bluuebunny/crossref_metadata_2025 huggingface dataset:
The impact of nocturnal light pulses on the activity pattern of terrestrial snails (Helix lucorum) entrained to a photoperiod of 12 h light: 12 h dark
Authors: Flari V. , Lazaridou-Dimitriadou M.
Published: July 2008

The effects of nocturnal light pulses, "asymmetrical skeleton photoperiod regimes," on the circadian locomotor activity rhythm in adults of the edible snail Helix lucorum previously entrained to a photoperiod regime of 12 h light : 12 h dark were examined. In all experiments the snails showed a clear bimodal rhythm of behaviour, with peaks at both dusk and dawn. Shifts occurred according to the timing of 2-h light pulses applied in the scotophase and were related to the phase of snails' entrained rhythms. It is suggested that a minimum dark period (up to 10 h) is necessary for H. lucorum to retain its normal daily rhythmicity.
Flight capacity of the reindeer warble fly, Hypoderma tarandi (L.), and the reindeer nose bot fly, Cephenemyia trompe (Modeer) (Diptera: Oestridae)
Authors: Nilssen Arne C. , Anderson John R.
Published: July 2008

The performance of tethered flies on a laboratory flight mill was used to assess the flight capacity of Hypoderma tarandi (L.) and Cephenemyia trompe (Modeer). Maximum total flying times for H. tarandi females were 31.5 h, but most flies flew < 20 h (mean 8.5 h (SD 7.2 h)). The longest continuous flight was 12 h. For both species, mating greatly altered the flight behaviour of females. Unmated laboratory-reared females were reluctant to fly, and flew less continuously than mated wild-caught flies. Hypoderma tarandi males typically flew for short periods of a few minutes with long rests between flights. Cephenemyia trompe females seldom exceeded 10 h of total flying time (mean 4.9 h (SD 3.2 h), maximum 10.8 h), but were capable of many hours of sustained flight. Field-trapped C. trompe males normally flew < 8 h (mean 2.8 h (SD 2.1 h), maximum 7.1 h). In free flight the speed of C. trompe males was ≈8 m/s. Maximum flight distances during the lifetime of a fly were estimated to be 600–900 km for female H. tarandi, 220–330 km for female C. trompe, and 200–400 km for males of both species. Hypoderma tarandi could maximally reduce its mass to about 40% of initial mass, and the mass loss rate during flight was 3.5-fold that of basal metabolism (i.e., without flying) at 22 °C. The adaptive significance of the extraordinary capacity for sustained flight of female oestrids is related to the migratory behaviour of their vertebrate host, Rangifer tarandus (L.).
New taxa of Rhagidiidae (Acari: Prostigmata) from North America. Part IIIB. Genus Rhagidia Thorell: the quadrisolenidiata species-group
Authors: Zacharda Miloslav
Published: July 2008

Two new species of rhagidiid mites from the Nearctic region, Rhagidia arizonaensis n.sp. and R. quadrisolenidiata n.sp. in the quadrisolenidiata species-group of the subgenus Noerneria, are described. Their interspecific relationships are discussed and a key to the known subgenera, species-groups, and adults of species in the genus Rhagidia Thorell from the Holarctic region is given.
Use of space by the woolly opossum Caluromys philander (Marsupialia, Didelphidae) in French Guiana
Authors: Julien-Laferrière Didier
Published: July 2008

Use of space by a woolly opossum (Caluromys philander) population in a primary forest of French Guiana was examined by trapping and radio tracking during 27 months over a period of 3.5 years. Mean home-range size was about 3 ha. Home ranges widely overlapped between both males and females. Use of space was more evenly distributed during the season of fruit scarcity than during the season of fruit abundance. The location of the core area within the home range was correlated with the location of feeding sites. A high dispersal rate was observed in both young and adults. Space-use patterns were influenced to some extent by factors relating to the environment (food availability) and the individual (energy needs of females related to maternal investment). Nevertheless, ranging behaviour varied greatly among individuals. Space-use patterns appear to be highly opportunistic in this species and may explain why C. philander has colonized a vast range of habitats over a wide geographical area.
Spatial patterns of burrowing owl (Speotyto cunicularia) nests within black-tailed prairie dog (Cynomys ludovicianus) towns
Authors: Desmond Martha J. , Savidge Julie A. , Seibert Thomas F.
Published: July 2008

The spatial patterns of burrowing owl (Speotyto cunicularia) nests in black-tailed prairie dog (Cynomys ludovicianus) towns were examined in the Nebraska panhandle during the spring and summer of 1989–1991. Because of higher nest densities (≥ 0.20 nests/ha) and internest distance requirements, it was not possible for owls to demonstrate patterns other than random in the smaller (< 35 ha) prairie dog towns. In large prairie dog towns (> 35 ha), burrowing owls were less dense (≤ 0.20 nests/ha), and choice of nest sites by pairs resulted in a clumped nest distribution. In prairie dog towns < 35 ha, nearest neighbor distance was positively related to prairie dog town size, whereas no relationship was found between prairie dog town size and nearest neighbor distance for towns ≥ 35 ha. Burrow availability was not responsible for clumping. Ample burrows were available throughout the towns in 1990 and 1991. In 1991, two towns with clumped distributions of owls showed no differences in numbers of burrows around active owl nests and random burrows throughout the towns. Other possible explanations for clumping, including food availability and reduced predation risk, are discussed.
Hemocytic rickettsia-like organisms inIxodes scapularis: transovarial and transstadial transmission
Authors: Magnarelli Louis A. , Mather Thomas N. , Yeh Min-Tsung
Published: July 2008

Unengorged, host-seeking female Ixodes scapularis were collected from the northeastern United States (Rhode Island and Massachusetts) in April 1992. Hemolymph preparations from F1males and females were tested to determine if hemocytic rickettsia-like organisms, having shared antigens with ehrlichiae, are passed transovarially and transstadially. Fluorescein-labeled dog anti-Ehrlichia canis antiserum was used to detect infected hemocytes by means of direct fluorescent antibody staining methods. In duplicate tests of F1ticks, hemocytes from 25 males and 25 females were tested by indirect fluorescent antibody staining methods with antisera from two persons who had Rocky Mountain spotted fever. These hemolymph preparations were nonreactive, but those from cohorts of ticks reared from five infected females and tested with anti-E. canis antiserum contained rickettsia-like organisms in the cytoplasm of hemocytes. Thirty-four (54.8%) of 62 males and 71 (63.4%) of 112 females were positive. Prevalence of positive males among the five cohorts ranged from 18.8 to 80%, while results for females varied between 21.2 and 91.7%. The unidentified rickettsia-like hemocytic organisms, which have shared antigens with Ehrlichia species, are transmitted transovarially and transstadially in I. scapularis.
Antler rubs by white-tailed deer: the importance of trees in a prairie environment
Authors: Oehler Sr. Michael W. , Jenks Jonathan A. , Bowyer R. Terry
Published: July 2008

Antler rubs (scent marks) by male white-tailed deer (Odocoileus virginianus) (n = 84) were characterized from 1 to 20 October 1993 on the Northern Plains Biological Field Station at Oak Lake, Brookings County, South Dakota. The northern Great Plains is characterized by low species richness and trees that often have aromatic properties and are confined to draws and riparian areas. Consequently, we hypothesized that the selection of trees for antler rubs by deer in prairie environments would differ from that in other regions of North America. Eight species of trees were rubbed. Juneberry (Amelanchier alnifolia) and chokecherry (Prunus virginiana) were selected, whereas green ash (Fraxinus pennsylvanica), fleshy hawthorn (Crataegus succulenta), boxelder (Acer negundo), and wild plum (Prunus americana) were avoided. From the available trees [Formula: see text], deer selected larger diameter trees [Formula: see text] for antler rubs. Height of first branch above the ground was greater for trees used for antler rubs [Formula: see text] than for random trees [Formula: see text]. Deer selected aromatic species of trees for scent marking and avoided those species with thorns. We hypothesize that recent changes in the distribution of trees in prairie environments have facilitated expansion of the range of white-tailed deer in the northern Great Plains.
Increase of parental effort in experimentally enlarged broods of Pallid Swifts
Authors: Cucco Marco , Malacarne Giorgio
Published: July 2008

Variation in parental effort of Pallid Swifts (Apus pallidus) was investigated for 3 years in a colony in northwestern Italy. The masses of adults and of bolus loads brought to chicks were monitored by electronic balances inserted under nests, and feeding rates were monitored by video cameras. Fluctuations in daily food availability were measured with an insect-suction trap. Manipulation experiments on broods originally consisting of three chicks were performed to increase (four chicks) or reduce (two chicks) adult effort, with the aim of determining if parents tend to allocate food primarily to themselves or to their offspring, and if mass loss in adults results from reproductive stress or from adaptive programmed anorexia. With the enlargement of brood size, mean bolus mass remained constant, but the visitation rate increased significantly. Daily food abundance did not influence the amount of food allocated to chicks (neither time spent foraging nor the bolus mass changed), but positively influenced the mass of adults, which showed large daily variations. These results indicate that parents tend to invest constantly in offspring, at their own expense when food is scarce. Our data lend support to the cost of reproduction hypothesis instead of adaptive anorexia, since adults lose mass mainly in the brooding period, when demand is highest, and always regain mass when prey availability is greater.
Effects of body size on investment in individual broods by male pine engravers (Coleoptera: Scolytidae)
Authors: Reid Mary L. , Roitberg Bernard D.
Published: July 2008

Large body size is generally associated with mating advantages and greater vigour in insects and other animals. Greater mating opportunities may favour reduced investment in individual broods, but greater vigour may contribute to greater brood success. To consider these issues, we examined the effect of body size of male pine engraver beetles, Ips pini (Coleoptera: Scolytidae), on the duration of paternal care and the reproductive success of their individual broods in a laboratory experiment. Larger males abandoned their mates and brood earlier than did small males. Nevertheless, larger males had more offspring and, when offspring emergence date was controlled by focusing on early emergers, larger males had larger offspring. There was no detectable effect of male size on the breeding behaviour of their mates. This study indicates that larger individuals realize higher fitness both through increased mating opportunities and through greater reproductive success in individual broods.
Growth rate and age at maturity in syntopic populations of Rana clamitans and Rana septentrionalis in central Ontario
Authors: Shirose L. J. , Brooks R. J.
Published: July 2008

Populations of the green frog (Rana clamitans) and the mink frog (Rana septentrionalis) in Algonquin Provincial Park, Ontario, Canada, were studied from May 1985 through October 1987 and from May 1991 through September 1993. Parameters estimated from fitting logistic curves to growth data obtained from marked individuals were used to test for interspecies and intersexual differences in growth trajectories. Female R. septentrionalis had a significantly greater asymptotic length than males. We found no sexual size dimorphism in R. clamitans. Asymptotic size was significantly greater for R. clamitans than for R. septentrionalis. Age was estimated from a combination of extrapolation from size-frequency data and from production of size-specific growth curves from recapture data. Age-specific size and growth rate were measured to test the hypothesis that differences in growth trajectories could be predicted from differences in patterns of survivorship. Both R. septentrionalis and R. clamitans were larger at transformation, and older at maturity, than has been reported in previous studies. Although significantly larger at transformation, R. septentrionalis was significantly smaller than R. clamitans in all subsequent age-classes. The growth rate of R. clamitans was significantly greater than that of R. septentrionalis for all age-classes except 0 years post transformation. The observed differences in growth trajectories and age at maturity were consistent with predictions based on differences in the pattern of survivorship.
Travel path characteristics for free-living white-footed mice (Peromyscus leucopus)
Authors: McMillan Brock R. , Kaufman Donald W.
Published: July 2008

Characteristics of the travel paths of white-footed mice (Peromyscus leucopus) were examined by tracking animals marked with fluorescent pigment in a wooded site in northeastern Kansas. Based on 84 trails made by 49 individuals, it was concluded that tops of structural features (rocks, branches, logs, or rock fence) were selectively used for nighttime travel. Trails averaged 41.7% structural features (SE = 6.0%), whereas sample points 20 cm away from trails averaged 18.0% structural features (SE = 1.8%). This pattern of use of structural features did not differ between male and female mice. Nighttime illumination (according to the moon phase) and season did not affect the proportion of structural features used along travel paths; this suggests that risk from visual predators was not driving the pattern of use of structural features for travel paths by white-footed mice. Rather, white-footed mice may have used surface structure for travel because structural features provide paths that are more easily traveled and remembered. Trees were climbed infrequently (0.6 trees per 100 m of trail), but more in autumn (1.9 trees per 100 m of trail) than in other seasons (0.2 trees per 100 m of trail), which likely resulted from greater availability of seeds, nuts, and fruits during autumn than during other seasons.
Effects of pH on embryo tolerance and adult behavior in the tiger salamander,Ambystoma tigrinum tigrinum
Authors: Whiteman Howard H. , Howard Richard D. , Whitten Kathleen A.
Published: July 2008

We examined adult discrimination ability and embryo performance under different pH conditions in the eastern tiger salamander, Ambystoma tigrinum tigrinum. We collected individuals from three populations in habitats that differed naturally in pH, thus allowing interpretation of population-specific responses in embryos and adults. We conducted pool-choice experiments in the field using two pH treatments to determine adult pH discrimination ability and controlled laboratory toxicity tests using eight pH treatments to evaluate embryo performance. Adult discrimination ability differed among source populations. Male salamanders from the locality with the highest pH were more likely to stay in neutral-pH pools and more likely to leave acidic ones. Males from the locality with the lowest pH were also more likely to remain within neutral pools, but their rates of staying and leaving acidic ones did not differ. These results suggest that the pH of the source-population habitat may influence breeding-habitat discrimination by adults. Decreasing pH produced similar patterns of lethal (survival) and sublethal (date and size at hatching) effects on embryos from the three populations, with reduced performance at low pH. Survival of embryos was more than 70% at pH 4.5 and above, but decreased dramatically at lower pH levels. The pH at which 50% mortality occurs (LC50) was estimated as 4.2, suggesting that tiger salamanders from our populations were relatively acid tolerant compared with congeners. However, significant sublethal effects could reduce the subsequent success of surviving hatchlings. Our results are consistent with the hypothesis that adult discrimination ability depends on pH levels in the breeding habitat. This suggests that adult behavior patterns could influence the success of population reintroductions to previously acidified areas. Thus, data on pH responses at all stages in the amphibian life cycle should contribute to management decisions.
Factors affecting abandonment and adoption of young in common eiders and other waterfowl: a comment
Authors: Pöysä Hannu
Published: July 2008

Factors affecting abandonment and adoption of young have been studied extensively in waterfowl. Several hypotheses have been advanced to account for these behaviours, and Bustnes and Erikstad (J.O. Bustnes and K.E. Erikstad. 1991. Can. J. Zool. 69: 1538–1545) recently evaluated these in common eiders (Somateria mollissima). They found, among other things, that young of "abandoners" had a lower survival rate than young of "tenders," but were not able to accurately time the mortality of ducklings. I propose a hypothesis based on brood success and parental investment theory to explain why some parents abandon their young exceptionally early and why some parents tend their own as well as foreign young. According to the hypothesis, parents provide relatively less care for offspring that are surviving less than average during the parental care period. The low survival of the young of abandoners while they are still with their own mother may have influenced the final decision of common eider females to abandon their broods early.
Annual variation in common eider egg size: effects of temperature, clutch size, laying date, and laying sequence
Authors: Robertson Gregory J.
Published: July 2008

Annual variation in volumes of eggs laid by common eiders (Somateria mollissima sedentaria) nesting at La Pérouse Bay, Manitoba (58°43′N, 93°27′W), was studied over 3 years (1991–1993). Temperatures during the egg-laying period were higher in 1991 than in 1992 and 1993. However, the eiders began nesting in 1993 at the same time as in 1991, whereas in 1992 the eiders began laying approximately 2 weeks later. Eiders laid significantly smaller clutches in 1992 than in the other 2 years. Egg size did not correlate with clutch size or laying date in any year. However, eiders laid smaller eggs in 1992 and 1993 than in 1991. In five egg clutches, the pattern of intraclutch egg-size variation was different among years. The last laid eggs of five egg clutches were disproportionately smaller in 1992 and 1993 (cold years) than those laid in 1991. Minimum daily temperatures before the egg-laying period (during rapid yolk development) were positively correlated with egg size. However, this effect was not significant when year and egg sequence were controlled for. Egg-size variation was correlated with the overall ambient temperatures during the laying period, whereas annual clutch-size variation was correlated with laying date, suggesting that the proximate mechanisms affecting clutch and egg size are different.
Evaluation of several indices for assessment of coyote (Canis latrans) body composition
Authors: Huot Jean , Poulle Marie-Lazarine , Crête Michel
Published: July 2008

The body composition of 27 coyotes (Canis latrans) of different ages and both sexes was determined on the basis of chemical analyses of homogenized samples of viscera, carcass, and skin. Regression analyses were used to identify the best indices for estimating fat (lipid reserves), protein, and water body contents. A combined index based on the kidney fat index and the percentage of femur marrow fat was the best indicator of fat reserves. Body mass (whole or skinned carcass) and eviscerated carcass mass were the best predictors of total body protein and total body water contents. A combination of indices is proposed to provide postmortem or in vivo estimates of coyote body composition.
Cholinergic and adrenergic regulation of heart rate and ventral aortic pressure in two species of tropical tunas,Katsuwonus pelamisandThunnus albacares
Authors: Keen John E. , Brill Richard W. , Aota Sumi , Farrell Anthony P. , Randall David J.
Published: July 2008

Tonic cholinergic and adrenergic control of heart rate and ventral aorta pressure was examined in two species of tropical tunas, the skipjack tuna (Katsuwonus pelamis) and the yellowfin tuna (Thunnus albacares). Unlike that of many other teleosts, the basal heart rate in spinally blocked tunas (at 25 °C) was dominated by a cholinergic rather than an adrenergic tonus. Infusion of atropine increased the heart rate by 143 and 58% in skipjack and yellowfin tunas, respectively. Ventral aortic pulse pressure was significantly decreased and mean ventral aortic pressure was slightly increased. Blockade of β-adrenergic receptors with propranolol produced small (<6%) decreases in both heart rate and mean ventral aortic pressure, indicating a low level of tonic β-adrenergic stimulation. The small magnitude of the drop, however, suggests that tonic adrenergic regulation of heart rate and pressure is of less importance in tunas than in other teleosts, despite comparable circulating levels of adrenaline and noradrenaline. The α-adrenergic blocker phentolamine did not affect either heart rate or pressure. The intrinsic heart rate (i.e., the heart rate in the absence of cholinergic or adrenergic stimulation) was 180 beats/min in skipjack tuna and 119 beats/min in yellowfin tuna; these are the highest reported values for any teleost to date.
Cyclops strenuus (Fischer, 1851) sensu lato in Alaska and Canada, with new records of occurrence
Authors: Reed Edward B. , McIntyre Nancy E.
Published: July 2008

References to Cyclops strenuus in the North American literature are reviewed. Male and female specimens of C. strenuus sensu lato from 20 sites in Alaska, Yukon, Northwest Territories, and Saskatchewan were measured and compared using several morphological parameters. Two or more phenotypes may be present among the 20 populations. The specimens examined differ sharply from Cyclops canadensis Einsle, 1988, especially in the length of the caudal ramus, length of the antennules, width of prosomites 4 and 5, and length of the lateralmost and medialmost terminal caudal setae. Thus, Einsle's conclusion that previous records of C. strenuus in North America are likely referable to C. canadensis may be premature. New records of C. strenuus away from northern coastal areas of Alaska and Canada include Saint Matthew and Nunivak islands, two interior Alaska locations, Galena and Chatanika, and four locations in central and southern Saskatchewan. Passive dispersal via migrating waterfowl may account for the presence of C. strenuus in Saskatchewan. To date, only a very few individuals of C. strenuus s.l. from a very large area in North America have been examined. Final decisions about relationships among Nearctic C. strenuus and their relationships to Palearctic congeners must await the examination of many more animals and investigations using biochemical or chromosomal techniques in conjunction with morphology.
Food habits and nutrition of black bears during a gypsy moth infestation
Authors: Kasbohm John W. , Kraus James G. , Vaughan Michael R.
Published: July 2008

During 1988–1991 we determined food habits and indices of diet quality for a black bear (Ursus americanus) population in Shenandoah National Park, Virginia, experiencing a severe gypsy moth (Lymantria dispar) defoliation event, and compared the results with data collected prior to defoliation (1982–1984). Gypsy moth infestation resulted in extensive summer overstory canopy loss and a complete acorn failure in affected areas. As in predefoliation years, analysis of scats collected during defoliation indicated that bears ate primarily herbaceous vegetation in spring, followed by squawroot (Canopholis americana) and fruits of black and sweet cherry (Prunus serotina and P. avium) in summer. However, in early and late fall bears switched from consuming predominantly acorns before defoliation to pokeweed (Phytolacca americana) berries and grapes (Vitis spp.), respectively, during defoliation. Despite acorn loss, no decline in dietary nutritional quality was observed in comparisons of the percentages of crude protein, crude fat, and crude fiber in seasonal diets before and during defoliation. When it is available, bears can successfully exploit soft mast as a fall food source and do not necessarily experience a substantial reduction in food quality if acorn crops fail.
Geographic and individual variation in haematozoan infections in the greenfinch, Carduelis chloris
Authors: Merilä Juha , Björklund Mats , Bennett Gordon F.
Published: July 2008

Among- and within-population variation in prevalence and intensity of haematozoan infections was studied in blood samples taken from nine geographically widely separated greenfinch (Carduelis chloris) populations. Within populations, there were no consistent differences in prevalence between sexes or between older age-classes, but prevalence was significantly lower among yearling birds (<5 months old) in one population. Individual heterozygosity, as revealed by analysis of five polymorphic protein coding loci, did not differ between infected and noninfected birds. However, significant differences in prevalence between Fennoscandian (high), central European (low), and Iberian (high) populations is consistent with the hypothesis that destruction of natural habitats has led to a significant decline of vector populations in central Europe. Given the high among-populations variation in prevalence, our results point to the need to consider the possibility of sampling bias in studies that seek to test, using avian blood parasites, Hamilton and Zuk's hypothesis that parasite resistance might be the target of female choice and drive the evolution of bright plumage and elaborate ornamentation.
Mating behavior of Columbian ground squirrels. I. Multiple mating by females and multiple paternity
Authors: Murie Jan O.
Published: July 2008

Patterns of multiple mating by female Columbian ground squirrels (Spermophilus columbianus) were investigated by observing mating behavior intensively over 5 years. Paternity of litters was assessed through electrophoretic analyses of blood proteins in samples collected from females, offspring, and putative fathers. On average, females mated with four males, and all mated with more than one male. Sixteen percent of 165 litters were multiply sired, but that is probably an underestimate of the rate of multiple paternity. Neither age of the female nor a crude estimate of the operational sex ratio affected number of mates. Litter size did not vary with the number of mates a female had. However, numbers and proportion of juveniles surviving to yearling age tended to increase (nonsignificantly) with the number of mates for mothers. These data suggest that mate choice for "good genes" via sperm competition is the most plausible benefit of multiple mating for females. Other possible benefits of multiple mating are either not plausible or untested with current data.
Prodissoconch morphology, planktonic shell growth, and size at metamorphosis inDreissena polymorpha
Authors: Martel André , Hynes Teresa M. , Buckland-Nicks John
Published: July 2008

Larval shell morphology and morphometry of the zebra mussel, Dreissena polymorpha, were examined using scanning electron and light microscopy. Larval shell morphology is typical of bivalves having planktotrophic development. The prodissoconch I (PI) has a pitted-punctate surface contrasting markedly with the conspicuous fine concentric or commarginal lines of the prodissoconch II (PII) and dissoconch (D) shells. Length-frequency distributions of the prodissoconch, which were obtained from disarticulated valves of bleached early juveniles (0.5–2 mm) (specimens from west-central Lake Erie), indicated a mean length (umbo to ventral margin) of 76.4 and 220 μm for PI and PII, respectively; these results corroborated those from direct measurements of early D-shaped veligers from the plankton and from early juvenile settlers from collectors (24- to 36-h deployments), respectively. Measurements of shell lengths at the PII–D boundary thus provided accurate information on size distributions of veligers at the time of settlement and metamorphosis. The estimated minimum and maximum larval shell growth or increment (PII length – PI length, or ΔP) (92 and 195 μm, respectively), combined with Smylie's in situ larval growth rates (3–20 μm∙d−1), suggest a surprisingly wide range in the duration of the planktonic period of D. polymorpha in Lake Erie: 1–9 weeks.
Age structure, mortality, and longevity in syntopic populations of three species of ranid frogs in central Ontario
Authors: Shirose Leonard J. , Brooks Ronald J.
Published: July 2008

Syntopic populations of bullfrogs (Rana catesbeiana), green frogs (Rana clamitans), and mink frogs (Rana septentrionalis) were monitored between May and October in each of 1985 through 1987 and 1991 through 1993 in Algonquin Provincial Park, Ontario, Canada. We assessed the descriptive and predictive utility of a dichotomous system for classification of anuran life histories by testing the hypothesis that large body size and large clutch size are associated with a survivorship curve in which mortality is highest for very small individuals. Ages of individuals were estimated from size-frequency and recapture data. Survivorship and longevity were estimated from standing age distributions smoothed with the log-polynomial method. Survivorship was also estimated by comparing the number of animals in an age-class in a given year with the number in the next age-class in the next year. Age distributions were unstable in all three species. The strengths and weaknesses of both methods of estimation of survivorship are discussed.
Nest-site selection by the Swainson's Hawk on the Regina plain, Saskatchewan
Authors: Groskorth Laura C.
Published: July 2008

Swainson's Hawk (Buteo swainsoni) nest sites on the Regina plain were compared with randomly selected sites. Various immediate and surrounding habitat variables were examined to determine whether this hawk shows a preference for nesting habitat. Results showed that hawks selected nest sites with significantly less surrounding wheatland and more surrounding grassland, trees, and shrubs than random sites. Nest sites were also farther from buildings and water and closer to larger communities than random sites. These results suggest that this hawk selects nest sites least affected by agriculture.
Impact of helminth parasitism on a snowshoe hare population in central Wisconsin: a field experiment
Authors: Bloomer Sara E. M. , Willebrand Thomas , Keith Ingegerd M. , Keith Lloyd B.
Published: July 2008

We tested the hypothesis that helminth parasitism is demographically significant to a noncyclic population of snowshoe hares (Lepus americanus) near the species' geographic boundary in central Wisconsin (U.S.A.). During November 1988 to December 1991, we injected 93 individuals (≥760 g, aged ≥2 months) with anthelmintics: Ivermectin for nematode and Droncit for cestode infections. We injected 98 control hares with propylene glycol, the common vehicle for both drugs. All treated and control hares were radio-collared with mortality-sensing transmitters and monitored daily to weekly from the ground or air. Prevalence and intensity of lungworms (Protostrongylus boughtoni), intestinal worms (Nematodirus triangularis), and stomach worms (Obeliscoides cuniculi) were markedly reduced by Ivermectin treatment. No other nematodes were found to be present. Treatment with Droncit to remove intestinal cestodes was apparently unnecessary, as prevalence among necropsied untreated hares and controls was just 10%. We compared body-condition indices (mass changes, response to trap stress, and bone-marrow fat), reproduction (pregnancy rate and litter size), home-range sizes, and time-specific survival rates of anthelmintic-treated versus control hares. None of these demographic variables differed significantly between treated and control cohorts, nor was there any evidence that parasitism increased the risk of death from predation, which was the proximate cause of 96% of all natural mortalities. We conclude that helminth parasitism played no detectable role in the dynamics of this Wisconsin snowshoe hare population.
Examination of orientation of the giant scallop, Placopecten magellanicus, in natural habitats
Authors: Stokesbury Kevin D. E. , Himmelman John H.
Published: July 2008

Observations in 1991 along randomly placed transects within two aggregations (beds) of the giant scallop, Placopecten magellanicus, in Port Daniel Bay, Baie des Chaleurs, Gulf of St. Lawrence, showed that scallops were oriented randomly. During 1992, tag–release experiments were conducted on scallops at four sites, two on gravel (one in each of the above beds), one on sand, and one on bedrock, to examine the effects of current on scallop orientation over time. Current directions and velocities were measured at each site. Circular statistics applied to orientation distributions showed that scallops at the sites with gravel or sand substrata were randomly oriented and also changed orientation between successive observations at random. In contrast, at the bedrock site, scallops were significantly oriented and shifts of 120°–150° between successive observations were less frequent than would occur at random. The differences at the bedrock site possibly occurred because the scallops could not recess into the substratum and were thus more directly exposed to bottom currents. Although giant scallops have the capacity to orient themselves to current, they likely do not do so on gravel or sand substrata if current velocities are below 18.3 cm∙s−1.
Effects of low pH and aluminum on body size, swimming performance, and susceptibility to predation of green tree frog (Hyla cinerea) tadpoles
Authors: Jung Robin E. , Jagoe Charles H.
Published: July 2008

Green tree frog (Hyla cinerea) tadpoles were exposed immediately after hatching to aluminum (nominally 0, 150, 250, 400 μg/L) at pH 4.5 or 5.5, plus a control (pH 7.0, 0 μg/L Al) for 96 h. Mortality increased with increasing Al concentration at pH 4.5 but not at pH 5.5. Among surviving tadpoles, body size was significantly reduced at higher Al concentrations at both pH 4.5 and 5.5. At pH 4.5, analysis of covariance indicated that maximal swimming speed was positively correlated with tadpole total length and differed among Al treatments; tadpoles at higher Al levels swam more slowly. Body Al and Na+concentrations also differed among treatments. In a second experiment, tadpoles exposed for 96 h to approximately 150 μg/L Al at 4.5 pH were preyed upon by dragonfly larvae (Libellulidae) at a higher rate than were tadpoles raised in pH 4.5 or 7.0 without Al. As in the first experiment, tadpoles exposed to Al were smaller and were slower swimmers. Sublethal concentrations of Al at low pH may result in lowered growth rates and hence reduced body size. Swimming performance is reduced by small body size, and size-adjusted performance is further reduced by Al and low pH, which might lead to higher predation on Al-stressed tadpoles.
Changes in reproductive potential of the leechNephelopsis obscura(Erpobdellidae) as biomarkers for cadmium stress
Authors: Davies Ronald W. , Singhal R. N. , Wicklum D. D.
Published: July 2008

The effects of exposure for 4–24 days to 0, 58, 145, 290, 435, and 580 μg∙L−1cadmium on the reproductive potential of the freshwater predatory leech Nephelopsis obscura were investigated. The numbers of ova and spermatozoa per unit biomass were significantly reduced with increasing cadmium concentration and exposure time, as were the masses of the ovisacs, testisacs, and epididymis plus cornu. It is concluded that these variables are effective biomarkers for identifying sublethal effects of direct importance to population dynamics.
Experimental evidence for the effect of depth and structure on the distribution, growth, and survival of stream fishes
Authors: Lonzarich David G. , Quinn Thomas P.
Published: July 2008

Water depth and physical structure are important components of habitat complexity for stream fishes. Experiments in a semi-natural stream, containing four depth and structure treatments, quantified the effect of these two habitat components on the distribution, growth, and survival of five fish species common to coastal streams of Washington State. When fishes were permitted to move freely among the various habitat types, most species and age-classes were underrepresented in shallow pools lacking structure. In some cases water depth or physical structure alone appeared to explain these distributions. However, assemblage- and species-level responses were strongly influenced by the combined effects of depth and structure. A subsequent 30-d experiment revealed that mortality (likely due to bird predation) of water-column species using the simplest habitat type was as much as 50% greater than in the other treatments. However, there were no differences in survival of the benthic species, coastrange sculpin (Cottus aleuticus), among the different treatments, nor were there significant differences in growth among treatments for any species. These results indicate that predation risk may help to explain the importance of both deep water and physical structure to fishes in coastal streams in Washington. The results of our habitat-selection experiment also support the growing view that a community-level approach may be more effective than the single-species approach in evaluating the effects of human activities on stream fishes.
Predation on zebra mussels (Dreissena polymorpha) by captive-reared map turtles (Graptemys geographica)
Authors: Serrouya Robert , Ricciardi Anthony , Whoriskey Fred G.
Published: July 2008

The suitability of the Eurasian zebra mussel, Dreissena polymorpha, as prey for the common map turtle, Graptemys geographica, was tested under laboratory conditions. The turtles, which were reared in captivity without contact with molluscs, readily consumed zebra mussels in every feeding trial. Mussels were ingested whole. Repeated exposure to zebra mussels in successive trials did not increase consumption rates (ca. 11 mussels/turtle per day), suggesting that the turtles required little time to recognize and efficiently utilize zebra mussels as prey. The turtles were offered zebra mussels ranging from 4 to 34 mm in length and consumed mussels as large as 32 mm, but mussels larger than 25 mm were consumed at lower rates. Turtles consumed lower numbers of zebra mussels in the presence of an alternative prey, the prosobranch snail Bithynia tentaculata, which is common in map turtle habitats in the Great Lakes – St. Lawrence River system. Populations of map turtles and zebra mussels are sympatric in the upper St. Lawrence River, Lake Champlain, the lower Great Lakes, and the upper Mississippi River basin. Our results suggest that map turtles may forage on zebra mussels in nature, but zebra mussels will be important prey only when preferred or more profitable prey are scarce.
Demography and growth of the exotic zebra mussel (Dreissena polymorpha) in the Rideau River (Ontario)
Authors: Martel André
Published: July 2008

Although many biological studies of the zebra mussel, Dreissena polymorpha, have been conducted in lake systems of Europe and, more recently, North America, there is little information about the life-history characteristics of this mollusc in river systems. In the present study, the demography and growth of D. polymorpha were studied in the Rideau River (over a distance of ca. 100 km), Ontario, in 1990, 1993, and 1994. This period coincided with the time of its discovery (October 1990) and rapid population increase (1994) in the river. During 1990, zebra mussels were discovered on the hull of a large steel boat but were not observed on any other substrate. During 1993, zebra mussels were common (1–24 mussels/m2) on reefs, locks, wharves, buoys, and boat hulls in the northern, downstream section of the river near Ottawa, Ontario. During 1994, densities of mussels increased 100- to 10 000-fold (156–23 000/m2) in the downstream section, but remained rare in the upstream section (0–1/m2). Size distributions of young of the year in 1993 and 1994 indicate that mean growth rates of D. polymorpha in the Rideau River (0.090–0.139 mm∙d−1) are comparable to those reported for the Great Lakes and European rivers.
Influences of age, body condition, and structural size on mate selection by dabbling ducks
Authors: Heitmeyer Mickey E.
Published: July 2008

Both members of pairs of mallards (Anas platyrhynchos), northern pintails (Anas acuta), northern shovelers (Anas clypeata), and American wigeon (Anas americana) were collected early in the pairing periods in fall and during spring migration (several months after most birds were paired) to provide insights into whether (i) assortative mating occurs; (ii) body condition changes synchronously among pair members; and (iii) characteristics of selected individuals ultimately confer advantages in survival and recruitment. Both members in 19 of 21 mallard, 16 of 16 pintail, 14 of 14 shoveler, and 14 of 15 wigeon pairs were adults. The predominance of adults in pairs in fall indicates that adults pair earlier than juveniles and suggests at least some assortative mating in relation to age. Generally, body and nutrient reserve masses of males and females within a pair were correlated for all species in both fall and spring, suggesting that individuals tend to form pairs with others of relatively similar body condition, and also that once paired, the body condition of the two members tends to change at the same time. In contrast to body condition, measures of structural size of pair members were not correlated. Field data suggest that older and heavier ducks have greater survival and reproductive potential than young, lighter ducks; consequently, selection of old and heavy mates is probably evolutionarily advantageous.
Umingmakstrongylus pallikuukensisgen.nov. et sp.nov. (Nematoda: Protostrongylidae) from muskoxen,Ovibos moschatus, in the central Canadian Arctic, with comments on biology and biogeography
Authors: Hoberg E. P. , Polley L. , Gunn A. , Nishi J. S.
Published: July 2008

Umingmakstrongylus pallikuukensis gen.nov. et sp.nov. is established for a protostrongylid nematode in muskoxen, Ovibos moschatus, from the Kitikmeot Region (central Arctic) of the Northwest Territories, Canada. It is distinguished from Cystocaulus and other Muelleriinae by characters that include the following: males: deeply incised, bilobed bursa, independent externodorsal rays, telamon composed of distal transverse plate, absence of falcate crurae, and spicules not distally split; females: absence of provagina; and first-stage larvae: presence of three cuticular folds on the tail. The great length of females (468 mm) and males (171 mm) is exceptional among the Protostrongylidae. Pathognomonic lesions include well-defined cysts dispersed through the lung tissue (maximum diameter 40 mm) containing adult and larval parasites in a dense matrix. Transmission involves a molluscan intermediate host, as indicated by experimental infections in the slug Deroceras reticulatum. The parasite is apparently restricted in its geographic distribution and has been found only in a population of muskoxen northwest of Coppermine, N.W.T. This may be indicative of a relictual host–parasite assemblage that has existed since the Pleistocene. The pathogenicity, high prevalence, and intensity of infection in the Coppermine herd suggest that the occurrence of U. pallikuukensis has implications for the management of muskoxen in the Holarctic region.
A morphological comparison of the phyllopodous thoracic limbs of a leptostracan (Nebaliasp.) and a spinicaudate conchostracan (Leptestheriasp.), with comments on the use of Phyllopoda as a taxonomic category
Authors: Martin Joel W. , Christiansen Jennifer C.
Published: July 2008

The fourth thoracic appendage of an adult female Nebalia sp. (class Malacostraca, order Leptostraca) is compared with that of an adult female Leptestheria sp. (class Branchiopoda, order Spinicaudata). Although these limbs are "phyllopodous" (flattened, leaflike) in both orders, they differ markedly in the size and arrangement of endites, type and number of setae, and function. Setal types found on the fourth thoracopod of Nebalia sp. are variations of a basic plumose or plumodentate seta, and the diversity of setal types is low. None of the setae is annulate, a distinction in setal formation. In contrast, on the fourth thoracopod of Leptestheria sp. there is a wide variety of setal types and stout spines, some of which have been reported from other "conchostracans" (orders Spinicaudata and Laevicaudata) but not from the thoracopods of any leptostracan. Nearly all of the setae are annulate. Thus, the single character (phyllopodous thoracic appendages) supposedly linking leptostracans and branchiopods in some classificatory schemes (e.g., the class Phyllopoda sensu Schram) has clearly arisen independently in these two taxa and in several other crustacean groups, and cannot be used as an indicator of phylogenetic affinity. The rejection of the class Phyllopoda as defined by Schram is supported, as are arguments for retention of leptostracans within the Malacostraca. The use of Phyllopoda as a taxonomic name, regardless of which crustacean groups are considered to compose the taxon, is discouraged in light of the rather convoluted history and inconsistent application of this term.
Réponses comportementales des polychètes Nereis diversicolor (O.F. Müller) et Nereis virens (Sars) aux stimuli d'ordre alimentaire : utilisation de la matière organique particulaire (algues et halophytes)
Authors: Olivier Marc , Desrosiers Gaston , Caron Alain , Retière Christian , Caillou Aline
Published: July 2008

Plant preference and feeding selectivity were studied in juveniles of Nereis diversicolor O.F. Müller) and Nereis virens (Sars) (Polychaeta: Nereidae) to evaluate the potential role of these species in the integration and transfer of vegetal debris to the littoral ecosystem. Results show that these annelids ingest the main plant species (algae and halophytes) that are abundant in the marshes of the bay of Mont-Saint-Michel (France) and (or) the À l'Orignal Inlet (St. Lawrence Estuary, Canada), independently of their origin or level of decomposition. Juveniles select detritus on the sediment surface (feeding area) and accumulate them in their burrow. Constant irrigation by young individuals (≈35% of time budget) maintains aerobic conditions favouring the decay process of plant debris by stimulating bacterial growth (gardening). Our results suggest that individuals of both N. diversicolor and N. virens play an important role in the transfer and integration processes and the residence time of vegetal detritus of the intertidal ecosystem.