bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal variation in body composition of European roe deer
Authors: Holand Øystein
Published: July 2008

Seasonal variations in whole-body composition of 43 European roe deer (Capreolus capreolus L.) collected in the southeastern part of Norway were examined. Adult deer showed a defined annual cycle in both body weight and body fat reserves. Fat accumulated in September and October, reaching a maximum of 9.2% of the ingesta-free body weight in does and 10.3% in bucks, in late fall (November and December). The depletion phase started in early January and ended in April. No intersexual differences in amplitude or synchrony of body weight or fat cycle were observed. This contrasts with results in other temperate and northern cervids and could be due to differences in life strategy, particularly reproductive effort (midsummer rut, delayed implantation, and mating territories), in European roe deer.
Physiological responses of cold-stressed blue and snow phase Lesser Snow Goose goslings
Authors: Beasley B. A. , Ankney C. D.
Published: July 2008

A comparison of cold-stressed Lesser Snow Goose (Chen caerulescens caerulescens) goslings revealed that the metabolic rates of light-colored (snow) and dark-colored (blue) goslings did not differ when they were measured in the dark. Small differences in plumage insulation (higher in snow goslings) and core body temperature (lower in blue goslings) seemed to balance each other so that there was no difference in rates of thermogenesis between morphs. We conclude that physiological thermoregulation does not compensate for potential differential radiative heat loads between the morphs.
Thermal constraints on hauling out by harbour seals (Phoca vitulina)
Authors: Watts Peter
Published: July 2008

Measurements of the thermal environment were made in conjunction with regular counts of hauled out harbour seals at three sites in the Pacific Northwest. Solar radiation, wind speed, and air temperature were all significantly correlated with numbers of seals on land. These were incorporated into a thermal index of heat flux (expressed in watts per square metre) between the seal and its environment. Numbers of seals hauled out at midday declined sharply as flux increased above 0 W∙m−2 (i.e., when seals theoretically gained net heat from their environment), but remained constant at all measured negative values of flux. This relationship could be described by a nonlinear piecewise regression equation [Formula: see text]. No significant differences in hauling activity were detected between sites throughout most of the year. During the summer, however, one site with significantly higher mean flux than the others also exhibited significantly lower hauling activity. These findings are consistent with the hypothesis that under temperate summer conditions, hauling out can result in overheating. This may be an important constraint on hauling behaviour.
Host tracking and photosensitivity in Chaetogaster limnaei limnaei (Oligochaeta)
Authors: Shaw Ross
Published: July 2008

Chaetogaster limnaei limnaei were separated from host snails (Physa skinneri) for increasing periods of time. The oligochaetes responded to a snail's slime trail by increased activity and distance moved along the slime trail. These responses increased with increasing periods of separation from the snail. When exposed to a directional light source, C. l. limnaei displayed an initial positive phototactic response. Movement towards light from the same direction decreased significantly in a second 4-h period, but movement towards light from a different direction was equivalent to the initial response, suggesting the response was an initial one to a change in light.
Sex, age, and seasonal differences in the diets and activity budgets of muskoxen (Ovibos moschatus)
Authors: Oakes E. J. , Harmsen R. , Eberl C.
Published: July 2008

During the spring–summer period on Banks Island, Northwest Territories, Canada, muskoxen (Ovibos moschatus) in mixed age–sex herds spent similar amounts of time foraging and resting. However, calves foraged less and rested more than adults and yearlings, and dominant rutting males foraged less but spent more time in active nonforaging behaviours than other adults. Based on fecal analysis, adult females, subadults, yearlings, and calves each consumed proportionately more dicotyledonous forages (dicots) than adult males. For adult females, subadults, and calves this was due to a proportionately greater consumption of forbs; for yearlings it was due to their proportionately greater use of both shrubs (mostly Salix spp.) and forbs. The feces of yearlings contained a significantly higher proportion of dicots (especially shrubs) than those of adult females, and those of juveniles a higher ratio of Salix leaves to stems than those of adults. Adult male feces contained a significantly greater proportion of sedges and rushes than those of adult females or calves, while the feces of adult females and calves contained significantly more sedges and rushes than those of yearlings. There was a seasonal decline in dicot consumption for all muskoxen except adult males. These age–sex differences in fecal composition were consistent with behavioural observations of time allocated to foraging in dicot-dominated habitats and suggest that young muskoxen and adult females satisfied their particular nutritional requirements by specifically selecting dicot-dominated habitats within the areas occupied by mixed age–sex herds.
In vivo pharmacology of spleen contraction in rainbow trout
Authors: Pearson Mike , Kraak Glen Van Der , Stevens E. Don
Published: July 2008

Rainbow trout, Oncorhynchus mykiss, were injected with an adrenergic agonist, an adrenergic antagonist, or a cholinergic antagonist, via a dorsal aorta cannula. Spleen size and haemoglobin content were measured at rest and, for antagonists, following an air exposure stress. Injection of phentolamine (an α-antagonist) blocked the spleen contraction induced by air exposure, suggesting that control is mediated by α-adrenergic receptors. Air exposure effects were unaffected by β-adrenergic blockade or muscarinic cholinergic blockade.
Patterns of nest site, territory, and mate switching in black-billed magpies (Pica pica)
Authors: Dhindsa Manjit S. , Boag David A.
Published: July 2008

A colour-marked population of black-billed magpies (Pica pica) was studied in Edmonton, Alberta, from 1982 to 1988. Between years, magpies changed nest sites within their territories significantly more often than they remained in the same site. Both sexes showed equally strong territory fidelity, with 72% of the males and 70% of the females nesting within their territories of the previous year. Breeding success in the previous year did not determine whether magpies switched nest sites within territories or changed territories, or how far they moved between years. In 1 year (1987), breeding failure (during a snowstorm) influenced the switching of neither nest sites nor territories. Although there was remarkable mate fidelity in some pairs (paired for 5–7 years), other magpies changed mates up to three times over the 7 years of the study. Both sexes showed a similar tendency to switch mates; 50% of the males and 63% of the females changed mates at least once in 7 years. Mate switching was independent of reproductive success in the previous year. There was a positive association between mate fidelity and territory fidelity in males: males that changed territories were also likely to change mates. These results are compared with those from other studies of black-billed magpies and discussed in the context of life-history strategies.
Unique biological characteristics of spring-spawning herring (Clupea harengus L.) in Minas Basin, Nova Scotia, a tidally dynamic environment
Authors: Bradford Rodney G. , Iles T. Derrick
Published: July 2008

The unusual occurrence of a spring-spawning (May–June) Atlantic herring population in a tidally dynamic environment (Minas Basin, Nova Scotia) is investigated. Adult growth and reproductive characters are similar to those of a geographically adjacent population that also spawns in a tidally energetic environment but during autumn (August–October), rather than to those of another May- to June-spawning population that reproduces in an environment with low tidal energy. Minas Basin herring are shown to feed intensively during gonad maturation up to and including spawning. This has not been previously documented for Atlantic herring. Condition factor analysis shows that somatic tissues lose weight during gonad maturation in spite of the feeding behaviour. It is concluded that the high fecundity of Minas Basin herring is accomplished by increased gonad production. This suggests that high fecundity is prerequisite to life-cycle closure in highly dispersive environments. Analysis of parasitic larval nematode infection suggests Minas Basin herring are distributed with other herring populations from the Bay of Fundy region that aggregate along the southwestern edge of the Scotian shelf during summer to feed.
Natal dispersal in Columbian ground squirrels: is body mass the proximate stimulus?
Authors: Wiggett Darwin R. , Boag David A.
Published: July 2008

Data on body mass and dispersal history of Columbian ground squirrels (Spermophilus columbianus) were collected at five colonies in southwestern Alberta. Two colonies were studied from 1983 to 1990 and three from 1984 to 1986. Body mass of yearling male dispersers did not differ significantly from that of nondispersers. Among dispersers, heavier animals did not disperse before lighter ones. Extremely small animals, however, may delay dispersal until they are 2 years old. Timing of dispersal was not apparently related to body mass; dispersing squirrels showed a wide range in body mass, with dispersal occurring synchronously at all colonies in all years despite significant differences in body mass of yearlings between colonies. The apparent lack of evidence for a critical body mass threshold for dispersal led us to conclude that the timing of dispersal in yearling male Columbian ground squirrels is not controlled at the proximate level by achieving a set point in body mass.
Effects of acute temperature change, in vivo and in vitro, on the acid–base status of blood from yellowfin tuna (Thunnus albacares)
Authors: Brill Richard W. , Bushnell Peter G. , Jones David R. , Shimizu Manabu
Published: July 2008

In most fishes, blood acid–base regulation following a temperature change involves active adjustments of gill ion-exchange rates which take hours or days to complete. Previous studies have shown that isolated blood from skipjack tuna, Katsuwonus pelamis, and albacore, Thunnus alalunga, had rates of pH change with temperature (in the open system) equivalent to those necessary to retain net protein charge in vivo (≈ −0.016 ΔpH∙ °C−1). It was postulated that this is due to protons leaving the hemoglobin combining with plasma bicarbonate [Formula: see text], which is removed as gaseous CO2, and that this ability evolved so that tunas need not adjust gill ion-exchange rates to regulate blood pH appropriately following ambient temperature changes. We reexamined this phenomenon using blood and separated plasma from yellowfin tuna, Thunnus albacares. Unlike previous studies, our CO2 levels (0.5 and 1.5% CO2) span those seen in yellowfin tuna arterial and venous blood. Various bicarbonate concentrations [Formula: see text] were obtained by collecting blood from fully rested as well as vigorously exercised fish. We use our in vitro data to calculate basic physiochemical parameters for yellowfin tuna blood: nonbicarbonate buffering (β), the apparent first dissociation constant of carbonic acid (pKapp), and CO2 solubility (αCO2). We also determined the effects of acute temperature change on arterial pH, [Formula: see text], and partial pressures of O2 and CO2in vivo. The pH shift of yellowfin tuna blood subjected to a closed-system temperature change did not differ from previous studies of other teleosts (≈ −0.016 ΔpH∙ °C−1). The pH shift in blood subjected to open-system temperature change was Pco2 dependent and lower than that in skipjack tuna or albacore blood in vitro, but identical with that seen in yellowfin tuna blood in vivo. However, pH adjustments in vivo were caused by changes in both [Formula: see text] and Pco2. The exact mechanisms responsible for these changes remain to be elucidated.
Variations in growth and mortality of juveniles of the phyllodocid Eteone longa (Fabricius) on a tidal flat
Authors: Olivier Marc , Desrosiers Gaston , Vincent Bruno
Published: July 2008

We sampled the Anse à l'Orignal tidal flat (in the lower St. Lawrence estuary) weekly during 1986 to follow variations in the density, growth, and mortality of recruits of the polychaete Eteone longa (Fabricius) in three zones characterized by different sediment types. Reproduction began in early April and continued for approximately 30 days. The presence of a postlarval stage could explain the length of the reproductive period at the three study sites. The development of individuals in their natural habitat from the nectochaete stage (6 segments) to the 70-segment stage was also followed. Recruit dispersion appeared to occur in a random fashion at the higher levels of the tidal zone, if not at all levels. However, the results failed to reveal any sediment preferences by E. longa recruits. Individual growth rates were similar in all sediment types. Survival curves were concave (type IV) and showed a high mortality for the younger stages. Life expectancy increased with the age of the recruit. These types of curves are commonly observed for species with high fecundity, such as E. longa.
Sexual dimorphism in mass and protein content of the forelimb muscles of the northern leopard frog, Rana pipiens
Authors: Yekta Naushaba , Blackburn Daniel G.
Published: July 2008

In certain frogs and toads, forelimb muscles that are used by the male to clasp the female during mating differ structurally and functionally between the two sexes. Sexual dimorphism in musculature of the northern leopard frog, Rana pipiens, was quantified with respect to wet mass, lyophilized dry mass, and total protein content of the major muscles of the adult forelimb. Of the 19 muscles studied, most were significantly heavier in males than in females in terms of dry mass (13 muscles) and wet mass (14 muscles), although females were larger in body mass and snout–vent length. Muscles exhibited a gradient of sexual dimorphism; mean dry mass of dimorphic muscles in females ranged from 8.8 to 90.9% of the mean mass of corresponding male muscles. The most dimorphic muscles were those that adduct the forearm, flex the elbow, flex the wrist, and abduct the first digit. Muscles that were sexually dimorphic in dry mass differed significantly between the sexes in total protein content but not in protein concentration or water content.
Territorial behavior and breeding frequency of male Weddell seals (Leptonychotes weddelli) in relation to age, size, and concentrations of serum testosterone and cortisol
Authors: Bartsh Sherie S. , Johnston Shirley D. , Siniff Donald B.
Published: July 2008

The onset of sexual maturity and changes in weight and serum testosterone and cortisol concentrations were studied in male Weddell seals during October–December, 1986, at a breeding colony in McMurdo Sound, Antarctica. Ages were estimated from length or known from tagging history. Underwater copulatory and territorial activities were monitored by colored grease transfer and radiotelemetry, respectively. Hormone concentrations were measured by radioimmunoassay. Of 37 male seals visiting the colony, 22 were resident for ~5 weeks. About one-third of the male residents defended territories into estrus and were called territorial (T). Another one-third appeared unsuccessful at defending a territory and were called transitional (TN). The remaining one-third were nonterritorial (N). Males were closely matched in size (coefficient of variation ≤ 15% for length, girth, and weight). Most N males were 5–7 years old. T males (≥ 7 years old), being older (P < 0.05) than N males, attained 19 of 20 observed copulations. T males were heavier initially (P < 0.10) than TN or N males, and they lost more weight during the breeding season (P = 0.08, 3.2 vs. 2.1 kg/day) than N males. In all males, serum testosterone and cortisol concentrations declined, approaching nadir as estrus and the breeding season ended. Mean (±SE) daily concentrations ranged from 6.8 ± 2.4 ng/mL to nondetectable concentrations for testosterone and from 104.8 ± 13.2 to 54.7 ± 4.5 μg/dL for cortisol. Concentrations of both hormones were higher in T males than in N males. Hormone profiles of TN males initially resembled those of T males, but at estrus resembled those of N males. Coincident with a change in competitive behavior was a transient rise in cortisol accompanied by a drop in testosterone.
Survival of dispersing spruce grouse
Authors: Beaudette P. Daniel , Keppie Daniel M.
Published: July 2008

Survival of dispersing spruce grouse equipped with radio transmitters was studied in central Ontario during autumn 1986 and 1987. Ninety-two percent of females and 74% of males dispersed from brood range. Females dispersed farther than males in only 1 year. Birds that dispersed did not exhibit lower survival than birds that did not disperse. There were no meaningful differences in survival between birds that dispersed and birds prior to dispersal, between short- and long-distance dispersers, or between sexes. Dispersal did not appear to contribute unduly to mortality.
Localisation du réflexe lucifuge dans les ganglions cérébroïdes dorsaux de la némerte marine, Lineus ruber (O. F. Müller): étude expérimentale
Authors: Vernet G.
Published: July 2008

The anterior part of Lineus ruber contains four successive "segments", an antecerebral segment, a second segment containing the cerebral ganglia, a third segment containing the cerebral organs, and lastly a preoesophageal segment. An experimental study involving microsurgical removal followed or not by grafts of different segments has shown that the negative phototaxis of this marine nemertean has its origins in the dorsal cerebral ganglia, in the photoreceptive structure that we have described.
Détermination de la période d'accouplement des orignales par la mise en évidence de spermatozoïdes dans le tractus génital
Authors: Claveau Robert , Courtois Réhaume
Published: July 2008

The presence of sperms in smears from the vaginal and uterine mucosae was examined to time the mating period in a population of moose (Alces alces) from Eastern Quebec. The highest frequency of smears with sperms occurred between October 5 and October 15 for the 1974–1982 period under study. First matings were observed during the last week of September, but a high proportion of positive smears still prevailed at the end of the hunting season (October 18). Hunting statistical figures show two peaks of vulnerability, one around September 25, the other around October 13. Data from the smears show that mating does not occur during the first peak of vulnerability, which corresponds rather to partner searching in animals that will mate only a few days later. Young females (1.5–2.5 years old) seem to mate about 1 week later than older females. The smear technique has proven easy to use, it is not cumbersome, and it allows direct recognition of the mating period when sampling overlaps the rut season.[Journal translation]
Juvenile male magpies dominate adults irrespective of size differences
Authors: Komers Petr E. , Komers Eva J.
Published: July 2008

For 55 captive male black-billed magpies, 11 morphological measurements and overall body size, as determined by principal-components analysis, were investigated for correlations with dominance ranks. Neither overall body size nor any of the single measurements was correlated with dominance rank among adults, but four measurements (bill length, tarsus, foot, and weight) were weakly correlated with dominance among juveniles. We suggest that these traits represent weaponry and could be important in contest situations among juveniles. Dyads containing one adult and one juvenile male were investigated for relationships between age, size, and dominance status. Because adults had longer bills than juveniles, one would expect that adults in such comparisons would dominate juveniles. This was not the case: juveniles dominated adults irrespective of differences in bill length or weight. We discuss the possibility that psychological factors such as familiarity with the environment may override morphological asymmetries among male black-billed magpies.
Inbreeding effects among inbred and outbred laboratory colonies of Peromyscus maniculatus
Authors: Ribble David O. , Millar John S.
Published: July 2008

We examined the effects of sibling matings upon reproductive performance among inbred and outbred laboratory colonies of Peromyscus maniculatus. The inbred colony was founded by 12 females collected from one locality in Alberta and bred for 20 generations, with 35–45 pairs each generation. The outbred colony consisted of first-generation mice born of wild-caught females from diverse areas in Alberta. Consistent with theoretical expectations, there were no differences in reproductive performance between sibling and control (outbred) pairs within the inbred colony of mice. In contrast, sibling pairs had significantly fewer young per litter than control pairs within the outbred colony. Reproductive performance measures (proportion breeding, days from pairing to first litter, number of litters, and total number of offspring produced) were also significantly lower among sibling pairs from the outbred colony than among sibling pairs from the inbred colony. Lastly, we predicted that reproductive performance of the control pairs from the outbred colony would be less than that of control pairs from the inbred colony, due to outbreeding depression. Contrary to our predictions, average litter survival rates were greatest among the outbred colony control pairs. We suggest that the benefits of inbreeding or outbreeding extend broadly across the inbreeding–outbreeding continuum in natural populations of northern Peromyscus.
Ultrastructural observations on an icosahedral cytoplasmic virus in leukocytes of frogs from Algonquin Park, Ontario
Authors: Desser Sherwin S.
Published: July 2008

An icosahedral virus was observed in mononuclear leukocytes and heterophils of a mink frog (Rana septentrionalis) and a green frog (Rana clamitans). Infected cells were grossly distorted, often containing a prominent juxtanuclear viroplasm in which nucleocapsids in various stages of assembly occurred. Viral particles were also observed occasionally within the nucleus of some cells. Mature nucleocapsids were usually hexagonal in profile, measuring about 131 ± 9.2 nm in diameter (n = 10) and were arranged in paracrystalline arrays. Individual viral particles were observed at the periphery of infected cells apparently budding from the plasma membrane. These observations extend both the geographic and host ranges of frog leukocytic virus which could serve as a useful model, not only for the study of viral function, but also for its effect on the immune system of the anuran host.
Fostering behaviour and milk stealing in Antarctic fur seals
Authors: Lunn N. J.
Published: July 2008

During the lactation period, female otariid seals alternate trips at sea to feed with visits ashore to nurse their pups. A female returning ashore must be able to recognize her own pup, and it is generally agreed that this is facilitated by auditory and olfactory cues. Instances of fostering behaviour (females nursing nonfilial pups) and milk stealing are reportedly rare among the otariids. In the austral summer of 1989, I observed eight and two instances of fostering behaviour and milk stealing, respectively, by Antarctic fur seals at Bird Island, South Georgia. The following summer, 26 cases of fostering behaviour and 71 cases of milk stealing were documented. In 1990, females appeared to have difficulty acquiring sufficient resources to feed their pups, so nutritional stress was probably responsible for the increase in milk stealing. The occurrence of fostering behaviour suggests that mothers were unable to recognize their own pups, although in the above cases the cause was not clear; neither human disturbance nor density appeared to be the primary factor. Maternal experience may have been a factor in 1990, as 10 of 14 females fostering pups were 5 years of age or less and had given birth to either their first or second pup.
Ultrastructure of autotomy-induced atrophy of muscles in the crab Carcinus maenas
Authors: Schmiege Donna L. , Ridgway Richard L. , Moffett Stacia B.
Published: July 2008

In Carcinus maenas and other decapod crustaceans, limb autotomy results in pronounced atrophy of coxal and thoracic muscles located proximal to the fracture plane. These muscles were not denervated or otherwise injured by autotomy. The atrophic changes are reversed after the subsequent molt, when a regenerated limb becomes functional. In this study, we examined the ultrastructure of the coxal head of the anterior levator (ALc) muscle from the fifth pereiopod of intermolt crabs (control ALc) and from crabs bearing a limb bud (autotomized and contralateral ALc). Control muscles exhibit small regions of myofilament erosion that may be the result of normal turnover of structural elements. Characteristic features of autotomy-induced atrophy are (i) decrease in fiber area, (ii) increase in interfibrillar space, (iii) extensive myofilament erosion, (iv) loss of organelles, (v) disruption of sarcomere organization, and (vi) degeneration of neural and vascular tissues. Similar changes occur to a lesser degree in the contralateral ALc, where they may be characteristic of muscle in the premolt condition. We propose that the atrophic changes in muscles proximal to a limb bud are superimposed on generalized premolt catabolism of muscle protein, the rate of which is elevated in crabs regenerating limbs.
The distribution of dragonfly nymphs across a pH gradient in south-central Ontario lakes
Authors: Pollard J. Bruce , Berrill Michael
Published: July 2008

Exuviae of 37 species of dragonflies were collected from the emergent vegetation of 19 small (<35 ha) lakes across a pH gradient (range 4.9–8.1) in south-central Ontario to assess the effect of low environmental pH on species richness and diversity. The number of species present in a lake was not significantly correlated with lake pH. Two measures of diversity (Keefe and Bergersen's TU and McIntosh's M) indicate an increase in species diversity with decreasing lake pH. Species shifts in the communities were also correlated with lake pH: five species were apparently excluded from lakes with a midsummer epilimnetic pH below 5.8, and seven species were apparently restricted to lakes with a pH of less than 6.2.
Segregation of resident trout in streams as predicted by three habitat dimensions
Authors: Bozek Michael A. , Hubert Wayne A.
Published: July 2008

We assessed the relation of three measures of habitat to the distribution of four species of Salmonidae, cutthroat trout (Oncorhynchus clarki), brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), and rainbow trout (Oncorhynchus mykiss), in streams of the central Rocky Mountains. We examined whether single measures of three habitat dimensions (climate, stream energy, and stream size) could account for current distribution patterns of four resident trout species in Wyoming. The three habitat dimensions were represented by three habitat variables: elevation, channel gradient, and wetted stream width. Considerable overlap in the ranges of elevation, gradient, and wetted width was observed among reaches where the four species were found, but differences in the mean values of these habitat features were observed among species. Using discriminant analysis, we categorized the presence and absence of individual species in stream reaches by the three habitat variables. We successfully predicted the presence of brook trout (87%), cutthroat trout (59%), brown trout (50%), and rainbow trout (39%) in streams, but the absence of each species was predicted more successfully (rainbow trout (94%), brown trout (94%), cutthroat trout (90%), and brook trout (57%)). The three habitat features were useful in describing the segregation of trout species in streams of the central Rocky Mountains.
Prevalence of lead exposure among age and sex cohorts of Canada geese
Authors: DeStefano Stephen , Brand Christopher J. , Rusch Donald H.
Published: July 2008

We examined the prevalence of lead exposure from ingestion of waste lead shot among age and sex cohorts of Canada geese (Branta canadensis) on the breeding, migration, and wintering grounds of the Eastern Prairie Population. Blood samples from 6963 geese were assayed for lead concentration by atomic absorption spectrophotometry. On the breeding grounds, no goslings and <1% of adults showed evidence of recent exposure to lead shot (i.e., concentrations in the blood elevated above the threshold value of 0.18 ppm lead). However, median background blood lead concentrations (i.e., blood samples with < 0.18 ppm lead) were higher in adults than goslings, indicating that exposure of adults to lead had occurred during previous seasons. Waste lead shot was available on the migration and wintering grounds, where a larger proportion of the blood samples from immatures (< 1 year old) than adults (> 1 year old) had lead concentrations ≥ 0.18 ppm. Median background lead levels remained higher in adults than in immatures throughout fall and winter. We also found that more immature males than immature females had elevated lead concentrations. Higher rates of intake of food and grit (including shot) probably partially account for the higher prevalence of elevated lead concentrations in immature Canada geese.
Effects of temperature on the oncospheres of the cestode Microsomacanthus hopkinsi and its implication for their over-winter survival
Authors: Lee John , Pilgrim Wilfred , McLaughlin J. D. , Burt M. D. B.
Published: July 2008

In an attempt to determine whether hymenolepidid oncospheres may overwinter and contribute to the pool of cysticercoids in the intermediate host population the following spring, we studied the survival of the oncospheres of the cestode Microsomacanthus hopkinsi following storage at 7 and 20 °C, following short-term freezing under laboratory conditions, and after overwintering (October–May) under natural conditions at depths of 0.5, 1, and 1.5 m in a local lake. Viability was tested by feeding the oncospheres to laboratory-reared amphipods (Hyalella azteca). The percentage of surviving amphipods that became infected following exposure to oncospheres stored at 7 °C declined steadily from 96% following 4 weeks storage to 43% after 24 weeks. Only 3% (2 of 60) were infected following exposure to oncospheres stored for 28 weeks. Oncospheres held overwinter under natural conditions failed to produce infections. These were slightly older (29 weeks) than the oldest oncospheres maintained at 7 °C in the laboratory, at the time of feeding to the amphipods. It appears that 28 weeks approaches the maximum survival time for the oncospheres of this species. Oncospheres subjected to short-term freezing also failed to produce infections when fed to amphipods. Oncospheres survived in sufficient numbers for up to 24 weeks to be of potential significance in the formation of infective pools in amphipods in the spring. However, there is a northern limit beyond which the inactive period of the amphipod host is too long for the oncospheres to bridge. Under these circumstances, they are of no consequence in the formation of the infective pool. Only 5% (3 of 60) of the amphipods exposed to oncospheres stored at 20 °C for 4 weeks became infected. Foci established in warmer conditions, as expected, are infective for much shorter periods.
Parental care as a constraint on male mating success in fishes: a comparative study of threespine and white sticklebacks
Authors: Jamieson I. G. , Blouw D. M. , Colgan P. W.
Published: July 2008

To investigate constraints imposed by male parental behavior on male mating success we compared mate competition in two related 'species' of stickleback, one showing parental care (threespine stickleback, Gasterosteus aculeatus), the other not (white stickleback, Gasterosteus sp.). Three males of each species (tested separately) competed for spawnings with gravid females over a 10-day period. Our findings showed that once a threespine male acquires its first clutch of eggs, the chances of it spawning successively over the next 4 days increase, after which courtship activity declines and parental care of eggs increases. This leads to a serial pattern of spawning amongst the three males in which the second male spawns successively in its nest after the first male has completed its spawnings, followed by the third male, if it spawns at all. However, the third male is more likely to steal fertilizations in the nests of the other two males; stolen fertilizations represented an estimated 29% of the spawning frequency of the third male, compared with 5 and 0% for the second and first males, respectively. The order in which threespine males spawned was correlated with the order in which they initiated nest construction and their ability to defend and maintain a nest site. Immediately after spawning, white stickleback males disperse their eggs among clumps of filamentous algae, where the eggs develop without further parental assistance. In contrast to threespines, white sticklebacks tested under the same competitive conditions showed a random pattern of spawning amongst the three males and stolen fertilizations were not observed. This difference in spawning pattern presumably reflects the time constraint imposed on the sexual phase by the imminent need for parental care once a threespine male obtains eggs. Without the need for parental care of eggs, white males that spawn are not under the same time constraints and therefore each successive spawning is of equal value among competing males, resulting in a random pattern of spawning. In contrast, an asymmetry exists in threespines in which males with freshly spawned eggs in their nest increase their courtship intensity relative to males without eggs, resulting in a serial or ordered pattern of spawning among the males. It is further suggested that stolen fertilizations may be a secondary adaptation to offset any inability to compete effectively for nest sites and females during the initial part of the breeding period.
Sneak spawning and egg stealing by male threespine sticklebacks
Authors: Jamieson I. G. , Colgan P. W.
Published: July 2008

Nest-raiding behavior by breeding male threespine sticklebacks was examined in a laboratory study to determine the contexts in which spawnings and egg stealing occur, and the effect, if any, of egg stealing on the mating success of the egg stealer. Of three males competing for mates at any one time, those that were last to complete construction of their nest and, subsequently, last to spawn in their own nest, raided most frequently. It was found that raids are initiated primarily during spawning by neighboring males and the majority of incidents of egg stealing are preceded by sneak spawnings. In many cases males steal eggs that they themselves potentially fertilized. However, the stolen eggs do not increase the chances of a male attracting a female to his nest to spawn. Stealing eggs may affect mating success in an open population, but under the conditions of the present experiment the adaptive significance of egg stealing remains unclear.
Seasonal patterns of weight, hematology, and serum characteristics of free-ranging female white-tailed deer in Minnesota
Authors: DelGiudice Glenn D. , Mech L. David , Kunkel Kyran E. , Gese Eric M. , Seal Ulysses S.
Published: July 2008

Weights, hematology, and serum profiles of white-tailed does in the central Superior National Forest of northeastern Minnesota were examined year-around to determine seasonal patterns of nutritional condition and metabolism. Deer were initially captured by Clover trap or rocket net. Between 15 February 1989 and 23 January 1990, we recaptured 12 adult (> 1.5 years) female deer 1–9 times each (a total of 59 recaptures) using a radio-controlled capture collar. Monthly weights of deer exhibited a cyclic seasonal pattern. Mean weight declined 22% from February to an annual minimum during May, then steadily increased 45% to a maximum in October. Seasonal patterns were most evident for hemoglobin concentration, red blood cells, packed cell volume, serum total protein, urea nitrogen, creatinine, the urea N to creatinine ratio, triiodothyronine, cortisol, and potassium. Wide seasonal variations of these characteristics were indicative of shifts in the deer's metabolic physiology. Although seasonal metabolic shifts are partially attributable to an endogenous rhythm, the intensity of their expression was most likely affected by nutritional changes and concomitant alterations of body condition. Annual changes in seasonal trends of blood characteristics may be useful in investigating nutritional effects of specific environmental and demographic factors. We compare our findings with those reported for deer on ranges farther south.
Comparative diets of sympatric nesting raptors in the eastern deciduous forest biome
Authors: Bosakowski Thomas , Smith Dwight G.
Published: July 2008

Diets and food-niche metrics of nesting raptors were studied in the eastern deciduous forest biome of northern New Jersey, southeastern New York, and northwestern Connecticut. Raptor diets were determined from 2506 prey individuals recovered from prey remains and pellets collected from nest sites of a community consisting of five hawk and four owl species. Food-niche overlaps were higher on average in the hawk guild (0.422) than in the owl guild (0.342), correlating with increased species packing and decreased body size differences in the hawk guild. Differences in activity times (diurnal versus nocturnal) did not result in reduced food-niche overlap between diurnal and nocturnal raptors. The lack of interference-type competition probably allowed greater exploitative-type competition but was offset by nearly exclusive use of certain prey types by several raptor species. Thus, temporal niche differences ultimately did aid in the resource partitioning of food between hawks and owls. Overall, the forest raptor community displayed significant food-niche overdispersion, with 35 of 36 food-niche overlap values below the 0.6 "competition" threshold. This result would be expected in a community structured by competition.
Comparisons of body size, field energetics, and water flux among populations of the skink Chalcides sexlineatus
Authors: Brown R. P. , Thorpe R. S. , Speakman J. R.
Published: July 2008

Within-island microgeographic variation in body size of the Gran Canarian skink, Chalcides sexlineatus, is described. Clear latitudinal patterns of variation were found for both males and females. Using Mantel tests we rejected within-island altitude-related ecological variation as the cause of the geographic variation, but found a significant relationship between body size and the pattern of lush–arid variation. Larger body size was found in populations from the lusher northern areas, and small body size in populations from the arid south. Studies with doubly labelled water showed higher energy expenditure per animal in a studied northern population than in a southern population, due to larger body size in the former. Mean mass-specific energy expenditure was found to be low in this species compared with other lizards, and did not differ significantly between populations (north, 150.1 J∙g−0.80∙d−1; south, 124.7 J∙g−0.80∙d−1). Mean mass-specific water fluxes were similar for lizards at both study sites (14.79 and 14.20 mL H2O∙kg−0.91∙d−1, respectively). Previous explanations invoking differences in water stress as the cause of variation in body size among populations of arid-zone lizards do not appear to be applicable to C. sexlineatus.
The Simuliidae (Diptera) of Sri Lanka. Descriptions of additional species of Simulium (Simulium), with a key for Sri Lankan species in the subgenus and a checklist for the country
Authors: Davies D. M. , Györkös H.
Published: July 2008

This is the fifth and final paper in a series treating the Simuliidae of Sri Lanka, and it contains a checklist of the species in the country. In this paper are described three new species of Simulium (Simulium): all stages of Simulium subpalmatum and Simulium cruszi (except the larva) and the male and pupa of Simulium paranubis. The female, male, and pupa of Simulium (Simulium) consimile and S. (S.) striatum are redescribed and the larva of S. (S.) consimile is described for the first time. Taxonomic comparisons are made with related species and keys are provided to separate the eight Sri Lankan species in the subgenus.
Similarity analysis of hydroid assemblages along a latitudinal gradient in the western North Atlantic
Authors: Calder Dale R.
Published: July 2008

Shallow-water (0–100 m depth) hydroid faunas reported from 26 locations along the western North Atlantic coast between the high Canadian Arctic archipelago and the Caribbean Sea were compared. Species numbers varied widely between locations, but were highest in the tropics and subtropics, lowest in arctic and subarctic waters, and intermediate in mid-latitudes. Percentages of species producing free medusae were lowest in high latitudes, intermediate in low latitudes, and highest in mid-latitudes (especially in estuaries). In a numerical analysis, similar hydroid faunas were identified at locations (i) between the high Canadian Arctic islands and the Strait of Belle Isle off western Newfoundland; (ii) between the Gulf of St. Lawrence and Chesapeake Bay; (iii) between North Carolina and southeastern Florida (south as far as St. Lucie Inlet), and including the northern Gulf of Mexico; (iv) in the Caribbean Sea, together with Dry Tortugas and the oceanic island of Bermuda. The greatest change in hydroid species composition along the coast appeared to occur around Cape Hatteras. An assemblage on the continental shelf off the middle Atlantic states of the United States appeared to be distinct because of its low hydroid diversity. Faunistically, however, its affinities were decidedly with assemblages at locations between the Gulf of St. Lawrence and Chesapeake Bay. In addition to latitudinal changes in faunal composition, dissimilarities in hydroid species assemblages were noted between certain inshore and offshore locations at comparable latitudes. Numerical classification of locations provides additional evidence for delineation of biogeographic regions along the western North Atlantic coast.
Architectural plasticity in net construction by individual caddisfly larvae (Trichoptera: Hydropsychidae)
Authors: Loudon Catherine , Alstad Donald N.
Published: July 2008

Multiple nets spun in different water velocities were collected from individual hydropsychid caddisfly larvae (Hydropsyche and Cheumatopsyche) in a flow tank. Mesh size (coarseness) decreased and the total area of the regular meshes of the net increased with increasing ambient velocity for nets spun by individual Hydropsyche larvae but not for those spun by individual Cheumatopsyche larvae in the range of velocities used (0.05–0.45 m/s). The functional significance of these observed structural changes for both particle capture rate and silk stress was evaluated theoretically on the basis of mechanical principles. The structural changes seen in faster water are predicted to increase the particle capture rate by about 75% and the stress in the silk of the net by about 25%. These increases due to structural changes are small compared with the predicted 25-fold increases in particle capture rate and stress due solely to experiencing faster water. The changes in construction do suggest that a greater investment of silk and spinning time is made by larvae in faster water, and this is also demonstrated by the greater proportion of nets that were spun in faster water.
Differential use of bank burrows and lodges by muskrats, Ondatra zibethicus, in a northern marsh environment
Authors: Messier François , Virgl John A.
Published: July 2008

We studied the differential use of lodges and burrows by muskrats in a large (293 ha) northern marsh, during a period characterized by a 100-fold variation in apparent density. Population size (as indexed by dwelling numbers), summer heat stress, rate of collapse of lodges, and over-winter occupancy of lodges and burrows were investigated as potential determinants of dwelling selection. Muskrats selected against lodges at low population size, even when water level was experimentally controlled within a normal range. Sun-exposed lodges in summer were not subject to extreme internal temperatures capable of impairing the survival of young muskrats confined to nests. Lodges were dynamic structures that required substantial and continual upgrade during the ice-free season. Lodges also had a lower probability of remaining active through the winter compared with burrows, possibly because of the freezing of surroundings. We suggest that higher maintenance cost and greater vulnerability to predators likely constitute two critical determinants for muskrat selection against lodges at low population size.
Cardiac physiology in tunas. I. In vitro perfused heart preparations from yellowfin and skipjack tunas
Authors: Farrell A. P. , Davie P. S. , Franklin C. E. , Johansen J. A. , Brill R. W.
Published: July 2008

An in situ heart preparation perfused with oxygenated saline was used to examine cardiac performance at 25 °C in yellowfin tuna (Thunnus albacares) and skipjack tuna (Katsuwonus pelamis). Heart rates (91–172 bpm in skipjack tuna and 101–157 bpm in yellowfin tuna) were comparable to those measured in vivo, and physiological stroke volumes were possible in yellowfin tuna with subambient filling pressures. In yellowfin tuna, maximum stroke volume and cardiac output were similar to the values obtained in vivo with spinally blocked animals; mean output pressures (up to 145 cmH2O, 1 cmH2O = 0.098 kPa) could exceed in vivo values without a major decrease in the resting cardiac output (homeometric regulation). In contrast, saline-perfused skipjack tuna hearts could not develop physiological output pressures without compromising cardiac output, with cardiac output being only 63% of the in vivo value at an output pressure near the in vivo ventral aortic pressure. The poor performance of the skipjack tuna heart is attributed to limited oxygen diffusion through the thicker walled ventricle. We conclude that the tuna heart is more dependent on its coronary circulation for normal function than the hearts of other fishes examined thus far. The coronary circulation was perfused with saline at various flow rates in isolated hearts from skipjack tuna to develop a pressure–flow relationship for the intact circulation. Coronary resistance reached a minimum of 24 cmH2O∙min∙g ventricular mass/mL at a flow rate of 2 mL/(min∙g ventricular mass) with perfusion pressure about 40 cmH2O. In vivo coronary blood flow was estimated from the pressure–flow relationship as 0.67 mL/(min∙g ventricular mass). Injections of adrenaline, noradrenaline, and phenylephrine into coronary circulation under constant flow conditions increased perfusion pressure, indicating the possibility of α-adrenergic vasoconstriction.