bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the efficacy of anti-parasite behaviour: a case study of tadpole susceptibility to cercariae of Echinostoma trivolvis
Authors: Koprivnikar Janet , Forbes Mark R. , Baker Robert L. 
Published: May 2007

Many animals respond behaviourally to the infective stages of parasites, but the efficacy of such responses in reducing risk of parasitism often is not established. It was found that tadpoles of Rana clamitans Latr., 1801 (green frogs) and R. sylvatica LeConte, 1825 (wood frogs) increased their activity when exposed to live infective stages (cercariae) of the trematode Echinostoma trivolvis Rudolphi, 1809. The susceptibility to parasitism for green frog tadpoles subjected to three different treatments was compared. Tadpoles were housed at 20 °C and allowed to respond to cercariae, held at 6–8 °C and showing reduced behavioural responses, or anesthetized and showing no responses. Low levels of parasitism were found for tadpoles that responded behaviourally to cercariae; such responses are expected to occur under normal field conditions in the absence of factors suppressing activity of tadpoles. We also demonstrate that infectivity of E. trivolvis cercariae to non-responding (anesthetized) wood frog tadpoles was higher at warm than at cool temperatures. Thus, lowered parasitism at warm temperatures in the first experiment likely resulted from host behavioural responses and not from low infectivity of cercariae. These results have implications for observing effects of environmental factors on susceptibility to parasitism where susceptibility is thought or known to be mediated by host behaviour.
Comparative branchial plume biometry between two extreme ecotypes of the hydrothermal vent tubeworm Ridgeia piscesae
Authors: Andersen A.C. , Flores J.F. , Hourdez S. 
Published: May 2007

The vestimentiferan tubeworm Ridgeia piscesae Jones, 1985 from the Juan de Fuca Ridge is a morphologically plastic species with two contrasted ecotypes. The “chimney-dwelling” ecotype lives along the sides of active hydrothermal chimneys, where temperature and sulfide concentrations are high, but oxygen concentrations are low. Its morphology corresponds to the “short-fat” morphotype. The “basalt-dwelling” ecotype lives on rock outcrops in surrounding basaltic fields, where temperature and sulfide concentrations are low, but oxygen is readily available. Its morphology corresponds to the “long-skinny” morphotype. We compared the ultrastructure and biometry of their branchial plumes, the essential organ for respiration and nutrition in this symbiotic tubeworm. The branchial epidermis of both ecotypes contains electron-dense organelles, which may be related to the presence of sulfides in their environment. The diffusion distance across the gill epidermis is about 20% shorter in the short-fat R. piscesae. For tubeworms of the same mass, specific branchial surface areas (SBSA) are similar in both ecotypes (mean 24 cm2/g for worms of 1–2 g body mass), which is comparable with the SBSA in the vestimentiferan vent tubeworm Riftia pachyptila Jones, 1981 . The SBSA of R. piscesae follows a power curve that is negatively correlated with total body mass. The implications for gas uptake efficiency between these two ecotypes are discussed.
Impact of diet-index selection and the digestion of prey hard remains on determining the diet of the Steller sea lion (Eumetopias jubatus)
Authors: Tollit D.J. , Heaslip S.G. , Barrick R.L. , Trites A.W. 
Published: May 2007

Nine prey species (n = 7431) were fed to four captive female Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) in 11 feeding trials over 75 days to investigate the effectiveness of different methods used to determine diet from prey hard remains. Trials aimed to replicate short (1–2 days) and long feeding bouts, and consisted of single species and mixed daily diets. Overall, 25.2% ± 22.2% (mean ± SD, range 0%–83%) otoliths were recovered, but recovery rates varied by species (ANOVA, P = 0.01) and were linearly related to otolith robustness (R2 = 0.88). Squid beaks were recovered at higher frequencies (mean 96%) than the otoliths of all species. Enumerating both non-otolith skeletal structures and otoliths (together termed bones) increased species recovery rates by twofold, on average (P < 0.001), with increases up to 2.5 times for Pacific herring ( Clupea pallasii Valenciennes in Cuvier and Valenciennes, 1847) and 3–4 times for salmonids. Using bones reduced interspecific differences (P = 0.08), but recovery varied among sea lions. Bones were distributed over more scats per meal (mean 2.9 scats, range 0–5) than otoliths (mean 1.9 scats, range 0–4). In three different 15-day mixed diet trials, biomass reconstruction (BR) indices performed better than frequency of occurrence indices in predicting diet fed. Applying our experimentally derived numerical correction factors (to account for species differences in complete prey digestion) further improved BR estimates, resulting in all 12 unweighted comparisons within 5% (for otoliths) and 12% (for bones) of the actual diet fed.
Influence of intraclutch egg-mass variation and hatching asynchrony on relative offspring performance within broods of an altricial bird
Authors: Bitton Pierre-Paul , Dawson Russell D. , O’Brien Erin L. 
Published: May 2007

Rates of growth and size of nestlings at fledging have important consequences for future survival and reproductive success in many passerine birds. Within broods of altricial species, these characteristics are often influenced by size hierarchies established early in the nesting period due to hatching asynchrony and within-clutch variation in egg mass, but the concurrent effect of these factors is poorly understood. We investigated the relative influence of these variables on nestling performance within broods of tree swallows, Tachycineta bicolor (Vieillot, 1808). Nestlings that hatched earlier within nests were heavier and larger than their later-hatched siblings at 4 days of age. Similarly, earlier-hatched nestlings grew their ninth primary flight feathers faster and had longer ninth primaries just prior to fledging than did later-hatched siblings. Differences in egg mass of siblings also contributed to mass and size hierarchies at 4 days of age, but did not affect any other difference in sibling performance. We conclude that within-clutch variation in performance of offspring is determined primarily by size hierarchies resulting from asynchronous hatching. Intraclutch egg-mass variation appears to have little effect on performance of siblings and may be best explained by proximate constraints on females.
Effect of oral suction and other friction-enhancing behaviors on the station-holding performance of suckermouth catfish (Hypostomusspp.)
Authors: Gerstner C.L. 
Published: May 2007

Effect of oral suction and other friction-enhancing behaviors on the ability to maintain position in a current (station-holding) was determined for the suckermouth catfish (genus Hypostomus Lacépède, 1803). Fish were tested using an increasing velocity test on three substrata (smooth Lucite®, rough Lucite®, and wire grid). On the smooth substratum, use of oral suction and other behaviors delayed the need to swim continuously out of ground contact from 9.1 ± 0.3 cm/s (uslip) to 89.2 ± 7.9 cm/s (uswim). Trials on the wire grid showed that oral suction was ineffective as predicted; however, fish were able to use other friction-enhancing behaviors instead to improve station-holding performance. Behaviors that increased friction by hooking the fish to the substrate via the odontodes and pectoral fin spines were very effective at delaying the need for steady swimming from 12.9 to 145.0 cm/s. On the rough substratum, fish were able to use both oral suction and the odontodes or fin spines to increase friction, and station-holding performance was similar to values on the wire substratum. Thus, while use of the oral suction disk was shown to improve station-holding performance, use of other morphological features such as the odontodes and fin spines may be equally important.
Utilization of stored energy reserves during fasting varies by age and season in Steller sea lions
Authors: Rea L.D. , Rosen D.A.S. , Trites A.W. 
Published: May 2007

Nine captive Steller sea lions ( Eumetopias jubatus (Schreber, 1776), 1.75–6 years of age) were fasted for 7–14 d to test the effect of short-term fasting on changes in body mass and body condition. Trials were repeated during both the summer breeding season and the nonbreeding season in seven animals to elucidate whether there was a seasonal component to the ability of Steller sea lions to adapt to limited food resources. Mean percent mass loss per day was higher during the breeding season in juveniles (1.8% ± 0.2%·d–1) than in subadults (1.2% ± 0.1%·d–1), but there were no significant age-related differences during the nonbreeding season (juveniles, 1.5% ± 0.3%·d–1; subadults, 1.7% ± 0.3%·d–1). A decrease in the rate of mass loss occurred after the first 3 d of fasting only in subadults during the breeding season. Percent total body lipid ranged from 11% to 28% of total body mass at the initiation of fasting trials. Animals with lower initial percent total body lipid exhibited higher subsequent rates of mass loss and a lower percentage of tissue catabolism derived from lipid reserves. There was no evidence of metabolic adaptation to fasting in juveniles, which suggests that juvenile sea lions would be more negatively impacted by food limitation during the breeding season than would subadults.
Habitat structure, climatic factors, and habitat use by European bison (Bison bonasus) in Polish and Belarusian parts of the Białowieża Forest, Poland
Authors: Daleszczyk K. , Krasińska M. , Krasiński Z.A. , Bunevich A.N. 
Published: May 2007

Białowieża Forest is divided into Polish and Belarusian parts that differ in habitat structure and degree of protection. The forest supports two European bison, Bison bonasus (L., 1758), populations that are isolated from each other. We analysed bison habitat use from relocations of 34 radio-collared bison from both populations collected in 1993–2003. The two bison populations differed considerably in habitat use, but home-range sizes were similar. The habitat structure in the Polish part is more advantageous for bison (deciduous forests prevail) than in the Belarusian part; however, open areas form a rich source of forage for ungulates in the Belarusian part, which presumably helped to eliminate the difference between the two parts. In 1977–2003, the annual temperature in this area rose and the total precipitation diminished. As a result, the habitat use by bison changed in both populations when compared with those in earlier studies; use of coniferous forests decreased, while use of deciduous forests and alderwoods increased. Generalized linear models on relationships among climatic factors and habitat use showed that the amount of water accessible in the period up to 4 years ago was the main factor affecting the use of various forest types. Habitat preferences differed between adult bulls and groups that included cows, but were similar in both populations irrespective of the differences in habitat composition.
Seasonal migration and home range of roe deer (Capreolus capreolus) in the Italian eastern Alps
Authors: Ramanzin M. , Sturaro E. , Zanon D. 
Published: May 2007

Although it has been demonstrated that European roe deer ( Capreolus capreolus (L. 1758)) may migrate seasonally in areas with snow gradients, this behaviour remains scarcely understood. From 1999 to 2002, radio-tracking techniques in an Italian alpine area showed that 40% of the 32 monitored roe deer migrated (12.0 ± 6.2 km, mean ± SD) from the high-elevation summer ranges to the low-elevation winter ranges. Proportions of migratory deer were similar for fawns and adults and for males and females. We documented a mixed migration strategy, with most deer migrating once to the winter range in years of heavy snowfalls, but many deer migrating inconsistently or only for a short period to the winter range in one year with very scarce snowfalls. Seasonal home-range sizes were similar for migratory and stationary deer, except in a winter with very shallow snow when migrators used unusually large home ranges. In all seasons, migrators showed a lower within home range site fidelity than did stationary deer. Our results indicate that seasonal migrations may be a common strategy exhibited by roe deer living in mountain areas to avoid deep snow, and that variability in climatic conditions might be responsible for the development of variable spatial strategies.
Litter size, sex ratio, and age structure of gray wolves, Canis lupus, in relation to population fluctuations in northern Belarus
Authors: Sidorovich V.E. , Stolyarov V.P. , Vorobei N.N. , Ivanova N.V. , Jędrzejewska B. 
Published: May 2007

Gray wolf ( Canis lupus L., 1758) population fluctuations in northern Belarus (Vitebsk region) between 1990 and 2003 were significantly affected by hunting pressure by humans. Mean litter size was inversely density dependent and varied from 4.8 to 7.7 pups (range 2–10). The increase in litter size with declining density of wolf population concerned only female pups, whereas the number of male pups in a litter was not related to population density. The sex ratio of pups varied significantly: the proportion of females reached 70% in a low-density wolf population and declined to 40%–50% in a high-density population. The age structure also varied. In years following heavy hunting pressure, 55% of individuals shot were juveniles <1 year old (with a strong predominance of females that constituted 69% of juveniles shot), and only 11% of wolves were older than 4 years. The mean age of all wolves shot was 1.5 years. In years following low hunting pressure, 34% of animals shot were juveniles and 20% exceeded 4 years. The mean age was 2.8 years. A female-biased sex ratio of wolf pups conforms to Hiraiwa-Hasegawa’s hypothesis of the advantaged daughter, proposed for species in which mothers are able to influence the reproductive success of their daughters through transmission of rank.
Landscape features and sea ice influence nesting common eider abundance and dispersion
Authors: Chaulk Keith G. , Robertson Gregory J. , Montevecchi William A. 
Published: May 2007

Factors that influence individual and colony spacing are still not well understood in many organisms. Common eiders ( Somateria mollissima (L. 1758)) nest on coastal islands and forage in intertidal and shallow subtidal waters. We considered several biotic and abiotic factors, their interactions, and how these might influence the distribution of eider colonies at several spatial scales in Labrador, Canada. At the island level, nest abundance was not related to intertidal prey density. At the 104 km2grid scale, eider nest abundance and the coefficient of dispersion (CD; the variance to mean ratio of colony size or grid cell, where CD indicates population dispersion) were negatively related to the number of islands. Spring ice cover was positively related to the number of islands but was negatively related to eider nest abundance and to CD. Ice cover – abundance and ice cover – CD were significant at two spatial scales (104 and 455 km2, respectively), but other relationships were weaker at the larger spatial scale. We hypothesize that during the spring, archipelagos with many islands trap ice, providing terrestrial predators access to nesting islands by acting as bridges and that increased predation reduces habitat quality causing nesting eiders to disperse. Our findings suggest that eiders respond to landscape features, including ice cover, a feature that is being influenced by climate change.
The influence of buoyancy and drag on the dive behaviour of an Arctic seabird, the Thick-billed Murre
Authors: Elliott Kyle H. , Davoren Gail K. , Gaston Anthony J. 
Published: May 2007

We used time–depth recorders to investigate the behaviour of free-ranging Thick-billed Murres ( Uria lomvia L., 1758) after attaching positively (n = 9), negatively (n = 10), or neutrally (n = 9) buoyant handicaps and increasing cross-sectional area by 3% (2.8 cm2; n = 8) or 6% (5.6 cm2; n = 6). When buoyancy was altered or drag increased, murres reduced dive depth and duration, suggesting that murres do not manipulate dive depth to obtain neutral buoyancy during the bottom phase. Ascent rate increased as the bird surfaced and mean ascent rate increased for deeper dives, presumably reflecting steeper dive angles and greater buoyancy during deep dives. For short dives (<150 s), preceding surface pauses were better correlated with dive depth and duration than succeeding surface pauses (surface pauses were “anticipatory”), suggesting that murres control inhalation rates based on anticipated dive depth and duration. Murres reduced ascent rate near the surface, possibly to reduce the risk of decompression sickness. Neutrally buoyant recorders attached to the legs had no effect on chick feeding frequencies or adult mass loss, suggesting that this attachment method may have the least effect on the foraging behaviour of alcids.
Neurophysiological Evidence for the Time Course of Activation of Global Shape, Part, and Local Contour Representations during Visual Object Categorization and Memory
Authors: Schendan Haline E. , Kutas Marta 
Published: May 2007

Abstract
Categorization of visual objects entails matching a percept to long-term representations of structural knowledge. This object model selection is central to theories of human visual cognition, but the representational format(s) is largely unknown. To characterize these neural representations, event-related brain potentials (ERPs) to fragmented objects during an indirect memory test were compared when only local contour features, but not global shapes of the object and its parts, differed between encoding and retrieval experiences. The ERP effects revealed that the format of object representations varies across time according to the particular neural processing and memory system currently engaged. An occipito-temporal P2(00) showed implicit memory modulation to items that repeatedly engaged similar perceptual grouping processes but not items that merely reinstantiated visual features. After 500 msec, memory modulation of a late positive complex, indexing secondary categorization and/or explicit recollection processes, was sensitive to local contour changes. In between, a frontocentral N350, indexing the model selection and an implicit perceptual memory system, showed reactivation of object representations whenever the same global shapes were reactivated, despite local feature differences. These and prior N350 findings provide direct neurophysiological evidence that the neural representations supporting object categorization include knowledge beyond local contours and about higher-order perceptual structures, such as the global shapes of the object and its parts, that can differ between object views. The N350 is proposed to index a second state of interactive, recurrent, and feedback processing in occipital and ventral temporal neocortex supporting higher-order cognitive abilities and phenomenological awareness with objects.
Prefrontal Cortical Response to Conflict during Semantic and Phonological Tasks
Authors: Snyder Hannah R. , Feigenson Keith , Thompson-Schill Sharon L. 
Published: May 2007

Abstract
Debates about the function of the prefrontal cortex are as old as the field of neuropsychology—often dated to Paul Broca's seminal work. Theories of the functional organization of the prefrontal cortex can be roughly divided into those that describe organization by process and those that describe organization by material. Recent studies of the function of the posterior, left inferior frontal gyrus (pLIFG) have yielded two quite different interpretations: One hypothesis holds that the pLIFG plays a domain-specific role in phonological processing, whereas another hypothesis describes a more general function of the pLIFG in cognitive control. In the current study, we distinguish effects of increasing cognitive control demands from effects of phonological processing. The results support the hypothesized role for the pLIFG in cognitive control, and more task-specific roles for posterior areas in phonology and semantics. Thus, these results suggest an alternative explanation of previously reported phonology-specific effects in the pLIFG.
What is Involved and What is Necessary for Complex Linguistic and Nonlinguistic Auditory Processing: Evidence from Functional Magnetic Resonance Imaging and Lesion Data
Authors: Dick Frederic , Saygin Ayse Pinar , Galati Gaspare , Pitzalis Sabrina , Bentrovato Simone , D'Amico Simona , Wilson Stephen , Bates Elizabeth , Pizzamiglio Luigi 
Published: May 2007

AbstractWe used functional magnetic resonance imaging (fMRI) in conjunction with a voxel-based approach to lesion symptom mapping to quantitatively evaluate the similarities and differences between brain areas involved in language and environmental sound comprehension. In general, we found that language and environmental sounds recruit highly overlapping cortical regions, with cross-domain differences being graded rather than absolute. Within language-based regions of interest, we found that in the left hemisphere, language and environmental sound stimuli evoked very similar volumes of activation, whereas in the right hemisphere, there was greater activation for environmental sound stimuli. Finally, lesion symptom maps of aphasic patients based on environmental sounds or linguistic deficits [Saygin, A. P., Dick, F., Wilson, S. W., Dronkers, N. F., & Bates, E. Shared neural resources for processing language and environmental sounds: Evidence from aphasia. Brain, 126, 928–945, 2003] were generally predictive of the extent of blood oxygenation level dependent fMRI activation across these regions for sounds and linguistic stimuli in young healthy subjects.
Predictive Learning, Prediction Errors, and Attention: Evidence from Event-related Potentials and Eye Tracking
Authors: Wills A. J. , Lavric A. , Croft G. S. , Hodgson T. L. 
Published: May 2007

Abstract
Prediction error (“surprise”) affects the rate of learning: We learn more rapidly about cues for which we initially make incorrect predictions than cues for which our initial predictions are correct. The current studies employ electrophysiological measures to reveal early attentional differentiation of events that differ in their previous involvement in errors of predictive judgment. Error-related events attract more attention, as evidenced by features of event-related scalp potentials previously implicated in selective visual attention (selection negativity, augmented anterior N1). The earliest differences detected occurred around 120 msec after stimulus onset, and distributed source localization (LORETA) indicated that the inferior temporal regions were one source of the earliest differences. In addition, stimuli associated with the production of prediction errors show higher dwell times in an eye-tracking procedure. Our data support the view that early attentional processes play a role in human associative learning.