bluuebunny/crossref_metadata_2025 huggingface dataset:
Source and distribution of factors in locust nervous system which stimulate rectal Cl− transport
Authors: Proux J. , Proux B. , Phillips J.
Published: March 2009

Corpus cardiacum (CC) of locusts contains a potent stimulant of rectal Cl transport, i.e., chloride transport stimulating hormone (CTSH). Extracts of other locust tissues which contain neuroendocrine cells were assayed for their ability to stimulate Cl-dependent, short-circuit current (Isc) across recta mounted in Ussing chambers. Dose–response curves indicated that only brain (particularly the pars intercerebralis, PI) contained substantial stimulatory activity, but this was still at very low concentrations compared with CTSH activity in CC. Destruction of either the PI or the nerve tract from PI to CC (i.e., NCC I) reduced CTSH levels in the CC. In contrast, destruction of lateral neurosecretory cells (NSCs) of the brain had no effect. The results suggest that CTSH is synthesized in NSCs of the PI and is transported down NCC I to the CC where it may mature to a more active form.
Hematological characteristics of grizzly bears (Ursus arctos) in central and northeastern Alaska
Authors: Brannon Robert D.
Published: March 2009

Eighty-five grizzly bears (Ursus arctos) were captured during 1981 and 1982 in the Alaska Range and in the Arctic National Wildlife Refuge, located in the Brooks Range, Alaska. Blood samples from these bears were examined for erythrocyte count, leukocyte count, hemoglobin, hematocrit, and erythrocyte indices. Erythrocyte count, hemoglobin, hematocrit, and mean corpuscular volume were significantly higher in the first of two samples collected 1 h apart. This difference suggsts a response to stress during the capture by splenic contraction to provide an increased oxygen supply to oxygen depleted muscle tissues, followed by splenic relaxation and decreased blood pressure with expansion of blood plasma volume. Leukocyte count was significantly higher in the second sample. This difference was probably a result of neutrophilia caused by tissue damage from darting and the removal of muscle tissue samples. Alaska Range bears exhibited higher values for all characteristics except mean corpuscular volume and mean corpuscular hemoglobin, indicating that these bears were more stressed by their capture than bears in the Arctic National Wildlife Refuge.
Corpus cardiacum stimulated trehalose efflux from cockroach (Periplaneta americana) fat body: control by calcium
Authors: Steele J. E. , Paul T.
Published: March 2009

Cockroach fat body incubated in a simple physiological saline solution releases trehalose to the surrounding medium. The output of trehalose occurs in the absence of ambient Ca2+ and decreases slowly with time. In two separate experiments, 0.1 mM CaCl2 added to the saline increased the output of trehalose on average by 70% but higher concentrations of Ca2+ did not further increase the efflux of trehalose. Stimulation of trehalose efflux by corpus cardiacum extract is absolutely dependent on extracellular Ca2+, no increase occurring beyond the basal level in the absence of the ion. The activity of corpus cardiacum extract increases as the concentration of CaCl2 is increased to 0.5 mM. This concentration of Ca2+ in the saline permits the extract to increase trehalose efflux by as much as 60% above the basal level. Corpus cardiacum extract, as well as the hypertrehalocaemic agents cyclic AMP and theophylline, increase significantly the influx of Ca2+ into fat body in vitro. The basal efflux of trehalose from fat body and that stimulated by corpus cardiacum extract is not dependent on extracellular Mg2+.
Seasonal and daily activity patterns in a Canadian population of the prairie rattlesnake, Crotalus viridus viridis
Authors: Gannon V. P. J. , Secoy D. M.
Published: March 2009

The seasonal and daily activity patterns of a Saskatchewan population of Crotalus viridus viridis is presented. Snakes emerged from hibernation in late April and migrated into the surrounding river valley and upland regions in early May. Adult migration preceded that of immature age-classes. Several gravid females occupied a rookery near the hibernaculum during the summer months and remained there until parturition. Females did not occupy this site in successive years and may have a biennial or greater reproductive cycle. Snakes returned to the hibernaculum in early September and remained active until early October. The behaviour of snakes in a field enclosure in response to time of day and body temperature (Tb) was recorded during the spring, summer, and fall. Significant differences in the Tb values of sunning, movement, and shading behaviours were noted. Gravid females were significantly more active in all seasons. However, no significant difference in mean Tb was found between males and females in the field, enclosure study, or laboratory thermal gradient. The observed greater level of activity may reflect the high energy demands of gravid females.
The role of dispersal in the population dynamics of snowshoe hares
Authors: Boutin Stan , Gilbert B. S. , Krebs Charles J. , Sinclair A. R. E. , Smith J. N. M.
Published: March 2009

We monitored dispersal of snowshoe hares (Lepus americanus) at Kluane Lake, Yukon, during a population increase, peak, and decline. Dispersal was measured by recording the number of immigrants to a removal grid and by tracking radiocollared individuals. The observed decline was not due to dispersal, as a maximum of 28% of all losses of radiocollared animals was due to dispersal. Dispersal rate (as measured by number of immigrants to the removal grid per individual on the control grid) was negatively correlated (−0.51, P < 0.01) with the rate of population increase. Highest dispersal rates occurred in the winters when hare populations were at peak and early decline densities. Dispersers at this time were lighter in weight than residents. We discuss our results in light of current hypotheses attempting to explain dispersal in cyclic small mammals and conclude that our results are consistent with the hypothesis that food shortage is responsible for increased rates of dispersal at peak population densities Comparison of dispersal, as monitored by radiotelemetry, versus immigration to a removal grid, suggests that removal grids overestimate dispersal, particularly at high densities when removal grids may attract animals because food supplies are relatively favorable there.
Ultrastructural effects of 3-trifluormethyl-4-nitrophenol on gills of the larval lamprey Petromyzon marinus
Authors: Mallatt Jon , Ridgway Richard L. , Paulsen Charles
Published: March 2009

Lamprey larvae (ammocoetes) are susceptible to 3-trifluormethyl-4-nitrophenol (TFM), a lampricidal toxicant which is administered through the ambient water. While this organic acid readily diffuses across gill cytomembranes, its actual mode of toxicity is uncertain. In this ultrastructural study, we examined the gills of larval Petromyzon marinus exposed to a nearly lethal dose (2.25 mg/L for 9 h, which is a median lethal concentration). Toxicant-associated damage was limited almost exclusively to a single gill epithelial cell type: presumed ion-uptake cells. These mitochondria-rich cells, which in normal ammocoete gills constitute the major portion of the respiratory surface, showed ultrastructural alterations ranging from abnormalities in microvilli and (or) cytoplasmic vacuolization to hypertrophy or even cytolysis. TFM-poisoned gills also differed from controls in having widened intercellular spaces within both respiratory lamellar epithelium and branchial interlamellar epithelium. Such intercellular spaces were particularly large in the vicinity of ion-uptake cells. These findings are consistent with a proposal that fish branchial ion-pumping cells function in extracting and extruding blood-borne organic acids, yet succumb to the damaging effects of such acids when intracellular concentrations exceed certain levels.
The ecology of a Mediterranean tortoise (Testudo hermanni): a declining population
Authors: Stubbs David , Swingland Ian R.
Published: March 2009

In France, wild tortoises occur at low densities (< 3/ha) in the mixed forest and maquis of the Massif des Maures. In an evergreen oak forest with scattered, traditional cultivations, distinct subpopulations still exist at relatively high density (> 10/ha). The population structure is heavily skewed in favour of old adults and recruitment is low. The population is declining due to habitat loss, both from fire and through the decline in traditional horticultural practices, leading to a reduction in nest site availability. The increase in nest density in the few suitable sites remaining leaves the eggs highly vulnerable to predation and losses of over 90% cannot be sustained. The active season is from March to November, but there is evidence of some activity during the hibernation period. Adult males maintain small, fixed home ranges, while females undertake distinct migrations to and from nesting sites in the spring and can switch to new home ranges. Juveniles are sedentary up to the age of 4 or 5 years, after which they may wander considerable distances in no particular direction, until the onset of sexual maturity. Sex ratio does not differ significantly from parity within any age cohort.
Individual feeding preferences in feral groups of rock doves
Authors: Giraldeau Luc-Alain , Lefebvre Louis
Published: March 2009

The crop contents of 57 urban rock doves (Columba livia) that died accidentally during a capture and tagging programme revealed a very strong degree of individual variation in feeding preferences. This demonstrates that gregarious foragers exploiting coarse-grained habitats do not always copy each other's food choices. The existence of such individual variability is a necessary condition for the establishment of skill pools in flocks of feral pigeons.
Distribution of aquatic gastropods across the Ordovician dolomite – Precambrian granite contact in southeastern Manitoba, Canada
Authors: Mckillop W. B.
Published: March 2009

Gastropod populations in 25 stream sites in southeastern Manitoba were studied over an 18-month period. Biological samples and water-quality samples were taken from each site at monthly intervals except during the winter. The gastropod distribution is described in relation to calcium concentration across a natural boundary. In addition to calcium, 16 other water-quality parameters were studied to ascertain whether these were important in regulating gastropod ecology. A multiple regression analysis indicated that the five most important of these were, in order of frequency of occurrence: calcium, nitrate and nitrite nitrogen, turbidity, magnesium, and alkalinity. Life history and additional conchological data are given for the 17 gastropod species encountered.
Surplus killing as exemplified by wolf predation on newborn caribou
Authors: Miller Frank L. , Gunn Anne , Broughton Eric
Published: March 2009

We searched for newborn calf carcasses of migratory barren-ground caribou (Rangifer tarandus groenlandicus) in June 1982 in the Northwest Territories. On 17 June, we found 34 calves killed by wolves (Canis lupus), clumped in a 3-km2 area. The calves had been killed apparently within minutes of each other and about 24 h before being found. Wolves had not fed on 17 of the carcasses and had only partially eaten the other 17. Ground observations illustrate the speed of and efficiency with which wolves can kill calves: a single wolf killed three calves on one occasion and three and possibly four calves on a second occasion at average kill rates of 1 calf/min, and 1 calf/8 min or 1 calf/6 min between the first and last deaths. We attributed the surplus killing of newborn caribou calves to their high densities and their vulnerability on the calving grounds. We recommend that a distinction be made between "surplus killing" and "excessive killing" by predators.
Characterization of mitochondria isolated from the freezing-tolerant larvae of the goldenrod gall fly (Eurosta solidaginis): substrate preferences, salt effects, and pH effects on warm- and cold-acclimated animals
Authors: Ballantyne James S. , Storey Kenneth B.
Published: March 2009

The mitochondria of the freezing-tolerant larvae of the goldenrod gall fly (Eurosta solidaginis) have been isolated and characterized. Proline is the preferred substrate of mitochondria from both warm- and cold-acclimated animals based on state 3 rates. Lipid is used as a substrate by warm- and cold-acclimated mitochondria assayed at 20 °C, but not by the mitochondria from cold-acclimated animals assayed at 1 °C. Cold-acclimated mitochondria assayed at 1 °C have a higher and broader optimal range of salt concentration for the oxidation of proline based on the respiratory control ratio (RCR) than those from warm-acclimated animals oxidizing the same substrate at 20 °C. The optimal pH for warm-acclimated mitochondria oxidizing proline at 20 °C is low (6.2) based on the RCR, but rises to pH 7.0 in cold-acclimated animals at 1 °C. It is suggested that the broad optimal salt concentration in the cold-acclimated animals and the very low optimal pH in warm-acclimated animals are adaptations for survival in this freezing-tolerant larva.
Occurrence of Histriobdella homari (Annelida: Polychaeta) on the American lobster in the Canadian Maritimes
Authors: Brattey John , Campbell Alan
Published: March 2009

Examination of 870 trap-caught lobsters, Homarus americanus, indicated that Histriobdella homari, an epizoic microphagous cleaning symbiont, was common and widely distributed on lobster populations in Canadian Maritime waters during 1980–1981. Prevalence (percent lobsters infected) and abundance (mean number of H. homari per lobster) ranged from 39.6 to 100% and 4.8 to 80.5, respectively. The polychaete was more abundant on ovigerous females than on male or nonovigerous female lobsters. The distribution of H. homari among lobsters was aggregated with a maximum of 669 H. homari on a lobster. In most infestations, the polychaete is probably beneficial to the lobster by removing encrusting microorganisms from the gill filaments and egg masses. However, on the few lobsters that have high abundance of greater than 200 H. homari per individual, the beneficial effects may be lost, since the polychaetes may reduce repiratory flow and success of egg hatching.
Control of lactate oxidation in fish hearts by lactate oxidase activity
Authors: Driedzic William R. , Stewart John M. , McNairn Gwen
Published: March 2009

Isolated hearts of ocean pout (Macrozoarces americanus) and sea raven (Hemitripterus americanus) were perfused with media containing [14C]lactate or pyruvate and the rate of 14CO2 production was monitored. Increases in exogenous lactate concentration resulted in increases in the rate of lactate metabolism. Under comparable perfusion conditions the rate of decarboxylation of pyruvate was three- to four-fold higher than that of lactate. This finding suggests that lactate oxidation was being limited by lactate oxidase. LDH was purified and the Km values for lactate and pyruvate assessed under conditions of saturating cofactor concentration. Both hearts had a muscle type LDH on the basis of Km (pyruvate). Lactate oxidase from ocean pout and sea raven heart displayed Km values of 25 and 20 mM for lactate, respectively. The Km values were well above the presumptive intracellular level of lactate in the perfused hearts. Considered together, the perfusion and isolated enzyme studies show that the catabolism of exogenous lactate is limited by the reaction catalyzed by lactate oxidase.
Implications of chemosensory feeding in catfishes: an analysis of the diets of Ictalurus nebulosus and I. natalis
Authors: Keast Allen
Published: March 2009

The implications of chemosensory feeding and associated ictalurid morphology were investigated through a seasonal study of the diets of the brown bullhead (Ictalurus nebulosus) and yellow bullhead (I. natalis) relative to food availability. Based on the attributes of chemosensory feeding (little discrimination between prey types) and bullhead morphology (poor sight, broad mouth), it was predicted that bullheads would be food generalists and opportunists, and that age-class diets would overlap. These predictions were generally supported for the brown bullhead. Some food types (amphipods) were harvested when most abundant; however, others (chironomid larvae) were consistently taken, and a few potential prey types were underutilized. The yellow bullhead, by contrast, was a food generalist only when young. Adults were specialized piscivores and crayfish feeders. The brown bullhead showed greater weight and length increases than co-occurring visually feeding centrarchids with diets of similar calorific values. Because of the similarity in calorific intake among species, a greater metabolic efficiency in brown bullheads was indicated. Other workers have shown that brown bullheads have lower standard and active metabolisms than some fish species.
The effects of ice cover over the colony site on reproductive activities of herring gulls
Authors: Morris Ralph D. , Chardine John W.
Published: March 2009

The substrate at a herring gull (Larus argentatus) colony on Lake Erie near Port Colborne, Ontario (Lighthouse), was completely covered by a thick layer of ice throughout April and early May 1982. Egg laying normally begins at this location in mid-April. An adjacent herring gull colony (Canada Furnace) was ice free. Herring gull pairs at the Lighthouse colony defended territories on top of the ice but only 3 of about 90 pairs built nests on the ice. Birds neither deserted the colony nor moved within it to ice-free areas as these became available. The mean date of egg laying at the Lighthouse colony in 1982 was about 2 weeks later than in the previous year. At the adjacent Canada Furnace colony, there was no difference in the mean date of egg laying between the 2 years. There were no differences in the distribution of clutch sizes, mean clutch sizes, or hatching success of three-egg clutches laid within ± 1 SD of the mean date of egg laying at either colony in the 2 years. By these measures, the ice-induced delay in breeding chronology of birds at the Lighthouse colony in 1982 did not adversely effect reproductive performance in that year.
Cuticular microstructures and their relationship to structural color and transpiration in the terrestrial isopod Porcellionides pruinosus
Authors: Hadley Neil F. , Hendricks Gregory M.
Published: March 2009

The microstructure of the dorsal surface of the terrestrial isopod Porcellionides pruinosus was examined by scanning electron microscopy. Surface structures detected include sensory tricorns, spherical particles (balls) of various diameter, plates formed from the fusion of adjacent balls, and extremely small granules. A rod-shaped bacterium was also present on the surface of most individuals. The cuticular balls scatter and reflect incident light, producing a grayish white color or frosted appearance in most intermolt isopods. Prior to a molt, individuals are characteristically brown or unfrosted owing to the loss of the balls from the cuticle surface. New balls appear within a few hours following ecdysis and the isopod soon reacquires the frosted appearance. The balls are insoluble in lipid solvents and are also resistant to acetic acid and KOH. Higher water loss rates in unfrosted versus frosted individuals suggest that one function of the balls is to reduce cuticular transpiration in this species.
Site of sex pheromone production in Ascaris suum (Nematoda)
Authors: Garcia-Rejon L. , Sanchez-Moreno M. , Verdejo S. , Monteoliva M.
Published: March 2009

The site of production of sexual pheromones in Ascaris suum was studied. Different organ and tissue homogenates were used as attractant sources and a single worm of the opposite sex was used as a responder. The possible attraction of the worms towards homogenates from their own sexes was tested also. Males were attracted significantly to sexual organs of females, whereas females were attracted to testes and male body fluid. Females were attracted weakly to male cuticles. Attraction to homosexual sources was not found. The sexual organs are proposed as the site of pheromonal production in both sexes, and the body fluid as the vehicle for transport of male pheromone.
Comparative flight behaviour of migrating hawks studied with tracking radar during autumn in central New York
Authors: Kerlinger Paul , Bingman Verner P. , Able Kenneth P.
Published: March 2009

Tracking radar with simultaneous visual observations was employed to study the flight behaviour of nine species of hawks during autumn migration, 1978–1979, in central New York. The predominant mode of flight for all species was thermal soaring and interthermal gliding. Although most species were seen in small flocks at some time, only Broad-winged Hawks (Buteo platypterus) could be considered flocking migrants, with most migrating in flocks < 40 individuals. Altitude of flight increased through the day as convective depth developed, with approximately 85% of all individuals flying below 1000 m. Climb rates of individuals soaring in thermals averaged 3 ms−1 and were greater than previously reported for larger soaring species. Short- to medium-distance migrants (Accipiter striatus, Falco sparverius) tended to fly at lower altitudes than longer distance migrants. The direction realized during thermal soaring was positively related to wind direction and was oriented to the southeast, a function of the prevailing northwest winds. Orientation strategy was considered to be a compromise between drift and complete compensation, resulting in an elliptical migratory flight path, probably shaped by prevailing northwest winds. Such a compromise promotes a faster and more energetically efficient migration.
Prey choice by Blue Jays based on movement patterns of artificial prey
Authors: Wourms Mark K. , Wasserman Fred E.
Published: March 2009

Movement patterns of prey animals may be used by aerial predators to distinguish noxious from palatable, injured and sick from healthy, or difficult to capture from easy to capture prey. This was investigated in the laboratory by presenting Blue Jays with mealworms on a chain and pulley flight pattern simulation device. Palatable prey were presented in one movement pattern, while noxious (quinine-soaked) prey were presented in a second pattern. All birds learned to attack and eat palatable prey and to sit, watch, and avoid noxious prey. The ability to distinguish prey types at a distance by movement patterns may also allow a predator to conserve energy and increase hunting efficiency by attacking only palatable prey that it is highly likely to capture.
Influence of temperature on life-history characteristics of two sibling species of Eurycercus (Cladocera, Chydoridae)
Authors: Hann B. J.
Published: March 2009

Life history characteristics of two sibling species of chydorid Cladocera, Eurycercus (Bullatifrons) longirostris and E. (B.) vernalis, were determined under controlled laboratory conditions. Temperature-dependent change in embryonic development time was described by the Bělehrádek rate–temperature function. Intra- and inter-specific variation was considerable and underlines the need for population-specific determinations of egg development time over a wide temperature range (especially low temperatures) if secondary production is to be assessed reliably. The relationships between (i) egg development time and (ii) generation time with temperature in geographically separated populations of both species exhibited compensation. The interaction between age-specific fecundity and temperature is discussed in relation to population dynamics. Values of r declined with temperature and, although comparable to those calculated for littoral Cladocera, are lower than most estimates available for limnetic species. Finally, the life history traits employed by these two large-bodied species with variable brood size are contrasted with those of the small species of chydorids with maximum brood size of two eggs.
Evolution and host specificity: dichotomous invasion success of Psithyrus citrinus (Hymenoptera: Apidae), a bumblebee social parasite in colonies of its two hosts
Authors: Fisher Richard M.
Published: March 2009

Psithyrus citrinus is an obligate bumblebee social parasite. It has two hosts. Based upon the attraction of P. citrinus females to nests of Bombus vagans, it appears that B. impatiens is a nonpreferred or secondary host. A total of 29 female P. citrinus were introduced into host colonies reared in the laboratory, containing from 0 to 90 workers. Workers and queens of B. impatiens attacked P. citrinus females, and very few parasites survived. In contrast, workers and queens of B. vagans did not defend their nests, and parasites invaded colonies of this species successfully. Specialization appears to facilitate the success of P. citrinus females in invading host colonies. Parasite females were successful in rearing offspring in nests of both host species, although reproduction was limited by the extent to which parasites were assisted by host bees in rearing brood. In the absence of suitable host colonies, ecological factors, including periods of nest initiation by host queens and the relative abundance of nests, may act to maintain secondary host affiliations.
The Sahel of Africa: ecology of a disaster
Authors: Sinclair A. R. E. , Fryxell J. M.
Published: March 2009

The Sahel is a fragile semiarid region extending through 10 countries south of the Sahara. Wild ungulate populations migrate to make use of nutritious but very seasonal food supplies. In doing this, they maintain a higher population size than they could as sedentary populations. Similarly, migratory pastoralists have traditionally lived with their cattle in balance with the vegetation. This balance was disrupted in the 1950's and 1960's by (i) the settlement of pastoralists around wells, and (ii) the expansion of agriculture north into the pastoralists' grazing lands. Land was lost both from overgrazing and from planting with cash crops coincident with increasing human and cattle populations. This has resulted in continuous famine in various parts of the Sahel since 1968. In addition, widespread soil denudation may be causing climatic changes towards aridity. Long-term climatic trends in the past 3000 years point to human interference rather than climatic change as the cause of the famine. The evidence suggests that the Sahel problem (i) is a man-made famine caused by overgrazing and not by lack of rain, (ii) was exacerbated by piecemeal development aid projects, and (iii) has been present for two decades. Also (iv) emergency food aid by itself will aggravate the problem, so that (v) food aid can only be acceptable if tied to long-term care of the people and regeneration of the vegetation.
Final maturation and ovulation of oocytes of the goldeye, Hiodon alosoides (Rafinesque), in vitro
Authors: Pankhurst N. W.
Published: March 2009

Oocytes from preovulatory goldeye were cultured in vitro and final maturation was observed in response to treatment with piscine gonadotropins (GtH) and progestational steroids. Final maturation consisted of nuclear migration and breakdown, and coalescence of yolk material to form a single large oil droplet. Both events were under hormonal control with median effective dose values of 1–5 μg∙mL−1 for piscine GtH and 0.1–0.6 μg∙mL−1 for pregnenolone, progesterone, 17αOH pregnenolone, 17αOH progesterone, and 17α,20β-dihydroxy-4-pregnen-3-one. Neither cortisol nor triiodothyronine potentiated the effects of GtH or progestogens, and both were ineffective alone as was human chorionic gonadotropin. Ovulation was observed in some treatments with GtH, and prostaglandin F2α salt stimulated ovulation of oocytes matured with GtH or 17α,20β-dihydroxyprogesterone. A synthetic analogue of luteinizing hormone-releasing hormone, LH-RHA, had no effect on maturation or ovulation, in contrast to its inhibitory action on GtH-stimulated steroid production in mammals. Follicles from fish in mid and late stages of vitellogenesis were unresponsive to hormone treatment in vitro.
Social organization, spatial distribution, and population density of wolves in relation to moose density
Authors: Messier François
Published: March 2009

This 4-year study compared population density and related behavioral attributes of wolves (14 packs) at two different moose densities: 0.23 (LP, low prey density), and 0.37 (HP, high prey density) moose∙km−2. Wolf densities in January averaged 0.8 and 1.4 animals∙100 km−2, packs consisted of 3.7 and 5.7 individuals, year-long territory sizes were 255 and 390 km2, and interstices between territories represented 30 and [Formula: see text] of available area, for the LP and HP areas, respectively. Territory size increased significantly with pack size. The LP wolf population suffered from a higher mortality rate owing to a higher occurrence of deaths from malnutrition and intraspecific strife, and from a lower success in producing pups (61% of the possible occasions, compared with 93% in HP). When no other ungulate species is present, a density of 0.2 moose∙km−2 would approximate the density threshold below which a pack could not subsist and (or) reproduce successfully. The study reveals that naturally regulated moose–wolf systems may stabilize at low prey and low predator densities.
Microdistribution of three genera of small terrestrial snails (Stylommatophora: Pulmonata)
Authors: Boag D. A.
Published: March 2009

The microdistribution of three genera of small terrestrial snails was determined by recording the number of individuals visible on or above the litter surface in terraria held out-of-doors. Observations were made at various times throughout the 24-h day from May to August. Members of each genus spent most of their time hidden in the litter; of the individuals in each population, never more than 44% of Vertigo, 70% of Discus, and 42% of Euconulus were visible during an observation. Moisture conditions seemed to influence the number of snails observed on or above the litter surface more than either temperature or light. When humidity was allowed to track relatively dry environmental conditions, proportions visible under given temperature and light conditions were significantly lower in all three genera than when humidity conditions were held near the dew point. The proportion of the population visible at the surface also varied diurnally but response to temperature was greater than to light conditions, and peaked between 6 and 15 °C. In all three genera the proportions visible at the surface diminished at higher temperatures, regardless of humidity. Of the snails visible some were moving and others motionless when observed. Relatively more individuals of Euconulus were moving when seen than of Discus. Vertigo showed the lowest proportion moving. Temperatures at which the greatest proportions of snails were moving were also those at which the greatest proportions were observed on or above the litter surface; consequently more were moving at night than during the day.
Comparative fecundity and egg survival of coho salmon (Oncorhynchus kisutch Walbaum) from lakes Ontario, Erie, and Michigan
Authors: Morrison P. F. , Leatherland J. F. , Sonstegard R. A.
Published: March 2009

Survival to hatch in 1982 of coho salmon (Oncorhynchus kisutch Walbaum) collected from two Lake Ontario stocks (Salmon River, New York, and Credit River, Ontario) and Lake Michigan and Lake Erie stocks in 1982 was 79, 86, 78 and 24%, respectively; eggs taken from smaller females (<2 kg) of the Lake Erie stock had a significantly lower survival (9%) than those of larger females (>2 kg). Poor fertilization success appeared to be the major cause of low survival to hatch of Lake Erie coho salmon eggs. There were no significant differences in egg size, embryo size, or development time to hatch, step E47, or first exogenous feeding in the four stocks studied, although the incidence of alevin deformity was significantly higher in the Lake Erie coho salmon than in the Lake Ontario or Lake Michigan stocks. Posthatch mortalities were low, except in the case of the Credit River (Lake Ontario) stock, which suffered an epizootic of a suspect viral disease that increased mortality 3 weeks after hatch.
Food-searching behaviour of the common merganser (Mergus merganser) II: Choice of foraging location
Authors: Wood C. C.
Published: March 2009

Factors influencing the choice of foraging location by the common merganser (Mergus merganser) were investigated by baiting three adjacent, enclosed sections of a natural stream with various densities of juvenile coho salmon (Oncorhynchus kisutch). Merganser abundance within 1 km of the enclosure site increased from < 3 to > 10 birds within 1 week of stocking the enclosures with 43-g coho smolt. Although abundance declined gradually thereafter (as expected from seasonal trends on other nearby streams), the frequency of visits to the enclosure site continued to increase for 22 d until the enclosures were stocked predominately with smaller (2-g) coho fry. Visits were more frequent when other mergansers were already present at the site. Also, the proportion of mergansers flying overhead that landed near a decoy "flock" increased with decoy flock size. In general, the duration of visits to the site was not affected by the number of birds present. Visit duration increased exponentially with increasing fish density and decreased with searching time required until first capture. Mergansers spent more time searching in the most profitable enclosure. Allocation of searching time among the enclosures was not consistent with a "giving up time" decision rule; however, mergansers appeared to follow an area-restricted search pattern both within and among the enclosures.
Feeding ecology and behavior of postbreeding male Blue-winged Teal and Northern Shovelers
Authors: DuBowy Paul J.
Published: March 2009

This study examined foraging strategies in male Northern Shovelers (Anas clypeata) and Blue-winged Teal (Anas discors). Differences in time–activity budgets and esophageal contents between the two species indicated major differences in the degree of foraging specialization. Preflightless male Northern Shovelers spent 84.2% of time foraging, with dabbling in the water column as the principal foraging mode (83.4%), while postflightless male shovelers spent 81.6% of time foraging (78.7% dabbling). Preflightless male Blue-winged Teal spent 68.6% of time foraging, with dabbling in mud (32.5%) and picking in vegetation (29.4%) as the two principal modes, whereas postflightless male bluewings spent 85.9% of time foraging (dabbling in mud 40.6%, and picking 34.2%). Most male Northern Shoveler food items were cladocerans (85.5%) or chironomid pupae (12.9%); this was related to the specialized foraging method employed by shovelers. Male Blue-winged Teal food items were principally gastropods (44.3%), culicids (29.2%), seeds and vegetation (15.5%), and chironomids (5.6%), which corresponded to the plastic feeding behaviors of bluewings. Examination of esophageal items revealed that male Northern Shovelers did little feeding during the summer flightless period, while male Blue-winged Teal fed throughout the period.
Variations inter-populations de la structure d'âge et de la croissance du Prosobranche Bithynia tentaculata L.
Authors: Vincent B. , Létourneau C.
Published: March 2009

The main variations in age structure and growth of different generations were studied in 25 populations of the prosobranch Bithynia tentaculata in the St. Lawrence River (Québec). The general unbalanced age structures of the populations reflect a low recruitment encountered during an odd year because of a general disturbance in the environment. The age structure is correlated to temperature, sediments, and current velocity. Water chemistry is largely responsible for the spatial variations in lengths of the adults, but these variations do not seem to influence the age at sexual maturity. Population densities may be regulated by an increase in the growth rate of young which would reduce the age at sexual maturity in populations with low densities; this mechanism would, however, be of little use to compensate a sudden decrease in density or an unbalanced age structure in a population. These results and those of previous studies on this species reveal the important role played by abiotic factors in regulating the spatio-temporal variations of the demographic profile of this prosobranch which possesses a high phenotypic plasticity.[Journal translation]
Impact of tidal salinity fluctuations on echinoderm and mollusc populations
Authors: Drouin Guy , Himmelman John H. , Béland Pierre
Published: March 2009

At two locations in the Archipel de Mingan, northern Gulf of St. Lawrence, eastern Canada, differences in the amplitude of tidal salinity fluctuations were marked, and quantitative transects were made from 0 to 10 m deep to examine the effect of salinity fluctuations on echinoderm and mollusc communities. The diversity of molluscs and the abundance and population size structure of individual mollusc species showed few differences between the two locations, indicating that the molluscs were not sensitive to the differences in salinity conditions. This is probably due to their ability to prevent or limit osmotic stress by closing their shell or by burrowing. By contrast, there were striking differences in the echinoderm diversity and in the abundance and population size structure of individual echinoderm species between the two sites. This suggests that salinity fluctuations have an important impact on echinoderm populations. Their greater sensitivity can be explained by the high permeability of their outer surfaces. The unusual size–frequency distributions of echinoderms at sites with strong salinity fluctuations were likely due to the lower tolerance of small individuals to hypoosmotic stress.
Food-finding behavior of selected aquatic detritivores: Direct or indirect behavioral mechanism?
Authors: Motyka Gail L. , Merritt Richard W. , Klug Michael J. , Miller James R.
Published: March 2009

In feeding tests, the aquatic detritivores Pycnopsyche guttifer and Pteronarcys pictetii consumed microbially colonized leaves more readily than uncolonized leaves. Videotape analysis of insect movements in bioassay arenas where colonized and uncolonized leaves were presented in both still and flowing water revealed no evidence for movement directed toward food resources (i.e., attraction). We suggest that gustatory cues sensed after random contact with food items are responsible for the differential arrestment and feeding on colonized versus uncolonized leaves. This is supported by the observation of well-developed gustatory receptors on P. pictetii and P. guttifer. Olfactory receptors of these detritivores resembled those of terrestrial arthropods and their effectiveness in the aquatic medium remains unknown.
Size and growth of heart, liver, and kidneys in North Atlantic fin (Balaenoptera physalus), sei (B. borealis), and sperm (Physeter macrocephalus) whales
Authors: McAlpine Donald F.
Published: March 2009

Size and growth of heart, liver, and kidneys in fin (Balaenoptera physalus), sei (B. borealis), and sperm (Physeter macrocephalus) whales taken commercially off Iceland during the 1980 season are compared and examined relative to organ weights for terrestrial mammals. In agreement with the work of previous investigators, the sperm whale is shown to have a relatively smaller heart. However, contrary to previous analysis, fin and sei whales are shown to have relative heart sizes not radically different from those of terrestrial mammals. It is suggested that the differences in relative heart size between the baleen and toothed whales are a reflection of the greater swimming speeds that the baleen whales are capable of attaining. This analysis confirms that marine cetaceans have relatively much larger livers than terrestrial mammals and that they also appear to have relatively larger kidneys. The results presented here, however, show fin, sei, and sperm whales to have relative kidney sizes less than half as great as those given in previous analyses. Growth gradients in the three organs show a distinct pattern of divergence between sperm (Odontocete) and fin and sei (Mysticete) whales.
Influence of photoperiod and photoperiod reversal on growth, mortality, and indicators of age of Dicrostonyx groenlandicus
Authors: Malcolm Jay R. , Brooks Ronald J.
Published: March 2009

After weaning, collared lemmings (Dicrostonyx groenlandicus) were exposed to 3 months of summer (S) photoperiod (18.5L:5.5D) or winter (W) photoperiod (6.5L: 17.5D) or to one of four 6-month photoperiod treatments (SS, SW, WW, or WS). Lemmings were weighed every 3 weeks, and at the end of treatment, eye lenses were weighed and 10 body and 22 skull measurements were taken. At the end of treatment, W, SW, and WW lemmings did not differ in weight, but were significantly heavier than S, SS, and WS lemmings. Animals in WS were significantly heavier than those in SS and both were significantly heavier than S lemmings. The marked contrast of the photoperiodically induced growth pattern of Dicrostonyx groenlandicus with that of other microtines may be due to a relatively larger investment in winter reproduction by collared lemmings. Lemmings that died during the experiment were significantly larger both in body weight and skull size than those that survived. Eye lens weights of S and W lemmings did not differ, but were significantly smaller than those of SS, SW, WW, and WS lemmings. Inequality of mean lens weights was evident among the 6-month treatments, but nevertheless, eye lens weight was the best univariate age criterion and performed approximately as well as linear combinations of body or skull measurements selected by stepwise discriminant analysis.
Do predaceous stoneflies and siltation affect the structure of stream insect communities colonizing enclosures?
Authors: Peckarsky Barbara L.
Published: March 2009

Experiments in Colorado and New York streams assessed the effects of predaceous stoneflies on benthic invertebrate community establishment in enclosures providing uncolonized habitat. Aspects of prey community structure measured were density, species richness, relative species abundance, and body size. Unexpected inorganic sediment deposition allowed evaluation of direct effects on Colorado stream benthos and indirect effects on predation. Predaceous perlids and perlodids consistently reduced the density and, therefore, rate of prey community establishment in enclosures. Although New York perlids disproportionately reduced densities of some prey species, Colorado stoneflies caused nonsignificant declines in individual prey species densities, the composite effect of which was a significant whole-community response. Predators did not affect prey species richness nor change the taxonomic composition (species additions or deletions) of communities colonizing enclosures. However, the relative abundance of prey taxa differed significantly between cages with and without predators. Most species showed no size differences between individuals colonizing enclosures with predators and those colonizing control enclosures, with a few interesting exceptions. The deposition of silt eliminated the predator effects on prey density, as well as directly causing significant reductions in many Colorado benthic populations. This result demonstrates that abiotic disturbances can periodically override the effects of predation on stream insect communities colonizing enclosures.
Selenium and glutathione peroxidase activity in mountain goats
Authors: Robbins Charles T. , Parish Steven M. , Robbins Barbara L.
Published: March 2009

Blood glutathione peroxidase (GSH-Px) activity in mountain goats (Oreamnos americanus) is a linear function of blood selenium. GSH-Px activity per unit of selenium (Se) in mountain goats is approximately double that published for the domestic cow and horse. It is hypothesized that high GSH-Px activity per unit selenium in mountain goats reduces their dietary selenium requirement relative to the above domestic species and is an essential adaptation for occupying low-selenium environments. GSH-Px activity peaked 20–30 days after injections of 0.1 and 0.3 mg Se/kg. A higher dose of 0.5 mg Se/kg delayed and decreased the development of peak GSH-Px activity relative to the two lower injection groups. When acute pathology owing to a selenium deficiency is demonstrated in wildlife capture programs, passive selenium supplementation, such as with selenium-containing salt blocks, should begin weeks to months before capture to provide adequate time for GSH-Px development.
Quantitative comparisons of body form and allometry in larval and adult Pacific sculpins (Teleostei: Cottidae)
Authors: Strauss Richard E. , Fuiman Lee A.
Published: March 2009

Morphometric analyses of body form were performed on samples of larvae and adults of five Pacific sculpin species (Ascelichthys rhodorus, Clinocottus acuticeps, Enophrys bison, Nautichthys oculofasciatus, and Rhamphocottus richardsoni) to investigate patterns of interspecific variation, intraspecific differences in allometry between larvae and adults, and relative shape changes that occur in the transformation from larva to adult. Within species, larvae are relatively more variable at a given size than adults, while adults are more variable among species because of divergence during development. Much nonallometric change in shape occurs during transformation, but the relative amount of change varies among species. The direction of change during transformation is not predictable from larval morphology alone. Some pairs of species become convergently similar during transformation, some change in parallel, and others become highly divergent in form.
Occurrence of alimentary tract helminth parasites of pollock (Pollachius virens L.) on the Scotian Shelf
Authors: Scott J. S.
Published: March 2009

Examination of the alimentary tracts of 456 pollock (Pollachius virens L.) revealed the presence of 15 helminth species or groups representing four phyla. Prevalence ranged from 76.6 in anisakid nematodes to negligible levels (<1.0) in some other species, with "ubiquitous" marine parasites Derogenes varicus, Hemiurus levinseni, anisakid nematodes, and Echinorhynchus gadi showing highest values. Changes in prevalence were related to a change from a largely crustacean diet to a largely fish diet with increasing fish length. Differences in prevalence of the more common parasites between the central and southwestern Scotian Shelf support evidence for separate pollock populations in the two areas.
Changes in the predator-avoidance behaviour of juvenile guppies (Poecilia reticulata) exposed to pentachlorophenol
Authors: Brown Joseph A. , Johansen Peter H. , Colgan Patrick W. , Mathers R. Alastair
Published: March 2009

The effects of pentachlorophenol on the predator-avoidance behaviour of the guppy (Poecilia reticulate) in response to largemouth bass (Micropterus salmoides) predation was investigated. There were no consistent effects of pentachlorophenol on habitat use or general behaviour of the guppies. In the presence of predators, all guppies occurred significantly more often alone, motionless, and in the top third of the water column in the nonopen areas. Nine variables associated with predator efficiency were monitored to determine which treatment groups of guppies were easiest to capture. The bass had significantly lower capture success, performed more strikes and chases, and spent more time chasing guppies from the untreated and 100 μg/L groups than those from the 500 and 700 μg/L groups. This suggests that the guppies from the two high treatment groups had a slower response to predator attack and could not maintain a prolonged escape burst of speed.