bluuebunny/crossref_metadata_2025 huggingface dataset:
Macroinvertebrates of a beaver-altered boreal stream of Alberta, Canada, with special reference to the fauna on the dams
Authors: Clifford Hugh F. , Wiley Gillian M. , Casey Richard J.
Published: July 2008

There were different macroinvertebrate assemblages on the face of and in beaver dams compared with beaver ponds and main stream sites. The beaver dam featured a large proportion of simuliid larvae compared with the main stream sites of this stream and with areas of other studies of beaver-altered streams. The fauna of the dams was typical of fast-flowing habitats, whereas animals of the main stream sites (including the beaver ponds) were more characteristic of slow-flowing or lentic habitats. Cluster analysis separated the dam and main stream sites for each sampling date and year of our study based on the composition of the macroinvertebrates. Although the invertebrate assemblages of the dams differed from those of the main stream sites, both habitats included similar functional feeding groups, except for a shredder found only at the dams. There are similarities between the beaver dam fauna and the faunas of debris dams, woody snags, and lake outlets. Beaver dams are important in supporting large populations of simuliids and generally in maintaining a lotic fauna in slow-moving, low-gradient boreal streams.
Dispersal of Atlantic salmon fry from a natural redd: evidence for undergravel movements?
Authors: Leaniz Carlos Garcia de , Fraser Neil , Huntingford Felicity
Published: July 2008

In this paper we describe a modified version of a box trap used for bank-to-bank trapping during a study of dispersal of Atlantic salmon fry (Salmo salar L.). Two such traps were positioned 2 m upstream and downstream of a single isolated natural redd and a third was placed 20 m downstream. All fry captured in each trap were marked and released beyond the trap. Of the fish caught in the second downstream trap, 64% were unmarked. The seasonal patterns of trapping for marked and unmarked fish were identical, but the unmarked fish were significantly smaller than their marked peers. We argue that these unmarked captures represent fish that evaded capture in the first downstream trap, either by dispersing from the redd deep within the gravel or by leaving the water column and burrowing into the gravel on encountering the trap. Implications for the interpretation of trapping data on newly emerged salmonids are discussed.
The rice rat Oryzomys palustris in a Delaware salt marsh: annual reproductive cycle
Authors: Edmonds Kent E. , Stetson Milton H.
Published: July 2008

A population of the rice rat Oryzomys palustris inhabiting the Canary Creek salt marsh in Lewes, Delaware, was sampled on a monthly basis from September 1988 to December 1990. Males were assigned to the following age-classes on the basis of body mass: juveniles, 0 – 30 g; subadults, 31 – 50 g; adults, 51 g or greater. Testicular mass exhibited a seasonal pattern with lowest adult values in late autumn and early winter and peak values in late spring and early summer. Females showed similar patterns in uterine mass and vaginal patency. Pregnant and (or) lactating females were found from March to late September. The data suggest that the breeding season of the rice rat in southern Delaware begins in late winter and extends into late summer. Favorable environmental conditions may extend the breeding season for some individuals into autumn.
Myxobolus lii nom.nov.: a replacement for M. gibbosus Li and Desser, 1985 (Myxosporea: Myxozoa), preoccupied
Authors: Desser Sherwin S.
Published: July 2008

Myxobolus gibbosus Li and Desser, 1985 described from sunfish, Lepomis gibbosus, from Lake Sasajewun, Algonquin Park, Ontario, is renamed Myxobolus lii nom.nov. because the original binomen was preoccupied by Myxobolus gibbosus Herrick, 1941, described from the same host from Lake Erie.
An accurate technique for estimating forage intake of tractable animals
Authors: Parker Katherine L. , Gillingham Michael P. , Hanley Thomas A.
Published: July 2008

We selected an average-sized plant unit for each forage species commonly eaten by black-tailed deer in southeastern Alaska. Those units, which were used to establish species-specific templates, typically represented single or small compound leaves that were usually eaten in one bite. We also determined an average mass for each plant unit. Using visual estimation of plant units in the natural environment, we were able to accurately predict actual plant mass (all r2 ≥ 0.94). The technique is an accurate and reliable method for estimating both bite sizes and cumulative forage intake of tractable animals in forb- and shrub-dominated communities. It provides an estimate of dry or wet matter intake within a foraging period or specific habitat patch, relative to diet selection at the plant species level.
Changes in mass, fat content, and water content with growth in adult Pachydiplax longipennis (Odonata: Libellulidae)
Authors: Dunham Martha
Published: July 2008

I present data on mass gain in individual Pachydiplax longipennis (Odonata: Libellulidae) adults as they matured in a large enclosure. I also compared individuals captured as tenerals with individuals captured as immature or mature adults. Males gained more mass than females. Mortality did not differ between males and females or between light and heavy individuals in the enclosure.
Ultradian and circadian rhythmicity of behavioral activities in the young snail Helix aspersa maxima (Gastropoda, Helicidae)
Authors: Blanc A.
Published: July 2008

The rhythm of behavioral activities was studied in 8- to 100-day-old young snails (Helix aspersa maxima) and compared with that of adults. The animals were individually tested. Locomotor activity made up the main part of the total activity. The temporal distribution of feeding closely matches that of locomotion (involving displacement), while movements without displacement (i.e., movements of the head or shell) appeared sporadically. The activity of both the young and adults could be entrained to a 24-h light–dark cycle. Under constant conditions (dim red light) both the young and adults displayed free-running circadian rhythms, which were less robust in the young. Young snails also displayed short-duration rhythms with periods between 3 h and 5 h 30 min. This ultradian component is weak when the animals are subjected to a 24-h light–dark cycle, whereas it persists beyond 3 months in animals raised under constant conditions.
Population trends and interactions among terns and gulls in Gros Morne National Park, Newfoundland
Authors: Howes Lesley-Anne , Montevecchi William A.
Published: July 2008

Although populations of Common Terns and Arctic Terns (Sterna hirundo, S. paradisaea) have been decreasing and gull (Larus spp.) populations have been increasing in eastern North America for more than 50 years, little is known about the population trends of these species in Newfoundland. Here we present data, spanning two decades, on the population trends and interactions of terns and gulls on five islands in Gros Morne National Park in western Newfoundland. Tern populations in this region are increasing despite interactions with gulls and low productivity. Immigration from disturbed colonies elsewhere is suggested as a possible source of the increase. Gull populations have also increased substantially since the early 1970s and closely follow local production of fisheries offal, as indicated by landing trends in the area. Implications for gull management strategies are discussed.
The contributions of body tissues, respiratory system, and plumage to buoyancy in waterfowl
Authors: Stephenson Richard
Published: July 2008

This study examines buoyancy partitioning between body compartments in diving and surface-feeding Anatidae. Body tissue and plumage densities and the volumes of air in the respiratory system and plumage were analyzed using cadavers and restrained live specimens of waterfowl. The densities of the skeleton and remiges of surface feeders were significantly lower than those of divers but the differences were not sufficient to significantly reduce the body tissue density and buoyant force of divers. There were no other statistically significant differences in the body tissue densities of diving and surface-feeding waterfowl. The densities of contour feathers, down, and remiges were markedly different from each other but the net buoyant force of the feathers was less than 5% of that caused by the air trapped in the plumage layer. All cadavers were negatively buoyant in the absence of air in the respiratory system and plumage. Despite similar net buoyant forces, there were large differences in the volumes of air in the respiratory system and plumage between restrained ducks and cadavers. These results indicate that the use of cadavers or restrained ducks to determine net buoyancy, and hence power output, during voluntary foraging behaviour is unreliable.
The life cycle of the aquatic snipe fly Atherix lantha Webb (Diptera Brachycera; Athericidae) in Quebec
Authors: Lauzon M. , Harper P. P.
Published: July 2008

The aquatic snipe fly Atherix lantha Webb in the rivière de l'Achigan in the Laurentian foothills of Quebec has a univoltine life cycle. The eggs were laid in great clusters under a small footbridge spanning the river and some 61 000 dead females were observed attached to their egg masses. Upon hatching, the hatchlings fell into the water. There were five larval instars. First-instar larvae appeared in June. Growth was rapid and by September most of the population had reached the fourth instar. Overwintering occurred mainly in the fifth and final instar. On the basis of measurements of the second antennal segment of the larvae, it was concluded that growth follows Dyar's law of constant growth rate between instars (growth rate = 1.31), except between the first two instars, where the growth rate was higher (1.41). In May the full-grown larvae left the river to pupate on the banks and adults were on the wing from mid-May to late June.
Morphological variation and cannibalism in a larval salamander (Ambystoma macrodactylum columbianum)
Authors: Walls Susan C. , Beatty Joseph J. , Tissot Brian N. , Hokit D. Grant , Blaustein Andrew R.
Published: July 2008

We document morphological variation and its association with larval cannibalism in a population of long-toed salamanders, Ambystoma macrodactylum columbianum. Larvae observed in a natural pond engaged in cannibalism. Additionally, these larvae possessed significantly longer and wider heads, as well as larger vomerine teeth, than did conspecifics of the same size reared in the laboratory for 1 month after capture. This variation in trophic structures is consistent with the characteristics of "cannibal" morphs that have been documented for larvae of another salamander species. We extend current knowledge of the development of this morphology by using multivariate statistical analysis to examine, further, a possible basis for this variation in head shape. Principal component analysis indicated that after the removal of the effects of body size, variation in the distance between the eyes (interocular width) accounted for most of the remaining total overall variation in head shape. Multivariate ontogenetic trajectories of head shape, constructed from linear regressions of principal components (measures of size and shape), were equivalent for the two larval samples. These statistical analyses indicate that this trophic polymorphism is not due to differences in either the rate of change in head shape relative to overall size or the size at which the divergence in head shape begins. Rather, morphological variation in larval A. m. columbianum may be due to fluctuations in the presence of key, influential environmental factors, as has been demonstrated for other larval amphibians that exhibit trophic polymorphism.
Age-related changes in the visual pigments of the white sturgeon (Acipenser transmontanus)
Authors: Loew E. R. , Sillman A. J.
Published: July 2008

Using in situ microspectrophotometry, the spectral absorbance characteristics of the photoreceptors in the retinas of larval, juvenile, and adult white sturgeon (Acipenser transmontanus) were determined. The adult has one type of rod, containing a visual pigment with maximum spectral absorbance (λmax) near 540 nm. There are three types of cones, morphologically identical but distinguished from one another by containing either a blue-sensitive (λmax 464 nm), green-sensitive (λmax 531 nm), or red-sensitive (λmax 605 nm) visual pigment. Juvenile sturgeon have visual pigments similar to those of the adult. However, no evidence could be found for the presence of either blue-sensitive or red-sensitive cones in larval white sturgeon through the age of 10 weeks. Larval sturgeon up to about 10 weeks yielded only green-sensitive rods and cones. The absence of red-sensitive cones in the larvae, and their presence in older fish, was confirmed by the use of 4,4′-diisothiocyanato-stilbene-2,2′-disulfonic acid, a fluorescent substance that binds selectively to photoreceptors sensitive to long-wavelength light. Regardless of age, all visual pigments are based on vitamin A2. Also regardless of age, white sturgeon retinas yielded no evidence for the presence of photoreceptors sensitive to ultraviolet light.
Effect of altered thyroid and adrenal activity on the seasonal reproduction of the Indian palm squirrel, Funambulus pennanti
Authors: Singh A. B. , Chaturvedi Chandra Mohini
Published: July 2008

Thiouracil and metyrapone administered during the progression phase of the annual reproductive cycle inhibited gonadal development in the Indian palm squirrel, Funambulus pennanti. In a further experiment, these drugs led to normal gonadal regression during the late breeding phase. Thyroxine and corticosterone treatment, on the other hand, maintained the gonads continuously in breeding condition, unlike those of controls, which exhibited characteristic post-reproductive regression. Since hypofunction of the thyroid and adrenal glands had inhibitory effects on the initiation of seasonal gonadal growth, and hyperactivity affects post-reproductive regression, it is suggested that an optimal level of hormones is required for the normal breeding cycle in this subtropical mammal. The results are discussed in terms of an interrelationship between the seasonal thyroid, adrenal, and gonad cycles under natural conditions.
Auditory influences on the flight behaviour of moths in a Nearctic site. II. Flight times, heights, and erraticism
Authors: Lewis Francine P. , Fullard James H. , Morrill Scott B.
Published: July 2008

While moths that possess ears protect themselves from bats by listening for their echolocation calls, earless species presumably use different defences. Tent-caterpillar moths (Lasiocampidae) are earless and emerge in very large numbers at our Nearctic site. One species, Malacosoma americanum, has a nightly peak emergence time mismatched to the peak activity times of certain sympatric bats, while that of another, M. disstria, is more coincident with that of the bats. These data suggest that while both species swamp bats with their large numbers, M. americanum gains additional protection by temporally separating itself from bats. Empirical flight observations and sticky-trap captures indicate that earless moths fly closer to the ground and more erratically than eared moths, although exceptions exist (e.g., high-flying sphingids and erratic geometrids). The foraging habits of most sympatric bats predict that small moths, in particular, will benefit from this behaviour. We suggest that low-altitude erratic flight in moths is a protean insurance defence against bats, as it should reduce the chance of their being detected by these predators.
Waterborne copper causes gill damage and hemolymph hypoxia in the shore crab Carcinus maenas
Authors: Nonnotte L. , Boitel F. , Truchot J. P.
Published: July 2008

The ultrastructure of gill lamellae was studied in shore crabs, Carcinus maenas, exposed to sublethal (0.5 mg∙L−1) and lethal (2 mg∙L−1) concentrations of waterborne copper for various durations. Oxygen tension, pH, and lactate concentration in arterial blood were determined in parallel studies. Extensive structural alterations involving cellular hyperplasia, vacuolization, and necrosis were found after 5–6 days of exposure to both sublethal and lethal copper levels. This led to considerable thickening of the gill epithelium and reduction of haemolymph spaces, resulting in restriction of respiratory gas exchange as shown by a marked hypoxemia. Ensuing lactacidemia suggests that tissue hypoxia was probably the major effect of the toxicant at lethal levels. In sublethal conditions, partial repair of gill tissue and recovery of normal blood oxygenation and pH were observed after 18 days of exposure.
Annual reproductive success in three cohorts of Columbian ground squirrels: founding immigrants, subsequent immigrants, and natal residents
Authors: Wiggett Darwin R. , Boag David A.
Published: July 2008

We compared, over an 8-year period, the annual reproductive success (RS) of male and female founding immigrants (FIs) with that of subsequent immigrants (SIs), and the latter with that of natal residents (NRs) in two recently established colonies of Columbian ground squirrels (Spermophilus columbianus) in southwestern Alberta. For males, actual annual RS was unknown and so was estimated; for females, RS was measured directly. Among females, FIs had significantly more juveniles at litter emergence, and more yearlings present to age of emigration annually than did SIs. Juvenile and yearling offspring of SI females suffered higher annual rates of disappearance (presumed mortality) over the active season than did those of FIs. Additionally, the matrilines of FIs produced significantly more juveniles, more yearlings to time of emigration, and more daughters to reproductive maturity annually than did the matrilines of SI females. Male FIs had higher annual survival rates (and consequently lived and were territorial significantly longer), and had more female neighbours per year than did SIs, which suggests that the former had higher annual RS. We suggest that the higher annual RS of male and female FIs resulted mainly from their monopolization of the best resources and a lower risk of predation as a result of their more central position in the colony. Comparison of the annual RS of SIs and NRs showed that most (~70%) adult males present in the colonies were SIs. These males were significantly more likely to hold territories and to do so for significantly longer periods than their NR counterparts. Conversely, SI females annually brought above ground significantly fewer juveniles and had significantly fewer yearling offspring present to time of emigration than did NR females. Furthermore, the young of SI females suffered significantly higher rates of disappearance (presumed mortality) during the active season than did those of NR females, possibly because the former resided in more peripheral areas within the colony where predation rates may have been higher. We found no differences between these groups of females in the number of female offspring reaching reproductive maturity in the natal colony. These results provide preliminary support for the hypothesis that females, apart from FIs, benefit from philopatry; whereas males gain reproductive advantage through dispersal.
Behavioural differences among adult male harbour seals during the breeding season may provide evidence of reproductive strategies
Authors: Walker Brian G. , Bowen W. Don
Published: July 2008

We studied the behaviour of 43 male harbour seals (Phoca vitulina) during the 1991 breeding season on Sable Island, Canada. Males were classified as subadults (n = 21) or adults (n = 22) based on their initial body mass. Throughout the 40-d study, twice-daily beach surveys were carried out to locate marked males. Two spatial (average distance moved between haul outs, and the proportion of possible sightings in which a male was hauled out) and three social (fighting and composition and number of different groups in which the male was observed) variables were used to describe the behaviour of males during the premating period, when there were no, or few, receptive females, and the mating period, when receptive females were increasingly numerous. Of 39 males with complete behavioural data, principal components and cluster analyses identified a subset of 7 adults that differed from the other males. These seven adults exhibited evidence of intermale fighting (i.e., wounding on the neck and hind flippers), showed greater fidelity to a single haul-out site, associated with fewer groups, and were more often sighted alone or in all-male groups. We suggest that these adults may represent the most successful males.
Nesting success, nest sites, and parental care of the least flycatcher in declining maple forests
Authors: Darveau Marcel , Gauthier Gilles , DesGranges Jean-Luc , Mauffette Yves
Published: July 2008

We compared nesting success, nest site characteristics, and parental care of the least flycatcher (Empidonax minimus) between healthy and declining sugar maple (Acer saccharum) stands in southern Quebec, from 1987 to 1989. On average, decline had caused a 20–30% foliage loss. A previous study showed that the least flycatcher was the most abundant species in these stands, even though some negative correlations between population densities and the intensity of decline were detected. Nesting success averaged 53% and did not differ between healthy and declining sites. Nests were located in larger trees in declining sites, and foliage loss in the canopy above the nest was twice as high as in healthy sites. Nestling feeding frequency was significantly higher in declining sites than in healthy ones. Mean meal size did not differ between sites, suggesting that nestlings received more food in affected stands in spite of evidence of lower insect abundance. The nestling diet was principally composed of Lepidoptera, Diptera, Hymenoptera, and Coleoptera in declining and healthy sites. Parents spent more time at the nest in declining sites in 1988, presumably because of increased brooding demand resulting from cold weather that year. We suggest that nestlings were thermally stressed in declining sites because of canopy foliage loss and that parents had to work more (i.e., provide more feeding and brooding) to maintain breeding success. Therefore, even though a moderate level of decline does not affect nesting success, flycatchers may still be negatively affected in more subtle ways.
Adaptations in pectoralis muscle, heart mass, and energy metabolism during premigratory fattening in semipalmated sandpipers (Calidris pusilla)
Authors: Driedzic William R. , Crowe Heidi L. , Hicklin Peter W. , Sephton Dawn H.
Published: July 2008

In late summer, semipalmated sandpipers (Calidris pusilla) migrate nonstop from eastern Canada to wintering sites on the northwest coast of South America. Before their transoceanic flight, the birds feed intensively for about 15 days during which time lipids are stored. The fat-free dry mass of the pectoralis muscle increases during the fattening period, probably increasing the maximal power output of the muscle. Plasma free fatty acids and triglycerides, pectoralis muscle lipid content, and the activity of carnitine oleoyl coenzyme A transferase are higher in heavy (fat) than in light (lean) birds. These alterations imply an enhanced capacity to utilize fatty acids as a metabolic fuel during migration. Total pectoralis muscle glycogen levels and the activity of pyruvate kinase increase, suggesting a higher capacity for glycogenolysis, which may be important during intense levels of energy demand. Heart size and protein content per gram of tissue increase in association with an increase in body mass. However, total levels of key mitochondrial enzymes, citrate synthase and carnitine oleoyl coenzyme A transferase, do not change, suggesting that in the heart an increase in total protein content occurs without an increase in mitochondrial proteins.
The ultrastructure of spermatogenesis and spermatozoa in Pseudodiplorchis americanus (Monogenea: Polystomatidae)
Authors: Cable J. , Tinsley R. C.
Published: July 2008

The basic characteristics of spermatogenesis and the ultrastructure of the mature spermatozoa show uniformity throughout the parasitic platyhelminths, and the monogenean Pseudodiplorchis americanus follows this general pattern. Primary spermatogonia undergo mitosis to produce 8 primary spermatocytes which divide by meiosis to produce 16 secondary spermatocytes and eventually a syncytial rosette of 32 spermatids. Each spermatid differentiates into a mature spermatozoon bearing two axonemes, a nucleus, a mitochondrion, and cortical microtubules. Although transmission of P. americanus is restricted to only a few nights each year, the production of male gametes appears to be continuous throughout adult life and exhibits no seasonality. Characteristically, cortical microtubules run the entire length of polyopisthocotylean spermatozoa but they are absent along part of the spermatozoon of P. americanus and one other polystomatid species previously examined. This variation on the standard pattern separates the Polystomatidae from the rest of the Monogenea and emphasises the distinctive taxonomic position and the homogeneity of many structural features within this platyhelminth family.
Postbreeding habitat selection by shorebirds, water birds, and land birds at Barrow, Alaska: a multivariate analysis
Authors: Smith Kimberly G. , Connors Peter G.
Published: July 2008

Habitat use by birds was studied at Barrow, Alaska, during the 1975–1978 postbreeding seasons, when birds moved from tundra breeding areas to coastal areas to feed prior to migration. Principal component analysis revealed three general habitat types used by birds: gravel beach, mudflat, and slough edge. Of four common shorebirds, red phalaropes (Phalaropus fulicaria) usually occurred along gravel beaches, semipalmated sandpipers (Calidris pusilla) and western sandpipers (Calidris mauri) occurred mostly on mudflats and slough edges, and dunlins (Calidris alpina) had an intermediate distribution. Considerable variation in habitat distribution existed among years, and similarity of distributions among species within years suggested that groups of species were influenced by common environmental factors. Gravel beaches were generally distinct from slough edges and mudflats, and two major groups of eight species each were found mainly on mudflats and slough edges or on gravel beach transects. However, habitat use by many species varied considerably among years, suggesting that birds assess local conditions within relatively small areas within habitats. Most species preferred either gravel beaches or mudflats and slough edges, but that may be modified by environmental factors including food availability.
Biodiversity and biogeography in heterospecific teleostean (Gadidae) – copepod (Lernaeocera) associations
Authors: Tirard Claire , Berrebi Patrick , Raibaut André , Renaud François
Published: July 2008

This genetic study confirms the validity of two controversial parasite species, Lernaeocera branchialis and Lernaeocera lusci (Copepoda, Pennellidae). These species cohabit throughout a large sector of the North Sea and the Atlantic Ocean, parasitizing Merlangius merlangus and Trisopterus luscus (Teleostei, Gadidae), respectively. In the Mediterranean Sea, it was L. branchialis that was described initially. We have shown, however, that it is L. lusci that parasitizes T. luscus and Merluccius merluccius in this geographical area. The distribution of L. lusci, as well as that of its host, T. luscus, must extend into the Mediterranean. Lernaeocera lusci has colonized a phylogenetically distant host (Merluccius merluccius) in the Mediterranean and our results show that this species has become the preferred host for the maturation of L. lusci in this region. In addition, we have demonstrated the existence of genetic differentiation between T. luscus from the Atlantic and from the western Mediterranean. Thus, it is possible that the specialization of L. lusci in a new resource (M. merluccius) in the Mediterranean might be related to biological changes undergone by this copepod's original host, Trisopterus luscus. In contrast to other parasite groups such as the Monogenea, the specialization of species of the genus Lernaeocera would appear to depend more on ecological parameters (relative abundance and availability of resources) than on phylogenetic constraints. The relationships within these host–parasite systems are therefore compared with the predator–prey relationships.
Ecology of metazoan parasites infecting Catostomus spp. (Catostomidae) from southwestern Lake Superior
Authors: Hogue Cheryl C. , Sutherland Daniel R. , Christensen Bruce M.
Published: July 2008

Ecology of the parasite fauna of two abundant nongame fish species, Catostomus catostomus (longnose sucker) and Catostomus commersoni (white sucker), from southwestern Lake Superior was examined. White sucker harbored a total of 17 parasite species compared with 8 species in longnose sucker. Echinorhynchus salmonis and Neoechinorhynchus crassus were the most abundant helminths in both sucker species. The only parasitic copepod found in this study, Ergasilus nerkae, was more prevalent in longnose sucker. In white sucker, Glaridacris catostomi, Capillaria catostomi, Ergasilus nerkae, Allocreadium lobatum, and Isoglaridacris bulbocirrus showed fluctuations in prevalence on a seasonal basis. Several helminth species showed a high degree of microhabitat overlap in the gut (e.g., A. lobatum, G. catostomi, and Echinorhynchus salmonis). Helminths that exhibited a higher mean intensity in certain sections of the intestinal tract included I. bulbocirrus in the anterior portion of the gut and Capillaria catostomi in the posterior region of the gut.
Individual lake characteristics modify the life cycle and diapause habitat of two neighbouring populations of the cyclopoid copepod Thermocyclops oithonoides
Authors: Naess Tore , Nilssen Jens Petter , Demmo Reidar
Published: July 2008

Thermocyclops oithonoides (Cyclopoida, Copepoda) populations were studied in two neighbouring lakes with similar seasonal hydrographical characteristics. The two populations showed different life-cycle and diapause characteristics. The major differences were found in the number of generations per year (three versus two), the timing of induction and termination of diapause, temperature and oxygen conditions during diapause migration to the sediment, and habitat selection for wintering. Diapause initiation occurred at about 12 h light: 12 h dark in one population, but about 8 h L: 16 h D in the other. Higher habitat temperatures (approximately 5 °C) seemed to allow completion of a further generation in the warmest lake. The population descending early into the hypolimnion utilized the deep profundal sediment as a diapausing habitat. These specimens were most likely physiologically prepared for diapause, including tolerance to low-oxygen or anoxic conditions. The population with an additional generation, probably not yet in the complete diapause phase, avoided low-oxygen conditions and utilized mainly the oxygenated part of the profundal sediment as a diapausing habitat. The major part of both populations diapaused in the sediment, but a small fraction was in "active diapause" in the plankton during winter. In these populations of T. oithonoides, day length, modified by habitat temperature, seemed to influence diapause initiation, whereas habitat distribution during winter seemed to be influenced by the combined effect of diapause ontology and oxygen conditions in the potential wintering habitat.
Water-bird population changes in 1976–1990 on Besnard Lake, Saskatchewan: increases in loons, gulls, and pelicans
Authors: Gerrard Jon M. , Dzus Elston , Bortolotti Gary R. , Gerrard P. Naomi
Published: July 2008

Declines in Common Loon (Gavia immer) populations associated with increasing human use of lakes have been reported from many areas of North America. In the present report we describe a lake in northern Saskatchewan, Besnard Lake, where there has been a substantial increase in the number of loons, from about 85 in 1976–1979 to about 165 in 1990. A comparison was made with numbers of other birds associated with water. Increases were also seen in American White Pelicans (Pelecanus erythrorhynchos), Osprey (Pandion haliaetus), Great Blue Herons (Ardea herodias), Herring Gulls (Larus argentatus), Ring-billed Gulls (L. delawarensis), and Bonaparte's Gulls (L. Philadelphia). No change was seen in mergansers (Mergus merganser and M. serrator), Bald Eagles (Haliaeetus leucocephalus), or Common Terns (Sterna hirundo). The period 1976–1990 has also seen increased human use on Besnard Lake. The reason for increased loon numbers is uncertain, but could possibly be related to an increase in the numbers of small fish in Besnard Lake as a result of increased fishing pressure disproportionately removing the larger, predatory fish.
Mating in moose: timing, behavior, and male access patterns
Authors: Ballenberghe Victor Van , Miquelle Dale G.
Published: July 2008

We observed mating wild moose (Alces alces) in a naturally regulated population in central Alaska during 1980–1991. The median date of observed copulations for all years was 2 October, with small shifts among years. Of 191 mounting sequences observed, all occurred between 24 September and 8 October. Only 2% of copulations (n = 86) involved the mating of a female and two males. Large males performed 82% of all mountings and 88% of all copulations. One male copulated with at least 12 females during one mating season. Male and female behavioral patterns associated with mating were similar to those observed in other cervids and included tongue flicking, courtship croaking, genital smelling, chinning by males, and tree rubbing by females. Both sexes displayed little obvious postcopulation behavior.
Differential mortality of sympatric snowshoe hares and cottontail rabbits in central Wisconsin
Authors: Keith Lloyd B. , Bloomer Sara E. M.
Published: July 2008

During 1990 and 1991 we livetrapped and radio-collared cottontail rabbits (Sylvilagus floridanus) and snowshoe hares (Lepus americanus) on five sites (three in lowland deciduous cover, two in conifer bogs) in central Wisconsin. The survival rates of these sympatric cottontails and snowshoes were equally high during snow-free periods from mid-March through October. With the onset of persistent snow cover (mean depth 20 cm) and low temperatures (mean daily minimum −14 °C) in November 1991, the 60-day survival rate of cottontails plummeted from 0.89 to 0.18 (P < 0.01) whereas snowshoe survival declined only moderately from 0.84 to 0.63 (P = 0.19). This interspecific difference reflected continued high survival of snowshoes (0.80), but not of cottontails (0.15), in the conifer bogs. Predation, primarily by coyotes, was the proximate cause of 37 of 39 rabbit and hare deaths, and was thus the overwhelming determinant of survival. We speculate that where persistent snow and low temperatures characterize winter, the cottontail's greater foot loading, brown coloration, and escape behavior markedly increase its vulnerability to predators. This probably explains the absence of cottontails from the forests of northern Wisconsin.
Diet overlap of collared lemmings and tundra voles at Pearce Point, Northwest Territories
Authors: Bergman Carita M. , Krebs Charles J.
Published: July 2008

We used a combination of faecal pellet analysis and feeding enclosure trials to determine the diets of collared lemmings (Dicrostonyx kilangmiutak) and tundra voles (Microtus oeconomus) at Pearce Point, Northwest Territories, and we looked for evidence of exploitative competition between the two species. Voles preferred monocotyledons (Carex and Eriophorum spp.) and lemmings preferred Dryas integrifolia. We found that there was little overlap in the natural diets of the two species, but that overlap was increased experimentally when both species were forced to forage in the same habitats. However, food preferences generally did not change. The diet of collared lemmings at Pearce Point was similar to that found in all other studies except those done in Alaska, where Dryas is uncommon. We conclude that exploitative competition for food is unlikely to be an important factor in interspecific relations between collared lemmings and tundra voles.
Halice hesmonectes, a new species of pardaliscid amphipod (Crustacea, Peracarida) from hydrothermal vents in the eastern Pacific
Authors: Martin Joel W. , France Scott C. , Dover Cindy Lee Van
Published: July 2008

A new species of the pardaliscid amphipod genus Halice, H. hesmonectes, is described from hydrothermal vents in the eastern Pacific Ocean. The species occurs in large monospecific swarms in the immediate vicinity of low temperature vent openings. Halice hesmonectes differs from other members of the genus in having the following combination of characters: extremely long pereopods 5–7 (exceeding length of pereon, and nearly twice the length of pereopods 1–4); minute dactylus on pereopods 3 and 4, unique, constricted at midlength; pleopods well developed, as long or longer than pereopods 1–4; telson cleft along approximately two-thirds its length and terminating in an acute tip on each lobe; short article 3 (about 1/3 length of article 2) on mandibular palp; and accessory flagellum of first antenna with only two articles, the distal one being approximately 1/6 the length of the proximal. In addition, the body and virtually all appendages are covered by minute cuticular scales, probably present also on other pardaliscids (visible only via SEM) and known from other peracarids. Problematic taxonomy within the family Pardaliscidae is discussed.
Seasonal activity in the blind mole rat (Spalax ehrenbergi)
Authors: Rado Rony , Shanas Uri , Zuri Ido , Terkel Joseph
Published: July 2008

The locomotor activity pattern of the blind mole rat Spalax ehrenbergi was determined in its natural habitat by means of a radiotelemetric device. Twelve adult mole rats were fitted with radiotelemetric transmitters (9 during winter and 3 during summer) and tracked for 5 noncontinuous days during which air and soil temperatures were measured. Mole rats were found to have a diurnal monophasic locomotor activity pattern with activity peaks from 08:00 to 13:00 and from 11:00 to 19:00 during summer and winter, respectively. Activity periods were punctuated by several rest breaks and, conversely, rest periods were interrupted by short spells of activity. Duration of activity was 6.6 ± 0.4 h (mean ± SD) in summer and 7.9 ± 2.3 h in winter. In the laboratory, mole rats were found to entrain their activity, under constant dim light, to a single daily 20-s light pulse. Moreover, such a light pulse given only once every 3 days was found to provide a stimulus sufficient to entrain the mole rats' locomotor activity. We propose that brief light pulses perceived through the mole rats' rudimentary eyes while they are pushing excess soil out of the tunnel to the ground surface, are the main Zeitgeber that entrains their locomotor activity to the diurnal pattern. Air and soil temperatures are the secondary cues that finely tune the activity to the morning during summer and the late afternoon during winter.
Clutch size in eastern phoebes (Sayornis phoebe) II: age effects and seasonal variation
Authors: Conrad Kelvin F. , Robertson Raleigh J.
Published: July 2008

We examined seasonal variation in clutch size among single- and double-brooding eastern phoebes to learn how the pattern of variation among female age-classes and early and late-season breeders contributed to overall seasonal variation in clutch size. Clutch sizes of eastern phoebes did not decline predictably (linearly or quadratically) with season when we considered all clutches laid over the season, nor when the first and second clutches of double-brooding birds were each regarded separately. Total seasonal egg production by double-brooding second-year (SY) females declined linearly with season but that of after-second-year (ASY) females did not. Among single-brooding females, which were nearly all SY birds, clutch size, and hence total seasonal egg production, were unaffected by season. In general, SY birds bred later, laid fewer eggs, and were less likely to double-brood than ASY birds. The large seasonal variation in clutch size for the entire population was influenced by two different groups of SY females: (1) double-brooding SY females that nested at the same time as double-brooding ASY birds and had similar clutch sizes, but showed a linear decrease in total seasonal egg production versus initiation date, and (2) single-brooding SY females that nested after double-brooding females, had clutch sizes similar to double-brooding females, and showed no linear decrease in total seasonal egg production versus initiation date. Combined with double-brooding ASY females, these two groups of SY birds increase the variation in clutch size observed on any given day and obscure the pattern of seasonal decline commonly reported for other species.
Reproductive status influences odor preferences of the meadow vole, Microtus pennsylvanicus, in winter day lengths
Authors: Gorman Michael R. , Ferkin Michael H. , Nelson Randy J. , Zucker Irving
Published: July 2008

Sporadic winter breeding is a common occurrence in populations of arvicoline rodents. To elaborate the olfactory basis of winter breeding, odor preferences of meadow voles that did or did not develop their reproductive systems in short day lengths were compared. Voles that did not respond to short days with reproductive inhibition were reproductively mature and are termed nonresponders, while voles that did respond to short days with reproductive inhibition were reproductively immature and are termed responders. Nonresponder females preferred odors of nonresponder males over those of nonresponder females and nonresponder female over responder female odors. Nonresponder males preferred nonresponder over responder female odors. The mutual attraction between male – female and female – female nonresponders may facilitate winter breeding and female – female dyad formation for communal rearing of young, respectively. Responder females preferred odors of female responders over those of male responders and responder over nonresponder male odors. Olfactory preferences of nonresponder short-day voles were not equivalent to those of reproductively competent long-day animals. Differences in odor communication between responder and nonresponder voles are attributable only in part to differences in gonadal hormone secretion.
Hormonal sensitivity and responsiveness in sea raven hepatocytes: changes with fasting and collagenase exposure
Authors: Foster Glen D. , Moon T. W.
Published: July 2008

Changes in the apparent sensitivity and responsiveness of carbohydrate metabolism to glucagon and insulin were examined in hepatocytes isolated from fed and 6-week-fasted sea ravens (Hemitripterus americanus), with and without collagenase. The fasted group demonstrated higher rates of total glucose production (TGP) and gluconeogenesis from alanine than the fed group. Metabolic sensitivity to glucagon was increased with fasting, while the maximal responsiveness to both hormones was decreased with fasting; this latter effect may result from elevated control rates in the fasted group. Glucagon increased CO2 production from alanine in the fed group and decreased it in the fasted group. Insulin antagonized the effects of glucagon with respect to TGP and CO2 production, while the effects of the two hormones on gluconeogenesis were additive at high insulin concentrations in the fasted group. Hepatocytes isolated without collagenase perfusion had lower TGP, decreased sensitivity to glucagon, and decreased responsiveness to insulin than cells prepared with collagenase. Furthermore, the additive effects of insulin and glucagon on gluconeogenesis were not apparent when cells were isolated in the absence of collagenase. These results indicate that the response of hepatocyte carbohydrate metabolism to glucagon and insulin is affected by nutritional status, and that collagenase preparation significantly affects sea raven hepatocyte metabolism.
Helminth and protist parasites of zebra mussels, Dreissena polymorpha (Pallas, 1771), in the Great Lakes region of southwestern Ontario, with comments on associated bacteria
Authors: Toews Sheila , Beverley-Burton Mary , Lawrimore Tara
Published: July 2008

Zebra mussels (Dreissena polymorpha) collected in June 1991 from three localities in the Great Lakes region of south-western Ontario were examined for helminth and protist parasites. In addition, the bacteria in both live and dead mussels were identified and the effects of Serratia liquefaciens and Escherichia coli on D. polymorpha were monitored experimentally. Helminths were not found in mussels from the Puce site (Lake St. Clair); the prevalence of plagiorchiid metacercariae in mussels from Port Colborne (Lake Erie) was 2.9% and of aspidogastrids (adults and juveniles of Aspidogaster conchicola) in mussels from Leamington (Lake Erie), 2.7%. These findings represent locality records and a new host record for the digenean. The ciliate Ophryoglena sp. was found in mussels from Puce (prevalence 1.3%), Port Colborne (prevalence 4.3%), and Leamington (prevalence 2.7%). The principal bacteria found in both living and dead mussels were Aeromonas sp., Pseudomonas sp., and Bacillus sp. Both high and low concentrations of S. liquefaciens that were tested were lethal to mussels, while similar concentrations of E. coli produced no effects. Both bacteria are recognized as being opportunistic pathogens in many organisms. These preliminary findings suggest that helminths will not play a major role in the control of zebra mussels. However, the potentially pathogenic ciliate protists and bacteria warrant further investigation.
Metabolizable energy of fish when fed to captive Great Blue Herons (Ardea herodias)
Authors: Bennett Darin C. , Hart Leslie E.
Published: July 2008

The efficiency with which the gross energy content of herring (Clupea harengus), mackerel (Scomber scombrus), and trout (Oncorhynchus mykiss) is metabolized was determined for 11 captive Great Blue Herons (Ardea herodias). There was a linear relationship between apparent metabolized energy and gross energy intake for the mackerel and trout. This relationship was lower and more variable for herring. Estimates of the apparent metabolizable energy coefficient for mackerel and trout were affected by the level of energy intake. Correcting for endogenous energy losses in the excreta yielded estimates of true metabolizable energy coefficients that were independent of gross energy intake. The true metabolizable energy coefficient of mackerel and trout did not differ and averaged 0.866 (SD = 0.014, n = 3 diets). Correcting for nitrogen retention did not improve the estimate of the metabolizable energy coefficient. The metabolizable energy coefficient of herring was highly variable and showed no consistent pattern in relation to energy intake.