bluuebunny/crossref_metadata_2025 huggingface dataset:
Cardiac physiology in tunas. II. Effect of ryanodine, calcium, and adrenaline on force–frequency relationships in atrial strips from skipjack tuna, Katsuwonus pelamis
Authors: Keen J. E. , Farrell A. P. , Tibbits G. F. , Brill R. W.
Published: July 2008

Force–frequency relationships and the dependence upon extracellular calcium as a source of activator calcium were investigated using atrial strips from the skipjack tuna (Katsuwonus pelamis). At 25 °C, active force generation increased over a stimulation range of 0.2–1.6 Hz and declined at higher stimulation frequencies. Ryanodine, a blocker of calcium release from the sarcoplasmic reticulum, decreased active force by ~30% but did not alter the shape of the force–frequency curve. Uniform contractions were maintained up to stimulation rates of 3.0 Hz following ryanodine application, compared with 3.4 Hz under control conditions. Active force increased with increasing extracellular calcium concentration in a concentration-dependent manner with greatest sensitivity over the range of 1.0–5.0 mM calcium. Activation duration decreased with increasing extracellular calcium concentrations up to 5.0 mM and with increasing contraction frequency up to 1.0 Hz. Relaxation duration also was reduced with increasing extracellular calcium over a range of 0.5–4.0 mM, and over a stimulation range of 0.2–0.6 Hz. Adrenaline increased active force threefold over the range of 10−8 to 10−5 M, with an EC50 value of 4.90 ± 0.57 × 10−7 M. The EC50 value was not dependent upon stimulation frequency. These results indicate that contraction in the skipjack tuna atrium is partially dependent upon intracellular calcium release from the sarcoplasmic reticulum. In this manner, the tuna heart more closely resembles the mammalian model of excitation–contraction coupling than that suggested for other fishes in which activator calcium is almost exclusively derived from extracellular influx.
Recovery metabolism of skipjack tuna (Katsuwonus pelamis) white muscle: rapid and parallel changes in lactate and phosphocreatine after exercise
Authors: Arthur Peter G. , West Timothy G. , Brill Richard W. , Schulte Patricia M. , Hochachka Peter W.
Published: July 2008

Lactate, glycogen, and high-energy phosphate levels were measured in serial biopsies from tuna white muscle during recovery from 15 min of enforced swimming. Exercise caused glycogen and phosphocreatine levels to decrease sharply and lactate concentration to increase markedly (up to 150 μmol∙g−1). Lactate was cleared from white muscle in less than 90 min, at rates comparable to those seen in mammals (about 1.3 μmol∙g−1∙min−1), and this was accompanied by nearly stoichiometric increases in white muscle glycogen (2 lactate:1 glucosyl unit). The plasma lactate concentration remained elevated (35–40 mM) until lactate clearance from white muscle was completed, whereas the level of plasma glucose was constant (12–16 mM) for the entire 3-h recovery period. The exercise routine caused minimal changes in white muscle purine nucleotides apart from a slight, but significant, increase in IMP content. Transient changes in ATP appear to have resulted from short-term intense swimming activity noted during anesthetization. Unlike other teleosts, lactate clearance in tuna paralleled creatine rephosphorylation during recovery from exercise. We suggest that the postexercise adjustment of intracellular pH is responsible for this relationship. Lactate was seemingly metabolized within the white muscle mass, as indicated by in situ conservation of lactate carbon apparent from stiochiometric increases in white muscle glycogen levels. This prospect is discussed in view of low estimates of lactate utilization rates by other tissues and contrasted with expected high rates of whole-body lactate turnover during recovery.
Myocardial sarcolemma isolated from skipjack tuna, Katsuwonus pelamis
Authors: Tibbits Glen F. , Kashihara Haruyo , Brill Richard W.
Published: July 2008

The high cardiac outputs observed in tuna compared with other teleosts may imply differences in the regulation of myocardial contractility. Sarcolemma is a critical organelle in the teleost heart in the regulation of intracellular calcium concentration and hence contractility. A procedure is described for the isolation of large quantities of highly purified sarcolemma from the skipjack tuna heart by differential and sucrose-gradient centrifugation in the presence of multiple protease inhibitors. The preparation was characterized using the sarcolemma marker K+-stimulated p-nitrophenylphosphatase (K+pNPPase). From a starting ventricular wet weight of about 60 g, a yield of > 20 mg sarcolemmal protein and a > 43-fold purification over the crude homogenate were achieved. The percentage recovery of the total K+pNPPase in the sarcolemma fraction was greater than 14%. Both the purification index and recovery were substantially greater than those achieved with a much smaller scale sarcolemma preparation recently described for the trout heart. The equilibrium binding of the dihydropyridine PN200-110 and ryanodine were determined in these preparations. In purified sarcolemma, the dihydropyridine receptor binding density (Bmax) and dissociation constant (Kd) were found to be 0.48 ± 0.07 pmol∙mg protein−1 and 0.09 nM respectively, similar to that found in mammals. In crude homogenates, the ryanodine receptor Bmax was approximately 0.12 ± 0.04 pmol∙mg protein−1 and thus was a little more than half the value observed for the dihydropyridine receptor. The large-scale sarcolemma isolation procedure described in this paper for tuna may be useful for developing a better understanding of the role of the sarcolemma in the regulation of ventricular function in teleosts.
Mitochondrial metabolism of cardiac and skeletal muscles from a fast (Katsuwonus pelamis) and a slow (Cyprinus carpio) fish
Authors: Moyes Christopher D. , Mathieu-Costello Odile A. , Brill Richard W. , Hochachka Peter W.
Published: July 2008

Tuna cardiac (atrium, compact and spongy ventricle) and skeletal muscle (red and white) were compared with carp tissues to determine the importance of mitochondrial differences in supporting the high aerobic capacities in tuna. Mitochondria isolated from red muscle of both species oxidized each of the physiological fuels at similar rates per milligram of mitochondrial protein, when differences in assay temperature are considered. The highest rate of oxygen consumption by ventricle mitochondria was 2 times greater in tuna than carp. The maximal oxidation rates were 3–4 times higher in ventricle than red muscle in both species. Tuna tissues had as much as 30–80% more mitochondrial protein per gram of tissue than carp. Morphometrically this was manifested as extremely densely packed mitochondrial cristae, rather than increased mitochondrial volume densities. In general, higher aerobic capacities of tuna ventricle and red muscle are primarily attributable to greater tissue mass and, to a lesser extent, differences in the nature or quantity of mitochondria per gram of tissue. Unlike ventricle and red muscle, tissues with relatively low mitochondrial contents in carp (white muscle, atrium) demonstrated several-fold higher mitochondrial contents in tuna. Enzyme analyses of tissue and isolated mitochondria suggest a greater dependence of tuna tissues on fatty acids as fuels. Activities of carnitine palmitoyl transferase (CPT) per milligram of protein were 2–2.5 times higher in tuna red muscle and ventricle mitochondria than in carp mitochondria from the same tissues. Whole tissue activity ratios of hexokinase/CPT, which indicate the relative importance of glucose and fatty acid metabolism, were 5 times higher in carp spongy ventricle and 12 times higher in carp compact ventricle. These data suggest that muscle aerobic capacity can be increased at several levels: tissue mass, mitochondrial volume density, cristae surface density, and mitochondrial specific activity. Large differences observed between carp and tuna muscles are due to cumulative effects of several of these factors.
Ageing studies on three species of freshwater mussels from a metal-polluted watershed in Nova Scotia, Canada
Authors: Metcalfe-Smith Janice L. , Green Roger H.
Published: July 2008

Freshwater mussels are increasingly used to monitor metal pollution in freshwater systems. Mussels are long-lived, and age is a factor that may influence metal concentrations in their tissues. Species that can be precisely aged are most suitable for biomonitoring because they can be standardized for this factor. Precise age estimates are also needed for determining the effects of contamination on population parameters such as growth rate. Elliptio complanata, Anodonta implicata, and Alasmidonta undulata (family Unionidae) were collected from two Nova Scotia lakes contaminated with arsenic and mercury. Mussel shells were weighed, measured, and sectioned, and two independent counts of internal growth bands were made. External rings were also counted for A. implicata. Age estimates based on internal bands were most precise for E. complanata (r2 = 0.71 vs. 0.35 for A. implicata and 0.29 for A. undulata). Estimates based on external rings were more precise (r2 = 0.69) than those based on internal bands for A. implicata, but were believed to include disturbance rings. Shell length and weight were similarly correlated with age for a given species and population, but relationships were less clear in the lake with the more variable habitat. Elliptio complanata were much smaller at a given age in the more contaminated lake.
Echolocation behaviour of vespertilionid bats (Lasiurus cinereus and Lasiurus borealis) attacking airborne targets including arctiid moths
Authors: Acharya Lalita , Fenton M. Brock
Published: July 2008

We observed the echolocation and hunting behaviour of Lasiurus borealis and Lasiurus cinereus from May to August of 1989, 1990, and 1991 to assess the role of feeding buzzes in the behaviour of echolocating bats attacking airborne prey. Feeding buzzes consist of short echolocation pulses produced at a rapid rate just before contact between a flying bat and its prey. The hypothesis that the duration of the feeding buzz reflects the size of the attacked prey was not supported by the data. The mean lengths of silent periods between the end of the feeding buzz and the next echolocation call were significantly longer after successful attacks than after unsuccessful attacks. There was, however, no threshold value unambiguously separating successful from unsuccessful attacks in either species. The responses of bats to tossed pebbles and to some insects indicated that during some feeding buzzes L. borealis and L. cinereus judged the nature and range of prey being attacked. Attacks by free-flying L. borealis on muted arctiid moths (Hypoprepia fucosa), combined with the rejection of these moths as food by captive bats, suggest that in this setting the clicks of these moths are aposematic signals, warning the bats of the moths' bad taste.
Prey selection in relation to insect availability by the common poorwill (Phalaenoptilus nuttallii)
Authors: Csada Ryan D. , Brigham R. Mark , Pittendrigh Barry R.
Published: July 2008

We determined the diet of common poorwills (Phalaenoptilus nuttallii) by analysing fecal samples collected from roost and nest sites in the Okanagan Valley of British Columbia. The two major insect orders present in the diet in 1989 were Coleoptera (47% by volume) and Lepidoptera (49%), which comprised only 15 and 3%, respectively, of the insects sampled using sticky traps in 1989. Based on the femur length of coleopterans consumed, all coleopterans eaten were longer than 6.7 mm (excluding the head), whereas 76% of the coleopterans caught on sticky traps were less than 6.7 mm long. We found no evidence to support the prediction, based on optimal foraging theory, that poorwills would broaden their diet to include other insect taxa or size classes during 1990, when wet conditions likely depressed prey availability and foraging opportunities. There was no difference in the proportions of various taxa consumed or the size of coleopterans eaten between 1989 and 1990. Acknowledging the bias of our insect sampling regime, we conclude that the apparent prey selection by poorwills results passively from the constraints imposed by detecting prey under conditions of low light.
Long-term effects of infant malnutrition on the behaviour of adult meadow voles, Microtus pennsylvanicus
Authors: Wong Kim Lee , Bondrup-Nielsen Søren
Published: July 2008

Several studies on laboratory mice and rats have shown that malnutrition during infancy has a variety of long-term effects extending into adulthood. These effects are manifested in reproduction, including reduced litter sizes, reduced growth rates of the young, and skewed sex ratios, and in behaviour, including increased nervousness, decreased problem-solving ability, and reduced pup retrieval to the nest by the mother. This study investigated the effects of early malnutrition on behaviour in adult meadow voles, Microtus pennsylvanicus. Experimental animals received a standard diet diluted with pure cornstarch (1 part standard diet to 2 parts pure cornstarch) through their mothers during lactation and directly for 3 weeks postweaning. Control individuals always received the standard diet ad libitum. The cumulative duration of 13 behaviours was measured in 10-min trial periods and compared between experimental and control animals. Experimental females differed from control females in a number of behaviours, especially those involving high activity levels, whereas experimental and control males showed little difference in the behaviours performed. The behaviour profile of previously malnourished females was similar to those of both control and experimental males. Increased activity, resulting from poor nutrition, may have consequences for dispersal and spacing behaviour.
Adaptations to environment in the mountain hare (Lepus timidus): thermal physiology and histochemical properties of locomotory muscles
Authors: Pyörnilä A. , Putaala A. , Hissa R. , Sulkava S.
Published: July 2008

Oxygen consumption of mountain hares (Lepus timidus) subjected to different ambient temperatures was measured. The basal metabolic rate was 3.91 ± 0.05 W∙kg−1 in winter and 4.75 ± 0.06 W∙kg−1 in summer. These values are 162 and 186% of the weight specific values, respectively. Minimum thermal conductances (winter, 0.076 ± 0.017 W∙kg−1∙°C−1; summer, 0.141 ± 0.018 W∙kg−1∙°C−1) were 74 and 134% of the values predicted from body weight, respectively. It appears that adaptation of the mountain hare to winter is largely based on insulation. The fibre type composition of a flexor and an extensor muscle in the hindlimb was studied from sections stained for succinate dehydrogenase and myosin adenosine triphosphatase. More than 60% of the cells were fast-twitch oxidative glycolytic fibres, and 30–40% were fast-twitch glycolytic fibres. The greatest difference between the muscles was in the relative number of the slow-twitch oxidative fibres, with the flexor containing 13.7 and the extensor 2.9% of this fibre type. The histochemical properties of the muscles studied are consistent with the locomotory pattern of the mountain hare, which is characterized by darting or sprinting movements, and endurance in flight run.
The morphology and cytochemistry of the blood leukocytes of Kemp's ridley sea turtle (Lepidochelys kempi)
Authors: Cannon M. Samuel
Published: July 2008

Blood leukocytes of Lepidochelys kempi were examined by bright-field microscopy and cytochemistry for the determination of glycogen, lipids, and several hydrolytic and oxidative enzymes. Mature large and small eosinophils and small lymphocytes were the principle leukocytes encountered; basophils were rarely seen, and neutrophils and monocytes were not demonstrated. The large eosinophils contained two types of granules and demonstrated periodic acid – Schiff (PAS) reactivity and some sudanophilia. The large eosinophils also possessed alkaline phosphatase, myeloperoxidase, adenosine triphosphatase, and some nonspecific esterase activity. The small eosinophils demonstrated acid phosphatase. No reactivity for β-glucuronidase, aryl-sulfatase, or for the oxidative enzymes, succinate, lactate, and glucose-6-phosphate dehydrogenases, or cytochrome oxidase, occurred in the large or small eosinophils. Small lymphocytes contained a few PAS-positive granules or intracellular particles; some nonspecific esterase activity but no reactivity for other hydrolytic or oxidative enzymes or for neutral lipids was observed.
Effects of salinity on aerobic metabolism and development of eggs and alevins of steelhead trout (Oncorhynchus mykiss) and fall chinook salmon (Oncorhynchus tshawytscha)
Authors: Morgan John D. , Jensen John O. T. , Iwama George K.
Published: July 2008

Metabolic rates, hatching success, alevin survival, time to hatch, and growth were measured for steelhead (Oncorhynchus mykiss) and fall chinook salmon (Oncorhynchus tshawytscha) embryos incubated in salinities of 0, 4, 8, and 12 parts per thousand (ppt) from the eyed stage. Metabolic rates of eyed steelhead trout eggs, and chinook salmon eggs and alevins were not significantly affected by the salinities tested. The metabolic rate of newly hatched steelhead trout alevins, however, was significantly lower in 8-ppt, and significantly higher in 12-ppt, than in 0- and 4-ppt salinities. Egg hatchability was high in all four salinities, but newly hatched alevins of both species showed decreased survival and were smaller in 12-ppt salinity. Salinity effects on alevin survival and size were greater for steelhead trout than for chinook salmon. The results suggest that 8-ppt salinity is the upper limit for the normal development of steelhead trout and chinook salmon eggs and alevins.
Excretion in the house cricket: role of second messengers in Malpighian tubule function
Authors: Clark Thomas M. , Spring Jeffrey H.
Published: July 2008

Three factors influencing diuresis, two stimulatory and one inhibitory, have been isolated from the corpora cardiaca of Acheta domesticus by means of high-performance liquid chromatography. Diuretic factor 1 provoked a fast-acting response (15 min to peak), whereas diuretic factor 2 caused a slow-acting (45 min to peak), longer lasting response. When dibutyryl-cAMP was added to the bath it increased secretion in a manner similar to diuretic factor 1. In unstimulated preparations, the divalent cation ionophore A23187 mimicked the action of antidiuretic factor, reducing the secretion rate by approximately 80%. In preparations pretreated with diuretic factor 1 or cAMP, addition of ionophore reduced the secretion rate by 60% or more, but the tubules continued to secrete at the reduced rate for at least 1 h. In contrast, when preparations were pretreated with diuretic factor 2, the addition of A23187 reduced secretion to zero within 15 min. Methanolic extracts of corpora cardiaca increased cAMP levels in tubule broken-cell preparations in a dose-dependent manner over the range of 0.03–1.0 corpus cardiacum equivalents, with a maximal increase of approximately 2 times that of the controls. Similar increases in cAMP levels were produced by homogenates of corpora cardiaca, diuretic factor 1, and sodium fluoride. In contrast, diuretic factor 2 significantly reduced cAMP concentrations. Possible mechanisms by which these three factors interact to regulate tubule secretion are discussed.
La biologie du suceur cuivré (Moxostoma hubbsi) comparée à celle de quatre autres espèces de Moxostoma (M. anisurum, M. carinatum, M. macrolepidotum et M. valenciennesi)
Authors: Mongeau Jean-René , Dumont Pierre , Cloutier Louise
Published: July 2008

The copper redhorse, Moxostoma hubbsi (Legendre), which was discovered in 1942, is a threatened and endemic fish species of the lowlands around Montréal (Quebec). A survey of historical data, an investigation of the preserved specimens, and a comparison of selected biological characteristics of the five Quebec Moxostoma species living in sympatry in the Richelieu River show that this redhorse has a unique combination of life history characteristics. Compared with the other redhorses, it is among the most long-lived (more than 20 years), has the highest growth rate and fecundity, and is the latest spawner, its reproduction probably taking place at the end of June or at the beginning of July. The copper redhorse shows a high degree of specialization in the use of alimentary resources and feeds almost exclusively upon molluscs. The comparison of the stomach contents of the different species living in sympatry shows little diet overlap. This may be due to the specialization of their pharyngeal apparatus and to a certain degree of spatial segregation. Similar to its congeners, the copper redhorse shows a predilection for lowland rivers of medium size characterized by abrupt banks and uniformly deep channels (4–7 m) flowing over a solid clay, sand, or gravel bottom. The most populated sections of river have rather slow currents; they are interspersed by sections of rapids suitable for spawning. In the St. Lawrence system, the range of the copper redhorse is much more restricted than that of other redhorses, and this species appears much more vulnerable to habitat degradation.
Seasonal activity and body mass of Columbian ground squirrels
Authors: Dobson F. Stephen , Badry Michael J. , Geddes Christine
Published: July 2008

Recent research on Columbian ground squirrels (Spermophilus columbianus) has invoked the lengths of the active season and plant growing season to explain differences in life history and social behaviours among populations at different elevations. We evaluated an assumption of these studies that the active season for individual ground squirrels is significantly shorter at high than at low elevation. Adult males and females were active for about 100 days at low elevation and about 86 days at high elevation. Juvenile ground squirrels also had a longer active season at low (50 days) than at high elevation (45 days), but for yearlings the active season was similar (about 87 days). The active season for adults was about 2 weeks shorter than the plant growing season at low elevation, but up to 2 weeks longer than the plant growing season at high elevation. Differences in body mass of adult ground squirrels between low and high elevations at spring emergence from hibernation and at fall immergence into hibernation were consistent with a shorter active season and lower annual energy intake at high elevation, where adults were generally lighter. Examination of rates of weight gain during the active season showed that differences in adult weight could be explained by the length of the active season, but that yearlings and juveniles grew more rapidly at low than at high elevation. These results support the assumption that the active season for individual ground squirrels is generally shorter at high than at low elevation.
Copepoda (Poecilostomatoida and Siphonostomatoida) from deep-sea hydrothermal vent areas off British Columbia, including Amphicrossus altalis, a new species of Erebonasteridae, with notes on the taxonomic position of the genus Tychidion Humes
Authors: Humes Arthur G. , Huys Rony
Published: July 2008

Amphicrossus altalis, n.sp., belonging to the primitive poecilostomatoid family Erebonasteridae, was found at a depth of 2420 m at the Juan de Fuca Ridge off British Columbia. The male of an Amphicrossus species is described for the first time. The new copepod differs from the two recognized species of Amphicrossus in its body surface being not highly ornamented with spinules, its smooth anterior surface of the labrum, and the dimensions of the fifth leg. New records for Benthoxynus spiculifer Humes, 1984, Aphotopontius forcipatus Humes, 1987, and Stygiopontius quadrispinosus Humes, 1987, are included. The clausidiid genus Tychidion is redescribed and its taxonomic position discussed.
The ontogeny of body composition and gut morphology in free-ranging muskrats
Authors: Virgl John A. , Messier François
Published: July 2008

We quantified changes in body composition, external morphology, and digestive tract morphology during the growth and development of muskrats from two marsh environments in central Saskatchewan, Canada. A total of 141 individuals were analysed, with body masses ranging from 20 g (newborns) to >800 g (prior to first reproduction). The growth rate of the digestive tract in nursing young was rapid, and at weaning juveniles had attained 75% of adult large and small intestine length, but only approximately 20% of adult body mass. At birth, muskrats contained no fat tissue, but accumulated fat reserves during the early stages of nursing. Fat reserves were then exhausted during weaning. Protein content also exhibited marked variation during the nursing–weaning period. As juveniles matured, the proportion of protein and ash became relatively constant at approximately 25 and 4.5% of body mass, respectively. Conversely, the proportion of fat tissue continued to increase with body mass, and was inversely related to water content. The accumulation of fat reserves from autumn through early winter was similar to that exhibited by adults and was probably associated with the presence of energy-rich food. Growth generally ceased in mid-October. Prior to the start of the reproductive season, juveniles had attained 77% of adult body mass and 95% of adult skeletal size. The growth diapause in juveniles from mid-October through March may limit their access to primary breeding habitat the following spring.
Spatial distribution patterns of larval cytotypes of the Simulium venustum/verecundum complex (Diptera: Simuliidae) on the Avalon Peninsula, Newfoundland: factors associated with cytotype abundance and composition
Authors: McCreadie J. W. , Colbo M. H.
Published: July 2008

Using principal component analysis and cluster and regression analyses, larval macrodistribution of Simulium venustum/verecundum complex cytotypes within a drainage basin and along a stream continuum was investigated. Cytotypes included ACD (= Simulium rostratum Lundström) and AA from the verecundum line of the complex and EFG/C (= Simulium truncatum Lundström), AC(gb) and CC2-3 (combined CC2 and CC3) from the venustum line. Abundance of both AC(gb) and CC2-3 increased with increasing stream size. The abundance of CC2-3 also increased at sites with warmer temperatures and lower conductivity, dissolved oxygen, and pH levels. Cytotype composition changed in a continuous, directional, and predictable (R2 = 52.4–92.2%) manner with increased distance from outlets. It is argued that changes in cytotype composition must be considered in future sampling protocols, as quantitative and qualitative changes in the cytotype assemblage can occur over distances as short as 100 m. Discontinuity in the frequency of the IIL-4 polymorphism suggested restricted gene flow due to limited adult AA dispersal over distances greater than 12 km.
Life history and production of Hyalella azteca (Crustacea: Amphipoda) in a hypereutrophic prairie pond in southern Alberta
Authors: Wenz Yuan Hua
Published: July 2008

The life history and production of the amphipod Hyalella azteca were studied over an 18-month period in a hypereutrophic prairie pond in southern Alberta, Canada. The population reproduced once a year, with breeding commencing in June and continuing until August. Population density was highest in June. The mortality rate of the adult population increased with the onset of reproduction, and remained high until the end of winter. The population density was lowest during winter and early spring (January to May). Biomass (B) fluctuated in a similar manner to population density, but the peak biomass occurred in August and September. Annual production (P) was 23.12 g∙m−2 (dry weight), estimated by the size-frequency method. The corresponding annual turnover ratio (P/B) was 5.68. The unusually high annual production and turnover ratio are attributed to the high density and large adult size of this population.
Enzyme electrophoresis, 18S rRNA sequences, and levels of phylogenetic resolution among several species of freshwater planarians (Platyhelminthes, Tricladida, Paludicola)
Authors: Riutort M. , Field K. G. , Turbeville J. M. , Raff R. A. , Baguña J.
Published: July 2008

Enzyme polymorphism and 18S rRNA sequences have been used to measure genetic distances between several species of Platyhelminthes belonging to different taxa including freshwater and parasitic forms. We have used these data to address unresolved phylogenetic and taxonomic problems with this group at several different levels ranging from phylum to subgenus. The main conclusions supported by the data seem to be the following: (i) 18S rRNA data strongly suggest that the Platyhelminthes are monophyletic, being a sister-group to the other Eubilateria; a similar conclusion applies to the Paludicola as to the rest of Platyhelminthes studied; (ii) 18S rRNA and enzyme data indicate that the family Dugesiidae of the Paludicola is monophyletic with respect to the other two families, Planariidae and Dendrocoelidae; and (iii) the subgenus Schmidtea of the genus Dugesia is monophyletic with respect to the other two subgenera of Dugesia, Dugesia and Girardia. Other aspects of the relationships of subgenera and families could not be satisfactorily resolved, but point to new problems that should be addressed in future studies, namely the taxonomic status of the family Planariidae and the relationships between the genera and subgenera of the family Dugesiidae.
The effects of fasting and feeding on hepatic thyroxine 5′-monodeiodinase activity in the rainbow trout, Oncorhynchus mykiss
Authors: Sweeting R. M. , Eales J. G.
Published: July 2008

The effects of fasting and feeding on the activity and kinetics of the hepatic microsomal L-thyroxine (T4) 5′-monodeiodinase enzyme system (5′D) responsible for generating 3,5,3′-triiodo-L-thyronine (T3) were studied in immature rainbow trout held on a 12 h L: 12 h D photocycle at 12 °C. The 5′D activity was determined from the essentially stoichiometric production of 125I− and 3,5,[3′-125I]T3 as the primary labeled materials from 3,5,[3′-125I],5′-T4 substrate, as judged by LH-20 Sephadex chromatography and HPLC. Relative to trout fed 2% body weight∙day−1 (2% ration), fasting depressed 5′D activity within 3 days. By 7 days a basal 5′D level was reached, which persisted for at least 20 days. In trout fed a 0.8% ration, fasting for 8 days depressed 5′D activity to a level lower than that of trout fed a 2% prefasting ration, suggesting 5′D response to energy reserves. However, following 8 days fasting, refeeding for 7 days reinstalled 5′D activity, regardless of prior maintenance on a 0.8 or 2% ration. There was a strong positive correlation between body weight gain and 5′D activity for trout fed rations of 0, 0.3, 0.6, 1, 2, or 3% for 14 days. Kinetic analyses showed that change in 5′D activity was due mainly to change in Vmax (quantity of functional enzyme units). However, fasting also decreased Km (Michaelis–Menten constant), suggesting the presence of a 5′D form with a higher T4 affinity. The 5′D activity was significantly correlated with the blood plasma T3 level, but not with the plasma T4 level. We conclude that (i) hepatic 5′D responds rapidly to both food deprivation and feeding and is also sensitive to energy reserves, (ii) the response primarily involves the level of functional 5′D units but some change in enzyme form may also occur, and (iii) the high positive correlations between 5′D activity, plasma T3 level, and gain in body weight are consistent with a role of hepatic 5′D in generating systemic T3, which in turn may regulate somatic growth.
Temporal and spatial dynamics of predation in a robber fly (Efferia staminea) population (Diptera: Asilidae)
Authors: O'Neill Kevin M.
Published: July 2008

To determine the effect of short-term temporal and small-scale spatial variation in availability of specific prey groups, field studies of prey use by a population of the robber fly Efferia staminea were undertaken. In one study, the appearance of mating swarms of winged males of the ant Formica subpolita was associated with a rapid increase in the proportion of E. staminea observed feeding, and an increase in the proportion of these ants taken as prey. The change in diet occurred over the same time scale as the change in the activity of the ants. When the swarms were absent from the same area, the fewer E. staminea observed feeding utilized a greater diversity of prey taxa and sizes. The proportion of conspecifics in prey records during swarms of F. subpolita was only one-tenth of that during non-swarm intervals, suggesting that high alternative prey availability decreases the incidence of cannibalism in this species. In the second study, E. staminea used a wider diversity of prey on an area of grassland with native vegetation than on a nearby area of grassland that had been reseeded with the grass Agropyron intermedium as part of a range-management program. In the latter area, a large population of crambine moths supplied a major portion of the robber flies' diet. The results of this population-level study illustrate the fine scale over which the composition of the diet of E. staminea varies, and show that the diet of a generalist predator is a function of the temporal and spatial scales over which sampling occurs. The implications of the data for interpreting the composition of the diet, population dynamics, and impact upon prey communities of robber flies are discussed.
Effects of water potential and temperature on survival of the nematode Meloidogyne hapla in frozen soil
Authors: Forge T. A. , MacGuidwin A. E.
Published: July 2008

The effects of water potential on the survival of Meloidogyne hapla second-stage juveniles in frozen soil were studied. Soil-water potentials and freezing temperatures tested ranged from 0 to −1910 kPa and from −1 to −4 °C, respectively. Survivorship was greater in soil at water potentials of −1910 to −520 kPa than in soil at higher water potentials. Saturating the soil immediately before freezing reduced survivorship, but it was still greater for juveniles exposed to low water potentials before saturation. Thus, low water potentials increased survivorship directly by reducing the pore space filled with ice and indirectly by causing physiological changes that increased the ability of juveniles to survive frozen conditions. Exposure to low water potentials in polyethylene glycol solutions at 24 °C also caused an increase in the percentage of juveniles that survived frozen conditions. Regardless of water potential experienced (−2050 to 0 kPa), subsequent exposure to 4 °C caused an additional increase in the percentage surviving frozen conditions. However, exposure to a low water potential (−1110 kPa) at 0 °C did not cause an increase in tolerance of frozen conditions. Juveniles extracted from frozen soil or solutions appeared desiccated. Survivorship in frozen solutions was compared with survivorship at water potential and temperature combinations equivalent to those of the frozen solutions. Survivorship was the same in both situations, indicating that desiccation may be an important stress responsible for mortality in frozen conditions.
The life history of Hysterothylacium analarum Rye and Baker, 1984 (Nematoda: Anisakidae) in Lepomis gibbosus (Pisces: Centrarchidae) in southern Ontario, Canada
Authors: Rye Leslie A. , Baker Michael R.
Published: July 2008

Larval stages of Hysterothylacium analarum are described from Lepomis gibbosus in Dawson Pond, Ontario (45°10′N, 78°50′W). Second-stage larvae were easily distinguished from all other stages by the presence of a conical boring tooth. Third-stage larvae lacked both a boring tooth and lips. Fourth-stage larvae had well-developed lips. The ratio of ventricular appendage length to intestinal caecum length varied greatly between larval stages and adults. Prevalence and intensity of larval stages and adult H. analarum showed a distinct seasonal pattern, with one generation of adult worms per year. In spring, third-stage larvae left nodules on the intestinal serosa of L. gibbosus and migrated to the intestinal lumen, where they rapidly moulted to the fourth-stage and then to adult worms. Eggs collected from gravid females developed to second stage larvae in approximately 5 days under laboratory conditions. In natural infections in the late summer second-stage larvae were found in nodules on the serosa and in the mesentery. Larvae apparently moulted to the third stage and overwintered in the nodules as third-stage larvae.
Factors influencing the production of turbidity by goldfish (Carassius auratus)
Authors: Richardson Michael J. , Whoriskey Frederick G.
Published: July 2008

Experiments were conducted to determine the effect of body size, population size and structure, and temperature upon the level of turbidity generation by goldfish foraging in laboratory pools. Water temperature correlated with turbidity generation, which peaked at 25 °C but declined at 30 °C. Goldfish exhibited diurnal activity at all temperatures except 25 °C, where nocturnal behaviour predominated. Both body length and population size positively influenced turbidity production. Groups of a few large fish produced significantly more turbidity than groups of many small fish of equal biomass. Biomass was therefore a poor predictor of the level of turbidity, making it difficult to predict the impact of goldfish upon multispecific pond communities following successful colonization.
Buoyancy regulation by the sticklebacks Culaea inconstans and Pungitius pungitius in response to different salinities and water densities
Authors: Gee John H. , Holst Heidi M.
Published: July 2008

The sticklebacks Culaea inconstans and Pungitius pungitius maintain buoyancy equilibrium in laboratory experiments by altering swim-bladder volume when held in a range of salinities (0–22.5 ppt). By holding C. inconstans in a Percoll solution in which water density is increased but tonicity remains similar to that of fresh water, we show that this species adjusts its buoyancy in response to a change in water density. When C. inconstans is transferred abruptly from fresh water to brackish water (10 ppt) buoyancy equilibrium is not regained until 96 h later. During this period of swim-bladder adjustment, hydrodynamic forces are used to provide the appropriate lift. Both species encounter variation in salinity in nature and the ability to respond to such changes could be highly adaptive.
An experimental study of red fox predation on arctic and snowshoe hares
Authors: Small Robert J. , Keith Lloyd B.
Published: July 2008

We tested the relative vulnerability of arctic (Lepus arcticus) and snowshoe (Lepus americanus) hares to predation by red foxes (Vulpes vulpes) in experimental trials on three islands off Newfoundland's southwest coast. Arctic hares were significantly more vulnerable than snowshoe hares to fox predation: they were killed at a higher rate, and though the probability of death increased slightly for arctic hares over a trial period, it decreased for snowshoe hares. Rates of fox predation on arctic hares were inversely related to home-range size and nutritional status, whereas predation on snowshoe hares was inversely related to the percentage of home-range core areas with dense understory cover. We believe the arctic hare's greater vulnerability to fox predation, found in this study, coupled with its apparent inability to utilize food resources in forested areas that support snowshoe hares, which we found in an earlier study, largely accounts for the current restriction of arctic hares in Newfoundland to certain mountain and coastal barrens. The status of arctic hare populations before the introduction of snowshoe hares is unclear. However, distribution and abundance likely decreased as red foxes and lynx (Lynx canadensis) increased and began to cycle with snowshoe hares. Dispersal of foxes, and perhaps of lynx, from forested areas following snowshoe hare declines would have periodically intensified predation on the barrens.
First Canadian record of Paralomis bouvieri Hansen, 1908 (Decapoda: Anomura: Lithodidae), infected by the rhizocephalan Briarosaccus callosus (Cirripedia: Peltogastridae) and carrying a hyperparasitic cryptoniscinid isopod (Epicaridea)
Authors: Pohle Gerhard W.
Published: July 2008

The stone crab Paralomis bouvieri is reported for the first time from Canadian Atlantic waters. Combined records now indicate a continuous boreal circum-Atlantic distribution. This is also the first documentation of the rhizocephalan parasite Briarosaccus callosus infecting P. bouvieri. Growth rings on the cuticular shield of B. callosus showed an age of about 4 years. A secondary hyperparasitic infection by a cryptoniscinid isopod was also noted. The crabs were found in much shallower waters than previously recorded. Host, parasite, and hyperparasite specimens have been deposited at the Atlantic Reference Centre, Huntsman Marine Science Centre, St. Andrews, New Brunswick, Canada.
Consumption of euphausiids by harbour porpoise (Phocoena phocoena) calves in the Bay of Fundy
Authors: Smith Richard J. , Read Andrew J.
Published: July 2008

We compared the contents of 31 stomachs of harbour porpoise calves killed in commercial gill nets in the Bay of Fundy between July and September, 1985–1991, with the stomach contents from 149 adult animals obtained from the same source between July and September, 1988–1991. The calves' most common prey item was the euphausiid Meganyctiphanes norvegica, found in 15 stomachs, whereas the adults fed primarily on clupeid and gadid fishes. Euphausiids were also found in the stomachs of several of these fish species, and we suggest that porpoise calves take euphausiids while their mothers are feeding on other euphausiid predators.
A hydrozoan, Zanclella bryozoophila n.gen., n.sp. (Zancleidae), symbiotic with a bryozoan, with a discussion of the Zancleoidea
Authors: Boero F. , Hewitt C. L.
Published: July 2008

A new genus and species of hydroid, Zanclella bryozoophila, symbiotic with bryozoans is described. The colony is polymorphic and highly integrated with its bryozoan host. The gastrozooids have one or, rarely, two tentacles; dactylozooids are without tentacles. The medusa stage is reduced to liberable eumedusoids produced on the hydrorhiza, and has exumbrellar nematocyst chambers. The cnidome of both stages consists of stenoteles and macrobasic euryteles. General morphology and cnidome structure place this newly described form in the Zancleidae. A new genus is recognized on the basis of polymorphism of the hydroid and reduction of the medusa stage. The association with the bryozoan is described as commensal. Hydranths appear to feed on particles gathered by ciliary action of the bryozoan lophophore, and the hydrorhiza is surrounded by the bryozoan skeleton. The advantage of this relationship to the bryozoan is believed to be protection, effected by the nematocysts of the hydroid.
Early movements and dispersal of juvenile snowshoe hares
Authors: O'Donoghue Mark , Bergman Carita M.
Published: July 2008

Juvenile snowshoe hares (Lepus americanus) were radio-tagged at birth to examine predispersal movements, maternal–juvenile interactions, and timing of natal dispersal. Hare litters stayed at their natal sites for an average of 2.7 days, after which each individual usually found a separate hiding place from its littermates. Observations at natal sites suggested that adult female hares nursed their litters only once per day, shortly after twilight. Some females aggressively defended their newborn litters before the juveniles left the natal site. Juvenile hares ranged progressively further from their natal sites as they grew, up to the age of 20 days. From 20 to 35 days of age, leverets stayed approximately 75 m from their natal sites, after which time their movements again increased. Natal dispersal of juvenile hares began shortly after weaning at 24–28 days of age. Many third-litter juveniles were nursed for a longer period lasting at least 29–40 days. Juvenile males may disperse sooner and travel further than females from their natal ranges.
Postmortem changes in avian gross intestinal morphology
Authors: Barton N. W. H. , Houston D. C.
Published: July 2008

To assess the reliability of data from carcasses that have been exposed to unknown environmental conditions after death, the effects of time and temperature post-mortem were examined in 2-week-old cockerels (Gallus gallus) by determining whether freezing and refrigeration before analysis affect the weight and length of the small intestine. Intestine weight decreases significantly with increases in temperature and time postmortem. Intestine length also increases but to a lesser extent. Freezing and (or) refrigeration of carcasses soon after death does not significantly affect intestine weight or length upon thawing. It is concluded that intestine length should be used in preference to intestine weight when the source of carcasses and the conditions to which they were subjected are unknown.
Western Palaearctic and Ethiopian species of Skrjabinoclava (Nematoda: Acuarioidea) in Icelandic shorebirds (Aves: Charadriiformes) en route to breed in the New World and Greenland
Authors: Anderson R. C. , Wong P. L.
Published: July 2008

Previous studies suggested that the unusual diversity of Skrjabinoclava spp. in New World charadriiforms is related to differences in the marine wintering and staging areas of the hosts where transmission occurs, foraging behaviour, food preferences, and the distribution of intermediate hosts. It was predicted that shorebirds in other regions of the world would have unique species of Skrjabinoclava, based on different wintering and staging areas. To test this hypothesis, shorebirds migrating to Greenland and the eastern Canadian Arctic from western Europe and Africa were collected in Iceland. Examination of these birds revealed seven species of Skrjabinoclava, six of them new: S. sealyi n.sp. in Charadrius hiaticula hiaticula; S. albae n.sp. and S. vogurensis n.sp. in Calidris alba; S. snorrasoni n.sp. in Numenius phaeopus phaeopus; S. kristjani n.sp. in Arenaria interpres; S. skulasoni n.sp. and S. aculeata in Calidris alpina schinzii. It was possible to trace transmission of some species to coastal staging and wintering areas in the United Kingdom and West Africa.
Heterogeneous survival rates of mallards (Anas platyrhynchos)
Authors: Rexstad Eric A. , Anderson David R.
Published: July 2008

We analyzed data of adult mallards (Anas platyrhynchos) banded throughout North America during the past 30 years, using a model developed to estimate heterogeneity in survival rates of marked individuals. The model incorporating heterogeneity in survival rates was often the most parsimonious model for the data sets analyzed, thus constituting an advancement over previous band-recovery models. Likelihood-ratio tests indicated that significant amounts of heterogeneity existed in the data sets analyzed. We were unable to detect significant differences in heterogeneity between sexes or between birds banded prior to the hunting season (July–September) and after the hunting season (January–February) in the same areas. Heterogeneity varied widely among banding areas. Changes in reporting rates confound the estimation of heterogeneity. Adjustment of estimates of heterogeneity for differences in recovery rates in the first year after banding and subsequent years results in lower estimates of heterogeneity for mallards. Coefficients of variation of survival rates for adult mallards, adjusted for variation in recovery rates, varied from 18 to 25%.