bluuebunny/crossref_metadata_2025 huggingface dataset:
Diel locomotory activity of deer mice (Peromyscus maniculatus) infected withTrichinella nativaorTrichinella pseudospiralis
Authors: Poirier Sylvain R. , Rau Manfred E. , Wang Xiaohui
Published: July 2008

The effects of infection by two species of sylvatic Trichinella on the diel locomotory activity of a wild rodent host, the deer mouse Peromyscus maniculatus, in a familiar environment were investigated in the laboratory using computer-linked activity chambers equipped with an infrared photocell. Locomotory activity data were collected on each mouse prior to and after sham inoculation or inoculation with graded doses of muscle-encapsulating Trichinella nativa or nonencapsulating Trichinella pseudospiralis larvae. Trichinella nativa infections induced activity deficits in deer mice that were proportional to the number of infective larvae recovered, whereas derived indices of locomotory activity of mice infected with T. pseudospiralis remained essentially within the range of those of sham-inoculated control mice. Quantitative differences between T. nativa and T. pseudospiralis in their potential to modulate the host's immune response may account for the observed difference in their effect on locomotory activity of the deer mouse host. Such variation in trichina-induced changes in diel locomotory activity may serve to channel transmission of the parasites to suitable hosts.
Changes in shape associated with growth in the loliginid squidPhotololigosp.: a morphometric approach
Authors: Moltschaniwskyj N. A.
Published: July 2008

This study examined growth of squid by describing changes in shape and relative size of body structures in juvenile and adult Photololigo sp. Animals change shape during growth because body structures increase in size at different relative rates. These changes are of particular interest because they are generally concomitant with changes in ecology. Length and mass measurements were taken from Photololigo sp. ranging in size from 2.77 to 117.03 mm dorsal mantle length. Small squid (< 50 mm dorsal mantle length) had round bodies with large head and eyes and poorly developed tentacles and arms. Larger squid (> 50 mm dorsal mantle length) were more elongate and narrow, and the head and eyes were proportionally smaller. As squid reached a dorsal mantle length of 50 mm, the changes in shape with growth become slower and individuals reached a final shape. Small individuals allocated energy predominantly in the arms and tentacles during early stages of growth, while the viscera and head grew at a much slower rate. Once individuals began producing gametic tissue and gonad growth occurred, the mantle muscle grew more slowly than the gonad. Changes in shape could be related to changes in locomotion and feeding that occur during ontogeny.
Sex, age, and seasonal variation in the foraging dynamics of muskoxen, Ovibos moschatus, in Greenland
Authors: Forchhammer Mads C.
Published: July 2008

The relationship between resources (forage availability and quality) and the foraging dynamics of muskoxen, Ovibos moschatus, was studied in Angujaartorfiup Nunaa, western Greenland, during spring (calving, post calving), summer, autumn (rut), and midwinter. Muskoxen did select among vegetation types in all seasons but calving. During the postcalving period, summer, and rut, the vegetation types meadow, moist dwarf shrub heath, and grassland were preferred, whereas meadow, moist dwarf shrub heath, and steppe were selected during midwinter. The relative availability of graminoids in vegetation types did not correlate with selection of vegetation types. Seasonal patterns of daily feeding time were negatively correlated with forage quality, whereas no correlation with forage availability was found. Seasonal rumination times were negatively correlated with both availability and quality of forage. The length of rumination time is apparently not solely explained by variations in forage quality. Results presented here indicate that rumination time is also a behavioural strategy of muskoxen. Movement rates did not correlate with forage availability. During midwinter, muskoxen did not respond to low forage quality by increasing daily feeding time as was seen during calving. Instead, an energy-conserving strategy was observed, where a relatively larger proportion of time was allocated to resting, i.e., nonruminating. Bachelor herds and mixed herds differed in daily feeding time and habitat use during the prerutting and rutting season. Prior to the rutting season, muskox bulls increased energy intake to compensate for the subsequent allocation of time to reproductive activities. During the short arctic growing season, muskoxen in western Greenland decreased daily feeding time, whereas those in eastern Greenland increased feeding time. This difference in foraging dynamics is hypothesised to be a result of differences in biotic and abiotic constraints imposed on muskoxen in these two regions.
The acoustic repertoire of hooded seals (Cystophora cristata)
Authors: Ballard Karen Ann , Kovacs Kit M.
Published: July 2008

Airborne and waterborne acoustic sounds of hooded seals (Cystophora cristata) were recorded during the breeding seasons of 1988 and 1989 in the Gulf of St. Lawrence, Canada. During 36 h of in-air focal-animal sampling and 9 h of ad libitum underwater sampling, 410 sounds, in total, were recorded and analyzed. In the field, the context of signals was noted whenever possible. This included the behaviour of the signaller and that of its nearest neighbour. Frequency and temporal variables, measured directly from sonograms, were analyzed using a combination of principal components analysis and cluster analysis. Three major classes of sounds containing 5 call types were suggested by the cluster analysis. Variation occurs in the structure of calls both within and between call classes. Sounds that were created using the hood and septum both under water and in air, as well as a variety of underwater clicks and knocks, were distinct from voiced, airborne calls. Not surprisingly, most acoustic signals were used in agonistic (79%) or sexual (12%) situations during the reproductive period.
Helminths of an endangered population of belugas,Delphinapterus leucas, in the St. Lawrence estuary, Canada
Authors: Measures L. N. , Béland P. , Martineau D. , Guise S. De
Published: July 2008

Helminths were identified in 38 belugas, Delphinapterus leucas, stranded in the St. Lawrence estuary and Gulf of St. Lawrence during 1984–1993. These helminth species were Anisakis simplex, Contracaecinea sp., Pseudoterranova sp., Stenurus arctomarinus, Pharurus pallasii, Halocercus taurica (new host record), Halocercus monoceris (new host record), Hadwenius seymouri, Diphyllobothrium sp., and Bolbosoma sp. (new host record). Of 21 helminths previously reported from populations of belugas worldwide, 7 were found in the St. Lawrence population. Lungworms, such as Halocercus monoceris, may prove useful in identification of beluga populations in the Arctic and may also be an important cause of morbidity and mortality of calves.
Temporal division of labor in the honey bee, Apis mellifera A developmental process or the result of environmental influences?
Authors: Calderone Nicholas W.
Published: July 2008

The association between the age of a worker honey bee (Apis melliferd) and her behavior is generally believed to be the result of an innate developmental process. An alternative model, called foraging for work, explains this association as being due to old and young workers being in functionally different parts of the nest as a result of their having been in the nest for different lengths of time. Previous studies also raise questions about the developmental-process model because they relied on sequential observations of workers from one age group, thereby confounding age and environmental effects, which also affect behavior. Environmental effects were controlled by making concurrent observations of workers from four age groups introduced to a colony at 6-day intervals. These groups behaved differently from one another, even though they were present in the same environment, thereby demonstrating age effects independent of environmental effects. The foraging-for-work model was evaluated by comparing workers from three age groups introduced to the colony on the same day. These groups also behaved differently, showing that the association between age and behavior is not simply an epiphenomenon resulting from old and young workers having been in the nest for different lengths of time.
Differences in bird species richness and abundance among three successional stages of aspen-dominated boreal forests
Authors: Schieck Jim , Nietfeid Marie , Stelfox J. Brad
Published: July 2008

Birds and vegetation were surveyed in young, mature, and old aspen-dominated boreal forests in Alberta. Height and size of live trees, density of large dead trees, and volume of downed woody material increased during succession, whereas density of live trees decreased. Canopy heterogeneity had a bimodal relationship with succession: old forests had the highest, mature forests the lowest, and young forests an intermediate canopy heterogeneity. Old forests had greater bird species richness than young forests, which in turn had greater richness than mature forests. Twenty-seven, 3, and 10 bird species had their highest abundances in old, mature, and young forests, respectively. Seven bird species that nest and forage in canopy gaps and three bird species that nest and forage in large trees and snags were more abundant in young and old forests than in mature forests. Contrary to our predictions, patterns of richness and abundance for bird species that nest and forage in the canopy or in tree cavities were similar to those for bird species that nest or forage in the lower strata. Bird species preferring coniferous forests tended to be more abundant in old than in young or mature aspen-dominated forests, possibly because old aspen forests had more conifers than younger aspen forests.
Relative abundance, richness, and diversity of small mammals at induced forest edges
Authors: Sekgororoane G. B. , Dilworth T. G.
Published: July 2008

To determine whether small mammals show "edge effect" at induced forest edges created by harvest cutting, small mammals were snap-trapped from 1990 to 1992 at 5 sites harvested 0–10 years previously in the University of New Brunswick Forest, Fredericton. Nine species were captured in 8686 trap-nights. There was edge effect in older (6–10 years) but not in recent (0–5 years) cuts. This was shown by both high relative abundance for all species combined and species diversity in the ecotone (from 10 m into the harvest cut to 10 m into the forest). Species richness did not show any edge-related pattern. Edge effect with respect to relative abundance was largely due to Peromyscus maniculatus and Clethrionomys gapperi. Peromyscus maniculatus reached the highest relative abundance 10 m in the forest and was not captured beyond 10 m in the harvest cut. Clethrionomys gapperi made use of the forest side of the ecotone and was not captured beyond 5 m in the harvest cut. Napaeozapus insignis, Zapus hudsonius, and Soricidae (Blarina brevicauda, Sorex cinereus, and S. fumeus) showed no attraction to, or avoidance of, the edge.
Development of macroinvertebrate community structure associated with zebra mussel (Dreissena polymorpha) colonization of artificial substrates
Authors: Wisenden Patricia A. , Bailey Robert C.
Published: July 2008

We used artificial substrates (rocks < 1500 cm2 surface area) in shallow water (2 m) to assess the development of epilithic macroinvertebrate communities in the presence of zebra mussels. At a turbulent site (Wheatley, Lake Erie), previously colonized (with a non-zebra mussel community) and uncolonized rocks left for 1 year both had lower densities of total invertebrates than previously colonized rocks recovered after only 1 day. As zebra mussels colonized the rocks, Gammarus sp. (amphipods) increased in density, while Chironomini and Tanypodinae (midges), Polycentropus sp. (caddisflies), and Physella sp. and Pleurocera sp. (snails) declined. At a protected site (Stoney Point, Lake St. Clair), previously colonized rocks initially (2 months) had higher densities of many taxa, including zebra mussels, than uncolonized rocks. This difference disappeared after 1 year, as zebra mussels increased on all rocks. Gammarus sp. maintained its numbers, while Tricladida (flatworms) increased and Oecetis sp. (caddisflies), Physella sp., Pleurocera sp., and Tanypodinae declined. Although a similar "zebra mussel – amphipod" community developed on rocks at both sites, we hypothesize that at the turbulent site, zebra mussels and amphipods have a shared tolerance of unstable habitats, and zebra mussels facilitate amphipod colonization of rocks by increasing microhabitat stability and food supply. At the protected site, zebra mussels outcompete other surface dwellers like snails for space, and facilitate the colonization of scavenger–omnivores like amphipods and flatworms.
Spring and summer prey of the Juan Fernández fur seal,Arctocephalus philippii
Authors: Acuña Hugo Ochoa , Francis John M.
Published: July 2008

The composition of Juan Fernández fur seal (Arctocephalus philippii) prey was assessed through analysis of 437 scats collected during five reproductive seasons (1987–1991). In total, 14 collections were analyzed and, based on 4172 fish otoliths and cephalopod beaks, 13 prey species were identified. The occurrences of fish families were as follows: Myctophidae (80.3%), Scomberesocidae (10%), Carangidae (9.5%), Engraulidae (1.0%), and Bathylagidae (0.7%). Cephalopod families included Onychoteuthidae (27.1%), Ommastrephidae (3.7%), and Tremoctopodidae (0.7%). In one year when data were available, Symbolophorus sp. B was found more frequently in subadult male and juvenile scats than in female scats (P < 0.004). Female scats contained larger numbers of the squid Onychoteuthis banksi than did subadult male and juvenile scats (P < 0.0001). When collections made in early December were compared, the occurrence of O. banksi in subadult male and juvenile scats differed significantly between years (P < 0.0001). Within-year variations in occurrence were significant only for O. banksi in 1989. The data suggest that the narrow range of species preyed upon by Juan Fernández fur seals is unlikely to represent specialization, but is probably related to overall prey availability in the pelagic environment. Although information on marine communities in this area is limited, it is possible to relate observed prey shifts to variations in sea-surface temperature.
Fine-scale vertical profiles of meiofauna in muddy subtidal sediments
Authors: Fleeger J. W. , Shirley T. C. , McCall J. N.
Published: July 2008

The fine-scale vertical profile (2-mm intervals to 2 cm) of meiofauna was surveyed at three water depths (20, 50, and 80 m) on the Louisiana continental shelf and at two depths (25 and 55 m) in a subarctic Alaskan bay. Meiofaunal densities at these sites measured through 4 cm were similar to those of other subtidal muddy-sediment sites, nematodes averaging about 1000 and 1500 and harpacticoid copepods averaging 125 and 30 per 10 cm2 in Louisiana and Alaska, respectively. Overall, harpacticoids were numerous at the sediment–water interface and exceptionally shallow in depth profile; densities decreased with increasing depth, with few individuals below 6 mm. Across all sites and water depths, weighted mean depths of harpacticoids averaged 5.4 mm. Nematodes were distributed to much greater depths, and generally increased in density with depth, with highest densities below 6 mm. In the Gulf of Mexico, nematode density peaked in the second centimetre. Across all sites and depths, nematode weighted mean depth averaged 10.5 mm within the upper 2 cm. Harpacticoids were the most abundant meiofaunal taxon in the upper 4 mm in the Gulf of Mexico at the 50- and 80-m sites. Overall, harpacticoids were disproportionately abundant at the sediment–water interface to a depth of 6 mm, and play a more significant role in events that take place at the surface than their down-core abundance would indicate. For example, harpacticoids are potentially more influenced by bottom-feeding fish and erosional events than are nematodes, and may exert an influence over the initial burial of sedimented phytodetritus.
Sex-biased parental-care allocation in three tern species (Laridae, Aves)
Authors: Fasola Mauro , Saino Nicola
Published: July 2008

We studied parental-care allocation by males and females in three tern species. Female Common Terns (Sterna hirundo) and Little Terns (S. albifrons) performed more incubation and brooding than males, whereas in the Sandwich Tern (S. sandvicensis) the sexes shared these duties equally. In all three species, agonistic behaviors were performed equally by females and males. Prey types brought by males and females of each species were similar, but males tended to bring larger prey and had higher delivery rates than females. Information on parental-care allocation by female and male seabirds of various species, 5 gulls, 6 terns, and 1 skimmer, indicates that females perform most of the incubation and brooding in both gulls and terns, whereas males perform most territory attendance and agonistic behavior (gulls) and more prey provisioning (terns). These patterns are qualitatively consistent with the explanation that the differences between gulls and terns in sex-biased parental care are related to the fact that gulls exhibit sexual size dimorphism but terns do not. Contrary to theoretical predictions that in monogamous birds, females contribute more reproductive effort than males, in all the seabird species studied so far the total parental expenditure by males seems to equal or outweigh that by females.
Reactions of reproductively photoresponsive versus unresponsive meadow voles to simulated winter conditions
Authors: Bronson F. H. , Kerbeshian M. C.
Published: July 2008

At least some populations of meadow voles (Microtus pennsylvanicus) comprise individuals that vary greatly in the degree to which their reproduction can be controlled by day length. Some individuals respond to the short days of winter with complete gonadal inhibition, others are insensitive to this cue and thus have the capacity to reproduce opportunistically during the winter, and still others are intermediate in their responsiveness. The relative costs and benefits associated with some of the nonreproductive dimensions of these different strategies are explored. The two extreme phenotypes, reproductively photoresponsive and unresponsive individuals, were exposed in the laboratory to winter versus summer conditions, as defined by photoperiod, temperature, and quality of diet. This was done in cages that required the voles to leave their nests and subject themselves to ambient conditions in order to feed. The winter condition exerted a potent influence on body mass, body fat, food intake, nest building, pelage depth, and the amount and temporal pattern of feeding, as well as reproductive potential. The results suggest that the major nonreproductive advantage enjoyed by the photoregulated phenotype is a decrease in body mass and hence a decrease in required foraging time that anticipates harsh winter conditions. The opportunists also may lose mass in response to harsh conditions, but this is a direct and immediate response for which they may be poorly prepared.
Respiratory and acid–base consequences of zebra mussel infestation on the valves of unionids
Authors: Byrne Roger A. , Burleson Mark L. , Smatresk Neal J. , McMahon Robert F.
Published: July 2008

Infestations of the zebra mussel (Dreissena polymorpha) on the valves of unionids purport to cause the eventual death of the host, although the means is uncertain. We examined the blood acid–base and respiratory gas state in a sample of the unionid bivalve Elliptio complanata, both with zebra mussels attached to the valves and with zebra mussels removed. Both sets of clams were exposed for 24 h to the following three environmental gas treatments: normoxia–normocapnia ([Formula: see text] 153 torr, [Formula: see text] 0.3 torr), moderate hypoxia–hypocapnia ([Formula: see text] 35 torr, [Formula: see text] 0 torr), and severe hypoxia–hypercapnia ([Formula: see text] 8 torr, [Formula: see text] 2.5 torr). Blood pH, [Formula: see text], [Formula: see text], total CO2, and osmolality were determined. Although the effects of gas treatment were profound, zebra mussel infestation had no effects on any of the variables measured. Zebra mussel infestation increased with size of the unionid host, but we detected no relationship between the degree of infestation and any blood variable. This suggests that competition for oxygen in the medium or reduction in ventilatory capability due to mechanical interference and consequent disruption in gas exchange by infesting zebra mussels does not apply at this level of infestation (mean 36.4 and maximum 80 zebra mussels per unionid host). The possibility of zebra mussels outcompeting unionids for suspended food particles and a resultant decline in unionid tissue energy stores are more likely consequences of infestation.
The effect of different nutrient formulations in artificial diets on gonad growth in the sea urchin Strongylocentrotus droebachiensis
Authors: Jong-Westman M. de , March B. E. , Carefoot T. H.
Published: July 2008

Several artificial diets were tested for their ability to promote growth of gonads in the green sea urchin, Strongylocentrotus droebachiensis, over a 9-month period. Survival and test growth were also monitored, as were gonad lipid levels and water content (at the middle and end of the reproductive cycle only). The artificial diets differed in amount of protein and in the presence of various additives such as mannitol, algin, cholesterol, and β-carotene; a diet of air-dried kelp (Nereocystis luetkeana) was included for comparison. Survival was > 95% for all diets save a low-protein one (82% survival). Test diameters showed no significant change over time or among dietary treatments. All high-protein formulations produced significantly higher gonad indices than low-protein ones. Addition of β-carotene to the high-protein formulation significantly increased gonad growth relative to all other diets; this was especially noticeable in December, at the time of best market quality for the roe. Lipid levels were not significantly different among dietary treatments in either November or March, but did show a slight statistically significant rise between these months (21.4–22.7% dry mass). Water content also showed no significant difference among treatments, but was significantly higher in March (82% live weight), just prior to spawning, than in November (70%). Gonad indices for all artificial-diet formulations were higher than any previously recorded for S. droebachiensis.
Parental-care strategies among muskrats in a female-biased population
Authors: Marinelli Lui , Messier François
Published: July 2008

In mammals, parental care is primarily maternal, male participation being influenced by access to mates. We studied parental behaviours of muskrats (Ondatra zibethicus) in a female-biased free-ranging population over two breeding seasons, with the objective of assessing the plasticity of parental care under differing mating strategies (monogamy versus polygyny). Weaned juveniles received predominantly paternal rather than maternal care, and the care provided was both direct (i.e., food harvesting) and indirect (i.e., burrow maintenance). Parental care appeared to be affected by the multiple mating opportunities available to some males. Polygynous males provided less parental care, presumably because they devoted extra time to pursuing a multiple-mating strategy. However, polygynous males provided care only to the offspring of their first mate (i.e., a mixed reproductive strategy). Females that were secondary mates of polygynous males appeared to compensate for the lack of male assistance by increasing their level of parental care compared with primary females. These results support the view that monogamy constitutes the fundamental social system in muskrats.
Assessment of habitat quality in the Mediterranean pine vole (Microtus duodecimcostatus) by the study of survival rates
Authors: Paradis Emmanuel , Croset Henri
Published: July 2008

Habitat quality should be usefully defined in a demographic perspective. Survival and fecundity rates are sufficient to allow population persistence in a high-quality habitat but not in a low-quality habitat. The Mediterranean pine vole (Microtus duodecimcostatus) occurs in apple orchards in southern France, but its populations in this habitat are often driven to extinction by chemical control. However, recolonization occurs promptly when control ceases. We tested the hypothesis that meadows surrounding the orchards are high-quality habitats (sources) for the Mediterranean pine vole. We livetrapped four populations, three in apple orchards and one in a meadow. Survival rates were estimated using probabilistic open-population models. Our analysis led us to conclude that meadows are low-quality habitats, particularly since no juveniles survived in this habitat during the main part of the study. Recolonization of chemically controlled patches is probably allowed by asynchronous control among orchards. We further discuss the usefulness of probabilistic open-population models for the investigation of variations in survival rates both within and between populations.
The diet of southern elephant seals (Mirounga leonina) from Heard Island
Authors: Slip David J.
Published: July 2008

Stomach contents were lavaged from 76 southern elephant seals (Mirounga leonina) at Heard Island between July 1992 and March 1993. Eighty-six percent of stomachs contained cephalopods of 17 species. Numerically the most important was Psychroteuthis glacialis (21.1%), and from estimated biomass the most important was Kondakovia longimana (40.4%). Three other species were also common prey: Moroteuthis knipovitchi (19.4% by estimated biomass), Moroteuthis ingens (13.0%), and Alluroteuthis antarcticus (10.2%). Sixty-six percent of stomachs contained fish remains, and four species, Dissostichus eleginoides, Electrona carlsbergi, E. antarctica, and Gymnoscopelus nicholsi, were identified from otoliths. The diet of adults differed from that of juveniles, particularly pups in their first year. Martialia hyadesi was the most important prey of juveniles and represented 57.1% of estimated biomass consumed. Furthermore, smaller seals ate smaller squid. The species and size of cephalopods eaten by southern elephant seals are similar to those of other Southern Ocean predators, particularly some beaked whales.
Effects of time–depth recorders on maternal foraging and attendance behavior of Antarctic fur seals (Arctocephalus gazella)
Authors: Walker Brian G. , Boveng Peter L.
Published: July 2008

We evaluated the difference in average durations of foraging trips and nursing visits to shore between one group of female Antarctic fur seals (Arctocephalus gazella) carrying radio transmitters only and another group carrying time–depth recorders (TDRs) and radio transmitters during their first five postpartum foraging trip – nursing visit cycles. Data were collected from 105 different fur seals in five breeding seasons (1989 – 1990 to 1993 – 1994) on Seal Island, Antarctica. Average foraging-trip and nursing-visit durations were significantly greater for the seals carrying TDRs and radio transmitters than for seals carrying radio transmitters only (two-way ANOVA, year × instrument type; trip, P = 0.004; visit, P = 0.04). Historically, instrument-effect studies on marine animals have focused on smaller species and larger instrument to body size ratios. Because of small sample sizes (the number of instruments successfully deployed and retrieved) and the typically variable nature of data from TDRs, the statistical power to detect significant differences due to instrument effects has been low. The evidence of instrument effects on Antarctic fur seals has possible implications for studies utilizing devices attached to similar-sized animals: results may not be representative of the natural (non-instrumented) population.
The first description of kinorhynchs from the Spitsbergen Archipelago (Greenland Sea), with a key to the genus Pycnophyes (Homalorhagida, Kinorhyncha)
Authors: Adrianov Andrej V.
Published: July 2008

Two new species of Kinorhyncha, Pycnophyes spitsbergensis and P. mokievskii, are described and illustrated from muddy sediments of the Greenland Sea, from the Isfjord of the West Spitsbergen Island (78°N) at a depth of 6 m. These are the first kinorhynchs described from Spitsbergen, and are the northernmost kinorhynchs found within the Arctic Circle to date. Pycnophyes spitsbergensis and P. mokievskii are the fifth and sixth members of this genus described from Arctic waters. The unique structure of the ventral posteriomesial pachycycli of the 12th segment, rectangular anteromesial ventral pachycycli of the 9th to 12th segments, and ventrolateral cuticular scars on the sternites clearly separate P. spitsbergensis from known congeners. The sympatric species, P. mokievskii, is easily separated on the basis of two closed midventral protrusions with sensory papillae at the posterior end of the body. Pycnophyes greenlandicus Higgins and Kristensen, 1988 from Greenland and P. maximus Reimer, 1963 from northern Europe are similar in size and general morphometric characters to the species described.
Winter peatland habitat selection by woodland caribou in northeastern Alberta
Authors: Bradshaw Corey J. A. , Boutin Stan , Hebert Daryll M. , Rippin A. Blair
Published: July 2008

Woodland caribou in northeastern Alberta are relatively sedentary, occur at low densities, and are classed as endangered in Alberta. Increasing encroachment of the forest and petroleum industries into the southern regions of the boreal woodland caribou range has highlighted the need for detailed habitat analysis for this species. We obtained approximately 1000 locations of 47 woodland caribou fitted with very high frequency telemetry collars, providing data on winter habitat use from 1991 to 1994. Telemetry data were combined with digital peatland coverages that best represented lowland habitat diversity. Woodland caribou selected forested fen peatland complexes at both the population and individual spatial scales. Woodland caribou concentrated feeding activity in forested, raised bog islands. The raised bogs provide more xeric substrate for increased lichen biomass, possibly a key factor in their selection during winter. The hypothesized connection between discontinuous permafrost and the maintenance of raised bog islands in terms of caribou forage distribution and availability is discussed.
Distribution and habitat partitioning by small odontocetes in the Gully, a submarine canyon on the Scotian Shelf
Authors: Gowans Shannon , Whitehead Hal
Published: July 2008

In this paper we examine the summer distribution of three species of small odontocetes in the highly productive waters in and near the Gully, a submarine canyon on the edge of the Scotian Shelf. Atlantic white-sided dolphins (Lagenorhynchus acutus) and common dolphins (Delphinus delphis) were not randomly distributed with respect to depth, sea-floor relief, month of sighting, or sea-surface temperature. Long-finned pilot whales (Globicephala melas) were not randomly distributed with respect to month or sea-surface temperature. These species used the Gully slightly differently, although there was overlap. White-sided dolphins were seen only in the core of the canyon, but were sighted at all temperatures, depths, and sea-floor reliefs and throughout the summer field season. Common dolphins had a modest range throughout the deeper waters and were not seen in the summer before July, when the water warms. Pilot whales ranged widely over the study area, preferring areas with fairly flat relief and were more common later in the summer, when the waters were warmer. It appears that white-sided and common dolphins partition the Gully temporally but not geographically.
Effects of long-term continuous GnRH administration on the pituitary–gonadal axis in Eld's deer stags (Cervus eldi thamin)
Authors: Monfort S. L. , Brown J. L. , Wood T. C. , Bush M. , Williamson L. R. , Wildt D. E.
Published: July 2008

Eld's deer stags (Cervus eldi thamin) (in groups of three) were continuously administered gonadotropin-releasing hormone (GnRH) in control, low, medium, or high doses (0, 20.1 ± 0.7, 83.3 ± 2.6, and 292.9 ± 4.9 ng∙kg−1∙d−1, respectively) via osmotic minipumps for ~80 d to investigate the potential for precociously reactivating the pituitary–testicular axis during the nonbreeding season. Secretory patterns of LH, FSH, and testosterone concentrations were qualitatively similar among treatments. However, in the low-dose group, basal LH and FSH concentrations were both increased (p < 0.05) and pituitary responsiveness to a superimposed GnRH challenge was augmented (p < 0.05) after 12 weeks of treatment compared with all other groups. Despite these endocrine changes, continuous low-dose GnRH administration was not effective for precociously inducing testicular activity in this seasonally breeding species. High-dose GnRH administration initially induced a transient increase in LH, FSH, and testosterone secretion and delayed, but did not prevent, the seasonal decline in spermatogenesis. After 6–12 weeks of high-dose GnRH administration, however, attenuated pituitary responsiveness appeared to delay the normal seasonal reactivation of the pituitary–gonadal axis. In conclusion, prolonged, continuous low-dose GnRH administration did not effectively translate into a precocious onset of testicular activity; therefore, this specific approach is unlikely to be useful for prolonging the fertile period in this seasonally breeding species.
Influence of Microphallus hoffmanni (Trematoda, Microphallidae) on the survival, sexual selection, and fecundity of Gammarus aequicauda (Amphipoda)
Authors: Thomas F. , Lambert A. , Meeüs T. De , Renaud F. , Cézilly F.
Published: July 2008

We investigated the influence of Microphallus hoffmanni (Trematoda) on the survival, mating success, and fecundity of its intermediate host, Gammarus aequicauda (Amphipoda). Despite the great size of M. hoffmanni metacercariae, the mean parasite abundance and the ratio of the variance to the mean abundance increased with host size, suggesting that accumulation of this parasite had no significant effect on the survival of its host. Size-assortative pairing was significant and we found no evidence of a parasite-mediated reduction in male competitiveness. Fecundity was reduced in infected females. Our results are in contrast to those obtained with helminths that alter the intermediate host's behaviour to favour their transmission to the definitive host.
Scanning electron microscopy of the digestive tract of larval Simulium ornatum Meigen (Complex) (Diptera: Simuliidae) and its associated microbial flora
Authors: Taylor Mark R. , Moss Stephen T. , Ladle Mike
Published: July 2008

The structure and microbial flora of the digestive tract of larval Simulium ornatum were investigated using scanning electron microscopy. Direct observations of the microbial communities associated with the endoperitrophic surface of the peritrophic membrane and the endocuticular surface of the hindgut are presented. The endoperitrophic surface was frequently devoid of bacteria, although the fungus Harpella melusinae (Harpellales, Trichomycetes) was commonly attached. Rarely, spirochaetes and coccoid bacteria were attached to the endoperitrophic surface. In contrast, the endocuticular surface was regularly colonized by a diverse microflora composed of rod-shaped, coccoid, spiral, and filamentous bacteria and two species of Harpellales (Trichomycetes). A freeze-fracture technique is compared with a dissection technique for exposing the endoperitrophic and endocuticular surfaces of the digestive tract.
La formation des spicules de Didemnidae (Ascidiacea)
Authors: Ballan-Dufrançais C. , Truchet M. , Jeantet A. Y.
Published: July 2008

The spicules of didemnids ascidians are concretions made of calcium carbonate in the form of aragonite. Their origin and composition have been analyzed by electron microscopy, electron probe microanalysis, and secondary ion mass spectroscopy. Our results, both morphologic and microanalytic, confirm clearly the intracellular origin of the spicules. In the cells of the lateral thoracic organs (LTO), which are differentiations of the epidermal mantle, Golgi secretory vesicles are formed and calcium and strontium are trapped on the organic matrix that is rich in sulfur. A crystalline precipitation occurs in the cell before or during its migration into the cavity of the LTO. Then, the new spicules, always surrounded by an organic envelope, are liberated in the LTO cavity and migrate into the tunic; the cells also migrate in the tunic. The spicules continue to grow extracellularly in the tunic. They have the same morphology and chemical composition as the young spicules, which demonstrates a control of the ionic balance by the cells, both intra- and even extra-cellularly where the mechanism of spicule growth remains to be determined.
Temporal variation in reproduction and body mass of polar bears in western Hudson Bay
Authors: Derocher Andrew E. , Stirling Ian
Published: July 2008

We studied annual and long-term variation in rates of reproduction in female polar bears (Ursus maritimus) in western Hudson Bay from 1966 to 1992. In addition, long-term trends in body mass were examined from 3146 captured polar bears. Reproduction rates declined in the late 1980s from higher levels in 1966–1984. Litter production decreased from 0.48 to 0.34 litters per female each year over the study. Recruitment to autumn declined from 0.75 to 0.52 cubs per female each year, in part because of cub mortality between spring and autumn, which increased from 25.0% in 1980–1984 to 50.9% in 1987–1992. Spring and autumn litter sizes of females with cubs did not vary annually, but litter sizes of females with yearlings varied between years. The proportion of yearlings independent of their mother in autumn dropped from 81% prior to 1980 to 34% in 1980–1992. After 1986, offspring remained with their mothers longer, resulting in the birth interval increasing from 2.1 to 2.9 years. Body mass of most age-classes of females and males declined in the 1980s. Unlike earlier studies that found reproduction rates to be higher in western Hudson Bay than in higher latitude populations, reproduction rates in 1986–1992 in western Hudson Bay were similar to those of other populations. Insufficient information was available to determine the cause of declines in reproduction and body mass.
The influence of larval size, temperature, and components of the functional response to prey density on growth rates of the dragonflies Lestes disjunctus and Coenagrion resolutum (Insecta: Odonata)
Authors: Krishnaraj Rangathilakam , Pritchard Gordon
Published: July 2008

Larval growth of Lestes disjunctus was completed in 70 d in the field, whereas in Coenagrion resolutum it took 10–22 months. This was not simply the result of occupying warmer microhabitats, because L. disjunctus larvae grew faster than C. resolutum at all constant temperatures between 10 and 25 °C in the laboratory. Multiple regression analysis showed that growth rates of both species were positively related to temperature and negatively related to larval size and to the square of temperature. The latter term is necessary to describe the decrease in growth rate at high temperatures. The equation predicted that the growth rate of L. disjunctus reached a maximum at 28.8 °C, whereas that of C. resolutum decreased above 22.4 °C. Small and medium-sized larvae of L. disjunctus ate more prey (Daphnia magna) in 15 min than C. resolutum at all prey densities. In 15-min experiments the attack coefficient for small L. disjunctus larvae was significantly larger than for small C. resolutum larvae and handling time for medium larvae was shorter. Other comparisons had large associated sampling errors, but the trends were the same. These differences may be associated with the relatively longer labia of L. disjunctus and its ability to change hunting methods from ambush to active search.
The impact of entanglements on two substocks of the western North Atlantic humpback whale,Megaptera novaeangliae
Authors: Volgenau Lisa , Kraus Scott D. , Lien Jon
Published: July 2008

Increased use of fishing gear in the marine environment can be detrimental to animals such as cetaceans, particularly through entanglement. Examination of the impact of such mortality on two substocks of the western North Atlantic humpback whale, Megaptera novaeangliae, indicates that when entanglement losses are added to natural mortality estimates and subtracted from birth rate estimates, annual mortality may be as high as 5.4% in the Newfoundland and Labrador population and 4.8% in the Gulf of Maine population. More effective entanglement reporting and assisting systems are needed in the Gulf of Maine and increased efforts are needed to decrease entanglements, entanglement mortalities, and damages to fishing gear. We conclude that monitoring of the size of humpback populations needs to continue, given their particular vulnerability to coastal fishing and the potential impacts of entanglement mortality.
Depth distribution and seasonal movements ofChionoecetes opilio(Brachyura: Majidae) in Baie Sainte-Marguerite, Gulf of Saint Lawrence
Authors: Lovrich Gustavo A. , Sainte-Marie Bernard , Smith Barry D.
Published: July 2008

Bimonthly beam-trawling from April 1991 to May 1992 and diver observations were used to assess distribution and large-scale movement of snow crabs, Chionoecetes opilio, over depths of 4–140 m in a bay of the northern Gulf of Saint Lawrence. Megalopae settled during October 1991. Immature crabs of instars I–IV (i.e., 3.3–9.7 mm mean carapace width, CW) were found predominantly on bottoms ≈50–80 m deep and were cryptic and sedentary. Most immature crabs of instars V–VIII (i.e., 14.1–34.5 mm mean CW) and adolescent males (i.e., producing sperm but not terminally moulted) migrated in winter to subtidal grounds, where they moulted. Movement to shallow waters was massive and resulted in a mean density of 860 crabs per 1000 m2at ≈15 m in December 1991. Adult males (i.e., producing sperm and terminally moulted) of <70 mm mean CW also moved to the shallow grounds from October to December 1991, where some mated with pubescent–primiparous females (i.e., adult, first brood) from January to April 1992. Adult males of >90 mm mean CW were mainly found at depths >80 m over most of the year, but from March to May 1992 an increase in mean CW of adult males at <80 m indicated some upslope movement, probably to mate with multiparous females (i.e., adult, second or ulterior brood). Adult females were more gregarious and sedentary than adult males. We expand on the hypothesis that interannual variability in recruitment to adulthood tends to reflect differences in year-class strength, and that year-class strength varies in accordance with megalopal supply and (or) survivorship of cryptic instars.
Widespread polyploid forms offLumbricillus lineatus(Müller) (Enchytraeidae: Oligochaeta): comments on polyploidism in the enchytraeids
Authors: Coates Kathryn A.
Published: July 2008

Studies of a small fresh collection of the marine intertidal enchytraeid oligochaete Lumbricillus lineatus (Müller) and taxonomic collections from 27 additional locations in Europe, Canada, and Australia reveal the presence of morphotypes corresponding to parthenogenetic autopolyploid forms, triploid, tetraploid, and pentaploid, of the species in all the regions represented by the collections. The extension of the range of these cytotypes from Europe to a virtually global distribution raises questions about the significance of parthenogenesis and polyploidism to their invasion of new habitats. Differences in reproduction rates and the ecological breadth of the different ploidy levels are not known. The geographical distribution and abundance of polyploids of L. lineatus, in themselves, do not provide conclusive evidence for the repeated origins of polyploids within the species, but strongly suggest that possibility. General theories link evolutionary polyploidy among animals with parthenogenesis, as seen in the polyploid forms of L. lineatus. However, polyploidism combined with out-crossing underlies the present taxonomic diversity of the family Enchytraeidae.
Diversity and distribution of mitochondrial DNA lineages among humpback whales, Megaptera novaeangliae, in the Mexican Pacific Ocean
Authors: Medrano-González Luis , Aguayo-Lobo Anelio , Urbán-Ramírez Jorge , Baker Charles Scott
Published: July 2008

We investigated the mitochondrial DNA (mtDNA) diversity of humpback whales, Megaptera novaeangliae, wintering off the Mexican Pacific coast and the Revillagigedo Islands. We amplified and sequenced a variable fragment of the mtDNA control region from skin samples of 65 whales and compared these with published sequences from whales in other regional habitats. Among the Mexican humpback whales, we distinguished eight haplotypes differing by 0.31–3.75% along a consensus sequence length of 320 base pairs. A diagnostic restriction site outside the consensus sequence identified a ninth common haplotype. A phylogenetic reconstruction of the control region sequences revealed two main groupings: an AE group, which is common throughout the North Pacific, and a CF group, which is closely related to haplotypes from the southern hemisphere. We found a significant degree of geographic subdivision in the wintering grounds of the eastern North Pacific. Within Mexico, whales off the Revillagigedo Islands are weakly but significantly differentiated from those of the Mexican Pacific coast. Our data also suggest that mtDNA haplotypes are clinally distributed along the American Pacific coast and we hypothesize that the present distribution of these lineages among humpback whales in the eastern North Pacific is probably associated with weather changes after the last glaciation.
Habitats préférentiels d'amphibiens ranidés dans des lacs oligotrophes du Bouclier laurentien, Québec
Authors: Courtois Daniel , Leclair jr. Raymond , Lacasse Sylvain , Magnan Pierre
Published: July 2008

From a study of riparian habitat structure and a quantitive distribution survey of bullfrog, Rana catesbeiana, mink frog, Rana septentrionalis, and green frog, Rana clamitans melanota, in 31 oligotrophic lakes, we looked for, among 18 physiographic parameters, those that could best explain the spatial organisation of the ranid community. The three species cohabitated in 18 lakes, the mink frog and the green frog in 10 lakes without bullfrog, and the bullfrog alone in 3 lakes. These frogs preferentially occupied (i) habitats with medium or high density of emergent vegetation, (ii) areas with extensive floating aquatic vegetation, (iii) muddy and silty areas, and (iv) especially for the green frog, shrubby habitats with ericaceae. Substrates had a poor explicative value. In lakes devoid of bullfrogs, the mink frogs and green frogs were more frequently abundant and showed a more even distribution in the different habitats than when they were sympatric with bullfrogs. A Spearman's rank correlation analysis confirmed the similarity of habitat preferences between the three species and the poor capacity of the habitat structure to predict the ranid community composition.