bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative morphology of zebra (Dreissena polymorpha) and quagga (Dreissena bugensis) mussel sperm: light and electron microscopy
Authors: Walker G. K. , Edwards C. A. , Black M. G.
Published: May 2008

Adult zebra (Dreissena polymorpha) and quagga (Dreissena bugensis) mussels were induced to release large quantities of live spermatozoa by the administration of 5-hydroxytryptamine (serotonin). Sperm were photographed alive using phase-contrast microscopy and were fixed subsequently with glutaraldehyde followed by osmium tetroxide for eventual examination by transmission or scanning electron microscopy. The sperm of both genera are of the ect-aquasperm type. Their overall dimensions and shape allow for easy discrimination at the light and scanning electron microscopy level. Transmission electron microscopy of the cells reveals a barrel-shaped nucleus in zebra mussel sperm and an elongated nucleus in quagga mussel sperm. In both species, an acrosome is cradled in a nuclear fossa. The ultrastructure of the acrosome and axial body, however, is distinctive for each species. The structures of the midpiece are shown, including a unique mitochondrial "skirt" that includes densely packed parallel cristae and extends in a narrow sheet from the mitochondria.
Reproduction and genetic variation in clam shrimps (Crustacea, Branchiopoda, Conchostraca)
Authors: Tinti Fausto , Scanabissi Franca
Published: May 2008

Samples of the three clam shrimp species, Eoleptestheria ticinensis and Leptestheria dahalacensis (Leptestheriidae) and Limnadia lenticularis were collected in north Italian rice paddies in Emilia and Lombardy. Sex-ratio analysis revealed that in the two species of Leptestheriidae, males are more frequent than females, whereas L. lenticularis has an all-female constitution. Allozyme analysis showed a low degree of genetic variation, the values of polymorphism parameters being very similar to those found for other Branchiopoda. In the Leptestheriidae it was generally found that genotypic frequencies conform to Hardy–Weinberg expectations, demonstrating a high outcrossing rate. No clear-cut relationship between the excess of males and cytological and genetic observations could be established, since neither sex chromosomes nor sex-linked genes were found. Nevertheless, male predominance could overcome the morphodynamic constraints that clam shrimps face during fertilization. The all-female constitution of the two populations of L. lenticularis and the hatching of unisexual progeny from virgin females suggest that they reproduce by obligate parthenogenesis; the almost complete lack of heterozygous genotypes at all the analyzed loci allows us to discard the previous hypothesis of automixis. Further analyses should be undertaken to fully clarify the sex-determination mechanisms operating in these clam shrimps, as was previously done in Eulimnadia texana.
Dominance affects resource partitioning in pigeons, but pair bonds do not
Authors: Robichaud David , Lefebvre Louis , Robidoux Lucie
Published: May 2008

Pigeons (Columba livia) show individual feeding specializations both in the field and in captivity. In competitive feeding conditions, these specializations change in a way that decreases dietary overlap between birds. We examine two potential status determinants of feeding competition, dominance and pair bonds. In pigeons, pair bonds are used in aggressive feeding coalitions at defendable patches, while dominance affects both feeding rate and priority of access to food. We compared the seed choices of pigeons feeding alone and in competitive conditions with those of a conspecific. In experiment 1, the competitor was either the mate or a familiar nonmate of the opposite sex; in experiment 2, the dominance rank of the competitors was known from a round-robin series of dyadic encounters in the presence of a defendable feeder. Pair bonds had no effect on competitive diet shifts, but dominance did: in competition, lower ranking pigeons ate less of the seed type they specialized on when feeding alone, while higher ranking pigeons ate more. Confirming previous results on resource partitioning, food choice showed less overlap between individuals in competition than in solitary feeding trials, but the magnitude of the change was not proportional to initial overlap.
Habitat selection by lynx in the Northwest Territories
Authors: Poole Kim G. , Wakelyn Leslie A. , Nicklen Paul N.
Published: May 2008

An understanding of habitat selection by lynx (Lynx canadensis) in the northern boreal forest is needed to evaluate the potential impacts of habitat modification (wildfire and timber harvesting) on lynx populations. We quantified habitat selection by lynx in a 290-km2study area in the western Northwest Territories from 1989 to 1993 by radio-collaring 27 adult lynx (12 females and 15 males). An 8-class habitat map, produced using Landsat thematic mapper data, was used to assess habitat selection. Lynx used habitats disproportionately to their availability (P < 0.001), both at the landscape level and within home ranges. Dense coniferous and dense deciduous forests had higher selection indices than other habitat classes, and wetland – lake bed complexes and open black spruce (Picea mariana) forests had lower selection indices. Habitat selection did not differ between the sexes or among years (P ≥ 0.4) Habitat alteration by wildfire in the northern boreal forest could significantly affect populations of the lynx and its primary prey, the snowshoe hare (Lepus americanus), particularly by maintaining or increasing the availability of dense forest and other preferred habitats.
11-Ketotestosterone stimulates growth of heart and red muscle in rainbow trout
Authors: Thorarensen Helgi , Davie Peter S. , Young Graham
Published: May 2008

The relative ventricular mass (RVM; 100 × ventricle mass/body mass) doubles in male rainbow trout (Oncorhynchus mykiss) as they mature and enter the breeding season, while the RVM of mature females remains unchanged. To examine if this increase in RVM was caused by elevated levels of 11-ketotestosterone (11-KT) in the males, we implanted immature trout of both sexes with Silastic pellets containing either 11-KT or testosterone. Control fish received blank implants. Implantation with 11-KT resulted in high plasma levels of 11-KT that were sustained for the duration of the experiment and were similar to those of maturing male trout. Increases in RVM in male and female fish treated with 11-KT and testosterone were comparable to increases seen in naturally maturing males. Furthermore, the cross-sectional area of the lateral red muscle increased in androgen-treated fish. These results suggest that heart growth of maturing males is stimulated by high plasma titres of 11-KT and testosterone just prior to and during the breeding season. However, the increase in RVM in males but not in females must be due to the interaction of high levels of 11-KT with other, unknown factors. The increase in RVM and red muscle area of the steroid-treated fish suggests that one role of androgens is to increase the swimming endurance of maturing males.
Spring diets of sympatric Greater Snow Geese and Canada Geese in southern Quebec
Authors: Giroux Jean-François , Bergeron Renée
Published: May 2008

We compared the diets of Greater Snow Geese (Anser caerulescens atlantica) and Canada Geese (Branta canadensis) during their spring staging period at Lake St. Pierre in southern Quebec. In waste cornfields, diet was established by examining the esophageal contents of birds shot while feeding, whereas in grasslands, diet was determined by microhistological analysis of plant fragments found in droppings. Corn accounted for >95% of the diet of both species when feeding in cornfields. Grasses, especially Phleum pratense, dominated the diet of both species in all grassland habitats (>86%), whereas legumes represented <5%. The relative proportions of some food items differed between the species but constituted only a small portion of the overall diet. The high degree of similarity in the diets of these two species when feeding in the same habitats suggests that there is little ecological segregation and, thus, potential for competition. Feeding by geese in cornfields has no impact on the subsequent crop yield. Although grazing can decrease harvestable biomass, this is presently unlikely in the Lake St. Pierre area because of the pattern of habitat use by geese.
Individual and geographical variation in age at maturity in female moose (Alces alces)
Authors: Sand Håkan , Cederlund Göran
Published: May 2008

Variation in age at maturity among 2764 female moose (Alces alces) in 14 populations in Sweden was investigated and related to patterns of body growth and characteristics of the environment. Data were collected from animals shot during the hunting season in 1989–1992, and all females were aged and examined for previous pregnancy by inspecting the uterus. Individual variation was large; 10 (1.3%) out of 776 yearlings were classified as previously pregnant, and must have become fertile during their first year of life. Among 2-year-old females 31.2% were mature, while the majority (80.5%) of females became mature at 3 years of age. Age at maturity, calculated as the age at which 50% of the females were mature, was also highly variable among populations and ranged between 2.06 and 3.17 years. Population-specific age at maturity was significantly related to mean yearling carcass mass among populations but not to juvenile, 2-year-old, or adult carcass mass. Approximately 50% of the variation in age at maturity among populations could be explained by the mean rate of body growth between juvenile and yearling stages. High initial rates of body growth and early maturity in a population were strongly associated with low rates of body growth after the yearling stage. No clear relationship was found between age at maturity and population density, amount of browse, latitude, or climatic conditions among populations. This suggests that multiple factors are involved in shaping the geographical pattern of age at maturity and that additional factors such as nutritional quality and age-specific survival must be considered when explaining the mechanisms behind the apparent variation in age at maturity among populations of female moose.
Long-term vegetation changes in a Snow Goose nesting habitat
Authors: Ganter Barbara , Cooke Fred , Mineau Pierre
Published: May 2008

Vegetation in a small section of nesting habitat in a Lesser Snow Goose colony was mapped in 1976 and again in 1993. During the 17-year period, ground cover changed dramatically from being dominated by salt-marsh graminoids and short grasses to being dominated by willows and areas of bare sediment. Lyme grass, Elymus arenarius, a plant strongly favoured by Snow Geese when selecting their nest sites, which covered 15% of the ground in 1976, had completely disappeared by 1993. Although the area had contained 79 Snow Goose nests in 1976, no nests remained in 1993. Degradation of the nesting habitat is caused by foraging activities of the geese themselves during the prenesting and nesting phase: salt-marsh graminoids and short grasses are removed by grubbing and the sediment is exposed; E. arenarius plants are removed by shoot pulling. Both clutch size and hatching success can be negatively affected by the decline in available food plants, and, presumably as a consequence, the area was abandoned by breeding geese. This habitat destruction and subsequent abandonment of nesting areas by breeding geese is a process similar to that documented for brood-rearing areas of Lesser Snow Geese.
Seasonal movements and foraging behaviour of northern resident killer whales (Orcinus orca) in relation to the inshore distribution of salmon (Oncorhynchusspp.) in British Columbia
Authors: Nichol Linda M. , Shackleton David M.
Published: May 2008

The hypothesis that northern resident killer whales (Orcinus orca) move in response to the seasonal availability of salmon (Oncorhynchus spp.) was tested using sightings and acoustic recordings of whales and data on the timing and abundance of salmon in Johnstone Strait, off Vancouver Island, between 1984 and 1988, and from King Island, on the central British Columbia coast, for a 2-month period in 1989. Whales were most abundant in Johnstone Strait between July and October when salmon migrate through the strait. Individual whales seen in the strait during summer were observed around King Island in spring 1989, coinciding with local sockeye and chinook salmon runs. In Johnstone Strait during summer 1988, whales foraged along the shore and in areas of strong current, where salmon occur in high densities. However, less than half of the 16 pods in the northern resident community were present on more than 15% of summer days (1984–1988). The occurrence of 6 pods (A1, A4, A5, C1, D1, and H1) in Johnstone Strait during summer was positively and significantly associated with sockeye and pink salmon abundance, whereas pod G1 was positively and significantly associated with chum salmon. Although we demonstrate an association between certain pods and certain salmon species, we cannot determine whether this reflects the true preference of pods or represents differences in the whales' arrival times in Johnstone Strait that are related to other factors. Our data suggest that within the northern resident community, pods may have seasonal ranges.
Density effects and snake predation: prey limitation and reduced growth rate of adders at high density of conspecifics
Authors: Lindell Lars Erik , Forsman Anders
Published: May 2008

To test the hypothesis that snakes limit the population growth of their prey, we measured the density of adders (Vipera berus) and field voles (Microtus agrestis) over several years on six small islands (1–12 ha) in the Baltic Sea. In both 1989 and 1990 we found a negative relationship (significant in one year) between the density of adders and voles across islands, indicating that on islands with high densities the adders exert such a high predation pressure that the voles become predator limited. In 1991 and 1993 we experimentally manipulated adder densities to rule out potential island effects. A comparison between transferred and resident snakes revealed no negative effects of being transferred to an unfamiliar environment. Furthermore, vole density decreased more on islands where we had experimentally increased adder density compared with islands with reduced densities and unmanipulated controls, but the difference was not significant. To test the hypothesis that adders at high densities of conspecifics decrease the vole population so much as to become resource limited, we calculated mean annual relative growth rate (a size-independent measure of growth rate) of adders on all islands during 1989 through 1993. In all 5 years we found a negative relationship across islands between adder density and growth rate of adders. Combining all years there was a significant negative effect of adder density, suggesting that on islands with high densities the adders suffer a reduction in growth rates that was due to intense exploitative competition.
Structure and development of larval antennae in embryos ofLytta viridanaLeConte (Coleoptera: Meloidae)
Authors: Heming B. S.
Published: May 2008

At time of hatch (252–264 h at 25 ± 0.5 °C), each antenna in Lytta viridana has three flagellomeres, three extrinsic muscles, and 25 sensilla of five different types, including a large composite sensillum of 19 sensory units on flagellomere II. Each antenna evaginates from epidermis on either side the stomodaeum beginning at 16% of embryogenesis. At 21%, a cell near its apex divides into two pioneer neurons that move into its lumen and project their axons to the brain by 29%. Sensillar stem cells begin to emerge at 23%, those of the appendix within a large embryonic placode and, from 26 to 48%, divide asymmetrically to generate the neurons and accessory cells of each sensillum. Sensillar axonogenesis begins at 34%, the first axons contact the brain at 35%, and antennal glomeruli begin to form within the deutocerebra at 57%. At 35%, the trichogen cell of each sensillum begins to grow out and larval cuticle is deposited about these, beginning at 57%. Upon withdrawal of trichogen cytoplasm from within the appendix at 81%, the dendrites of each sensory unit grow into it and begin to branch. Functional aspects are addressed and the observations compared with the limited information available on embryos of other insects.
Habitat selection and clutch fate of Piping Plovers (Charadrius melodus) breeding at Lake Diefenbaker, Saskatchewan
Authors: Espie Richard H. M. , Brigham R. Mark , James Paul C.
Published: May 2008

We studied habitat selection by Piping Plovers (Charadrius melodus) at Lake Diefenbaker, Saskatchewan, during the 1992 and 1993 breeding seasons. Habitat selection was investigated at three levels: beach, territory, and nest site. Nest beaches had significantly more gravel substrate than non-nest beaches (F[1,11] = 21.52, p < 0.01). There was no significant difference in width between nest and non-nest beaches. All Piping Plover nests were located on gravel, though this substrate only accounted for approximately 43% of nest beach area. Nest sites were significantly farther from the nearest water (F[1,181] = 12.24, p < 0.01), the main water body (F[1,181] = 6.55, p < 0.05), and had significantly more stones (F[1,161] = 10.98, p < 0.01) and rocks (Z = 2.93, p < 0.01) than random sites. Distance to the nearest water source, number of stones per square metre, and distance to the vegetation line were the three variables used by the stepwise discriminant function analysis to correctly classify 41.8% of nest sites and 87.1% of random sites. This was still significantly better than chance (Z = 3.66, p < 0.01). The low percentage of correctly classified nest sites may indicate that some plovers at this lake used nest sites on lower quality substrate. Flooded nests were significantly closer to water than successful nests and depredated nests were closer to the vegetation line than successful nests.
Growth of Dovekie (Alle alle) chicks under conditions of increased food demand at the nest: two field experiments
Authors: Gębczyński Andrzej , Taylor Jan R. E. , Konarzewski Marek
Published: May 2008

To test whether Dovekies, Alle alle (small arctic alcids laying single-egg clutches), can increase parental effort, we increased food demand in their nests in two experiments. First, we introduced a second chick to the nests. Second, we rotated a number of chicks among a smaller number of nests, producing equivalents of 2, 1.5, and 1 (control) chicks per nest. Fledging success in the nests with twins (0.63 chick per nest) was higher than in unmanipulated broods of 1 chick (0.46 chick per nest). Chicks that fledged successfully in the two experiments grew at significantly lower rates and fledged at lower body masses and later than did rotated control chicks and unmanipulated single chicks. The latter two groups did not differ one from another. Growth rates and body masses of the chicks from the 2/1 rotation group (equivalent to 2 chicks per nest) were too low to indicate any substantial increase in the rate of provisioning by adults (over the rate satisfying the maximum energy consumption of an unmanipulated single chick). We associate this with the adults' energetically expensive mode of foraging and high field metabolic rates. However, the deferred fledging of rotated and twinned chicks might have considerably increased the total food demand in their nests (from hatching to fledging) that had to be met by the parents.
Seasonal and between-year variations in the diet of harbour seals in the Moray Firth, Scotland
Authors: Tollit D. J. , Thompson P. M.
Published: May 2008

Predictions concerning the effect of seals upon prey stocks require an understanding of temporal variations in diet composition. This study examined the extent of between-year and seasonal variations in the diet of harbour seals (Phoca vitulina) from the Moray Firth, Scotland, between 1989 and 1992. Analyses of fish otoliths and cephalopod beaks collected from 1129 faecal samples were used to derive estimates of the contribution made by each of 35 prey species, based on the number and mass consumed. The key prey, by mass, were sand eels (Ammodytidae) (47%), lesser octopus (Eledone cirrhosa) (27%), whiting (Merlangius merlangus) (6%), flounder (Platichthys flesus) (5%), and cod (Gadus morhua) (4%). Between-year and seasonal fluctuations in the contributions of these species were observed. Sand eels contributed 86–20% in summer and 91–49% in winter. Lesser octopus contributed 0–62% in summer and < 5% in winter, whilst whiting and cod contributed 2–34% in winter and 1–4% in summer. In contrast to 1988, clupeids were unimportant in winter. Differences in diet composition appeared to reflect local changes in the availability of food, especially overwintering clupeids. Results indicate that dietary information obtained from short-term studies can be a poor indicator of subsequent diet composition and should be treated with caution when used to predict the effect of seals on prey populations.
Relationship of larval density and heterozygosity to growth and survival of juvenile marbled salamanders (Ambystoma opacum)
Authors: Chazal Anne C. , Krenz John D. , Scott David E.
Published: May 2008

Intraspecific competition and enzyme variability have been observed to influence the bioenergetics of many organisms. In amphibians, larval growth affects body size at metamorphosis, which in turn can lead to differences in adult survival and fecundity. We manipulated larval density in a population of the marbled salamander, Ambystoma opacum, and measured body size and enzyme variability in surviving newly metamorphosed juveniles. Crowded larval conditions resulted in lower survival and smaller body sizes at metamorphosis. Multilocus heterozygosity showed no relation to body size at high larval densities; however, at low larval densities relatively homozygous animals were larger. There was a significant interaction between heterozygosity and larval density in their effects on larval traits. Competition had a greater effect on body size at metamorphosis than did heterozygosity. Survival may be enhanced by heterozygosity but in a manner unrelated to body size.
Habitat-related variation in movements and fledging success of American black duck broods in northeastern Nova Scotia
Authors: Seymour Norman , Jackson Winston
Published: May 2008

Female American black ducks (Anas rubripes) are known to move their broods from low- to high-nutrient rearing sites. We studied the extent of brood movement and fledging success in a northeastern Nova Scotia watershed. Annually, about half the broods moved either overland or along three rivers from small, widely dispersed oligotrophic–mesotrophic wetlands to a large hypertrophic tidal marsh. Mean brood size at fledging was 3.50 in the tidal marsh but 7.05 at the dispersed freshwater wetlands. Females that remained at dispersed sites fledged more ducklings than females that moved to the marsh. Attrition occurred predominantly in the marsh or in transit. Females fledged fewer young when they raised broods at the marsh than when the same females raised broods at inland sites. Females were as successful at nutrient-poor sites as at nutrient-rich sites. The study suggests that concentrating birds in nutrient-rich sites may be counterproductive in terms of female reproductive fitness and population recruitment.
The influence of predators on adoption behaviour in adult convict cichlids (Cichlasoma nigrofasciatum)
Authors: Fraser Shannon A.
Published: May 2008

The adoption of unrelated young by brood-guarding convict cichlid (Cichlasoma nigrofasciatum) parents is influenced by several factors. Three of these are the risk of intrabrood aggression, the risk of differential predation of their own young, and the trade-off between the benefits of brood dilution and the costs of differential predation. This study introduces the "adoptable fry size hypothesis" model, which synthesizes the findings of earlier studies on each of these factors and details the range of adoptable fry sizes that increase foster brood survival across fry development. The influence of predation risk on the behaviour of parents toward foreign fry of different sizes was examined. Brood-guarding adults approached and mouthed at foreign fry larger than the upper limit of the model least often, but bit at them most often, thus excluding them. As host fry size increased, the number of behaviours directed at foreign fry decreased. Predator number did not significantly influence the size of foreign fry toward which the adults directed their behaviour. However, the overall frequency of these behaviours increased with increasing predator number, confirming previous studies suggesting that alloparental care is motivated by high predation risk.
Energy partitioning in torpor-sensitive and torpor-resistant deer mice (Peromyscus maniculatus)
Authors: Sheafor Brandon A. , Snyder Gregory K.
Published: May 2008

We examined metabolic rates in 25 deer mice, Peromyscus maniculatus nebrascensis, held at an ambient temperature of 10 °C and found that all of them had the ability to enter torpor. However, we found a gradation between the most torpor-sensitive and the most torpor-resistant animals, suggesting that the expression of torpor is more than a simple all-or-nothing phenomenon. On a daily basis, the most torpor-sensitive and torpor-resistant mice partition energy similarly when food is not restricted. On restricted food, both groups of mice decrease the amount of time spent active and increase the amount of time spent at rest and in torpor. In addition, both groups of mice decrease oxygen-consumption rates and body temperatures during rest and the most torpor-sensitive mice further decrease energy costs by entering longer and deeper bouts of torpor. However, the overall energy saving due to torpor is only about 6%. Thus, the widely held view that the adaptive advantage of daily torpor is a large energy saving may be open to question. Alternatively, daily torpor may be important for reducing the rate of energy turnover when these small rodents must rely on body fat reserves.
Size-specific resource use in juvenile little brown bats, Myotis lucifugus (Chiroptera: Vespertilionidae): Is there an ontogenetic shift?
Authors: Adams Rick A.
Published: May 2008

This paper correlates shifts in habitat use and diet with morphological transitions occurring during postpartum growth and development (ontogenetic niche) in little brown bats, Myotis lucifugus. Juveniles were captured in mist nets as they foraged in different microhabitats that were defined and quantified using "clutter indices" ranging from 0 (least cluttered) to 5 (most cluttered). I analyzed fecal samples from captured individuals to assess diet. Chi-squared analyses showed that there was a significant difference in habitat use and diet among juveniles captured in early, mid, and late July. Juveniles with smaller wings foraged in the least cluttered habitats, whereas juveniles with larger wings foraged in habitats with a high degree of clutter. Juveniles with larger wings were captured in all microhabitats, whereas those with smaller wings were captured predominantly in open microhabitats. Juveniles with relatively higher aspect ratios and lower wing loadings used a greater diversity of habitats than those with lower aspect ratios and higher wing loadings. In addition, differences in diet were significant and correlated with wing size. My results suggest resource partitioning between juveniles as a function of wing size. These data have important implications regarding how relative size among juveniles may effect intraspecific structuring of populations.
Aspects of survival in juvenile polar bears
Authors: Derocher Andrew E. , Stirling Ian
Published: May 2008

We captured, weighed, tagged, and monitored polar bear (Ursus maritimus) cubs and yearlings in western Hudson Bay to examine survival rates and correlates with survival. Cub survival between spring and autumn increased with cub mass and maternal mass, but was not related to maternal age or maternal condition. Cub survival between spring and autumn varied annually between 39.0 and 100.0% and averaged 53.2%. Whole-litter loss between spring and autumn was 30.8%, and only 38.0% of the females did not lose any cubs. Survival of spring twins was similar regardless of size, but in triplet litters, survival between spring and autumn varied according to cub size. Minimum cub survival from one autumn to the next was 34.7% and was related to cub mass, maternal mass, and maternal condition. Cub survival during autumn was estimated at 83.0%. Survival during the first year of life was no more than 44.0% but we could not estimate an annual survival rate because of the sampling regime. Possibly because harvesting was the major mortality factor for yearlings (19.4% of the yearlings were removed from the population per year), no factors examined correlated with survival of yearlings. We found no sex-related differences in survival of cubs or yearlings in any period. Relationships between survival in polar bear cubs and their condition suggest that lack of food availability, sometimes due to low maternal fat stores for lactation, leads to starvation and may be the main cause of mortality.
Helminth community structure and pattern in two allopatric populations of a nonmigratory waterfowl species (Anas fulvigula)
Authors: Fedynich Alan M. , Pence Danny B. , Gray Paul N. , Bergan James F.
Published: May 2008

Helminth communities of mottled ducks (Anas fulvigula) from Florida and Texas were species rich and diverse. The helminth component community in the mottled duck population from Texas contained more species than were found in the Florida host population. However, infracommunities of birds from Florida and Texas contained 9.5 ± 0.7 (mean ± SE) and 9.3 + 0.7 species, respectively. Similarity indices indicated less commonality of helminth species between the 2 host populations; 23 of the 42 species found across the 2 populations co-occurred. Eight helminth species from each host population were recurrent group or associate members; however, only 3 species (Amidostomum acutum, Capillaria contorta, and Tetrameres spp.) maintained group membership across both host populations. Maritrema paracadiae and Psilochasmus oxyurus were absent in birds from Florida but were recurrent group members in the host population from Texas. Only 2 recurrent group members (A. acutum and Epomidiostomum uncinatum) in birds from Florida were members of the same feeding guild and shared the same microhabitat. Three distinct feeding guilds, each containing 2 species, were found in birds from Texas. Results suggest that habitat diversity of the host plays an important part in determining species richness; however, important helminth species in both mottled duck populations are those commonly found in other Anatini from North America.
Limited morphological differences between genetically identified cryptic species within theLeptasteriasspecies complex (Echinodermata: Asteroidea)
Authors: Foltz D. W. , Breaux J. P. , Campagnaro E. L. , Herke S. W. , Himel A. E. , Hrincevich A. W. , Tamplin J. W. , Stickle W. B.
Published: May 2008

Sea stars of the Leptasterias species complex are common members of the rocky intertidal community of the temperate and subarctic North American Pacific coast. Variation in 53 morphological characters was studied in 645 Leptasterias spp. collected at 13 intertidal locations from the Aleutian Islands to Oregon. The sea stars were also examined for restriction-site polymorphisms in polymerase chain reaction amplified DNA representing the putative mitochondrial DNA (mtDNA) control region and flanking sequences; these polymorphisms have recently been shown to discriminate among Leptasterias species in the Puget Sound region and southern Alaska. Ten mtDNA haplotypes were identified (designated A–J); five of these (D, E, H, I, and J) had not been reported in earlier surveys and were found at single locations only. Canonical discriminant analysis of morphological variation could partially separate nine of the haplotypes (A–I), but there was some overlap in canonical variable scores between most pairs of haplotypes. Morphologically, the haplotypes formed three major clusters based on canonical variable scores, composed of haplotypes A/C/D, B/E/F/G/H, and I.
Limitations to collared lemming population growth in winter
Authors: Reid D. G. , Krebs C. J.
Published: May 2008

We investigated the roles of ermine predation and temperature and snowfall regimes in limiting population growth of collared lemmings (Dicrostonyx kilangmiutak) at low densities (< 3/ha) in winters between 1987 and 1992 at Pearce Point, Northwest Territories, Canada. We estimated winter population growth, for four study populations, as the instantaneous weekly rate of population change from late August to early in the subsequent June. Population growth was not significantly related to the intensity of ermine predation, based on data from two winters. Variance in rates of growth among five winters was significantly explained by a combination of (i) cold intensity in autumn, i.e., the mean daily temperature in September and October, when lemmings change from summer to winter morphology, and (ii) the insulative potential of the snow, i.e., centimetre-days of snow cover per degree-day of frost from November through March, when lemmings potentially breed. Arvicoline winter nests were strongly associated with remnant snow in spring, indicating selection for areas with deepest snow. Low autumn temperatures and shallow winter snow appear to be strong limiting factors in winter, and may prolong the period of low density of Dicrostonyx populations.
Revision of the milliped genus Xystocheir Cook (Polydesmida: Xystodesmidae)
Authors: Shelley Rowland M.
Published: May 2008

The California milliped genus Xystocheir Cook, occurring along the Pacific Coast and the western slope of the Sierra Nevada, comprises nine species, three being divided into a total of seven subspecies; the species are combined into four species-groups named for the oldest component. Xystocheir dissecta (Wood), abundant around San Francisco – San Pablo and Monterey bays, comprises intergrades, one true subspecies, and two apparent semispecies that are treated as subspecies; additionally, a local population in southern Mendocino County has achieved reproductive isolation and attained species status. Two new combinations, X. reducta (Causey) and X. modestior (Chamberlin), are proposed, along with the following new synonymies: Paimokia Chamberlin under Xystocheir, X. acuta Cook, X. francisca and X. milpitas, both by Chamberlin, and Cheirauxus sapiens Chamberlin under X. d. dissecta, new status; and Delocheir conservata and D. dalea, both by Chamberlin, under X. dissecta taibona Chamberlin, new status. The following new species-group taxa are diagnosed: the subspecies Xystocheir dissecta microrama, Xystocheir modestior haerens, and Xystocheir stolonifera uncinata, and the species X. prolixorama, X. solenofurcata, X. brachymacris, X. stenomacris, X. bistipita, and X. stolonifera.
Distribution and abundance of immature Tabanidae (Diptera) in a subarctic Labrador peatland
Authors: McElligott Paul E. K. , Lewis David J.
Published: May 2008

During the summers of 1990 and 1991, 406 larval tabanids were extracted from samples of peat collected at eight sites in a subarctic Labrador peatland. Although not all larvae could be identified to species, five deer fly (Chrysops spp.) and six horse fly species (five Hybomitra spp., one Atylotus sp.) were identified. Chrysops probably zinzalus and Chrysops nigripes were the dominant deer fly species and Hybomitra arpadi was the most commonly collected horse fly. Deer fly larvae accounted for 88% of specimens collected. Chrysops larvae were collected most frequently from sites where the water table was at or below the substrate surface, and were rarely observed at sites where the substrate was submerged. The opposite was true for horse fly larvae, which were commonest at sites where the substrate was submerged. The density of tabanid larvae in the peatland was 14.04/m2 in regions of the fen where the water table was 3–5 cm below the substrate surface, 23.20/m2 in regions where the water table was at or slightly below the substrate surface, and 2.20/m2 in regions where the substrate was submerged. Tabanid pupae and pupal exuviae were collected from moss hummocks in the peatland.
The tripartite relationship in gill-knot disease of the oyster mushroom, Pleurotus ostreatus (Jacq.: Fr.) Kummer
Authors: Tsuda Kaku , Futai Kazuyoshi , Kosaka Hajime
Published: May 2008

A disease that causes knots on the gills of the oyster mushroom, Pleurotus ostreatus, has been reported from western Japan. Nematodes inhabit and lay many eggs inside the gill knots. It is surprising that the nematodes causing this disease live in the fruiting body of this fungus, which is known to be nematophagous. In the present study, the fungus gnat Rhymosia domestica (Mycetophilidae, Diptera) was confirmed to be the vector of the nematodes inside the gill knots. This nematode has different adult stages, i.e., a mycetophagous adult female, an adult female infective to the fungus gnat, an adult male, and a mature entomophagous adult female. The occurrence of gill-knot disease was investigated in the field. Laboratory experiments determined that the fungus gnat could not itself form gill knots, because formation of knots was not observed on the gills of fruiting bodies incubated with nematode-free gnats. Observation by means of microscopy and the spore patterns of diseased fruiting bodies confirmed that the knots consist of dedifferentiated hyphal tissues, which do not form spores.
Estimating population growth of grizzly bears from the Flathead River drainage using computer simulations of reproduction and survival rates
Authors: Hovey Frederick W. , McLellan Bruce N.
Published: May 2008

Using survival and reproduction data obtained from radio-tracking 23 adult female, 24 subadult female, 49 yearling, and 44 cub grizzly bears (Ursus arctos) in the Flathead River drainage of British Columbia and Montana, we estimated the finite rate of population increase [Formula: see text] from 1979 to 1994 at 1.085 ± 0.026, with ≈95% confidence limits of 1.032–1.136. Estimated annual survival rates were 0.946 ± 0.026 for adult females, 0.931 ± 0.038 for subadult females, 0.944 ± 0.039 for yearlings, and 0.867 ± 0.050 for cubs (rates for cubs and yearlings represented both sexes). The estimated annual reproduction rate and age at first parturition were 0.422 ± 0.042 female cubs per female and 6.44 ± 0.45 years, respectively. We found that uncertainty in [Formula: see text] was mostly attributable to uncertainty in survival rates (76.7%), with subadult (47.5%) and adult (21.9%) survival contributing the largest portions. These results indicated that to reduce uncertainty in [Formula: see text], further research on grizzly bears in our study area should focus on improving estimates of adult and subadult female survivorship. Other demographic variables are not as important in estimating the grizzly bear population trend in the North Fork of the Flathead River drainage.
The developmental stages of Caligus elongatus von Nordmann, 1832 (Copepoda: Caligidae)
Authors: Piasecki W.
Published: May 2008

The morphology of all developmental stages of the fish parasite Caligus elongatus (Copepoda; Caligidae) is described. The entire life cycle consists of 8 stages: 2 nauplii, 1 copepodid, 4 chalimi, and adults. A preadult stage does not occur as it does in some other caligids. In this respect C. elongatus differs substantially from the other major sea louse species, Lepeophtheirus salmonis, which has two preadult stages.
Movements of southern elephant seals
Authors: McConnell B. J. , Fedak M. A.
Published: May 2008

Twelve southern elephant seals (Mirounga leonina) were tracked for an average of 119 days as they left their breeding or moulting beaches on the island of South Georgia between 1990 and 1994. Females travelled either eastward up to 3000 km away to the open Southern Ocean or to the continental shelf on or near the Antarctic Peninsula. Males either stayed close to South Georgia or used South Georgia as a base for shorter trips. The females all left South Georgia in a directed manner at an average rate of 79.4 km/day over at least the first 15 days. Thereafter travel was interrupted by bouts of slower travel or stationary phases. The latter were localized at sites on the continental shelf or along its edge. Three seals that were tracked over more than one season repeated their outward direction of travel and used some of the same sites in subsequent years. The magnitude of the movements makes most of the Southern Ocean potentially available to elephant seals.
Hatching factor(s) in corn seedling leachate for the eggs of Heterodera zeae
Authors: Hashmi Sarwar , Krusberg Lorin R. , Jarvis Bruce B.
Published: May 2008

Evidence is presented for the presence of a hatching factor or factors in corn seedling leachates that enhances egg hatching in Heterodera zeae. This study was undertaken to gain information on selected characteristics of the hatching factor(s). Fresh corn seedling leachates were heat- and storage-stable. The hatching factor partitioned into diethyl ether but not into hexane or chloroform.
Echeneibothrium canadensis n.sp. (Tetraphyllidea: Phyllobothriidae) in the spiral intestine of the thorny skate (Raja radiata) from the Canadian Atlantic Ocean
Authors: Keeling Christopher P. , Burt Michael D. B.
Published: May 2008

From a study of 124 skates (Raja radiata Donovan, 1808) in the Canadian Atlantic Ocean, Echeneibothrium canadensis n.sp., is described, and the nomenclatural confusion of this species with E. variabile Van Beneden, 1849 is discussed. Echeneibothrium canadensis n.sp. is most closely related to E. variabile and other members of the genus with a large, robust myzorhynchus but is differentiated by possessing 12 distinct loculi within each bothridium, a large robust myzorhynchus, 18–26 testes per proglottis, and an armed cirrus and vitellaria extending posterior to the ovary.
The efficacy of anthelmintic treatment on the parasite abundance of free-ranging snowshoe hares
Authors: Murray Dennis L. , Keith Lloyd B. , Cary John R.
Published: May 2008

We examined the efficacy of an anthelmintic agent (ivermectin, Merck–Agvet) on the parasitic nematodes of free-ranging snowshoe hares (Lepus americanus) during 27 months in southern Manitoba. Marked hares on six 25-ha sites were injected bimonthly with ivermectin (treatment, n = 134) or propylene glycol (control; n = 149) and carcasses were necropsied to determine prevalence and intensity of Obeliscoides cuniculi, Nematodirus triangularis, Trichuris leporis, Dirofilaria scapiceps, and Protostrongylus boughtoni. We supplemented the control sample with hares (n = 175) captured off the study sites and not given propylene glycol. Mean prevalence (percentage of hosts infected) and intensity (number of parasites among infected hosts) of each nematode species decreased after treatment and were 35 – 85% lower than controls after 20–40 days. Treatment significantly reduced prevalence of D. scapiceps and P. boughtoni for about 50 days and of O. cuniculi and N. triangularis for longer periods. Overall intensity of O. cuniculi, N. triangularis, and P. boughtoni was significantly lower in treated than in control hares, and intensity of D. scapiceps was marginally (P < 0.10) lower for 50 days post treatment. Total reductions in nematode abundance (prevalence × intensity) ranged from 29 to 88% among the five species. Neither prevalence nor intensity of ticks (Haemaphysalis leporispalustris) was reduced following treatment. We conclude that ivermectin is effective at controlling nematodes in snowshoe hares but that its efficacy is variable among species. We use our results as a basis for discussing the applicability of anthelmintics to the conservation and management of free-ranging wild mammals.
Spatial and temporal trends and effects of population size on the frequency of color phenotypes in the wild red fox (Vulpes vulpes)
Authors: Swanson Bradley J. , Johnson Donald R.
Published: May 2008

We analyzed the hypothesized relationships of temporal, spatial, and harvest trends with frequency of red fox (Vulpes vulpes) color morphs in 57 Hudson's Bay Company posts over a 20- to 26-year period, but found none of the strong relationships postulated to exist. A meta-analysis of each data set suggested a weak inverse relationship between latitude and frequency of the red morph. Meta-analysis further indicated a weak positive relationship with time and the frequency of the red phase, although this trend was not due to climate change. No relationship was found between harvest size and color phase, or between a 1-year lagged harvest size and color phase, which evaluated the effects of dispersal. The data sets did not allow conclusive determination of the mechanisms behind the trends, but it is postulated that a slight selective advantage is found for the dark morphs at high latitudes, while the temporal increase in frequency of the red phenotype is probably the result of northward dispersal from southern populations.
Spawning and early life history of a northern population of striped bass (Morone saxatilis) in the Miramichi River estuary, Gulf of St. Lawrence
Authors: Robichaud-LeBlanc Kimberly A. , Courtenay Simon C. , Locke Andrea
Published: May 2008

Ichthyoplankton surveys between 14 May and 15 July 1992 in the tidal fresh waters of the Northwest Miramichi River, New Brunswick, provide the first description of spawning by striped bass, Morone saxatilis, in any Gulf of St. Lawrence river. Surveys showed that striped bass spawned between late May and mid-June. Most eggs were produced in a single brief peak of abundance between 31 May and 2 June at daily average surface water temperatures of 15.6–16.6 °C. Spawning occurred largely within the first 12 km of tidal fresh water above the edge of the salt wedge. Peak spawning was centred along a 2-km stretch of river directly upriver of the salt wedge. Peak densities of larval stages were found near or upstream of the area of peak egg density. Larval densities were highest near the salt wedge.
Cover is safe during the day but dangerous at night: the use of vegetation by European wild rabbits
Authors: Moreno Sacramento , Delibes Miguel , Villafuerte Rafael
Published: May 2008

The use of protective cover by prey animals is commonly associated with high predation risk. Rabbits (Oryctolagus cuniculus) in southern Spain use vegetated patches in daylight but open prairie during the night, although predation rates are high during both periods. Hiding under vegetation may be adaptive for rabbits during the day because they suffer predation by visually oriented birds of prey, but may be dangerous during the night, when they are hunted by carnivorous mammals that need cover to stalk. Therefore, the heavily predated Spanish rabbits may leave dense cover in nighttime and exploit the rich prairie food.