bluuebunny/crossref_metadata_2025 huggingface dataset:
Chronic blockade of brain "ouabain" prevents sympathetic hyper-reactivity and impairment of acute baroreflex resetting in rats with congestive heart failure
Authors: Huang Bing S , Yuan Baoxue , Leenen Frans HH
Published: April 2011

In rats with congestive heart failure (CHF) post myocardial infarction (MI) acute blockade of brain "ouabain" reverses sympathetic hyperactivity and chronic blockade prevents the desensitization of baroreflex function. This study was conducted to determine: i) if chronic blockade of brain "ouabain" maintains normal sympathetic reactivity; andii) if acute baroreflex resetting (another parameter of baroreflex function) also becomes impaired, and if so, does brain "ouabain" contribute to impairment in acute baroreflex resetting. CHF post MI was induced by acute coronary artery ligation in Wistar rats. Animals were treated with 200 µg·day-1 i.c.v. or i.v. Fab fragments (which bind brain "ouabain" with high affinity), or treated with 200 µg·day-1 i.c.v. gamma-globulins (control group). The length of treatment was 0.5-8 weeks or 4-8 weeks post MI. At 8 weeks mean arterial pressure (MAP), central venous pressure (CVP), heart rate (HR), and renal sympathetic nerve activity (RSNA) were recorded in concious rats at rest and in response to: i) air-jet stress, ii) i.c.v. guanabenz (an α2-adrenoceptor agonist), and iii) a 30 min i.v. infusion of nitroprusside (NP). Excitatory responses to air stress and inhibitory responses to guanabenz of MAP, HR, and RSNA were significantly enhanced in rats with CHF versus the sham-operated treated group. This enhancement was prevented in the CHF group treated with i.c.v., but not i.v., Fab. Nitroprusside induced a sustained decrease in MAP (~ 25 mmHg) and a transient decrease in CVP. Heart rate and RSNA increased significantly within 1 min of beginning the infusion. The peak increases as well as the product of changes in MAP-HR and RSNA-HR were significantly smaller in rats with CHF treated with gamma-globulins versus sham rats and versus CHF rats treated with i.c.v. Fab. In sham-operated rats and CHF rats treated with i.c.v. Fab, RSNA and HR began to decrease within 3-4 min of beginning the NP infusion and had returned to baseline by 20 min. In contrast, RSNA and HR remained increased throughout the infusion in the CHF rats treated with gamma-globulins. These data indicate that in rats with CHF acute resetting of the arterial baroreflex in response to a lower BP becomes impaired, and chronic blockade of brain "ouabain" prevents both this change in baroreflex resetting as well as sympathetic hyperactivity.Key words: heart failure, acute baroreflex resetting, sympathetic hyperactivity, nitroprusside.
Plasma and cerebrospinal fluid concentrations of neuropeptide Y, serotonin, and catecholamines in patients under propofol or isoflurane anesthesia
Authors: Grouzmann E , Borgeat A , Fathi M , Gaillard R C , Ravussin P
Published: April 2011

Propofol is a widely used anesthetic for both induction and maintenance of anesthesia during surgery. A strong feeling of hunger has been reported during the early recovery period after propofol anesthesia. We have investigated the effect of propofol on appetite in 10 patients undergoing a craniotomy and in parallel measured neuropeptide Y (NPY), catecholamines, and serotonin levels in the cerebrospinal fluid and plasma during anesthesia. Ten patients anesthetized with a volatile agent (isoflurane) served as a control group. Plasma NPY and catecholamines levels were not affected by surgery at any time. We observed a strong increase in NPY concentrations in the cerebrospinal fluid independently of the anesthetic technique agent used, whereas catecholamines were unchanged. We found that serotonin concentrations decreased significantly in the plasma (but not in the cerebrospinal fluid) of patients treated by propofol when compared with the control group; this decrease was associated with an increase of hunger early postoperatively. We concluded that the proappetite effect of propofol is mediated through a decrease of serotonin at the peripheral level.Key words: catecholamines, serotonin, neuropeptide Y (NPY), cerebrospinal fluid, serum, appetite.
Neuropeptide Y phase advances the in vitro hamster circadian clock during the subjective day with no effect on phase during the subjective night
Authors: Harrington Mary E , Schak Kathryn M
Published: April 2011

The mammalian daily (circadian) clock is located in the suprachiasmatic nuclei of the hypothalamus. Clock function can be detected by the measurement of the circadian change in spontaneous firing rate of suprachiasmatic nuclei cells in a brain slice preparation in vitro. We investigated the effects of neuropeptide Y on this rhythm of firing rate in hamster suprachiasmatic nuclei neurons. Slices were prepared using standard techniques. On the 1st day in vitro, neuropeptide Y (200 ng/200 nL; 47 pmol) was applied as a microdrop to the suprachiasmatic nuclei region at various times. Spontaneous single-unit firing was measured for 6-12 h on the 2nd day in vitro. Peak firing rate in treated slices was compared with that of untreated control slices to measure phase shifts induced by the peptide. Neuropeptide Y induced phase advances of circa-3h when applied during the subjective day (ZT 2-10) but did not significantly alter phase when applied during the subjective night. The phase shifts to neuropeptide Y in the hamster tissue in vitro are similar in phase dependency and magnitude to shifts measured in vivo.Key words: circadian, neuropeptide Y, rhythm, suprachiasmatic.
Effects of long-term pretreatment with isoproterenol on bromocriptine-induced tachycardia in conscious rats
Authors: Lahlou Saad , Lima Guilherme C , Leão-Filho Carmelo SC , Duarte Gloria P
Published: April 2011

It has been shown that bromocriptine-induced tachycardia, which persisted after adrenalectomy, is (i) mediated by central dopamine D2 receptor activation and (ii) reduced by 5-day isoproterenol pretreatment, supporting therefore the hypothesis that this effect is dependent on sympathetic outflow to the heart. This study was conducted to examine whether prolonged pretreatment with isoproterenol could abolish bromocriptine-induced tachycardia in conscious rats. Isoproterenol pretreatment for 15 days caused cardiac hypertrophy without affecting baseline blood pressure and heart rate. In control rats, intravenous bromocriptine (150 µg/kg) induced significant hypotension and tachycardia. Bromocriptine-induced hypotension was unaffected by isoproterenol pretreatment, while tachycardia was reversed to significant bradycardia, an effect that was partly reduced by i.v. domperidone (0.5 mg/kg). Neither cardiac vagal nor sympathetic tone was altered by isoproterenol pretreatment. In isolated perfused heart preparations from isoproterenol-pretreated rats, the isoproterenol-induced maximal increase in left ventricular systolic pressure was significantly reduced, compared with saline-pretreated rats (the EC50 of the isoproterenol-induced increase in left ventricular systolic pressure was enhanced ~22-fold). These results show that 15-day isoproterenol pretreatment not only abolished but reversed bromocriptine-induced tachycardia to bradycardia, an effect that is mainly related to further cardiac beta-adrenoceptor desensitization rather than to impairment of autonomic regulation of the heart. They suggest that, in normal conscious rats, the central tachycardia of bromocriptine appears to predominate and to mask the bradycardia of this agonist at peripheral dopamine D2 receptors.Key words: bromocriptine, blood pressure, heart rate, isoproterenol pretreatment, peripheral dopamine D2 receptors, desensitization.
Length dependence of staircase potentiation: interactions with caffeine and dantrolene sodium
Authors: Rassier Dilson E , MacIntosh Brian R
Published: April 2011

In skeletal muscle, there is a length dependence of staircase potentiation for which the mechanism is unclear. In this study we tested the hypothesis that abolition of this length dependence by caffeine is effected by a mechanism independent of enhanced Ca2+release. To test this hypothesis we have used caffeine, which abolishes length dependence of potentiation, and dantrolene sodium, which inhibits Ca2+release. In situ isometric twitch contractions of rat gastrocnemius muscle before and after 20 s of repetitive stimulation at 5 Hz were analyzed at optimal length (Lo), Lo- 10%, and Lo+ 10%. Potentiation was observed to be length dependent, with an increase in developed tension (DT) of 78 ± 12, 51 ± 5, and 34 ± 9% (mean ± SEM), at Lo- 10%, Lo, and Lo+ 10%, respectively. Caffeine diminished the length dependence of activation and suppressed the length dependence of staircase potentiation, giving increases in DT of 65±13, 53 ± 11, and 45 ± 12% for Lo- 10%, Lo, and Lo+ 10%, respectively. Dantrolene administered after caffeine did not reverse this effect. Dantrolene alone depressed the potentiation response, but did not affect the length dependence of staircase potentiation, with increases in DT of 58 ± 17, 26 ± 8, and 18 ± 7%, respectively. This study confirms that there is a length dependence of staircase potentiation in mammalian skeletal muscle which is suppressed by caffeine. Since dantrolene did not alter this suppression of the length dependence of potentiation by caffeine, it is apparently not directly modulated by Ca2+availability in the myoplasm.
Endothelium and aortic contraction to endothelin-1 in the pregnant rat
Authors: Dièye Amadou Moctar , Gairard Alexis
Published: April 2011

Endothelium-derived factors modulate tone and may be involved in hyporeactivity to vasoconstrictors, such as norepinephrine or angiotensin II, as has been previously described during gestation. The endothelium produces endothelin-1, a major vasoconstrictor peptide, therefore aortic contractions to endothelin-1 (10-10 to 3 ×10-7 M) were used to assess the role of the endothelium in pregnant Wistar rats (at 20 days of gestation). Late pregnancy is characterized by a significantly diminished systolic blood pressure in conscious rats (-17 mmHg, P < 0.001, n = 14). In pregnant and in age-matched nonpregnant female rats, endothelin-1 induced aortic contraction was greater when endothelium was present (at least P < 0.01). Indomethacin significantly reduced this contraction in aortic rings with intact endothelium in all groups. In aortic rings that had endothelium physically removed, contraction to endothelin-1 was greater in pregnant rats than in nonpregnant ones. Indomethacin decreased contraction of aortic rings in pregnant rats only. These results suggest an enhanced synthesis of vasoconstrictors by cyclooxygenases in vascular smooth muscle during pregnancy. In vessels with intact endothelium, we did not find hyporeactivity to endothelin-1 during late pregnancy. Contraction to endothelin-1 involved ETA receptors because it was decreased by BQ-123, an ETA receptor antagonist, whereas there was no significant change when using BQ-788, an ETB receptor antagonist.

Key words: endothelin-1, endothelium, contraction, aorta, gestation.
Substrate selection by settling zebra mussels, Dreissena polymorpha, relative to material, texture, orientation, and sunlight
Authors: Marsden J Ellen , Lansky David M
Published: April 2011

Zebra mussels (Dreissena polymorpha) invaded the Great Lakes in 1986 and are considered to be a nuisance species, because of their rapid population growth and their strong byssal attachment to a variety of man-made and natural surfaces. Research on possible antifouling materials or coatings has revealed few nontoxic substrates that even retard attachment of mussels. The influence of several substrate characteristics in combination (material, texture, orientation, and sunlight) on zebra mussel settlement was examined. Settlement of post-veliger mussels on experimental plates indicated that the mussels attached in higher numbers on upper versus lower horizontal surfaces, textured versus smooth surfaces, shaded versus sunlit surfaces, PVC versus Plexiglas, and plastic (PVC and Plexiglas) versus glass. Zebra mussels did not show strong preferences among several additional substrate materials (wood, Fiberglas, concrete, limestone, aluminum, and raw steel) but they strongly avoided galvanized steel. These results confirm field observations of locations in which mussels are most likely to be found. Information about zebra mussel substrate preferences may enhance the design of monitoring programs and the integrated management of mussels in vulnerable areas.
Validation of otolith daily increments in the tropical eel Anguilla celebesensis
Authors: Arai Takaomi , Limbong Daniel , Tsukamoto Katsumi
Published: April 2011

To validate daily increments in otoliths of the tropical freshwater eel Anguilla celebesensis, a time-reference mark was incorporated in the otoliths of glass eels by immersing the eels in alizarin complexone (ALC) solution. They were subsequently reared in aquaria for 10 or 20 days, and the increments outside a fluorescent red ALC mark were counted. The numbers from the 10- and 20-d experiments were 9.4 ± 0.9 (mean ± SD) and 19.4 ± 1.4, respectively, suggesting daily deposition of otolith increments. Precise examination of otolith microstructure from the core to the edge showed gradual changes in increment width with no discontinuous structural features, suggesting that increments were deposited continuously from hatching to time of sacrifice. It was thus concluded that otolith increments in this species can be used for daily age determination.
Effects of canine heartworm (Dirofilaria immitis) on body condition and activity of free-ranging coyotes (Canis latrans)
Authors: Sacks Benjamin N , Blejwas Karen M
Published: April 2011

We used radiotelemetry to study relationships among canine heartworm (Dirofilaria immitis) infection, body condition, and activity of free-ranging coyotes (Canis latrans). Average body mass at death was lower for 17 coyotes in a high-intensity infected group (mean = 33.6 heartworms) than for 18 coyotes in a control group (mean = 3.6 heartworms; p < 0.01). Coyotes in the infected group lost body mass at an average rate of 20% per year relative to the control group (p < 0.01). Bone marrow fat was negatively correlated with heartworm burden (R2 = 0.27; p < 0.01). Average body mass of coyotes at initial capture (i.e., potentially before infection) did not differ between infected and control groups (p = 0.90; 1β = 0.70). Activity was negatively correlated with heartworm burden during the last 2 months of life (R2 = 0.30; p < 0.01), but no correlation was found 24 months before death. Activity of the infected group (n = 13) declined over time (p = 0.01), whereas no difference in activity was observed in the control group (n = 13; p = 0.50). Our findings indicate that heartworm infection reduced body condition and activity of coyotes but that nutritional status did not significantly affect susceptibility to infection.
Health impact of phytohaemagglutinin-induced immune challenge on great tit (Parus major) nestlings
Authors: Hõrak Peeter , Ots Indrek , Tegelmann Lea , Møller Anders Pape
Published: April 2011

Assuming that immune function is resource-limited, it can be expected to compete with other important functions of an organism for the total resource pool, giving rise to trade-offs in resource allocation. To test whether such a trade-off exists between immune defence and growth, the physiological impact of an immune challenge was examined in great tit (Parus major) nestlings, using phytohaemagglutinin (PHA) as a novel antigen. Nestlings injected intradermally with PHA in wing webs at 8 days of age produced a heterophilic response, while their growth was not suppressed in comparison with untreated control siblings. Nestlings that grew poorly produced a weaker cutaneous response to PHA inoculation than well-growing nestlings. These two results suggest that the response to PHA (a measure of the intensity of T-lymphocyte mediated immune responsiveness) is resource demanding, but these resources are not reallocated from those used for growth. This finding can be reconciled with current hypotheses, which propose that the currency in trade-offs between immune response and other demands on the organism is not necessarily energy or macronutrients but may instead be based on immunopathology, carotenoids, or production of free radicals.
Immunocompetence in workers of a social insect, Bombus terrestris L., in relation to foraging activity and parasitic infection
Authors: Doums Claudie , Schmid-Hempel Paul
Published: April 2011

The immune system is a general mechanism that reduces the fitness cost of parasitism. In this study, we examined variation in immune responses under natural conditions in the bumblebee Bombus terrestris. Using 14 colonies reared in the field, we compared the immune response to an artificial implant between workers that could or could not forage (86 control and 91 nonforaging workers). Foraging activity was prevented by cutting a large part of the wings. As expected, control workers had lower immune responses than nonforaging workers in 10 of 14 colonies. Overall, the treatment effect was significant even though weak, suggestive of a trade-off between immune defence and foraging activity. We also examined the environmental factors that might covary with the immune response in workers. The immune response significantly decreased in workers that were naturally infected by the intestinal parasite Crithidia bombi and increased with a measure of colony success, the maximum number of workers. These correlations suggest that the strength of immune responses reflects individual, and hence colony condition.
Social status of male Iberian rock lizards (Lacerta monticola) influences their activity patterns during the mating season
Authors: Martín José , López Pilar
Published: April 2011

Not all individual lizards in a population are simultaneously active even when thermal conditions are suitable for activity. We examined inter-individual variability in activity levels of male Iberian rock lizards (Lacerta monticola) in a seminatural enclosure during the mating season, and analyzed whether social status affects their activity levels, time budgets, and body-mass changes. Activity levels of lizards varied significantly with time of day. However, activity levels of individual males were significantly correlated with their rank in the social hierarchy. When the males were active, their status did not influence the time spent basking, resting, or moving, but males with a higher status spent more time in social activities. Higher activity levels were costly, causing males to lose more body mass, although this could have been mainly due to the costs of maintaining a higher social status. We conclude that because attaining a higher status may require a male to be more active and more involved in agonistic encounters, subordinate individuals decrease their activity in order to decrease the costs of social behavior.
Satellite-monitored movements of radio-tagged bowhead whales in the Beaufort and Chukchi seas during the late-summer feeding season and fall migration
Authors: Mate Bruce R , Krutzikowsky Gregory K , Winsor Martha H
Published: April 2011

From 30 August to 6 September 1992, we tagged 12 juvenile bowhead whales (Balaena mysticetus) with Argos satellite-monitored radio tags in the Canadian Beaufort Sea off the Mackenzie River Delta. Eight tags documented [Formula: see text]9820 km of movements between 392 locations during 111 whale-tracking days. The whales did not move in unison. Individual movements and average speeds (1.1-5.8 km/h) varied widely. One whale stayed in Mackenzie Bay for 23.5 d, while the rest stayed an average of only 2.4 d. The majority of locations for all whales were in shallow water: 65% at <50 m depth and 87% at <100 m depth. Seven whales went into water >100 m deep and four were in water >500 m deep. The whale with the longest record traveled [Formula: see text]3886 km to Siberia in 32.5 d, averaging 5.0 km/h. Its westerly route through the Beaufort and Chukchi seas was between 70° and 72°N and primarily in heavy ice ([Formula: see text]90% coverage), which was continuous west of 151°W. This whale's speed was faster, though not significantly, in heavy ice than in more open water. This is the first detailed documentation of the route and speed of a bowhead whale during its fall migration from Canadian to Russian waters.
Larval colonisation and recruitment in the Pacific giant salamander (Dicamptodon tenebrosus) in British Columbia
Authors: Ferguson Heather M
Published: April 2011

Dicamptodon tenebrosus is a species at risk in Canada and little is known about its ability to recover from disturbance at any scale. I tested whether stream-dwelling larvae are capable of recolonising regions subjected to small disturbances (25- to 40-m artificially depleted reaches) within 1 year, and compared the contributions of larval dispersal and adult reproduction to repopulation of barren areas. Numerical recovery from depletions in these stream sections was predicted to take 6-42 months. Only 4-5% of larvae in reaches adjacent to the depleted zones became colonists in 13 months. Colonisation occurred both by upstream and downstream movements and by larvae of different sizes. Local reproduction appears to be a more effective means of repopulating an area than larval immigration. In one reproductive event, an adult female could provide an equal or greater number of colonists than is supplied by neighbouring stream sections holding 200+ larvae.
Habitat utilization and breeding success in Leach's Storm-Petrel: the importance of sociality
Authors: Stenhouse Ian J , Montevecchi William A
Published: April 2011

Models like "ideal-free distribution" that have been developed to predict the spatial distribution of animal populations typically assume that high densities will occur in preferred habitats. We investigated habitat utilization in Leach's Storm-Petrels (Oceanodroma leucorhoa) at the centre of the species' breeding range in the North Atlantic by comparing microhabitat features and breeding success in forest and open meadows on Great Island, Newfoundland. Leach's Storm-Petrels utilized forest more than open habitat. Overall, forest provided consistently better breeding habitat, with burrow density and activity and occupancy rates higher than in open habitat. A strong positive relationship between occupancy and both hatching and breeding success suggests that sociality plays an important role in habitat utilization and reproduction in Leach's Storm-Petrel.
Effect of temperature on preference for dietary unsaturated fatty acids in the Djungarian hamster (Phodopus sungorus)
Authors: Hiebert Sara M , Fulkerson Erin K , Lindermayer Kirstin T , McClure Sarah D
Published: April 2011

Previous studies have shown that hibernators preparing for winter prefer a diet rich in unsaturated fat. This study was designed to determine if a daily heterotherm, the Djungarian hamster (Phodopus sungorus), shows a similar preference when given simultaneous access to two diets, one rich in saturated fat and the other rich in unsaturated fat. In two experiments, hamsters that had been exposed to short days for 8-10 weeks were exposed to 8°C for 10 days. When half of these animals were moved to a warm environment (26-29°C), they developed a significantly lower preference for the unsaturated diet than controls that remained at 8°C (P < 0.01). This difference in preference disappeared when the experimental group was returned to 8°C (P = 0.4). Although mean body temperature (Tb) was significantly lower (mean difference = 0.35°C) in experimental animals in the cold environment, most animals did not enter daily torpor at any time during the experiment. Together, these results suggest that the large decreases in core Tb accompanying torpor, originally assumed to necessitate the incorporation of unsaturated fatty acids into cell membranes of hibernators and daily heterotherms, are not necessary to stimulate changes in food choice.
Red blood cell and white blood cell counts in sandpipers (Philomachus pugnax, Calidris canutus): effects of captivity, season, nutritional status, and frequent bleedings
Authors: Piersma Theunis , Koolhaas Anita , Dekinga Anne , Gwinner Eberhard
Published: April 2011

Captive ruffs (Philomachus pugnax) and red knots (Calidris canutus) kept in small flocks in outdoor aviaries maintained body mass and plumage cycles resembling those of free-living conspecifics. The persistence of identifiable annual cycles enabled us to study variability in two blood parameters, one a measure of red blood cell count (hematocrit) and the other an index of white blood cell (WBC) abundance (percentage). In both species hematocrit values averaged 0.43, somewhat lower than those measured in free-living red knots. Hematocrit varied little with time of year and we were unable to convincingly confirm predicted elevated hematocrit levels during periods of storage of fat for migration. In both species the percentage of WBCs (percent WBCs) initially declined from 0.6 to 0.8%; levels stabilized at 0.4% in ruffs and 0.3% in red knots after half a year in captivity. Using observations of the same individual red knots in the years before and after the experimental year as controls, biweekly extraction of about 30% of blood volume did not negatively affect seasonal changes in body mass and moult and breeding-plumage cycles. In nutritionally stressed red knots, hematocrit levels were low, and in these birds only, the small wounds inflicted by bleeding healed with difficulty.
Home-range ecology, aggressive behaviour, and survival in juvenile lizards, Psammodromus algirus
Authors: Civantos Emilio
Published: April 2011

Individual animals are assumed to gain possession of areas where they win fights or chases, while those that lose agonistic interactions leave areas where they were defeated. Thus, the more dominant animal secures the territory, often excluding subordinates from optimal habitat. This assumption forms the basis for concluding that the degree of aggressiveness or relative dominance of an individual may be important in determining the size or quality of a territory that it can secure. I examined in the field the relationships between home-range size, quality of home range, and degree of aggressiveness and their effects on survivorship in juvenile male lizards (Psammodromus algirus). The degree of aggressiveness was determined using tethered intruders presented to resident individuals in the field. The more aggressive individuals had larger home ranges than the less aggressive ones. Furthermore, home-range size and vegetative cover in the home range also influenced the probability of survival: survivors had larger home ranges, with a greater amount of vegetative cover, than nonsurvivors.
Habitat use by woodland caribou near Takla Lake in central British Columbia
Authors: Poole Kim G , Heard Douglas C , Mowat Garth
Published: April 2011

Caribou (Rangifer tarandus) living in the mountainous areas of British Columbia are usually classified as either northern caribou, which spend much of the winter in low-elevation relatively young forests foraging primarily on terrestrial lichens, or mountain caribou, which winter in high-elevation old subalpine forests foraging exclusively on arboreal lichens. The forest-management practices necessary to conserve caribou differ substantially between these two categories of animals with different life-history strategies. Because of this variability in winter-habitat use, information relating specifically to Takla Lake caribou was required for forest management. To provide this information, we radio-collared 15 female caribou in two subherds in the vicinity of Takla Lake and determined their distribution and movements between January 1996 and May 1998 in relation to topography and vegetation cover. Habitat selection was examined using a classified satellite image. At the landscape scale, Takla Lake caribou avoided low-elevation forests (presumably because of the associated high risk of predation from wolves (Canis lupus)), occupying small seasonally overlapping home ranges (mean 151 km2) at intermediate and high elevations. Within home ranges in all seasons, caribou were most often found in the forest but, relative to availability, they selected forests only during calving. When in the forest, caribou selected open hybrid white-Engelmann spruce (Picea glauca × Picea engelmannii) - subalpine fir (Abies lasiocarpa) forests over lodgepole pine (Pinus contorta) and deciduous forests in all seasons except spring. Caribou selected open spruce-fir stands over dry and closed spruce-fir stands in all seasons except calving. We conclude that caribou feed primarily on arboreal lichens in winter, because the open spruce-fir forests that they use have moderate to high arboreal lichen abundance, deep snow, and few terrestrial lichens. Takla Lake caribou were not typical of either mountain or northern caribou, but as is typical of insular populations of any species, have adapted to the food, topography, and cover types available to them on their mountain islands in a sea of moose (Alces alces) and wolves.
Marking decisions and host discrimination in a parasitoid attacking concealed hosts
Authors: Hoffmeister Thomas S
Published: April 2011

Host discrimination by the parasitoid wasp Halticoptera rosae was found to be based upon an external marking pheromone applied to the surface of rose hips in which the host, a fly (Rhagoletis basiola), had deposited its eggs in the fruit pulp. Female wasps marked the sites by repeatedly dabbing the tip of their ovipositor on the fruit surface and discriminated against conspecific marks through antennal contact with marked sites, resulting in cutting off the behavioural sequence leading to oviposition. The same behaviour was observed when wasps were offered fruits on which flies' oviposition sites were artificially marked with methanol extracts of female reproductive tracts, which suggests that the mark is chemical in nature and that the substance is associated with female oviducts and Dufour's or poison glands. Although the host flies respond to fruits that had been previously searched by wasps, no effect on wasp searching behaviour was found on fruits previously searched by conspecifics but without parasitization of the host. The adaptive significance of marking and discrimination decisions made by the parasitoid is discussed.
Variations in lake-outlet Ephemeroptera, Plecoptera, and Trichoptera communities amongst regions of eastern Newfoundland, Canada
Authors: Lomond T M , Colbo M H
Published: April 2011

Ephemeroptera, Plecoptera, and Trichoptera communities at 23 lake-outlet sites in four regions of boreal eastern Newfoundland, Canada, are described and compared. Faunal richness was low, with a total of 51 taxa collected (14 for Ephemeroptera, 3 for Plecoptera, and 34 for Trichoptera). Hydropsychids (Trichoptera) predominated in both diversity and abundance of taxa. Analysis of variance revealed differences in taxon diversity and abundance among regions, even within the relatively small geographic area studied. Diversity and abundance also varied among sites within regions, despite the low diversity and large number of widespread taxa. The data show that lake outlets are useful for comparative studies, even in areas with a reduced insect fauna.
Energetics of free-ranging large herbivores: when should costs affect foraging behaviour?
Authors: Armstrong Helen M , Robertson Antony
Published: April 2011

Published relationships were used to build a mathematical model that predicts the daily net energy balance of free-ranging domestic sheep (Ovis aries L.) grazing in the U.K. hills. Net energy balance was predicted for a plausible range of environmental conditions. The behaviour of the model suggested the following predictions. Locomotion will be a relatively unimportant energetic cost. Ambient temperature and rainfall alone will rarely affect energy expenditure, whereas wind will greatly increase energetic costs in winter. These are further increased, but to a relatively small extent, by any concurrent rainfall. Predictions of foraging behaviour based on maximisation of energy intake alone are likely to significantly overestimate dry matter intake from climatically exposed vegetation in winter. Where shelter is available, such models will also overestimate total intake in winter by not taking account of sheltering behaviour. This effect will be most pronounced when forage is of low digestibility or availability, wind speeds are high, or the level of coat insulation is low. Foraging models based instead on maximisation of net energy balance are likely to greatly improve predictions of the impact of large herbivores on vegetation and the mechanisms driving their population dynamics.
Phylogeography of the tailed frog (Ascaphus truei) in British Columbia
Authors: Ritland Kermit , Dupuis Linda A , Bunnell Fred L , Hung Wesley LY , Carlson John E
Published: April 2011

The tailed frog (Ascaphus truei) is highly philopatric, with naturally disjunct populations. To infer the historical pattern of range expansion and contraction in A. truei of British Columbia (B.C.), we conducted a randomly ampli fied polymorphic DNA (RAPD) survey, using 16 primers, of 469 individuals sampled from 22 populations in four regions. Genetic distances, based on 169 putative RAPD loci, clustered populations into three clear groups: mid/north-coastal B.C., south-coastal B.C., and interior B.C. The interior populations were the most distinct group, but their genetic distance from other groups equals that expected from isolation by physical distance alone, as opposed to taxonomic differentiation. FST values within coastal regions were moderately low (0.02-0.05) but were high in the interior (0.12) and across all populations (0.18). Within the mid/north-coastal and south-coastal regions, genetic distance showed no relationship with physical distance, while among regions and within the interior region there was a strong relationship. Gene diversity varied significantly among regions, with both the interior and south-coastal populations showing about 25% less diversity than the mid/north-coastal populations. These data indicate a complex history of geographic restrictions to multiple refugia, followed by various types of range expansion. The implications of these results for conservation efforts in this species are discussed.
The role of thermal environment in determining the life history of a terrestrial salamander
Authors: Camp Carlos D , Marshall Jeremy L
Published: April 2011

Largely using previously published data, we analyzed geographic variation in adult body size of terrestrial salamanders of the Plethodon glutinosus complex. Maximum body size of adult males is determined by size at maturity. In turn, size at maturity is determined by a negative relationship with environmental temperature. Moreover, both age at maturity and growth rate are correlated with size at maturity, but apparently only as coincidental correlates through the influence of temperature. The number of degree-days, estimated using temperature data from respective geographic locations, accurately predicts age at maturity for salamanders living in these areas. Development under cooler thermal regimes is more depressed than growth and, consequentially, adult body sizes are greater in cooler climates. This pattern of size variation fits thermal predictive models proposed for larval development in amphibians that breed in ponds. Phenotypic variation in adult body size appears to be accounted for largely by plastic responses to variation in thermal environments and may reflect a single reaction norm for the complex.
Directional and fluctuating asymmetry in the black-winged damselfly Calopteryx maculata (Beauvois) (Odonata: Calopterygidae)
Authors: Pither Jason , Taylor Philip D
Published: April 2011

Directional asymmetry (DA) has received considerably less attention than fluctuating asymmetry (FA) in the literature. Evidence for DA, however, is building among insect taxa. We examined asymmetries in two wing traits within both sexes of the damselfly Calopteryx maculata (Beauvois) (Odonata: Calopterygidae) sampled from three sites in southeastern Ontario. After accounting for measurement error, we show that proximal segments within right fore and hind wings are consistently longer than those in the left in all but one sample group. Full wing lengths, however, exhibited FA rather than DA. Mean asymmetry values for both traits (segment and length) occurred in the direction of right-wingedness significantly more often than expected by chance. Patterns of asymmetry were generally consistent among the sexes and sites, although males tended to exhibit more pronounced DA. We suggest that the wings of C. maculata may undergo compensatory development, so that full lengths are more bilaterally symmetrical than their component parts.
Predation on seabird eggs by Keen's mice (Peromyscus keeni): using stable isotopes to decipher the diet of a terrestrial omnivore on a remote offshore island
Authors: Drever M C , Blight L K , Hobson K A , Bertram D F
Published: April 2011

We used stable isotope techniques to analyze tissues of Keen's mice (Peromyscus keeni) and Townsend's voles (Microtus townsendii cowani) and a subset of prey items at Triangle Island, British Columbia, western Canada's largest seabird colony. Isotope analysis allowed us to investigate the importance of seabird prey in rodent diets in a system where seabirds and non-introduced rodents occur sympatrically. The δ15N values for terrestrial plants and terrestrial invertebrates on Triangle Island exceeded levels found in many terrestrial biomes and are typical of localities with high inputs of marine-derived N. We used multiple-source mixing models to estimate the relative inputs of potential prey items to vole and mouse diets. The δ13C and δ15N values of liver and muscle tissues of voles indicate that voles on Triangle Island derived their protein primarily from terrestrial plants, with some contribution by terrestrial invertebrates. In contrast, isotopic values of liver and muscle tissues of mice on Triangle Island indicated that mice prey primarily on seabird eggs and terrestrial invertebrates. Our results show that egg predation on Triangle Island is a general phenomenon in the mouse population, rather than occurring in only a few specialist feeders. Mice appear to feed on eggs once they become available and continue to utilize seabird prey, likely in the form of abandoned eggs or carcasses of chicks and adults, throughout the breeding season.
Long-term cold tolerance in Arctic invertebrates: recovery after 4 years at below -20°C
Authors: Coulson S J , Birkemoe T
Published: April 2011

Soil samples were collected from a High Arctic Cassiope heath site on Svalbard (West Spitsbergen) in midwinter 1995 and transferred directly to -22°C. Survival was unexpectedly high in Collembola (Hypogastrura tullbergi and Folsomia quadrioculata) and Nematoda, but there was also isolated survival in two species of mites (Diapterobates notatus and Ameronothrus lineatus) and one enchytraeid (Henlea perpusilla). The unexpectedly extreme cold tolerance has implications for the range of polar habitats available for soil fauna to colonise and for migration between isolated regions.
Individual foraging behaviour indicates resource limitation: an experiment with mallard ducklings
Authors: Nummi Petri , Sjöberg Kjell , Pöysä Hannu , Elmberg Johan
Published: April 2011

The linkage between individual behaviour and population processes has recently been emphasized. Within this framework we studied the effect of resource limitation on the behaviour of mallard (Anas platyrhynchos) ducklings in boreal lakes. One group of 12 human-imprinted ducklings (4-16 days old) were taken to 11 "rich" lakes, i.e., with a relatively high concentration of total phosphorus in the water, and the other group of 12 ducklings to 11 "poor" lakes to forage for a period of 6 h. During this, a time budget study lasting 5 min was done of each of the 12 ducklings. In the rich lakes, ducklings fed significantly more and moved less than in the poor ones. This difference was particularly striking in above-surface feeding. Variation in foraging performance was associated with change in body mass of the ducklings: the less distance the ducklings moved and the more they fed above water, the more they gained mass. Earlier results had suggested that at least some of the boreal wetlands that lack duck broods year after year (70% of the total in one study) do so because they do not harbour enough food. Hence, it is possible that mallard populations are resource-limited at the brood stage during the breeding season.
Ecological correlates of mate fidelity in two Arctic-breeding sandpipers
Authors: Sandercock Brett K , Lank David B , Lanctot Richard B , Kempenaers Bart , Cooke Fred
Published: April 2011

Monogamous birds exhibit considerable interspecific variation in rates of mate fidelity between years, but the reasons for this variation are still poorly understood. In a 4-year study carried out in western Alaska, mate-fidelity rates in Semipalmated Sandpipers (Calidris pusilla; mate fidelity was 47% among pairs where at least one mate returned and 94% among pairs where both mates returned) were substantially higher than in Western Sandpipers (Calidris mauri; 25 and 67%, respectively), despite the similar breeding biology of these sibling species. Divorce was not a response to nesting failure in Western Sandpipers, and mate change had no effect on the reproductive performance of either species. Nor were mate-fidelity rates related to differential rates of breeding dispersal, because the species did not differ in site fidelity. Reunited pairs and males that changed mates showed strong site tenacity, while females that changed mates moved farther. Differences in local survival rates or habitat are also unlikely to explain mate fidelity, since the two species did not differ in local survival rates, ϕ (Western Sandpipers: ϕ hat = 0.57 ± 0.05 (mean ± SE), Semipalmated Sandpipers: ϕ hat = 0.66 ± 0.06), and they bred in the same area, sometimes using the same nest cups. Although we were able to reject the above explanations, it was not possible to determine whether mate retention was lower in Western Sandpipers than in Semipalmated Sandpipers because of interspecific differences in mating tactics, time constraints imposed by migration distance, or a combination of these factors. Western Sandpipers exhibited greater sexual size dimorphism, but also migrated for shorter distances and tended to nest earlier and more asynchronously than Semipalmated Sandpipers. Finally, we show that conventional methods underestimate divorce rates, and interspecific comparisons may be biased if breeding-dispersal and recapture rates are not considered.
DNA profiles of the eastern Canadian wolf and the red wolf provide evidence for a common evolutionary history independent of the gray wolf
Authors: Wilson Paul J , Grewal Sonya , Lawford Ian D , Heal Jennifer NM , Granacki Angela G , Pennock David , Theberge John B , Theberge Mary T , Voigt Dennis R , Waddell Will , Chambers Robert E , Paquet Paul C , Goulet Gloria , Cluff Dean , White Bradley N
Published: April 2011

The origin and taxonomy of the red wolf (Canis rufus) have been the subject of considerable debate and it has been suggested that this taxon was recently formed as a result of hybridization between the coyote and gray wolf. Like the red wolf, the eastern Canadian wolf has been characterized as a small "deer-eating" wolf that hybridizes with coyotes (Canis latrans). While studying the population of eastern Canadian wolves in Algonquin Provincial Park we recognized similarities to the red wolf, based on DNA profiles at 8 microsatellite loci. We examined whether this relationship was due to similar levels of introgressed coyote genetic material by comparing the microsatellite alleles with those of other North American populations of wolves and coyotes. These analyses indicated that it was not coyote genetic material which led to the close genetic affinity between red wolves and eastern Canadian wolves. We then examined the control region of the mitochondrial DNA (mtDNA) and confirmed the presence of coyote sequences in both. However, we also found sequences in both that diverged by 150 000 - 300 000 years from sequences found in coyotes. None of the red wolves or eastern Canadian wolf samples from the 1960s contained gray wolf (Canis lupus) mtDNA sequences. The data are not consistent with the hypothesis that the eastern Canadian wolf is a subspecies of gray wolf as it is presently designated. We suggest that both the red wolf and the eastern Canadian wolf evolved in North America sharing a common lineage with the coyote until 150 000 - 300 000 years ago. We propose that it retain its original species designation, Canis lycaon.
Voles looking for an edge: habitat selection across forest ecotones
Authors: Kingston Steven R , Morris Douglas W
Published: April 2011

We searched for the presence of "edge effects" in the occupation of adjacent boreal-forest habitats by red-backed voles (Clethrionomys gapperi). First, we reviewed four models that differ in their predictions of abundance at habitat boundaries. Three of the models predicted an edge effect, while the so-called matrix or habitat model served as a null expectation. We then developed a protocol to detect, objectively, the ecotone between two habitats that is necessary to differentiate among the four models. The protocol revealed both abrupt and gradual ecotones along transects crossing conifer to cutover and conifer to deciduous habitats. Though vole density was almost always higher on one side of the ecotone than on the other, we were unable to detect an edge effect of any kind. Vole density within ecotones was intermediate to that on each side (refuting the existence of an ecotone effect). There were also no differences in the pattern of density between abrupt and gradual ecotones (refuting the existence of a permeability effect), and no consistent pattern of vole density away from either type of ecotone (refuting the existence of a habitat-selection effect). Simulations that manipulated vole densities along the transects suggested, however, that the habitats may have been too similar to allow a habitat-selection effect to be detected. We suspect that our result will be common to moderately generalised species, and we recommend that controlled experiments be carried out to evaluate the conditions under which habitat-selecting species may exhibit edge effects.
Freezing susceptibility and freezing tolerance in Palaearctic Cetoniidae (Coleoptera)
Authors: Vernon P , Vannier G
Published: April 2011

Insects have evolved various adaptations that allow them to survive adverse seasons. In terms of cold-hardiness, they may classically be divided into freezing-susceptible versus freezing-tolerant species. But this concept of two alternative cold-hardiness strategies is now amendable, and to better understand these adaptive mechanisms, it is of interest to study freezing resistance in taxonomically related insect species, i.e., belonging to the same family or to a group of closely related organisms sharing similar resources. Freezing susceptibility and freezing tolerance have previously been recorded in the larvae of species in the same guild of the family Cetoniidae, which mainly colonise wood mould in hollow trees. We compared freezing hardiness in five species of Cetoniidae, three species in the subfamily Trichiinae, Gnorimus nobilis (Linné), Trichius fasciatus (Linné), and Osmoderma eremita (Scopoli), and two species in the subfamily Cetoniinae, Cetonia aurata (Linné) and Cetonischema aeruginosa (Drury). Our results mainly show that two contrasting mechanisms are used during winter by third-instar larvae: those of the Trichiinae (apart from O. eremita) are probably characterized by year-round freezing susceptibility, and those of O. eremita and the Cetoniinae are probably distinguished by seasonal freezing susceptibility (summer) and seasonal freezing tolerance (winter). We question the current taxonomic position of the genus Osmoderma. Morphological, ecological, and behavioural arguments may be put forward to support the transfer of O. eremita from the Trichiinae to the Cetoniinae, and we stress that ecophysiological arguments, often neglected in this kind of taxonomic revision, must also be taken into account.