimental infections using Otostrongylus circumlitus (Crenosomatidae), a lungworm of pinnipeds, suggested that this metastrongyloid uses fish as intermediate hosts. Various marine organisms (crustaceans, molluscs, and fish) were exposed to first-stage larvae from naturally infected young-of-the-year ringed seals (Phoca hispida) from northern Quebec (Salluit). The first and second moults occurred 3 and 56 days post exposure in the mucosa and muscularis of the intestine of American plaice (Hippoglossoides platessoides) kept at 4 °C. Third-stage larvae were found under the intestinal serosa. Attempts to infect invertebrates were unsuccessful. Transmission to seals may occur from mid-June through the autumn as young seals start feeding intensively on invertebrates and fish. First-stage larvae leave the lungs via the bronchial escalator and are swallowed and released into the sea with the faeces of seals, where they would be available to benthic or pelagic fish. The morphology of the first three larval stages is described.
Taxonomic significance of host-egg mimicry by facultative brood parasites of the avian genusCoccyzus(Cuculidae)
Authors: Hughes Janice M.
Published: April 2008

Black-billed (Coccyzus erythropthalmus) and Yellow-billed (C. americanus) cuckoos are facultative brood parasites that occasionally lay their eggs in the nests of 10 and 11 other bird species, respectively. This study demonstrates that both cuckoo species produce blue–green eggs that fully or nearly match the eggs of over 70% of their reported host species, a proportion significantly greater than if hosts were being selected at random from the potential host pool. These results suggest that the cuckoos may be selecting hosts on the basis of their egg colour, and support a hypothesis of egg mimicry. Since egg mimicry is unlikely to evolve in a facultative parasite, its existence in Coccyzus would imply a historically intense relationship between these birds and their hosts. This hypothesis is corroborated by recent phylogenetic analyses which suggest that the ancestral Coccyzus was an obligate parasite. Factors responsible for the loss of obligate parasitism in this genus may also have contributed to the general paucity of obligate parasitism in New World cuckoos. Competitive exclusion or resistance to invasion by parasitic cowbirds (Molothrus spp.) should be considered.
Postemergence behaviour of neonates in a northern peripheral population of Blanding's turtle,Emydoidea blandingii, in Nova Scotia
Authors: Standing K. Lorraine , Herman Thomas B. , Hurlburt Donna D. , Morrison Ian P.
Published: April 2008

The early postemergence behaviour of neonate Blanding's turtles, Emydoidea blandingii, was studied in Nova Scotia in 1994 and 1995 to test the hypothesis that hatchlings go to water immediately upon emergence from the nest. At the northeastern limit of the species' range, hatchling turtles should seek aquatic hibernacula to avoid freezing; where emergence from the nest is delayed until late autumn, selection pressure for water-seeking behaviour should be strong. Using pigmented powder that fluoresces under UV light, 78 hatchlings from 12 lakeshore nests and 2 inland nests were tracked for a maximum of 11 days. On the first day after emergence, hatchling movement was random with respect to water. Hatchlings did not orient themselves with respect to slope, vegetation, or nestmates, nor did individuals follow a consistent compass bearing among days. Often trails were convoluted in the open and relatively straight under dense vegetation. Evidence suggests that hatchlings in this population may overwinter in terrestrial as well as aquatic hibernacula.
Comparative propensity for dispersal of apterous and alate morphs of three potato-colonizing aphid species
Authors: Boiteau Gilles
Published: April 2008

The relative ability of apterous and alate morphs of aphids to disperse from one potato leaflet to another was similar within species. Three species were tested: the buckthorn aphid, Aphis nasturtii Kaltenbach, the potato aphid, Macrosiphum euphorbiae (Thomas), and the green peach aphid, Myzus persicae (Sulzer). The average percentage of aphids moving daily from one leaflet to another never exceeded 2.5% for nymphs of the three species, but reached 45% for the adult winged buckthorn aphid. During the first half of the reproductive period, adult potato aphids were 1.5 times as likely as buckthorn aphids and twice as likely as green peach aphids to relocate daily. In a flight chamber, buckthorn aphids flew 4.5 times longer than green peach or potato aphids. The maiden flights of these summer forms were interrupted by repeated landings lasting less than 2 min. The maiden flights were interrupted more than twice as often for the buckthorn aphid as for the potato aphid. The number of flight interruptions was intermediate for the green peach aphid. Selected dispersal parameters for these aphid species are compared with those for the black bean aphid, Aphis fabae Scopoli, an occasional potato-colonizing species. The percentage of green peach and potato aphids taking flight was significantly correlated with the temperature in the flight chamber. The implication of these results for the distribution of aphid populations and the epidemiology of viral diseases is discussed.
Egg-size manipulations in the seed beetle Stator limbatus: consequences for progeny growth
Authors: Fox Charles W.
Published: April 2008

Studies that have demonstrated consequences of variation in egg size for progeny growth and development are often confounded by genetic correlations among life-history characters; relationships between egg size and progeny life-history characters do not always reflect cause and effect. Thus, experimental approaches to manipulating egg size in order to quantify the consequences of egg-size variation for progeny growth and development have been developed. I used egg-size plasticity in response to oviposition environment to manipulate egg size in a seed beetle, Stator limbatus, to test the hypothesis that progeny developing from larger eggs survive better, develop faster, and attain a larger adult body size than progeny developing from smaller eggs. Females exposed to Cercidium floridum during egg maturation laid eggs that were substantially larger than those laid by females exposed to Acacia greggii during egg maturation. The larger eggs laid by females exposed to C. floridum took significantly longer to hatch but had shorter total egg-to-adult development times than eggs laid by females exposed to A. greggii (when reared to adulthood on A. greggii). There was no evidence from the between-treatment comparisons that egg size affected egg-to-adult survivorship or the size at which progeny emerged as adults. Within-treatment correlations between egg size and progeny life-history characters were generally consistent with the between-treatment analyses, except that female progeny developing from larger eggs tended to emerge as larger adults than female progeny developing from smaller eggs. This result is interpreted as a consequence of heritable variation in body size rather than a cause-and-effect relationship between egg size and progeny body size.
Formation, transfer, and assimilation of the spermatophore of the hermaphroditic flatworm Dugesia gonocephala (Tricladida, Paludicola)
Authors: Vreys C. , Schockaert E. R. , Michiels N. K.
Published: April 2008

The spermatophore of the simultaneously hermaphroditic planarian Dugesia gonocephala consists of a large stalked bladder that gradually forms inside the ejaculatory duct of the penis between successive copulations. In solitary individuals, spermatophore formation begins with the development in the penis of a tube that is sealed at the distal end and may protrude slightly from the penis tip. In courting individuals, this protruding part is widened into a bladder that further increases in size when penises are mutually inserted. Spermatozoa are pumped into the bladder after the first few minutes of copulation and the resultant spermatophores are exchanged 3–4½ h after the start of copulation. Reciprocal transfer is slightly asynchronous. After the spermatophore is transferred into the bursa copulatrix, the stalk of the spermatophore is usually in or near the entrance to the bursal canal. Sperm start to leave the spermatophore immediately after the partners separate and continue to do so for 3–4 days. During this period, the bladder of the spermatophore shrinks but remains intact. Following spermatophore donation, the penis may hold a new spermatophore after 1–2 days. Individuals that engage in a new copulation rarely do so because they are allosperm depleted. In fact, the bursa may still hold a spermatophore from a previous copulation. We discuss the adaptive significance of spermatophore formation, transfer, and assimilation.
The effect of group size on vigilance and feeding rate in spice finches (Lonchura punctulata)
Authors: Beauchamp Guy , Livoreil Barbara
Published: April 2008

We investigated group-size effects on individual vigilance levels and feeding rates in captive groups of spice finches (Lonchura punctulata). The "many-eyes" hypothesis predicts a reduction in vigilance levels in larger groups that can cause higher feeding rates if the time thus saved is used for foraging. We adopted a within-subject procedure whereby in each of six replicates we observed one adult male searching for food in groups varying in size from one to five. As predicted, vigilance levels decreased with group size up to four birds but increased in groups of five. Birds also collected seeds more quickly in larger groups, reflecting (i) a decrease in vigilance levels in larger groups, (ii) a decrease in handling time, and (iii) an increase in search speed. Nearest neighbour distances were smaller in larger groups, a potential confounding factor in the analysis of vigilance time. Although the results are partly consistent with the many-eyes hypothesis, we suggest that the arrow of causation from vigilance to feeding time could be reversed: the increase in feeding rates in larger groups, with a concomitant decrease in vigilance levels, would be caused by increased competition.
Wing-feather mite (Acari: Proctophyllodidae) abundance correlates with body mass of passerine hosts: a comparative study
Authors: Rózsa Lajos
Published: April 2008

Data from a 4-year study of wing-feather mites on passerines in Portugal (Behnke et al. 1995. Exp. Appl. Acarol. 19: 443–458) were used to investigate whether avian body mass influences the abundance of mites. When 17 host species were used as statistically independent observations, the mite infestation score correlated positively with avian body mass. This correlation is not a phylogenetic artefact, having been also found when avian phylogeny was controlled for. Three non-exclusive hypotheses might explain this finding: (1) larger birds may provide larger "habitat islands," enabling more mites to coexist; (2) larger birds may provide more topographic refugia for mites to evade host preening; (3) larger birds may provide greater longevity of habitat islands, thus reducing the decimating effects of transmission.
Reproductive success of bald eagles (Haliaeetus leucocephalus) and its association with habitat or landscape features and weather in southeast Alaska
Authors: Gende Scott M. , Wilson Mary F. , Jacobsen Mike
Published: April 2008

Long-term data have been collected on nesting bald eagles (Haliaeetus leucocephalus) in three areas of southeast Alaska. The average density of active nests was among the highest recorded, but nest productivity (average number of young fledged per active nest) and success (percentage of active nests that fledged at least one young) were similar to values in other areas. Using logistic regression, nest productivity was associated with several habitat or landscape features (productivity was highest in proximity to spawning herring and at a particular location), each of which could be related to the availability of prey (fish) in the early spring (April, May) during egg laying and incubation. Consistency of nesting success was associated with the presence of tidal flats at one study site. Nest use, but not nesting success, was related to nesting success the previous year. Multiple regression showed that fewer nests per kilometre were successful in years with a high frequency of spring rains.
Transport of exogenous 5-hydroxytryptamine across the outer plasma membrane of the syncytial tegument ofHymenolepis diminutais by simple diffusion
Authors: El-Razek Mona Abd , Webb Rodney A.
Published: April 2008

The uptake of 5-hydroxytryptamine (5HT) from a 10 μM solution of exogenous [3H]5HT into the tegument of Hymenolepis diminuta was linear for the first 20 min of incubation. The rate of transport was 0.04 ± 0.01 pmol∙mg wet mass−1∙min−1, and there were no significant differences in the rate of uptake by the anterior, middle, and posterior regions of the body. The initial uptake was not Na+-dependent, was not saturable at up to 100 μM, was not highly temperature-dependent (Q10~ 1.2), and displayed activation energy of 11.8 kJ∙mol−1. Furthermore, uptake was not inhibited by p-chloromercuriphenyl sulphonic acid, imipramine, amiloride, or 5HT analogues, which collectively support a non-carrier-mediated uptake mechanism. Washing of the tissues with 10 mM 5HT after incubation in 10 μM [3H]5HT displaced less than 10% of the remaining [3H]5HT associated with the tissues, and little radioactivity was extracted by washing in acetone or chloroform. The uptake of [3H]5HT, however, was pH-dependent, the rate of uptake being closely correlated with the proportion of unprotonated 5HT. Only a small portion of the transported [3H]5HT was metabolized to a product associated with 5-hydroxyindoleacetic acid, and metabolism was significantly inhibited by the monoamine oxidase inhibitors iproniazid phosphate, deprenyl, and clorgyline. The present study showed that small amounts of [3H]5HT were taken up by H. diminuta by simple diffusion, little of the [3H]5HT was adsorbed to the surface of the worms or dissolved in the lipid phase of the plasma membrane, and some of the [3H]5HT taken up was metabolized by a monoamine oxidase-like enzyme.
Comparison of the benzyl viologen and bimane HPLC assays for the determination of sulfide-oxidizing capability in the tissues of hydrothermal vent and non-vent polychaetes
Authors: Martineu Pascale , Juniper S. Kim
Published: April 2008

Two commonly used methods for in vitro measurement of tissue-level sulfide oxidation in animals were compared using homogenates of hydrothermal vent (Paralvinella sulfincola and P. palmiformis) and non-vent (Nereis virens and Nephtys caeca) polychaetes. All examined worms showed heat-labile sulfide-oxidizing ability and rates were slightly higher in the two vent species. A previously observed discrepancy between the results of the spectrophotometric benzyl viologen (BV) and bimane high-performance liquid chromatography (HPLC) assays was confirmed. We explain this discrepancy firstly by the fact that H2S removal measured by the bimane HPLC assay is only the first step in a cascade of several possible sulfur-oxidation steps recorded by BV. Secondly, we show that the low H2S/protein ratio used in the bimane HPLC assay can result in undersaturation of the catalyst responsible for H2S oxidation. The latter can lead to underestimation of potential oxidation rates and may be as important as the nonspecificity of BV in explaining differences between assay results. Tissue-level sulfide oxidation is clearly widespread in marine invertebrates, but the catalyst(s) responsible remain(s) unidentified. The fact that sulfide-oxidation rates in vent polychaete tissues are similar to rates in non-vent species and appear to reflect a common basal level of sulfide-oxidizing activity in many animal tissues suggests that other defense mechanisms may be more important in the adaptation of these worms to the hydrothermal milieu.
Size-dependent foraging behaviour and use of cover in juvenile coho salmon under predation risk
Authors: Reinhardt Ulrich G. , Healey Michael C.
Published: April 2008

Foraging and use of cover by juvenile coho salmon (Oncorhynchus kisutch) were affected by predation threat in both seminatural channels and laboratory streams. In the field, coho salmon preferred stream sections with brushy cover only when under threat from hunting common mergansers. The mergansers had their highest capture success in pools without cover. Predation threat also caused coho salmon to use cover more as foraging habitat and to aggregate more in favourable positions at the head of the pool. In the laboratory, under simulated predation threat, fish using a refuge were significantly larger than those in the risky habitat. This pattern persisted for 2 days after the predation threat was discontinued. The average growth of coho salmon under predation threat was depressed and the difference in growth between large and small individuals was less than in control groups. We argue that larger fish were more averse to predation risk than smaller fish and that the smaller fish took advantage of feeding opportunities indirectly provided as a result of the predation risk. We speculate that in natural environments, predation may depress growth rates because of risk-avoidance behaviour but may also serve to reduce growth-rate differences among size classes within a cohort.
Summer diving behaviour of lactating New Zealand sea lions, Phocarctos hookeri
Authors: Gales N. J. , Mattlin R. H.
Published: April 2008

The diving behaviour of 14 female New Zealand sea lions (Phocarctos hookeri) was recorded during early lactation in January and February 1995 on the Auckland Islands, New Zealand. During 73 trips to sea, 19 720 dives were recorded. The average duration of a foraging cycle was 2.9 days (range 1.4–4.8 days), of which 1.7 days (57%) (range 1.1–3.4 days) were spent at sea and 1.2 days (43%) (range 0.8–2.3 days) ashore. At sea the sea lions dived almost continuously at a rate of 7.5 dives/h and spent a mean of 45% of the time submerged (≥ 2 m). Dive behaviour varied among individuals but showed no diel pattern overall. The dive depth for all dives ≥ 6 m was 123 ± 87 m (mean ± SD) (median 124 m, maximum 474 m) and ranged among individuals from 79 ± 85 to 187 ± 166 m. About half of the dives were in the 101- to 180-m range. The duration of all dives was 3.9 ± 1.8 min (median 4.33 min, maximum 11.3 min); about half (51%) of the dive durations were between 4 and 6 min. Surface interval was 4.5 ± 15.8 min (median 1.9 min). Almost half (44%) of all dives exceeded the calculated aerobic dive limit of each sea lion (range 16–73% for individuals). Most dive profiles were flat bottomed and, we believe, are to the benthos. A mean of 51.5% of all dive time was spent in the deepest 85% of the dive. Prey remains found during this study were primarily of benthic and demersal organisms. Phocarctos hookeri is the deepest and longest diving of any of the otariids recorded to date. We suggest that the dive behaviour may reflect either successful physiological adaptation to exploiting benthic prey and (or) a marginal foraging environment in which diving behaviour is close to physiological limits.
Variability of spring habitat selection by isards (Rupicapra pyrenaica)
Authors: Pépin Dominique , Joachim Jean , Ferrié Eric
Published: April 2008

We studied the influence of snow cover and habitat heterogeneity on altitudinal distribution, grouping patterns, and habitat selection in the isard or Pyrenean chamois (Rupicapra pyrenaica) in a protected area from the beginning of May to mid-June 1992. Data were recorded from a single vantage point that allowed visual observations to be made over a wide range of elevations. Variations occurred in the spatial extension of groups, with no sightings above 1900 m when snow was abundant at high altitude and only a few sightings below 1700 m when small patches remained at high altitude. During a late heavy snowfall, however, most sightings were made at the middle altitudinal range, where adjoining habitats of steep terrain provided areas of reduced snow depth. The frequency of observations of solitary animals increased slightly and was higher in closed than in open habitats. Both a significant habitat effect and a significant interaction between habitat and time period of observations were found for groups of the average size, ≥ 2 individuals. Montane pastures at low altitude were first selected. Then, when snow melted, this habitat was vacated for 1800- to 2000-m subalpine pastures. Regardless of the time period, the areas dominated by rhododendrons and rocks or scree were systematically avoided. We suggest that in order to gain a better understanding of habitat selection by large ungulates, especially in mountainous areas, short-term variations in environmental heterogeneity be considered.
Spacing patterns and territoriality of the stone marten
Authors: Genovesi P. , Sinibaldi I. , Boitani L.
Published: April 2008

Sixteen stone martens (Martes foina) were intensively radio-tracked in central Italy in order to assess their spacing patterns. Home-range sizes and distances travelled per night were analysed with respect to sex, age, season, and habitat. Intrasexual territoriality is confirmed for the species; home-range edges appeared to be determined by the dispersion of neighbours' territories. Home-range size was positively correlated with the presence of woodland (less abundant and more dispersed resources). Males travelled longer distances than females, although home-range sizes did not differ significantly by sex; males did not move more during the rutting season than in other seasons. Subadults were tolerated by adults for varying periods, then in some cases they started an exploring phase before settling into a vacant territory. Stone martens' spacing patterns were affected by sex, age, social interactions, and resources. In particular, social patterns appear to be a key influencing factor, as territoriality, parental behaviour, mating interactions, and dispersal of young can account for site fidelity, dispersion of home ranges, and distance travelled. In particular, our data indicate the importance of the extended relationship between the mating pair, which is probably related to male parental investment, in determining the spacing patterns of the species.
Factors regulating kit fox populations
Authors: White P. J. , Garrott Robert A.
Published: April 2008

Recent declines in several populations of kit foxes (Vulpes macrotis) have been attributed to decreased prey abundance and increased coyote-related mortalities. However, it is not known if short-term fluctuations in prey abundance or interference competition by coyotes can regulate the population dynamics of kit foxes. We coalesced data from all pertinent studies of kit and swift foxes and examined their numerical responses to changes in prey abundance. We also explored the influence of coyote-related mortalities on fox population dynamics. Fox density was positively correlated with leporid abundance, and fox reproduction rates were density-dependent at low prey densities. The proportion of the fox population killed by coyotes increased linearly over low to moderate fox densities, and survival rates of adult foxes decreased as the proportion of mortalities caused by coyotes increased. Hence, prey abundance and interference competition by coyotes may regulate fox populations. We suspect that prey abundance, and behavioral spacing mechanisms, are the major factors regulating fox densities. Coyote-related mortalities may be a less predominant factor, but could still act in concert with prey abundance to reduce the amplitude of fox population dynamics and keep foxes at lower densities than they might otherwise attain.
An experimental test of habitat selection by rodents of Algonquin Park
Authors: Schulte-Hostedde Albrecht I. , Brooks Ronald J.
Published: April 2008

Using an enclosure experiment, we tested whether substrate selection by deer mice (Peromyscus maniculatus), redback voles (Clethrionomys gapperi), and woodland jumping mice (Napaeozapus insignis) matched habitat-use patterns determined from trapping data. Mice were introduced into a 5 m diameter enclosure containing substrates from three habitats: maple, mixed, and coniferous forest. Trapping data were taken from a long-term monitoring study of small-mammal populations in Algonquin Park, Ontario. We used data from 1991 – 1995 from the three habitats used in the enclosure experiment. If competition or predation affects habitat distribution patterns, then, given a choice, mice should select different substrates in the enclosures from those they use in the field. Alternatively, if habitat use is not constrained by interactions with competitors or predators (i.e., if small mammals select habitats), then habitats used in the enclosure should match habitat distributions observed in the field. Habitats used in the field did not match habitats selected in the enclosure experiment for either deer mice or woodland jumping mice. Redback voles selected habitats similar to those used in the field. We conclude that interspecific competition and (or) predation may limit availability of habitats for deer mice and woodland jumping mice.
Ecology of parasitism of nestling American kestrels by Carnus hemapterus (Diptera: Carnidae)
Authors: Dawson Russell D. , Bortolotti Gary R.
Published: April 2008

Little is known about the basic biology of Carnus hemapterus (Diptera: Carnidae), a haematophagous parasite of nestling birds. We therefore explored the patterns of C. hemapterus infestations by repeatedly examining American kestrel (Falco sparverius) nestlings from 50 nests in north-central Saskatchewan. Most infestations occurred before chicks were 12 days old and were more frequent early in the breeding season. Nestlings from larger broods had higher prevalences of C. hemapterus, but we did not detect differences in intensity of infestations between broods of different sizes. Within broods up to 5 days old, the heaviest nestlings were preferentially infested by C. hemapterus. Although evidence suggests that ectoparasite infestations are harmful to hosts, we did not detect any mortality attributable to C. hemapterus. Similarly, we did not observe negative effects of C. hemapterus infestations on nestling mass, length of the tenth primary flight feather, haematocrit, or total plasma protein concentration at 24 days old.
Pupillometry in seals and sea lions: ecological implications
Authors: Levenson David Hendrik , Schusterman Ronald J.
Published: April 2008

Phocid and otariid pinnipeds forage almost exclusively under water, where observing them is difficult. As a result, little is known of how their senses are used while diving to locate and capture prey. In this study we used pupillometric methods to describe the relative visual abilities of three pinniped species: the northern elephant seal (Mirounga angustirostris), the harbor seal (Phoca vitulina), and the California sea lion (Zalophus californianus). The range of pupillary area and lower limit of pupillary adjustment were determined for each species. The northern elephant seal exhibited the largest range of pupillary area of the species examined. Furthermore, the elephant seal's pupil was found to reach maximum size only under extremely dim conditions. Both the harbor seal and California sea lion exhibited maximum pupillary dilation in conditions several log units brighter. These results indicate that the elephant seal's visual system is designed to function in dimmer conditions and to respond to greater changes in light levels than those of the harbor seal and sea lion. Such findings support the hypothesis that the visual systems of these pinnipeds are adapted for use in their respective foraging environments, and thus suggest that the visual sense is probably an important sensory modality used to locate and capture prey while diving.
Predator–prey relationship between insect larvae: growth ofSphaeridiumlarvae (Coleoptera: Hydrophilidae) under time constraints through predation onMusca autumnalismaggots (Diptera: Muscidae)
Authors: Sowig Peter , Himmelsbach Rolf , Himmelsbach Waltraud
Published: April 2008

Beetles in the genus Sphaeridium (Coleoptera: Hydrophilidae) and face flies, Musca autumnalis (Diptera: Muscidae), oviposit in freshly deposited cow dung. The carnivorous Sphaeridium larvae prey on M. autumnalis maggots. Most larvae reach their third instar within 4 days, before M. autumnalis maggots emigrate and food becomes scarce. The results of field studies indicate that Sphaeridium larvae prey heavily on M. autumnalis maggots: predator and prey densities are negatively correlated. In feeding experiments carried out in small plastic boxes, growth rate, measured as the relative increase in mass of a Sphaeridium larva at 24-h intervals, was correlated with the biomass of the fly maggot ingested. The results of predation experiments with one Sphaeridium larva in a 100-g portion of dung containing maggots at various densities showed that a predator searching for prey in a dung pat requires energy, so in most cases the growth rates measured in the predation experiments were lower than those predicted from the feeding experiments.
Parasitism of asymmetrical pelvic phenotypes in stickleback
Authors: Reimchen T. E.
Published: April 2008

Subtle departures from bilateral symmetry in morphological traits result from environmental and genetic stresses and may signal an inferior genetic background. Because one correlate of an inferior genome is reduced resistance to infection, such asymmetry may provide a phenotypic signal of susceptibility to parasitism. I tested this hypothesis in a population of threespine stickleback (Gasterosteus aculeatus) with cestode and nematode infections and bilateral asymmetry of the pelvis. Seventeen percent of the fish had an asymmetrical pelvis and, of these, 78% had greater expression on the left side; this directionality suggests a genetic influence. Females had consistently greater left-side asymmetry than did males. The incidence of total infection (all parasite species) in the largest adult fish (> 60 mm body length) was greater in asymmetrical phenotypes, and this occurred in both sexes and for each parasite species (Schistocephalus solidus, Cyathocephalus truncatus, Eustrongylides spp.), even when multiple-species infections were excluded. Contrary to prediction, however, in juvenile fish (< 20 mm) and yearlings (20–40 mm) but not subadults and adults (40–60 mm), asymmetrical phenotypes had significantly lower infection rates than symmetrical fish. This pattern occurred in both sexes, but the extent of the association varied over the 14 years of sampling. Consequently, if the directional asymmetry of the pelvis is under genetic control, asymmetry would be favoured during early ontogeny but selected against during the adult stages. The data support the hypothesis that asymmetry is a phenotypic signal of parasitism, but the unexpected bidirectionality of the association within a single population suggests increased complexity of the processes coupling asymmetry and genetic background.
Porcupine feeding patterns: selectivity by a generalist herbivore?
Authors: Snyder Marc A. , Linhart Yan B.
Published: April 2008

The North American porcupine (Erethizon dorsatum) is a feeding generalist, but can feed primarily on phloem of the ponderosa pine (Pinus ponderosa) during winter months in areas of the Rocky Mountains where ponderosa pine occurs in nearly pure stands. This pine is highly variable both in resin monoterpene composition and at the allozyme level. Porcupines can girdle branches or whole trees when eating phloem, and in the process often damage or kill the trees. Trees that had been fed upon (target trees) differed biochemically and genetically from adjacent trees that had not been fed upon (nontarget trees). Target trees had lower levels of the monoterpene limonene in the xylem oleoresin than matched nontarget trees, and there was a significant negative association between levels of limonene and the amount of phloem removed from individual trees. Target trees differed only slightly from nontarget trees in allele frequencies at two of nine polymorphic loci tested. When the feeding patterns of porcupines were compared with those of a previously studied mammal that feeds primarily on the phloem of ponderosa pine, Abert's squirrel (Sciurus aberti), the level of feeding selectivity was found to be far less pronounced in the porcupine.
A POINT-BASED ASYNCHRONOUS REMOTE VISUALIZATION FRAMEWORK FOR REAL-TIME VIRTUAL REALITY
Authors: GE JINGHUA , SANDIN DANIEL J. , PETERKA TOM , KOOIMA ROBERT , GIRADO JAVIER I. , JOHNSON ANDREW
Published: April 2008

High speed interactive virtual reality (VR) exploration of scientific datasets is a challenge when the visualization is computationally expensive. This paper presents a point-based remote visualization pipeline for real-time virtual reality (VR) with asynchronous client-server coupling. Steered by the client-end frustum request, the remote server samples the original dataset into 3D point samples and sends them back to the client for view updating. From every view updating frame, the client incrementally builds up a point-based geometry under an octree-based space partition hierarchy. At every view-reconstruction frame, the client continuously splats the available points onto the screen with efficient occlusion culling and view-dependent level of detail (LOD) control. An experimental visualization framework with a server-end computer cluster and a client-end head-tracked autostereo VR desktop display is used to visualize large-scale mesh datasets and ray-traced 4D Julia set datasets. The overall performance of the VR view reconstruction is about 15 fps and independent of the original dataset complexity.
WAVELET ANALYSIS OF NONLINEAR SELF-SIMILAR DISTRIBUTIONS WITH OSCILLATING SINGULARITY
Authors: MABROUK ANOUAR BEN
Published: April 2008

In the present paper, the properties of some nonlinear self-similar distributions involving both Hölder and oscillating singularities are studied. Wavelets are applied to prove that such distributions do not satisfy the classical multifractal formalism whereas they satisfy a grand canonical one. The paper in its subject is an extension of our work in Ref.7.
SYSTEMATIC DESIGN OF COMPLEX ARTEFACTS: ROBOT VISION
Authors: SITTE JOAQUIN , WINZER PETRA
Published: April 2008

In this paper we use the design of an innovative on-board vision system for a small commercial minirobot to demonstrate the application of the demand compliant design (DeCoDe) method. Vision systems are amongst the most complex sensor systems both in nature and in engineering and thus provide an excellent arena for testing design methods. A review of current design methods for mechatronic systems shows that there are no methods that support or require a complete description of the product system. The DeCoDe method is a step towards overcoming this deficiency. The minirobot robot design is carried from the generic vision system level down to first refinement for a minirobot vision system for visual navigation.
Physical synthesis for FPGA interconnect power reduction by dual-Vdd budgeting and retiming
Authors: Hu Yu , Lin Yan , He Lei , Tuan Tim
Published: April 2008

Field programmable dual-Vdd interconnects are effective in reducing FPGA power. We formulate the dual-Vdd-aware slack budgeting problem as a linear program (LP) and a min-cost network flow problem, respectively. Both algorithms reduce interconnect power by 50% on average compared to single-Vdd interconnects, but the network-flow-based algorithm runs 11x faster on MCNC benchmarks. Furthermore, we develop simultaneous retiming and slack budgeting (SRSB) with flip-flop layout constraints in dual-Vdd FPGAs based on mixed integer linear programming, and speed-up the algorithm by LP relaxation and local legalization. Compared to retiming followed by slack budgeting, SRSB reduces interconnect power by up to 28.8%.
A multiprocessor system-on-chip for real-time biomedical monitoring and analysis
Authors: Khatib Iyad Al , Poletti Francesco , Bertozzi Davide , Benini Luca , Bechara Mohamed , Khalifeh Hasan , Jantsch Axel , Nabiev Rustam
Published: April 2008

In this article we focus on multiprocessor system-on-chip (MPSoC) architectures for human heart electrocardiogram (ECG) real time analysis as a hardware/software (HW/SW) platform offering an advance relative to state-of-the-art solutions. This is a relevant biomedical application with good potential market, since heart diseases are responsible for the largest number of yearly deaths. Hence, it is a good target for an application-specific system-on-chip (SoC) and HW/SW codesign. We investigate a symmetric multiprocessor architecture based on STMicroelectronics VLIW DSPs that process in real time 12-lead ECG signals. This architecture improves upon state-of-the-art SoC designs for ECG analysis in its ability to analyze the full 12 leads in real time, even with high sampling frequencies, and its ability to detect heart malfunction for the whole ECG signal interval. We explore the design space by considering a number of hardware and software architectural options. Comparing our design with present-day solutions from an SoC and application point-of-view shows that our platform can be used in real time and without failures.
Heterogeneously tagged caches for low-power embedded systems with virtual memory support
Authors: Zhou Xiangrong , Petrov Peter
Published: April 2008

An energy-efficient data cache organization for embedded processors with virtual memory is proposed. Application knowledge regarding memory references is used to eliminate most tag translations. A novel tagging scheme is introduced, where both virtual and physical tags coexist. Physical tags and special handling of superset index bits are only used for references to shared regions in order to avoid cache inconsistency. By eliminating the need for most address translations on cache access, a significant power reduction is achieved. We outline an efficient hardware architecture, where the application information is captured in a reprogrammable way and the cache is minimally modified.
Efficient simulation of Internet worms
Authors: Nicol David M.
Published: April 2008

Simulation of Internet worms (and other malware) requires tremendous computing resources when every packet generated by the phenomena is modeled individually; on the other hand, models of worm growth based on differential equations lack the significant variability inherent in worms that sample targets randomly. This article addresses the problem with a model that focuses on times of infection. We propose a hybrid discrete-continuous model that minimizes execution time subject to an accuracy constraint on variance. We also develop an efficiently executed model of preferential random scanning and use it to investigate the sensitivity of worm propagation speed to the distribution of susceptible hosts through the network, and to the local preference probability. Finally, we propose and study two optimizations to a fluid-based simulation of scan traffic through a backbone network, observing an order-of-magnitude improvement in execution speed.
Deterministic and stochastic models for the detection of random constant scanning worms
Authors: Rohloff Kurt R. , Bacşar Tamer
Published: April 2008

This article discusses modeling and detection properties associated with the stochastic behavior of Random Constant Scanning (RCS) worms. Although these worms propagate by randomly scanning network addresses to find hosts that are susceptible to infection, traditional RCS worm models are fundamentally deterministic. A density-dependent Markov jump process model for RCS worms is presented and analyzed herein. Conditions are shown for when some stochastic properties of RCS worm propagation can be ignored and when deterministic RCS worm models can be used. A computationally simple hybrid deterministic/stochastic point-process model for locally observed scanning behavior due to the global propagation of an RCS scanning worm epidemic is presented. An optimal hypothesis-testing approach is presented to detect epidemics of these under idealized conditions based on the cumulative sums of log-likelihood ratios using the hybrid RCS worm model. This article presents in a mathematically rigorous fashion why detection techniques that are only based on passively monitoring local IP addresses cannot quickly detect the global propagation of an RCS worm epidemic with a low false alarm rate, even under idealized conditions.
What makes the competitive contribution of ERP strategic
Authors: Ragowsky Arik , Gefen David
Published: April 2008

In 1984, McFarlan suggested in his HBR article that a company might be able to use Information Technology (IT) to achieve strategic advantage in the marketplace. Although widely cited and recently elaborated on (Nolan & McFarlan, 2005), there is little empirical evidence to support it in the specific context of ERP (Enterprise Resource Planning) systems where IT is especially posed to have such a major impact. The objective of this study is to fill this gap, applying a contingency approach. The results, supporting Nolan and McFarlan (2005), show that while some ERP systems provide strategic advantage to some companies, ERP systems may not necessarily provide similar advantage to other companies due to the specific operational characteristics of each company and the way the ERP is used.

The data collected from senior managers in different manufacturing companies who were closely involved in the implementation of ERP systems in their respective companies, show that McFarlan's (1984) and Nolan and McFarlan's (2005) propositions about IT in general apply also to ERP. Both competitive strategies enabled by the ERP and specific operational characteristics can place the organization in a strategic position, and when this happens, the IT unit is more likely to be under the authority of senior management. These findings seem to contradict Carr (2003) who clamed that IT cannot provide a company with competitive advantage.