bluuebunny/crossref_metadata_2025 huggingface dataset:
Potentiation of carbon monoxide-induced relaxation of rat aorta by YC-1 [3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole]
Authors: McLaughlin Brian E , Chretien Marc L , Choi Christine , Brien James F , Nakatsu Kanji , Marks Gerald S
Published: April 2011

The hypothesis that endogenous carbon monoxide (CO), produced during the oxidation of heme catalyzed by heme oxygenase (HO), plays a role similar to that of nitric oxide (NO) in the regulation of cardiovascular tone has been criticized because of the low potency of CO compared with NO in relaxing blood vessels and stimulating soluble guanylyl cyclase (sGC). This criticism has been muted by the demonstration that, in the presence of YC-1 [3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole], CO has similar potency to NO in stimulating sGC activity. In this study, we determined that YC-1 potentiated CO-induced relaxation of rat aortic strips (RtAS) by approximately ten-fold. Furthermore, CO-induced relaxation of RtAS was shown to be mediated through stimulation of sGC because vasorelaxation was inhibited by ODQ (1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one), a selective sGC inhibitor, in the absence and presence of YC-1. A gas chromatographic-headspace method was used to measure CO concentration in Krebs' solution following the addition of CO-saturated saline solution to the tissue bath, in order to provide an accurate determination of RtAS exposure to CO. The tissue bath concentration of CO was shown to be approximately one-half of that calculated to be present. We conclude that should an endogenous compound exist with properties similar to that of YC-1, then the potency of CO as a vasorelaxant in the presence of this factor would be increased. As a consequence, CO could play a role in the regulation of cardiovascular tone, comparable to that of NO.Key words: carbon monoxide; YC-1 [3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole]; vasodilation; rat aorta; gas-chromatographic analysis.
Vasodilation in human subcutaneous arteries induced by neuropeptide Y is mediated by neuropeptide Y Y1 receptors and is nitric oxide dependent
Authors: Nilsson T , Lind H , Brunkvall J , Edvinsson L
Published: April 2011

Neuropeptide Y (NPY) is known as a potent vasoconstrictor of peripheral blood vessels both in vivo and in vitro. There have been reports suggesting that NPY also has a dilatory effect. The aim of the present study was to elucidate whether NPY dilates small human subcutaneous arteries. Subcutaneous arteries, obtained from patients undergoing abdominal surgery, were mounted in in vitro tissue baths, and the vascular responses to NPY were investigated. The presence of mRNA encoding the human NPY Y1 receptor in endothelial cells from human umbilical veins was studied by the use of reverse transcriptase - polymerase chain reaction (RT-PCR). In arteries precontracted with the prostaglandin analogue U46619, NPY induced a concentration-dependent vasodilation (Emax 30 ± 10% of the U46619-induced contraction), which was significantly inhibited by the NPY Y1 receptor antagonist BIBP3226 (1 µM), causing a rightward shift of the concentration-response curve, pEC50 7.1 ± 0.3 vs. 7.7 ± 0.3 for NPY alone. After pretreatment with the nitric oxide synthetase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) (10 µM), the dilation was abolished (Emax 6 ± 5% of the U46619-induced contraction). mRNA encoding the human NPY Y1 receptor was detected in endothelial cells from human umbilical veins. It was concluded that NPY induces vasodilation in human subcutaneous arteries. The dilation is mediated via the NPY Y1 receptor and is dependent on nitric oxide.Key words: vasodilation, neuropeptide Y, BIBP3226, nitric oxide, human.
The effect of postural adjustment on the thermal environment of greater snow goose goslings
Authors: Fortin Daniel , Gauthier Gilles
Published: April 2011

This study examines how changing from a standing to a sitting posture influences the thermal environment of greater snow goose goslings (Chen caerulescens atlantica). This was investigated by estimating the standard operative temperature of four heated taxidermic mounts (3, 10, 20, and 30 d old) exposed to various wind velocities (0-5 m/s) and ground (16-23°C) and air (0-15°C) temperatures, in three orientations (head, flank, or tail toward the wind) and two postures (sitting and standing). Changes in posture influenced both conductive and convective heat exchanges. At low wind speeds, sitting on the sand reduced the standard operative temperature of goslings, while at high wind speeds sitting enhanced this temperature index. We calculated that a net thermal gain would be obtained by sitting on cold sand at air temperatures of 5, 10, and 15°C when the wind speed exceeded 3 m/s for most orientations toward the incoming wind. However, this critical wind speed would be 23% lower following a 7°C increase in ground temperature. Our study suggests that postural changes can have important consequences on goslings' thermal environment. It also stresses the importance of considering the synergistic impact of conductive and convective heat transfer processes, when studying the impact of postural changes on thermal environments.
Metabolic response to fasting in 6-week-old Steller sea lion pups (Eumetopias jubatus)
Authors: Rea L D , Rosen D AS , Trites A W
Published: April 2011

Four Steller sea lions (Eumetopias jubatus) aged 6 weeks were fasted for 2.5 d to determine how young pups mobilize energy reserves during short periods of fasting similar to those experienced in the wild. At 6 weeks of age, the pups lost 5.1 ± 0.3% of their body mass during 2 d of fasting, with an average daily mass loss of 0.7 ± 0.1 kg·d-1. Plasma blood urea nitrogen (BUN) concentration increased significantly from 3.0 ± 0.1 mM, after an overnight fast, to 4.8 ± 0.5 mM, after 2.5 d of fasting. It is apparent that BUN levels are quickly depressed, since after only an overnight fast, these pups showed BUN levels 2- to 4-fold lower than those measured after the same pups, when 9 months of age, had recently been fed fish. Plasma ketone body (β-HBA) concentrations of the 6-week-old pups increased significantly from 0.32 ± 0.08 to 0.42 ± 0.08 mM between 0.5 and 1.5 d of fasting. There was no significant change in mean plasma concentration beyond 1.5 d, owing to variable individual responses to extended fasting. Plasma β-HBA levels at 9 months of age ranged from 0.07 to 0.18 mM. Six-week-old Steller sea lion pups showed blood chemistry consistent with metabolic adaptation to fasting within 16 h but were unable to sustain a protein-sparing metabolism for a prolonged period. The pups appeared to revert to protein catabolism after only 2.5 d of fasting. This infers a decrease in lipid catabolism that might be due to the depletion of available lipid resources.
Genetic homogeneity based on skin histocompatibility and the evolution and systematics of parthenogenetic Cnemidophorus laredoensis (Sauria: Teiidae)
Authors: Abuhteba Ramadan M , Walker James M , Cordes James E
Published: April 2011

The parthenogenetic whiptail lizard Cnemidophorus laredoensis of Texas and México was derived from one or more hybrids between the gonochoristic species Cnemidophorus gularis and Cnemidophorus sexlineatus. We analyzed clonal structure in C. laredoensis on the basis of histocompatibility reactions to reciprocal skin grafting. Individuals of C. laredoensis rejected skin grafts from both parental species and from a hybrid between C. gularis and an undescribed parthenogenetic species. One lizard initially identified as C. laredoensis was found to be a triploid C. laredoensis × C. gularis hybrid, based on its histocompatibility reactions. The hybrid accepted grafts from individuals of C. laredoensis; however, C. laredoensis rejected grafts from this and a second hybrid. Seventeen individuals of C. laredoensis from six sites located throughout the range of the species in Texas were fully histocompatible, based on a large number of reciprocal skin grafts. Only three individuals of C. laredoensis from three sites donated grafts to other individuals of the species, but they were unable to host all or most of the reciprocal grafts. The skin histo compatibility among 17 individuals of C. laredoensis from six widely separated geographic sites points to a high level of genetic homogeneity in the species due to clonal descent from one parthenogenetic C. gularis × C. sexlineatus hybrid. Unidirectional rejection of skin grafts by three lizards could be a result of postformational mutations within this lineage, though this suggestion is open to question. The name C. laredoensis should be restricted to populations in Texas and México that are diagnostically identical with the parthenogenetic species described from two sites in Laredo, Webb County, Texas, in 1973.
Resource use of five sympatric turtle species: effects of competition, phylogeny, and morphology
Authors: Lindeman Peter V
Published: April 2011

I quantified resource use with respect to habitat, diet, and diel and seasonal use of basking time for five sympatric turtle species in a cove on Kentucky Lake, an impoundment of the lower Tennessee River in western Kentucky, U.S.A. I used pseudocommunity analyses to test for significant structure in resource use, compared resource-use matrices with matrices representing phylogenetic similarity, and measured morphological characteristics related to resource use. Three strictly riverine species (Graptemys pseudogeographica, Graptemys ouachitensis, and Apalone mutica) with relatively long limbs and digits used outer portions of the cove near deeper waters to a greater extent than did two shorter-limbed species (Trachemys scripta and Pseudemys concinna), which inhabit both lotic and lentic waters. Only the difference in habitat between A. mutica and the other four species was shown to be significant in pseudocommunity analysis, a result that can be better explained by differences in basking substrates than by competition. Dietary studies indicated two guilds, omnivore and algivore, in spite of the low pairwise overlap values that resulted from overall prey diversity. Analysis of use of diel and seasonal basking time revealed significant structure (partitioning) at only the rank of second-nearest neighbor for seasonal time. Clustering phenograms for resource similarity among the five species were overall highly similar to two phylogenetic hypotheses. Phylogeny was thus shown to be of greater importance in structuring resource use in Kentucky Lake than interspecific competition. In addition, the similarity in clustering phenograms was not consistent with the hypothesis of niche complementarity, suggesting that interspecific competition was of little importance.
Geographic variation in population cycles of Canadian muskrats (Ondatra zibethicus)
Authors: Erb John , Stenseth Nils Chr. , Boyce Mark S
Published: April 2011

We investigated the dynamic properties of population cycles in Canadian muskrats (Ondatra zibethicus). Ninety-one historic time series of muskrat-harvest data obtained from the Hudson's Bay Company Archives were analyzed. Most series were 25 years in length (19251949) and were distributed primarily throughout five ecozones. For each series, we estimated period length and coefficients for a second-order autoregressive model. Estimated period length varied between 3 and 13 years, with 3- to 5-year periods located in Subarctic-Arctic ecozones. We hypothesize that the 4-year cycles are largely a result of predation by red fox (Vulpes vulpes), which exhibit 4-year cycles in Arctic regions. The remaining ecozones generally averaged 89 years in period length. However, the relative contributions of direct and delayed density dependence varied along a latitudinal gradient. We hypothesize that both social and trophic interactions are necessary to produce the observed dynamics, but that shifts in the nature of mink predation were responsible for the changes in the relative contribution of direct and delayed density dependence. Essentially, there is a tension between population-intrinsic and trophic interactions that may bound the length of the cycle.
Effects of parental quality and egg size on growth and survival of herring gull chicks
Authors: Risch T S , Rohwer F C
Published: April 2011

We performed a clutch-transfer experiment with herring gulls (Larus argentatus) to quantify how parental attributes and egg size affect chick growth and survival. The quality of parents was assessed by their average egg mass. There was no association between hatching success and egg mass in either unmanipulated or experimental nests. Among experimental treatments, the high-quality parents had a significantly higher chick survival rate than low-quality parents in 1991 and when data from 1990 and 1991 were pooled. A positive effect of egg size on chick survival was apparent only when data from both years were pooled. Chicks raised by high-quality parents had higher structural growth rates (tarsus) than chicks raised by low-quality parents. We discount the likelihood for selection of larger eggs because egg size has trade-offs with other life-history traits that have a strong influence on fitness. Despite the correlation between parental quality and chick survival, we doubt that there is character displacement for greater parental quality. Parental quality is probably affected by nutrition and is expected to have low heritability.
Protein synthesis in vitro by mantle tissue of the land snail Otala lactea: possible insulin-like peptide function
Authors: Abdraba A M , Saleuddin A SM
Published: April 2011

Mantle-collar tissue from adult land snails Otala lactea continuously incorporated labelled amino acids over a 72-h period of incubation in modified culture medium. Acid-saline extract of cerebral ganglia stimulated protein synthesis by the mantle-collar tissue in vitro. This effect was dose-dependent, with the minimum and maximum doses at 0.5 and 2 cerebral ganglion equivalents, respectively. The protein synthesis-stimulating factor(s) from the cerebral ganglia appeared to be proteinaceous and hydrophobic in nature. The cerebral ganglion extract was fractionated by means of a size-exclusion HPLC column. The biological activity was induced by three fractions with estimated molecular masses of 0.82, 1.88, and 4.33 kilodaltons (kDa). Porcine insulin antiserum abolished the activity of the 4.33- and 1.88-kDa fractions but had no significant effect on the activity of the 0.82-kDa fraction. The results suggest the existence in the cerebral ganglia of more than one factor with protein synthesis-stimulating activity. One of these factors could be related to mammalian insulin. Porcine insulin, however, had no significant effect on protein synthesis by the mantle collar in vitro.
Spatial distribution of the intertidal snail Ilyanassa obsoleta in relation to parasitism by two species of trematodes
Authors: McCurdy Dean G , Boates J Sherman , Forbes Mark R
Published: April 2011

We studied the spatial distributions of mud snails (Ilyanassa obsoleta) infected by two trematodes, Lepocreadium setiferoides and Gynaecotyla adunca, on a macrotidal mudflat in the Minas Basin, Bay of Fundy. Snails, as first intermediate hosts, were castrated by both parasites, and we found no evidence of sex differences in parasitism. Similar to previous work, prevalence of L. setiferoides in I. obsoleta increased exponentially with host size (and age). Unexpectedly, prevalence of G. adunca decreased over the largest size classes of snails, a result that may be due to several causes. Distributions of both parasites across the intertidal zone differed from previous accounts in that snails infected with L. setiferoides were found only in the middle of the intertidal zone, whereas prevalence of G. adunca increased exponentially moving seaward. Several species of polychaetes could be infected by L. setiferoides in the laboratory and may act as appropriate second intermediate hosts, whereas only the amphipod Corophium volutator served as a second intermediate host for G. adunca. Finally, the vertical distributions of I. obsoleta infected by either species of trematode overlap with distributions of apparent or known second intermediate hosts.
Demographic analysis of the Columbia spotted frog (Rana luteiventris): case study in spatiotemporal variation
Authors: Reaser Jamie K
Published: April 2011

This study examined size, mass, sex ratios, and age structure of the Columbia spotted frog (Rana luteiventris) at seven sites in the Toiyabe Range in central Nevada from 1994 through 1996. Age structure was estimated using skeletochronology. Demographic composition was found to be significantly different among sites, suggesting that localized factors influence recruitment and mortality rates. Demographics among years at the sites were also significantly different, indicating that the population dynamics of this system are complex and are also driven by one or more temporal factors. Knowledge of local land-use patterns and anecdotal observations were incorporated in an attempt to identify potential stress agents in need of further research and possible intensive management. Differences in recruitment, survivorship, and mortality rates among sites may be due to microclimate, food availability, and predation rates. Introduction of exotic trout and cattle are likely the most important anthropogenic factors limiting the distribution and persistence of R. luteiventris in the study area. Extreme variations in annual weather patterns may account for many differences observed at some sites. This study demonstrates that adequate assessment of amphibian population status requires knowledge of subpopulation demographics across a broad landscape.
Dive and surfacing characteristics of bowhead whales (Balaena mysticetus) in the Beaufort and Chukchi seas
Authors: Krutzikowsky Gregory K , Mate Bruce R
Published: April 2011

We received data from eight bowhead whales (Balaena mysticetus) equipped with satellite-monitored radio tags for 3-33 days. Of 42 306 dives made by the eight whales during 1695 h, 9573 were sounding dives (>1 min duration). The mean duration of sounding dives for individuals varied from 6.9 to 14.1 min (mean = 10.4 ± 2.4 min, n = 8). Five whales made dives [Formula: see text]61 min; the longest dives for the other three lasted 56, 45, and 32 min. Five tags measured maximum depths of 29 499 dives during 1220 h and time at depth during 1228 h. All five whales dived >100 m; the deepest dive was 352 m. Whales spent most of their time at depths [Formula: see text]16 m, but three whales spent most of their time at depths >48 m during some sampling periods. Mean surfacing rates ranged from 18.2 to 47.0/h (mean = 26.2 ± 9.0/h, n = 8). Tags were exposed to air for 4.0-7.3% of the time (mean = 5.5 ± 0.95%, n = 8), and whales were potentially visible from aircraft for 8.5-16.4% of the time (mean = 11.1 ± 2.4%, n = 8). Three whales made longer sounding dives and had lower surfacing rates when in [Formula: see text]90% ice cover. No consistent diel patterns were found.
Allometric relationships and character evolution inOnthophagus taurus(Coleoptera: Scarabaeidae)
Authors: Palestrini Claudia , Rolando Antonio , Laiolo Paola
Published: April 2011

Allometric relationships in primary sexual traits (male and female genitalia), secondary sexual traits (male horns and female carinae), and non-sex-related traits (external body traits, epipharynx traits) were studied in the dung beetle Onthophagus taurus. Model II regressions of log-transformed data were used to quantify relationships, with pronotum width as regressor and indicator of overall body size. Slopes (allometric values) for the different trait categories were significantly different, with secondary sexual traits showing the highest values (higher than 1.0), followed by external body traits (slightly lower than 1.00) and epipharynx traits (around 0.2). Primary sexual traits and body size were mostly uncorrelated and genital sizes were virtually constant. Allometries of secondary sexual traits were quite different in the two sexes: the relationship between male horn length and pronotum width was approximately sigmoidal, while that between female carina length and pronotum width was linear. External body traits had significantly higher allometric values in females than in males. Our results suggest that traits in the different categories are under different kinds of selection. Genital allometries can be explained on the basis of sexual selection by cryptic female choice or by the lock-and-key hypothesis. Among secondary sexual characters, male horn morphology seems to be mostly "environmentally" determined and sexual selection would affect only a component of the developmental mechanism of horn expression. External body characters are likely under natural selection, even though a few traits could be sex-related. Finally, in both sexes, internal epipharynx traits seem to be subject to the same selective pressure, probably because males and females use the same feeding niche. The constancy of genital sizes in O. taurus suggests that in developmental processes, more is invested in primary sexual traits (to produce genitalia of the proper size) than in secondary sexual or body traits. Males receiving low quantities of food may incur costs associated with a small horn or small body size, but do not incur costs associated with small genitalia. Females probably share the same developmental pattern.
Effects of oiling on exercise physiology and diving behavior of river otters: a captive study
Authors: Ben-David M , Williams T M , Ormseth O A
Published: April 2011

Following the Exxon Valdez oil spill (EVOS), river otters (Lontra canadensis) on oiled shores had lower body mass, selected different habitat characters, and had larger home ranges and less diverse diets than did otters living in non-oiled areas. We explored the possibility that these changes were due to the effect of crude oil contamination on physiological and behavioral processes in otters. Fifteen otters were exposed to two levels of oil contamination under captive controlled conditions at the Alaska Sealife Center in Seward, Alaska, U.S.A. We collected blood samples for hematological examinations and measured oxygen consumption in otters exercising on a motorized treadmill. We also observed diving and foraging behavior of otters offered live fish. Otters exposed to oil became anemic relative to controls. While oxygen consumption of resting river otters was not related to changes in hemoglobin concentration, exercising river otters with decreased hemoglobin levels displayed significantly increased oxygen consumption (P = 0.042). Oiled otters also performed fewer dives when chasing fish (P = 0.04), representing a potential decrease of 64% in the capture rate of prey. Our data strongly support the hypothesis that changes in prey types and home-range utilization by oiled river otters following EVOS were influenced by hematological changes, associated increases in energetic costs, and reduced diving ability.
Using stable carbon (δ13C) and nitrogen (δ15N) isotopes to infer trophic relationships among black and grizzly bears in the upper Columbia River basin, British Columbia
Authors: Hobson Keith A , McLellan Bruce N , Woods John G
Published: April 2011

Ecological segregation of species is difficult to determine using conventional dietary analysis techniques. However, stable-isotope analysis may provide a convenient means of establishing trophic segregation of species and of groups of animals within a species in the same area. We measured stable carbon (δ13C) and nitrogen (δ15N) isotope values in hair of black bears (Ursus americanus) and grizzly bears (Ursus arctos) inhabiting the upper Columbia River basin in southeastern British Columbia, together with samples of potential foods ranging from plant material through invertebrates and ungulate meat. We found extensive overlap in both δ15N and δ13C values of hair from male grizzly bears and black bears of both sexes. Female grizzly bears, however, had lower δ15N values in their hair than the other groups of bears, indicating either less animal protein in their diet or a reliance on foods more depleted in 15N, possibly related to altitude. Our isotopic model generally confirmed a herbivorous diet for both bear species (a mean estimated plant contribution of 91%). Bears showing the highest δ15N values were those captured because they posed a management problem. We suggest that the slope of the relationship between tissue δ15N and δ13C values might provide a convenient means of evaluating the occurrence of consumption of animal protein in populations, regardless of local isotopic end-points for dietary samples. We examined three black bear cubs from dens and found them to be about a trophic level higher than adult females, reflecting their dependence on mother's milk, a result generally confirmed by an analysis of eight mother-cub pairs from Minnesota. Our study demonstrates how stable-isotope analysis of bear tissue can be used to monitor the feeding habits of populations, as well as provide dietary histories that may reveal dietary specializations among individuals.
Does testosterone or coloration affect growth rates of adult males of the lizard Psammodromus algirus?
Authors: Salvador Alfredo , Veiga José P
Published: April 2011

Elevation of circulating testosterone levels during the breeding season stimulates the development of breeding coloration and favors traits that maximize reproductive success, but it may have several costs. Retardation of growth by testosterone has been proposed as one of these costs to males of long-lived species. We examine the results of a field experiment on the short-term (within the breeding season) and long-term (1 year) effects of heightening levels of testosterone on the growth of males of the lacertid lizard Psammodromus algirus. Testosterone did not affect the mass gain of males during the reproductive period or between years. The between-years increase in snout-vent length in testosterone-supplemented males tended to be less than in control individuals. Within-season individual mass gain was mainly determined by body mass at emergence: the lower the body mass the higher the mass gain. Our results do not support the idea that the production of ornamental traits limits growth, as the negative correlation between degree of head coloration and mass gain disappeared when body mass was controlled for.
Blood volume in hooded seals: implications for diving capacity
Authors: Cabanac A J
Published: April 2011

Plasma volumes of seven adult hooded seals, Cystophora cristata (two males and five females; body mass (M) range = 110-234 kg), captured on sea ice off east of Greenland during breeding (March-April), ranged between 35 and 54 mL/kg M (median = 46.5 mL/kg M). Linear regression analysis of haemoglobin (Hb) concentrations (g/dL) and hematocrit (Hct; %) levels in venous blood yielded: Hb = 0.296Hct + 5.53 (r2= 0.96, n = 7). Aortic Hct of 11 adult and juvenile seals with contracted and dilated spleens ranged between 62 and 67% (median = 66.5%, n = 5) and 50 and 67.5% (58.5%, n = 6), respectively, with the differences between groups being significant (p < 0.05). The calculated blood volume range was 104-162 mL/kg M (median = 139 mL/kg M, n = 7). The skeletal muscle mass of two adult females represented 30.8 and 28.1% of their M. Based on this, the body oxygen store of a 150-kg seal was estimated to be 9.8 L O2, of which only about 0.9 L O2(9%) could be stored in the fully dilated spleen. In assuming a diving aerobic metabolic rate of 1-2 times the predicted basal metabolic rate, the calculated aerobic dive limit was estimated to be 11.3-22.6 min.
Diving behaviour of lactating bearded seals (Erignathus barbatus) in the Svalbard area
Authors: Krafft Bjørn A , Lydersen Christian , Kovacs Kit M , Gjertz Ian , Haug Tore
Published: April 2011

This study documents activity patterns and diving behaviour of four bearded seal (Erignathus barbatus) mothers during the lactation period. The females spent 8 ± 3% (mean ± SD) of their time hauled out on the ice and 92 ± 3% in the water. Approximately half of their time was spent diving. During the study 15 077 dives were recorded. The duration of dives was 2.0 ± 2.3 min and diving depth was 17.2 ± 22.5 m (maximum 18.7 min and 288 m, respectively). Haulout periods occurred 3 ± 2 times per day (duration = 44.0 ± 98.1 min). The overall distance swum per day was 48.1 ± 23.2 km. Three dive types were differentiated using a combination of hierarchical and k-means clustering, one V-shaped grouping and two U-shaped groupings. The most common dive type was U1; these dives were the deepest and longest type (depth = 28 ± 32 m, duration = 185 ± 146 s), and bottom time occupied a significant fraction of the total dive time (120 ± 120 s). These dives are likely foraging dives. Lactation is energetically demanding for bearded seals, and females do forage while they have dependent pups.
Winter distribution of woodland caribou in relation to clear-cut logging in west-central Alberta
Authors: Smith Kirby G , Ficht E Janet , Hobson David , Sorensen Troy C , Hervieux David
Published: April 2011

The responses of a herd of migratory woodland caribou (Rangifer tarandus caribou) to timber harvesting that fragmented about 11% of their winter range in west-central Alberta were examined in this study. From 1981 to 1996, 45 caribou were radio-collared and monitored during the initiation and completion of first-pass timber harvest (50% removal). Variables examined were home-range size, daily movement rates, and distance to the nearest cut block for radio-collared individuals. Daily movement rates and individual winter range sizes decreased as timber harvesting progressed. Caribou avoided using recently fragmented areas by an average of 1.2 km. If fragmentation of the winter range continues through timber harvesting and other industrial activities, the "spacing out" antipredator strategy used by caribou may be compromised. Based on these findings, timber-harvesting strategies are recommended that (i) ensure an adequate area of usable habitat to support the current population, (ii) minimize the amount of fragmented area, and (iii) in the short term avoid presently defined core use areas.
Nestling survival and population cycles in the prairie vole, Microtus ochrogaster
Authors: Getz Lowell L , Simms Laura E , McGuire Betty
Published: April 2011

We live-trapped a population of the prairie vole, Microtus ochrogaster, occupying an alfalfa habitat twice weekly for 63 months. The population underwent four high-amplitude cycles during this time. The most consistent factor associated with population increases was an increase in the number of young animals recruited into the population. Recruitment of young was more a function of survival of offspring during the nestling period than of the proportion of pregnant females in the population. Increased adult survival and reproduction in the population only partly explained the increase phase of the cycles. The decline phases resulted from a combination of decreased reproduction and increased adult mortality. Precipitous declines were associated with major mortality episodes, some less than a week in duration.
Effects of winter food supplementation on reproduction, body mass, and numbers of small mammals in montane Australia
Authors: Banks Peter B , Dickman Chris R
Published: April 2011

We used a food-supplementation experiment to test the hypothesis that small-mammal populations are food-limited during winter in southeastern Australia. We trapped small mammals along 120- to 150-m transects at 12 creek and 12 ridgetop sites (representing high- and low-quality habitats) for 2 months prior to winter and 2 months during winter. High-quality food (peanut butter, honey, oats, and dried cat food) was provided ad libitum for 7 weeks during winter at four sites in each habitat. Eight sites were provided with empty feeding tubes and eight were untreated. Seven weeks of food supplementation caused numerical increases of 4.0- and 5.0-fold for the rodents Rattus fuscipes and Rattus lutreolus, respectively. Increases were due largely to immigration, and were only observed in the high-quality creek habitats (R. lutreolus were exclusively captured at creek sites). Food supplementation also led to an increase in body mass and reversed the hiatus in winter breeding for rodents. These results suggest that populations of both species are limited by winter food availability. However, survival rates (indexed from recapture rates) were not affected by food supplementation. Mean body mass of the marsupial Antechinus stuartii also increased with food supplementation, but other demographic parameters showed no response; numbers declined at creek sites after additional food was provided. Trapping-revealed measures of interspecific association showed that A. stuartii avoided areas of high rat numbers after additional food was provided. It is thus likely that interference competition from the much larger and more abundant rodents forced A. stuartii out of the food-supplemented creek sites, hence mediating the direct effects of food supplementation on this species.
Peculiarities in ovarian structure leading to multiple-year delays in oogenesis and possible senescence in Atlantic cod, Gadus morhua L.
Authors: Rideout Rick M , Burton Margaret PM
Published: April 2011

Five specimens of female Atlantic cod, Gadus morhua L., four collected during regular surveys of the northwest Atlantic Ocean, had ovarian structures that suggested that multiple-year interruptions were occurring in the spawning cycle of these fish. One specimen was experiencing a minimal 2-year delay in its reproductive cycle because the ovary contained only oogonia, which would have had to mature before any spawning could occur. Two other specimens did not contain oogonia or perinucleolar-stage oocytes, suggesting that these ovaries were senescent. Another two ovaries, one removed from a broodstock female and one taken from a female collected off Newfoundland's east coast, contained large masses of resorbing hyaline oocytes, which would likely have impaired the normal release of hydrated oocytes in the next spawning season.
Moose (Alces alces) survival in three populations in northern Norway
Authors: Stubsjøen Tonje , Sæther Bernt-Erik , Solberg Erling Johan , Heim Morten , Rolandsen Christer Moe
Published: April 2011

We used radio-collared individuals to examine the seasonal, annual, and regional variation in age-specific survival of moose (Alces alces) in three populations (Vega, Beiarn, and Troms) in northern Norway. In the two populations subject to a regular hunt, the annual mortality from hunting was higher, on average, than that from natural mortality for adult cows. In these study areas, the hunting mortality rate was higher for calves than for cows. For both age groups there was significant annual variation in hunting mortality, which was associated with differences in quota size among years. The survival rate of adult cows was high outside the hunting season (96%). There was seasonal variation in survival among calves, the highest significant mortality being found among neonates during summer in Vega and Troms and significantly higher mortality being found during winter in Beiarn. The natural mortality of calves differed significantly among regions during both summer and winter. The combined effects of density dependence, changes in age structure, and environmental stochasticity may explain this variation in calf-survival rate. In contrast, no significant seasonal or regional variation occurred in the survival rate of adult females.
Mechanism for maintaining oxygen consumption under varying oxygenation levels in the freshwater clamCorbicula fluminea
Authors: Tran Damien , Boudou Alain , Massabuau Jean-Charles
Published: April 2011

The basic adaptation mechanisms that allow the Asian freshwater clam Corbicula fluminea to maintain its oxygen (O2) consumption constant under resting conditions when the partial pressure of O2([Formula: see text]) in the water varies from 4 to 40 kPa were studied at plankton concentrations which were high enough that ventilation was not affected. Steady-state values for O2consumption, [Formula: see text], and O2concentration in the arterial and venous blood, [Formula: see text] in the expired water, and ventilatory and circulatory blood flow were determined after 24-h periods of exposure to selected water [Formula: see text] values. The key adaptation after 1 day of acclimation was the maintenance of O2consumption, which was achieved exclusively by ventilatory adjustment, with no change in the oxygenation status of the internal milieu. Specifically, arterial [Formula: see text] remained constant at 3 kPa and venous [Formula: see text] at 2 kPa. Arterial and venous blood O2concentrations and blood-flow rate also remained constant. The data are discussed in terms of feeding versus respiratory control of ventilation in filter-feeders in an environmental context. The agreement between the homeostasis strategy described here and previous results reported for the freshwater mussel Anodonta cygnea, crustaceans, and teleosts is emphasised.
Molecular phylogeny of the Annelida
Authors: McHugh Damhnait
Published: April 2011

Traditionally, the Annelida has been classified as a group comprising the Polychaeta and the Clitellata. Recent phylogenetic analyses have led to profound changes in the view that the Annelida, as traditionally formulated, is a natural, monophyletic group. Both molecular and morphological analyses support placement of the Siboglinidae (formerly the Pogonophora) as a derived group within the Annelida; there is also evidence, based on molecular analysis of the nuclear gene elongation factor-1α, that the unsegmented echiurids are derived annelids. While monophyly of the Clitellata is well-supported by both molecular and morphological analyses, there is no molecular evidence to support monophyly of the polychaete annelids; the Clitellata fall within a paraphyletic polychaete grade. Relationships among groups of polychaete annelids have not yet been resolved by molecular analysis. Within the Clitellata, paraphyly of the Oligochaeta was indicated in a phylogenetic analysis of cytochrome c oxidase I, which supported a sister relationship between the leeches, including an acanthobdellid and a branchiobdellid, and two of the four oligochaetes in the analysis. There is some evidence from analysis of 18S rRNA sequences for a sister-group relationship between the clitellates and the taxon Aeolosoma. There is no agreement regarding the body form of the basal annelid, and while molecular analyses provide strong support for the Eutrochozoa, the identity of sister-group to the Annelida among the Eutrochozoa remains enigmatic. It is recommended that future investigations include additional conserved gene sequences and expanded taxon sampling. It is likely that the most productive approach to resolving annelid phylogeny, and thus increasing our understanding of annelid evolution, will come from combined analyses of several gene sequences.
Feeding preferences of supralittoral isopods and amphipods
Authors: Pennings Steven C , Carefoot Thomas H , Zimmer Martin , Danko Jean Paul , Ziegler Andreas
Published: April 2011

We examined the feeding preferences of 3 supralittoral crustacean species in the Pacific Northwest of North America. The isopod Ligia pallasii (Brandt, 1833), the rocky-shore amphipod Traskorchestia traskiana (Stimpson, 1857), and the sandy-beach amphipod Megalorchestia californiana (Brandt, 1851) had similar feeding preferences, suggesting that feeding preferences were based on general algal traits rather than on adaptations particular to specific herbivores. No single trait clearly distinguished low- and high-preference seaweeds, although pH and phenolic compounds may have been important for two chemically defended seaweeds (Desmarestia sp. and Fucus sp., respectively). Feeding preferences of L. pallasii were affected by dietary history, but effects were minor compared with differences among seaweeds. All 3 consumers tended to prefer wrack (aged, stranded seaweeds) over fresh seaweeds of the same species. Our results suggested that increased organic and mineral contents of wrack were important in mediating these preferences, but that toughness and salt and nitrogen contents were not. Reduced levels of defensive compounds may have made wrack more palatable than fresh seaweeds in the case of the two chemically defended seaweeds.
Life cycles and population dynamics of enchytraeids (Oligochaeta) from the High Arctic
Authors: Birkemoe T , Coulson S J , Sømme L
Published: April 2011

We report the results of the first study of the population dynamics and life cycles of Arctic enchytraeid populations. Sampling was undertaken in a Salix heath in Adventdalen, Svalbard, during one summer and the succeeding spring. In addition, a Cassiope heath at a more northerly site close to Ny-Ålesund, Svalbard, was sampled twice. The Arctic enchytraeids were generally smaller at maturity than their temperate-zone relatives. The three most numerous species in the Salix heath, Henlea perpusilla, Henlea glandulifera, and Bryodrilus parvus, hatched from cocoons in early summer and attained adult size early in their second summer. A few H. perpusilla and H. glandulifera reached mature size in their first summer; since the summer of investigation was unusually cold, these species may have a 1-year life cycle in warmer years. Life cycles were apparently longer in the Cassiope heath than in the Salix heath. Henlea perpusilla, H. glandulifera, and B. parvus produced eggs throughout the summer in the Salix heath, though hatching was restricted to early summer. Therefore, the hypothesis that cocoons require a cold period to hatch was tested in a laboratory experiment. When soil containing cocoons was incubated at -5°C for 3 weeks, a significant increase in juveniles was demonstrated for H. perpusilla and Bryodrilus diverticulatus compared with soils kept at constant summer temperatures. This is the first time that breaking of dormancy by an external stimulus has been demonstrated in enchytraeid cocoons.
Colonization-extinction dynamics of opossums on small islands in Panama
Authors: Boyett William D , Endries Mark J , Adler Gregory H
Published: April 2011

We studied the distributions and colonization-extinction dynamics of five species of opossums (Didelphis marsupialis, Marmosa robinsoni, Philander opossum, Caluromys derbianus, and Metachirus nudicaudatus) on 12 small islands in Gatun Lake in central Panama. Opossums were censused by monthly livetrapping from 1991 (eight islands) or 1993 (four islands) through 1995. We recorded 75 colonizations over the course of the study. Didelphis marsupialis was the most frequent colonizer and accounted for 56% of all colonizations recorded. However, only four D. marsupialis populations that reproduced successfully resulted from these colonizations, and most populations went extinct. Marmosa robinsoni and P. opossum also frequently colonized these islands but rarely established successful populations. Multiple linear regression was used to relate the mean numbers of colonizations and population establishments per year and mean and standardized persistence times of all five species of opossums to island size and isolation. These four dependent variables were not related to island area or isolation distance. This system, characterized by frequent colonizations and extinctions, fit the mainland-island metapopulation model, and nearby mainland areas that maintained persistent populations of all five species provided colonists to the small islands.
Diurnal behaviour and habitat use of nonbreeding Marbled Teal, Marmaronetta angustirostris
Authors: Green Andy J , Hamzaoui Mustapha El
Published: April 2011

The diurnal behaviour and habitat use of the globally threatened Marbled Teal, Marmaronetta angustirostris, were studied in Morocco and Spain from October to March. This is the first study of nonbreeding Marbled Teal, the most primitive member of the pochards (tribe Aythyini). Like other Aythyini, Marbled Teal pair relatively late: only 35% of individuals were paired by mid-March. Feeding was mainly nocturnal, and less than 2% of daytime was spent feeding from November to March. Feeding behaviour was similar to that of dabbling ducks (tribe Anatini). A steady increase in swimming activity from October to March was related to increased courtship activity and raptor-avoidance behaviour. Teal selected areas close to the shoreline and avoided open water. Selection of shoreline habitats and distance to shoreline covaried with month and behaviour type. The Marbled Teal is an aberrant pochard with a stronger ecological affinity with the Anatini.
Space and habitat use by resident and transient coyotes
Authors: Kamler Jan F , Gipson Philip S
Published: April 2011

We radio-tracked 10 coyotes (Canis latrans) from April 1996 to March 1998 on Fort Riley Military Reservation, Kansas, to compare movements, habitat use, and survival between resident (breeders and pack associates) and transient coyotes. Home ranges of resident coyotes were mutually exclusive, whereas those of transient coyotes overlapped the home ranges of other coyotes. Excursions from home ranges were made by all resident pack associates but not by resident breeders. Grassland habitats were used more than expected by resident coyotes but less than expected by transients. Woodlands and cultivated lands were used more than expected by transients. Transient coyotes used areas between the home ranges of resident family groups. Annual survival rates were higher for resident than for transient coyotes. Avoidance of resident coyotes by transient coyotes may explain differences in space and habitat use by coyotes.
Foraging strategies of sympatric lagomorphs: implications for differential success in fragmented landscapes
Authors: Smith Douglas F , Litvaitis John A
Published: April 2011

In recent decades, the distribution of New England cottontails (Sylvilagus transitionalis) has declined substantially in response to forest maturation and fragmentation. Populations of eastern cottontails (Sylvilagus floridanus) have expanded into the range of S. transitionalis, since they are apparently less affected by the consequences of habitat modifications. We suspected that S. floridanus was able to exploit small patches of habitat where S. transitionalis was vulnerable to intense predation and we evaluated this explanation using large enclosures within which we manipulated the quality and distribution of food in relation to escape cover. In trials with low-quality food in cover and high-quality food in open areas, S. transitionalis sacrificed food quality for safety by remaining in close proximity to cover. Sylvilagus floridanus avoided low-quality food in cover and foraged at sites containing high-quality food away from cover. When food was removed from cover, S. transitionalis was reluctant to forage in the open and lost a greater proportion of body mass and succumbed to higher rates of predation than did S. floridanus. We applied these results to patterns of foraging by free-ranging rabbits in a fragmented landscape and estimated that S. transitionalis could successfully exploit only 32% of the available habitat without experiencing elevated rates of predation, whereas S. floridanus could exploit 99% of the habitat. Thus, the consequences of habitat fragmentation (especially higher predation risk) may not be as detrimental to S. floridanus, and this species will likely persist, whereas populations of S. transitionalis will continue to decline.