bluuebunny/crossref_metadata_2025 huggingface dataset:
Variability of Density Estimates and the Optimization of Sampling Programs for Stream Benthos
Authors: Morin Antoine
Published: May 2008

Several sets of published data were reanalyzed to examine the effect of mean density size and type of sampler, and functional group of the collected organisms on the variance in estimates of stream benthos density. The logarithm of variance (log s2) is a quadratic function of the logarithm of mean density ([Formula: see text], individuals∙m−9). Because of the curvilinear relationship between the logarithm of variance and the logarithm of mean density, I suggest that none of the commonly used transformations (square root, fourth root or logarithmic) will stabilize the variance at all the densities encountered. Information about sampler size (Q, square metres) further improves the prediction of the logarithm of sampling variance, which increases with an increase in mean density and decreases with an increase in the size of the sampler On average density estimates obtained with artificial substrates were as variable as those from natural substrates, although some artificial substrates (baskets of rocks) yielded less variable density estimates than average. The number of replicates necessary to obtain a given precision decreases with increasing mean density and sampler size, whereas the total area to be sampled increases with sampler size. Although I suggest that the use of small samplers reduces the cost of estimates of density, the sampler size that minimizes the sum of the sampling and processing effort can depend on the mean density.
A Laboratory Study of the Effects of Aluminum and pH on Amphibian Eggs and Tadpoles
Authors: Clark Karen L. , Lazerte Bruce D.
Published: May 2008

Bufo americanus and Rana sylvatica eggs and tadpoles were exposed in laboratory bioassays to a range of pH and aluminum concentrations commonly encountered in ponds and streams of central Ontario. Bufo americanus and R. sylvatica hatching success was reduced at pH 4.14. The addition of 10 μg inorganic monomeric aluminum (IMAl)/L at pH < 4.35 further reduced hatching success of B. americanus. Rana sylvatica was slightly less sensitive, with hatching success being reduced by addition of 20 μg IMAl/L at pH 4.14. Increasing aluminum concentrations at pH 4.14 appeared to have no further effect except at the highest level used (200 μg/L). IMAI that was toxic at pH 4.35 or 4.14 had no effect at pH 4.75 or 5.75. Toxicity was not dependent on the aluminum speciation, since similar levels of Al3+ and Al(OH)x complexes that were toxic at pH 4.14 were not toxic at pH 4.75; also, Al(F)x complexes were as toxic as Al3+. Egg mortality due to hydrogen ion stress was correlated with a delay in time of hatch and a reduction in egg size; however, there was no consistent pattern with respect to aluminum stress. Bufo americanus and R. sylvatica tadpoles were not sensitive to up to 200 μg IMAl/L and pH as low as 4.14.
Effect of Nile Tilapia (Oreochromis niloticus) on the Ecosystem of Aquaculture Ponds, and Its Significance to the Trophic Cascade Hypothesis
Authors: Diana James S. , Dettweiler Daniel J. , Lin C. Kwei
Published: May 2008

The trophic cascade hypothesis holds that an increase in fish biomass causes a decline in food organisms of the fish, which cascades down to regulate lower trophic levels by altered consumptive demands. This hypothesis was evaluated by stocking Nile tilapia (Oreochromis niloticus) at densities of 0, 1, 2, or 3 fish/m3 in triplicated 220-m3 ponds near Bangkok, Thailand. All ponds were fertilized with 500 kg chicken manure∙ha−1∙wk−1. We measured phosphorus, nitrogen, chlorophyll a, primary productivity, zooplankton abundance, and fish yield in all ponds. Increased stocking density resulted in decreased adult fish growth but similar yields among the three density treatments. Regressions relating the abundance of each trophic level to the next higher trophic level were either positive or nonsignificant, which is contrary to trophic cascade predictions. Zooplankton became significantly more dense over time in fishless ponds than the other three treatments, but no other trophic level differed among treatments. These results indicate that presence of fish had a significant effect on zooplankton in ponds, but biomass of fish or abundance of zooplankton did not significantly affect other trophic levels.
Decomposition of Rainbow Trout (Oncorhynchus mykiss) Carcasses in a Forest Stream Ecosystem Inhabited only by Nonanadromous Fish Populations
Authors: Minshall G. Wayne , Hitchcock Evelyn , Barnes James R.
Published: May 2008

The overall dynamics of rainbow trout (Oncorhynchus mykiss) carcass decomposition in a woodland stream ecosystem was examined in two experiments conducted in the West Fork of Mink Creek, Idaho: one during winter–spring (mean water temperature 4.2 °C) and one during summer (mean water temperature 8.6 °C). Relative weight loss (%AFDW) from fish during both periods was essentially constant. In spring, mean daily loss per day was 1.5%. Although this rate is comparable with the decay of high-quality ("fast") leaves, it took much longer than expected (> 120 d) for the even higher quality fish protein. In summer, decay was more rapid (4.9%/d) and was completed in less than half the time (~50 d). Most decay appeared to progress from inside the carcasses outward to the skin. The skin remained intact throughout most of both experiments. Nutrients leached from the fish appeared to be utilized rapidly by microbes associated with the carcass, since no stimulation of algal growth occurred immediately downstream of the carcasses. This suggests extremely tight nutrient spirals and high nutrient retention in Mink Creek and other comparable Rocky Mountain headwater streams.
Spatial Variation in the Distribution of Phosphorus Species in the Surficial Sediments of Canadohta Lake, Pennsylvania; Implications for Internal Phosphorus Loading Estimates
Authors: Ostrofsky M. L. , McGee G. G.
Published: May 2008

The concentrations of total, loosely sorbed, metal-bound, calcium-bound, and organic phosphorus, iron, and organic matter (loss on ignition) were determined for 71 surface sediment samples from Canadohta Lake, Pennsylvania. The results indicate that lake sediments can be highly variable with respect to these parameters. Most of these parameters were highly intercorrelated, and some general patterns appear to exist based on these and previously published data. Given the highly variable nature of sediment quality, particularly among these parameters which have been shown to be good predictors of sediment phosphorus release rates, estimates of internal phosphorus loading based on a few incubated cores taken from the deepest area of a lake may contain serious errors. We recommend that sediment heterogeneity be assessed in order to determine an appropriate number and distribution of cores to be incubated for internal loading estimates.
Survival, Contribution, and Return of Hatchery Coho Salmon (Oncorhynchus kisutch) Released into Freshwater, Estuarine, and Marine Environments
Authors: Solazzi Mario F. , Nickelson Thomas E. , Johnson Steven L.
Published: May 2008

We released six groups of marked yearling hatchery coho salmon (Oncorhynchus kisutch) in six locations each year for five years beginning with the 1981 brood. Fish were released immediately below Bonneville Dam (control), at the Tongue Point Coast Guard Station (head of saltwater intrusion in the Columbia River), between the jetties at the Columbia River bar, in the Columbia River plume water, in coastal water approximately 19 km north and 19 km offshore of the mouth of the river, and in oceanic water approximately 38 km offshore. We found a 1.6-fold increase in the survival index (ocean catch through September 18 each year) for the fish released at Tongue Point compared with the control group. After adjusting for differences in the survival index between release groups, we found a 2.5-fold increase in the contribution to the Columbia River gillnet fishery from the fish released at Tongue Point compared with the control group. We found no significant difference between survival of the other release groups and survival of the control group. We also found that the percentage of adult fish that returned to locations other than the Columbia basin increased as the distance the fish were transported offshore increased.
Fecundity and Reproductive Output in Nine Species of Cancer crabs (Crustacea, Brachyura, Cancridae)
Authors: Hines Anson H.
Published: May 2008

The major variables of reproductive output and fecundity were compared among brooding females of nine species of Cancer from the North Pacific and North Atlantic: C. oregonensis, C. gracilis, C. irroratus, C. antennarius, C. productus, C. borealis, C. anthonyi, C. magister, and C. pagurus. Female body size is the principal determinant of reproductive output, with dry body weights spanning two orders of magnitude from 1.2 to 199.5 g among species and often one order of magnitude within species. Mean dry brood weights ranged from 0.21 to 26.7 g among species, with relative brood size varying from 11 to 19% of female weight. The brood mass is partitioned into eggs ranging among species from 311 to 442 μm, resulting in mean fecundities ranging among species from 18 200 to 2 208 000 eggs per brood. Most species produce one or two broods per year over the winter–spring season over a reproductive span averaging 6.6 yr (range 4–10 yr). Cumulative reproductive output and cumulative fecundity over the maximum estimated life span exhibited approximately isometric functions of maximum body size, and they ranged among species from 1.88 to 316 g brood weight and 158 000 to 22 300 000 eggs per lifetime, respectively. The pattern of covariation of reproductive traits in the Cancridae corresponds well with the overall pattern previously determined for a diverse array of brachyurans from seven families.
Abundance and Distribution of Narwhals (Monodon monoceros) in Northern Hudson Bay
Authors: Richard Pierre R.
Published: May 2008

Aerial surveys for narwhals (Monodon monoceros) were conducted in August 1981, in July 1982, 1983, and 1984, and in March 1983 in the Repulse Bay area between Roes Welcome Sound and Lyon Inlet, north of Southampton Island. About 1300 narwhals were estimated to occupy waters between northern Roes Welcome Sound and Lyon Inlet in July 1982, 1983, and 1984. Narwhals were found throughout the study area but were more concentrated in three areas: northern Roes Welcome Sound, southern Frozen Strait, and, in 1984, Lyon Inlet. Only four narwhals were observed during August 1981 reconnaissance surveys of these areas. No narwhals were seen during the March 1983 survey of Roes Welcome Sound and leads of Frozen Strait. A winter concentration of narwhals observed by others in eastern Hudson Strait was of similar size to that which we observed in July, suggesting that they could be the same stock. If this is so, the northern Hudson Bay narwhals could be distinct from the stock that inhabits Davis Strait and Baffin Bay.
Usefulness of Fourier Analysis of Otolith Shape for Atlantic Mackerel (Scomber scombrus) Stock Discrimination
Authors: Castonguay Martin , Simard Patrick , Gagnon Pierre
Published: May 2008

We compared shapes of Atlantic mackerel (Scomber scombrus) sagittae between the two contingents (i.e. spawning groups) from the Northwest Atlantic and between the stocks from the Northwest Atlantic and the North Sea to evaluate whether otolith shape could differentiate between the two contingents in a mixed fishery. We quantified shapes with the Fourier series, an objective and rapid method which decomposes a shape's outline into a series of sinusoids. To determine a correct way to compare contingents/stocks, we first assessed four intracontingent effects on otolith shapes. Age and year-class effects were significant, while sex and bilateral position effects were not. This temporal instability in shapes indicates that confounding effects of age and year-class on otolith shapes need to be assessed carefully before drawing conclusions on stock structure. It also shows that comparative studies of otolith shapes with Fourier descriptors are not useful for mackerel contingent discrimination. The power of discriminant functions to correctly classify test mackerel samples separated by age and sampling year, on the basis of otolith shape, was better for comparisons between the stocks than for those between the contingents.
Comparison of Catch Rates among Small and Large Bongo Sampler for Calanus finmarchicus Copepodite Stages
Authors: Anderson John T. , Warren William G.
Published: May 2008

Comparison of catch rates between small (20-cm, 0.165-mm-mesh nets) and large (61-cm, 0.333- and 0.505-mm-mesh nets) plankton samplers was carried out for Calanus finmarchicus copepodite stages sampled simultaneously during six different times. It is concluded that C. finmarchicus stages CI and CII were undersampled in 0.333-mm-mesh samples, while stages CIV–CVI were undersampled in 0.165-mm-mesh samples. Stage CIII catch rates were not different for these two samplers. Comparison of catch rates between 0.165- and 0.505-mm-mesh samples demonstrated that stages CI–CIII were undersampled in the 0.505-mm-mesh samples, stages CV and CVI were undersampled in the 0.165-mm-mesh samples, and there was no difference in catch rates for stage CIV. There was evidence of substantial variability in results among cruises for most stages. This is attributed to inherent variability associated with plankton sampling due to their patchy distribution. Due to the large variation in catch rates between these different samplers, it is recommended that the appropriate sized sampler be used to collect different stages of C. finmarchicus copepodites rather than attempting to correct for catch rate differences among different sized samplers.
Modelling Bioaccumulation of Organic Pollutants in Fish with an Application to PCBs in Lake Ontario Salmonids
Authors: Barber M. Craig , Suárez Luis A. , Lassiter Ray R.
Published: May 2008

A model describing passive accumulation of organic chemicals from the aqueous environment and contaminated food in fish is developed. This model considers both biological attributes of the fish and physicochemical properties of the chemical that determine diffusive exchange across gill membranes and intestinal mucosa. Important biological characteristics addressed by the model are the fish's gill morphometry, feeding and growth rate and fractional aqueous, lipid, and nonlipid organic composition. Relevant physicochemical properties are the chemical's molar volume and n-octanol/water partition coefficient (Kow), which are used to estimate the chemical's aqueous diffusivity and partitioning to the fish's lipid and nonlipid organic fractions respectively. The model is used to describe and to analyze the bioaccumulation of polychlorinated biphenyls (PCBs) in Lake Ontario alewife (Alosa pseudoharengus), coho salmon (Oncorhynchus kisutch), rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), and lake trout (Salvelinus namaycush).
A General Framework for Developing Sequential Fisheries Models
Authors: Schnute Jon T.
Published: May 2008

A sequential fisheries model relates observed data to the biological dynamics of an underlying stock. Either model component, dynamic or observational, can be subject to statistical variation. Current fisheries literature includes models with (1) variable dynamics and no observation error, (2) deterministic dynamics and observations subject to measurement error, and (3) combined dynamic and measurement variability. This paper presents a general framework for developing sequential fishery models and estimating model parameters from available data. The framework encompasses most traditional stock assessment models and suggests new, potentially useful extensions. It generalizes the conventional definition of state space model to include nonlinear equations with nonnormal error. The paper rigorously compares two paradigms (KF: Kalman filter, EV: errors in variables) used for parameter estimation. Each paradigm is formulated in both frequentist and Bayes contexts, where Bayes is shown to be most appropriate for the EV paradigm. Model design concepts are illustrated with a simple example oriented to catch data and a more complex example with catch-at-age data. Because the framework forces essential questions to be asked about underlying processes, observed data, and sources of variability, it can help delineate the limits of current knowledge and establish rational priorities for future data collection.
Impact of Nutrients and Physical Factors on the Shift from Cyanobacterial to Chlorophyte Dominance in Shallow Danish Lakes
Authors: Jensen J. P. , Jeppesen E. , Olrik K. , Kristensen P.
Published: May 2008

Phytoplankton dominance (as biomass) by heterocystous cyanobacteria, nonheterocystous cyanobacteria, and chlorophytes was studied along a trophic gradient (0.011–2.2 mg P∙L−1) by analyzing regularly collected semiquantitative data from 178 shallow Danish lakes (mean depth < 3 m) and quantitative data from 32 lakes. Heterocystous cyanobacteria were dominant at low total P (TP) (< 0.25 mg P∙L−1) and nonheterocystous cyanobacteria at intermediate TP (0.25–0.8 mg P∙L−1), while chlorophytes often were dominant at high TP (> 1 mg P∙L−1). In contrast with many earlier findings, heterocystous cyanobacteria were not dominant at low total N (TN):TP or low inorganic N concentrations; chlorophytes were dominant at extremely high pH, and the shift from cyanobacterial to chlorophyte dominance could not be explained by a change in the photic zone to mixing zone ratio. We suggest that chlorophyte dominance in hypertrophic shallow lakes is attributable to continuous input of nutrients and carbon from the sediment and external sources. This renders the fast-growing chlorophytes a superior competitor compared with the relatively slow-growing cyanobacteria, even when inorganic nutrient concentration is low and pH high. New predictive models relating phytoplankton dominance to TP in shallow lakes were developed, as former models failed to predict our observations satisfactorily.
Isolation, Partial Characterization, Induction, and the Occurrence in Plasma of the Major Vitelline Envelope Proteins in the Atlantic Halibut (Hippoglossus hippoglossus) during Sexual Maturation
Authors: Hyllner Sven Johan , Norberg Birgitta , Haux Carl
Published: May 2008

The vitelline envelope of Atlantic halibut (Hippoglossus hippoglossus) is composed mainly of two major and two minor proteins. Estradiol-17ß induces the two major vitelline envelope proteins in halibut of both sexes. These proteins were also found in plasma of vitellogenic females. The origin of the two major vitelline envelope proteins is not restricted to the ovary, as male halibut synthesize these proteins after treatment with estradiol-17ß. Individual female halibut were followed and plasma sampled from May to March. Plasma levels of estradiol-17ß increased in October, peaked in early February, and declined until the last ovulation in March. In October, the two major vitelline envelope proteins were first detected in plasma and the amount remained elevated until early March. Prior to the last ovulation, the amount decreased. Plasma vitellogenin varied in a similar way. The results provide strong evidence that the physiological regulation of the synthesis of the major vitelline envelope proteins in teleosts is controlled by the female sex steroid estradiol-17ß.
Influence of Environmental Factors on Heavy Metal Concentration in Lake Sediments in Southern Norway Indicated by Path Analysis
Authors: Fjeld Eirik , Rognerud Sigurd , Steinnes Eiliv
Published: May 2008

We studied relationships between environmental factors and accumulation of Hg, Cd, Pb, and Ni in sediments in 132 lakes in southern Norway. Generally, the concentrations of Hg, Cd, and Pb in surface sediments were considerably elevated as compared with sediments deposited in preindustrial times whereas Ni concentrations showed only minor increases. By path analysis, we modelled how different environmental factors may influence the metal concentrations in surface sediments. The models indicated that both Hg and Pb were associated with sedimenting organic matter, and sediment concentrations were strongly influenced by atmospheric deposition (indirectly measured as metal concentration in mosses) and the amount of organic carrier particles in lake water. Cd behaved similarly, except for a weaker association with organic matter and a positive effect from pH, indicating that Cd is mobilized during acidification. Ni was associated with the inorganic fractions in lake sediments and seemed also to be mobilized during acidification. Geochemical contributions of Ni were larger in sediments than atmospheric deposition whereas atmospheric deposition was the major source of Pb. For the other two elements, estimates of geochemical contributions were lacking.
Modelling Pelagic Fish and Plankton Trophodynamics off Southwestern Vancouver Island, British Columbia
Authors: Robinson Clifford L. K. , Ware Daniel M.
Published: May 2008

A trophodynamics model is used to estimate annual plankton and fish production for the southern British Columbia continental shelf during 1985–89. The model describes the feeding interactions among diatoms, copepods, euphausiids, juvenile and adult Pacific herring (Clupea pallasi), Pacific hake (Merluccius productus), chinook salmon (Oncorhynchus tshawytscha), and spiny dogfish (Squalus acanthias) and is forced by empirical seasonal patterns in upwelling, sea surface temperature, and solar radiation. The most important simulation results are that (1) there is an imbalance between fish consumption and euphausiid production during the summer upwelling season, (2) the biomass and arrival timing of migratory hake significantly influence plankton and fish production, and (3) about 11% of the 332 g C∙m−2∙yr−1 annual diatom production is transferred to copepods and euphausiids and 1.0% of the diatom production to fish, while 27.5% of the 11.9 g C∙m−2∙yr−1 euphausiid production is consumed by herring and hake. The high plankton and fish production on the southern British Columbia shelf is comparable with other productive coastal upwelling regions.
Myriophyllum spicatum Pumps Essential and Nonessential Trace Elements from Sediments to Epiphytes
Authors: Jackson Leland J. , Rowan David J. , Cornett R. Jack , Kalff Jacob
Published: May 2008

To test the hypothesis that elements can be transferred from freshwater sediments to macrophytes and to epiphytes, we grew Myriophyllum spicatum in natural sediments containing 60Co and 54Mn (essential) and 137Cs, 152Eu, 154Eu, and 155Eu (nonessential). We found no differences between shoot or epiphyte to sediment bioaccumulation factors (BAFs) and only found differences between root and shoot to sediment BAFs for 60Co and 54Mn, probably because these elements adsorb onto root surfaces. We found no differences in BAFs for any elements between shoots and epiphytes, suggesting no differences in the transfer of essential and nonessential elements. There were, however, interelement differences for the roots, again probably due to surface adsorption related to redox sensitivity. Using isotope specific activity ratios, we calculated that over 75% of the Co and 100% of the Mn in M. spicatum was obtained from the sediments and that all Co and Mn in the epiphytes was sediment derived through the host. Although the net flux of trace elements from the sediments to the water via macrophytes has been shown to be small in most situations, buried pulses of nonessential elements may be reintroduced to the littoral food web by epiphytes being grazed by invertebrates and fish.
Determinants of Postmolt Size in the American Lobster (Homarus americanus). II. Folding of Premolt Cuticle
Authors: Cheng Jin-Hua , Chang Ernest S.
Published: May 2008

The effects of eyestalk ablation, regeneration, and rearing condition on the size of new cuticles before and after expansion were studied in juvenile Homarus americanus. Both eyestalk-ablated and intact lobster grew larger in large spaces than in small spaces. In contrast, regeneration reduced molt increment. Despite large differences in molt increment (percentage of size increase during a molt) among experimental groups, the percentage of postmolt size increase that could be accounted for by unfolding of the new cuticle was large and constant in each group. In addition, transferring freshly molted lobster to dilute seawater did not produce any further size increase but instead caused cuticle breakage in some animals. We conclude that molt increment in lobster is determined by regulating the size of the cuticle before ecdysis. The size of the postmolt cuticle is primarily a result of unfolding of the new, previously folded cuticle.
A Predation Bioassay to Quantify the Ecological Significance of Sublethal Responses of Juvenile Chinook Salmon (Oncorhynchus tshawytscha) to the Antisapstain Fungicide TCMTB
Authors: Kruzynski G. M. , Birtwell I. K.
Published: May 2008

The lumber protection antisapstain fungicide 2-(thiocyanomethylthio)benzothiazole (TCMTB) is leached by rainfall from treated wood awaiting shipment from outdoor lumber storage facilities. Stormwater discharges of this pesticide into estuarine reaches of the Fraser River, British Columbia, have raised concern about toxic effects on juvenile salmon rearing in this habitat. Simulated stream flow conditions were used to expose underyearling chinook salmon (Oncorhynchus tshawytscha) to a sublethal (10 μg∙L−1) concentration of TCMTB. Equal numbers of fin-clipped control and exposed fish were subsequently transferred to a vertically stratified (fresh over seawater) 15 500-L outdoor tank where they were challenged with the combined stressors of salinity and the presence of a marine predator (yellowtail rockfish (Sebastes flavidus)). After 5 d under these simulated estuarine conditions, survivors were enumerated. Chinook salmon that had been exposed to the toxicant were consumed in preference to the control group by a factor of 5.5:1. Inasmuch as predator avoidance represents the successful integration of appropriate biochemical, physiological, and behavioural responses, the predator bioassay provides an ecologically relevant technique to determine the significance to survival of the complex multifactorial interactions of individually "sublethal" stressors.
Responses of Benthic Communities to Episodic Acid Disturbances in a Lake Outflow Stream at the Experimental Lakes Area, Ontario
Authors: Hall Ronald J.
Published: May 2008

Effects of episodic experimental pH depressions on water chemistry and structure of benthic communities were investigated in northwestern Ontario, a location with low H+deposition. Acidity levels were increased from background values of pH 6.9 to 5.0, 4.5, and 4.0 to simulate snowmelt and rainstorm events observed in south-central Ontario. Conductivity and concentrations of Ca and Mn increased significantly for all three pH disturbances. Fe and dissolved organic C remained unchanged at pH 4.5 and 4.0 but Fe increased at pH 5.0. Total and inorganic monomeric Al increased at pH 4.5 and 4.0 relative to reference areas. At pH 5.0, density decreases were observed for Baetis, Ectemnia, Simulium, and Prosimulium, at pH 4.5 for Baetis, Lepidostoma, Micropsectra, Simulium, and Prosimulium, and at pH 4.0 for Baetis, Tanytarsus, and Cricotopus. Densities of collector/filterers and clingers decreased at all pH levels, but diversity decreased in the experimental reach at pH 4.0 only. Drift density of the above genera was correlated with H+concentration. Large reductions in macroinvertebrate densities occurred at higher pH (5.0) and during shorter exposure times compared with previous experiments in areas of higher H+deposition in south-central Ontario and New Hampshire.
Shift in the Intestinal Microflora of Atlantic Halibut (Hippoglossus hippoglossus) Larvae during First Feeding
Authors: Bergh Øivind , Naas Kjell E. , Harboe Torstein
Published: May 2008

Isolates of aerobic intestinal bacterial flora from unfed Atlantic halibut (Hippoglossus hippoglossus) larvae revealed a population dominated by nonfermentative rods of the Cytophaga/Flexibacter/Flavobacterium group. Following the onset of feeding, the flora gradually changed towards a fermentative flora dominated by the Vibrio/Aeromonas group. This transition occurred faster in a group which was reared in water containing cultivated phytoplankton, in contrast with groups where the larvae were kept in filtered water. No major differences in the bacterial flora of the tank water were found among the groups.
Ultrastructural studies of the in vitro chitin and cuticle secretions in the wing pads of Locusta
Authors: Cassier Pierre , Papillon Marguerite
Published: May 2008

Cuticle deposition and chitin synthesis in the wing pads of 1-day-old fifth-instar larvae of Locusta were stimulated in vitro by 20-hydroxyecdysone and makisterone A. Stimulation was dose-dependent from 2 × 10−7 to 2 × 10−5 M. The response appeared after a 36- to 48-h lag period characterized by inhibition of the postecdysial activity of the previous cuticular cycle. The hormones stimulated deposition of the epicuticular layers, triggered uptake of the chitin precursor N-acetyl-D-glucosamine and biosynthesis of chitin, and initiated microtubular bundle orientation. Ecdysone has no effect on these processes. Ecdysone and 20-hydroxyecdysone do not act synergistically on chitin biosynthesis. These data confirm earlier observations on the differential effects of the major forms of ecdysteroids, ecdysone and 20-hydroxyecdysone, on the activity of epidermal cells of locusts. Chitin biosynthesis by 20-hydroxyecdysone stimulated cells requires the integrity of the microtubular system and the chitin–synthetase complex. It was inhibited by colcemid, a microtubular poison, and by diflubenzuron, an inhibitor of chitin synthetase. These drugs had no effect on apolysis and epicuticular secretion. The in vitro biosynthesis of chitin was also inhibited by azadirachtin, a cytotoxic drug.
Genetic relationship of wood and plains bison based on restriction fragment length polymorphisms
Authors: Bork A. M. , Strobeck C. M. , Yeh F. C. , Hudson R. J. , Salmon R. K.
Published: May 2008

To evaluate the genetic relationship within and between wood and plains bison of Elk Island National Park, genomic DNA samples were screened for restriction fragment length polymorphisms (RFLP) with cDNA probes for growth hormone, growth hormone releasing factor, somatostatin, and insulin-like growth factor-1. Of the 28 fragments identified, two revealed RFLPs, both of which were associated with the growth hormone releasing factor locus. The observed frequencies of the polymorphic sites did not differ from a Hardy–Weinberg distribution in either population, which is indicative of random mating populations. The contingency χ2 tests for homogeneity indicate that the fragment frequencies of the polymorphic restriction sites differ significantly (P = 0.00) between the wood and plains bison. The number of net nucleotide substitutions between the two populations was 0.0007, indicative of a recent divergence. Conversion of the bison nucleotide divergence results in a relative protein divergence of 0.007 to 0.018. This converted divergence corresponds closely to the divergence reported for other geographically isolated populations; thus, this preliminary analysis suggests the bison have at least reached the stage of geographic isolation in their evolutionary divergence.
Factors influencing foraging time in two aerial insectivores: the bird Chordeiles minor and the bat Eptesicus fuscus
Authors: Aldridge H. D. J. N. , Brigham R. M.
Published: May 2008

An energetic model was used to analyze factors important in determining foraging time in two species of aerial insectivore, the bird Chordeiles minor and the bat Eptesicus fuscus. Our results suggest that E. fuscus and C. minor, though feeding at the same site and taking predominantly the same prey, use different foraging strategies and their foraging times are limited by different factors. Chordeiles minor forage for relatively short periods. We predict that this species may attack more than one prey item simultaneously. As predicted, it seems likely that foraging time of the birds is limited by the duration of twilight. Foraging bouts tend to be short and remain relatively constant in duration throughout the summer. Eptesicus fuscus, on the other hand, is not limited by the duration of twilight, but alters its foraging time in response to changes in its energy requirements, although other factors such as the duration of prey activity periods also have an effect. The abundant availability of prey at our study site meant that foraging time was determined primarily by the animals' daily energy demands.
Preservation of avian blood and tissue samples for DNA analyses
Authors: Seutin Gilles , White Bradley N. , Boag Peter T.
Published: May 2008

A problem frequently faced by researchers involved in collecting tissues for DNA isolation is the preservation of samples in the field prior to and during their transportation to the laboratory. Prevention of DNA degradation is usually achieved through freezing. As this is not always practical, we have tested the efficiency of chemical solutions containing high concentrations of salts (e.g., NaCl, EDTA, and diaminocyclohexanetetraacetate) and detergent at preserving DNA in bird tissue and blood samples stored at ambient temperature for extended periods of time. For blood samples, we recommend the use of a buffer that lyses the cells and nuclei and contains 0.01 M Tris, 0.01 M NaCl, 0.01 M EDTA, and 1% n-lauroylsarcosine, Ph 7.5. Tissue samples are best preserved as small pieces in a saline solution made of 20% dimethyl sulfoxyde, 0.25 M EDTA, saturated with NaCl, pH 8.0. DNA extracted from samples preserved in these solutions for up to 24 weeks was compared with DNA recovered from tissue samples stored at −70 °C and blood samples stored at −70 and −20 °C. Yields were similar, averaging 300 μg/0.2 g of tissue and 500 μg/50 μL of blood. Quality of DNA in terms of fragment size, ability to be cut by restriction enzymes, and ability to hybridize to radioactive probes was also similar between cryopreserved and chemically preserved samples. Yields of DNA recovered from tissue samples preserved in 70% ethanol for 6 or 11 weeks was very low and significant degradation was observed. We have also examined how DNA contained in crude avian blood samples withstands freeze–thaw cycles. We found normal yields and no significant degradation of DNA in samples that experienced up to six cycles. We encourage field researchers who refrain from preserving tissue samples because of logistical problems, such as transporting liquid nitrogen containers in the field, to consider using these solutions. Both solutions can also facilitate exchanges of samples between laboratories, and they form an alternative to storage of samples at −70 °C for laboratories and museums with limited access to deep-freezing facilities.
Sexual and subspecific variation in the numbers of rectrices of blue grouse
Authors: Zwickel Fred C. , Degner Mark A. , McKinnon Donald T. , Boag David A.
Published: May 2008

We examined numbers of rectrices of all subspecies of blue grouse (Dendragapus obscurus), determined from our own studies and reported in the literature. Approximately 8% of all birds had an uneven number of rectrices, with no difference between males and females. More birds from a presumed subspecific "hybrid" population had uneven numbers of rectrices than those from "nonhybrid" samples. Of North American tetraonines, sage grouse (Centrocercus urophasianus) and blue grouse appear most variable in this character. Within subspecies, males and females had the same modal numbers of rectrices. The sexes differed, however, in the overall distribution of numbers of rectrices; most birds with submodal numbers were females and most birds with supermodal numbers, males. Males and females in one hybrid population differed in modal numbers of rectrices: males 20, and females 18. Eighty per cent of all coastal blue grouse had 18 rectrices, with no differences among subspecies. In contrast, all interior subspecies differed from each other. The two northern interior subspecies, D. o. pallidus and D. o. richardsonii, had modes of 20 rectrices, with that for pallidus weaker than that for richardsonii (70 and 81% modal, respectively). Dendragapus obscurus obscurus had a mode of 18 rectrices, not different from that for coastal birds. A small sample of D. o. oreinus was equally divided between birds with 18 and 20 rectrices, suggesting relationships with D. o. pallidus to the north and D. o. obscurus to the east. Northern interior blue grouse emerge as a distinct group with respect to modal number of rectrices, which parallels the pattern for the presence or absence of tail bands. Based on these two characteristics, coastal blue grouse appear more closely related to southern interior than to northern interior subspecies. The blue grouse is the only tetraonine with clear evidence of subspecific variation in numbers of rectrices.
Ecology and host relationships of the whale-louse Isocyamus delphini (Amphipoda: Cyamidae) parasitizing long-finned pilot whales (Globicephala melas) off the Faroe Islands (Northeast Atlantic)
Authors: Balbuena J. A. , Raga J. A.
Published: May 2008

In cooperation with an international research program concerning the biology of the long-finned pilot whale (Globicephala melas) in the Northeast Atlantic, 152 pilot whales taken in the Faroese drive fishery were examined for ectoparasites. The whale-louse Isocyamus delphini was detected on 45(29.61%) of the whales. Four whale groups were established, according to sex and sexual status: immature or pubertal males, mature males, immature females, and mature females. Whale-lice showed over-dispersed distributions on these four whale groups. Prevalence, abundance, and spatial distribution of I. delphini on sexually mature males were significantly different from those on the other whale classes. Heavy infections were only observed on mature males. Behavioral differences between males and females and between adults and juveniles could account for these results. The genital slit was by far the site most preferred by I. delphini. This location seems to be one of the few that offers appropriate shelter for this cyamid.
Seasonal changes in populations of Chabaudgolvania waldeni (Quimperiidae; Seuratoidea) in Ambystoma gracile (Ambystomatidae; Caudata)
Authors: Adamson Martin L. , Richardson Jane P. M.
Published: May 2008

Ambystoma gracile (Ambystomatidae; Caudata) were sampled at regular intervals from March through October, in 1986 and 1987, and examined for the presence of the nematode Chabaudgolvania waldeni (Quimperiidae; Seuratoidea). Nematodes were present throughout the lower mainland of British Columbia, but only aquatic stages (juveniles and neotenic adults) were infected. Prevalence ranged from 40 to 100% in individual samples and worms were most prevalent and abundant in March and April. There is probably a single generation a year; transmission occurs in summer, and adults (males and subgravid females) winter in the host. Gravid females occurred in spring. Worms were overdispersed in the host population; the index of dispersion, k, was about 0.79.
Changes in brain levels of gonadotropin-releasing hormone and serum levels of gonadotropin and growth hormone in goldfish during spawning
Authors: Yu K. L. , Peng C. , Peter R. E.
Published: May 2008

Changes in serum levels of gonadotropin (GtH) and growth hormone (GH) and in levels of gonadotropin-releasing hormone (GnRH) in the pituitary and discrete brain areas were studied in male goldfish during spawning with spontaneously ovulating females. Spontaneous ovulation in females was induced by raising water temperature from 12 to 20 °C and providing spawning substrate of artificial floating vegetation. Spawning occurs naturally in sexually mature male goldfish in the presence of ovulating females. Serum GtH levels in spawning male goldfish exposed to ovulatory females increased markedly in synchrony with the ovulatory GtH surge in females. There was also a significant increase in serum GH levels in the spawning males. GnRH levels in the olfactory bulbs, telencephalon, hypothalamus, and pituitary of the spawning males showed marked decreases at the same time as serum levels of both GtH and GH peaked; these events in the males corresponded to the approximate time of ovulation, and similar changes in serum GtH and GH levels and brain GnRH levels, in the females. This temporal correlation between changes in GnRH levels in the brain and pituitary and increases in serum levels of GtH and GH in males as well as females supports the idea that activation of the GnRH neuronal system may be a common pathway for the stimulation of pituitary GtH and GH secretion in goldfish during spawning.
Effects of phytoseiid predators on the sex ratio of the spider mite Panonychus ulmi
Authors: Johnson Dan L. , Proctor Heather C.
Published: May 2008

The effect of predator presence on the adult sex ratio of a spider mite (Panonychus ulmi) was examined in a field experiment. Phytoseiid predators (chiefly Typhlodromus occidentalis) were removed from 32 trees harboring P. ulmi populations, and allowed to remain at natural levels on 32 other trees. Both total population density and proportion of males in the prey population were significantly higher in predator-free trees. Mechanisms that could explain the increase in the proportion of males are examined. The most probable is that greater male activity results in a higher encounter rate between predator and prey, and that subsequent higher male mortality when predators are present exaggerates the female-biased sex ratio. The theoretical effects of sex-biased predation on diplo-diploid and haplo-diploid organisms are discussed.
Highly polymorphic genetic markers in meadow voles (Microtus pennsylvanicus) revealed by a murine major histocompatibility complex (MHC) probe
Authors: Plante Yves , Boag Peter T. , White Bradley N. , Boonstra Rudy
Published: May 2008

We performed cross-species hybridization at the major histocompatibility complex (MHC) to evaluate the ability of murine probes to reveal polymorphism in wild meadow vole populations. Genomic hybridization of a mouse MHC class II I-Aα cDNA revealed extensive restriction fragment length polymorphisms when meadow vole genomic DNA was cleaved with BamHI EcoRI, HindIII, or HincII. The polymorphisms were interpreted by analyzing 10 half-sib families, comprising 6 sires, 10 dams, and 34 offspring. At least 26 different alleles were found with HincII in the family material, and the estimated heterozygosity at those sites is 96%. Several other alleles were found in a population sample. The high degree of genetic variation revealed by this system indicates that it is a viable alternative to multilocus "genetic fingerprinting" probes for the analysis of small mammal pedigrees or strains. Several mouse MHC probes are readily available and they provide a quick route to screening populations and remove the need to extract species-specific markers from genomic libraries.
To slide or stride: when should Adélie penguins (Pygoscelis adeliae) toboggan?
Authors: Wilson Rory P. , Culik Boris , Adelung Dieter , Coria N. Ruben , Spairani Hugo J.
Published: May 2008

We noted whether Adélie penguins (Pygoscelis adeliae), when travelling over snow, walked or tobogganed according to gradient, snow friction, or snow penetrability. Both walking and tobogganing penguins reduced stride length and stride frequency, and thus speed, with increasing uphill gradient although tobogganing birds travelled faster and with fewer leg movements. The incidence of tobogganing increased with decreasing friction between penguin and snow. The percentage of penguins tobogganing was also highly positively correlated with increasing snow penetrability. Penguins walking on soft snow must expend additional energy to pull their feet through the snow, whereas tobogganing birds do not sink. It is to be expected that Adélie penguins would utilize the most energetically favourable form of travel which, under almost all conditions, appeared to be tobogganing. Although tobogganing appears to be energetically more efficient than walking, rubbing the feathers over snow increases the coefficient of friction in unpreeened plumage. We propose that a high incidence of tobogganing necessitates increased feather care and that the decision whether to walk or toboggan probably represents a balance between immediate energy expenditure and subsequent energy and time expended maintaining plumage condition.
Negative covariance between larval Arrenurus sp. and Limnochares americana (Acari: Hydrachnidia) on male Leucorrhinia frigida (Odonata: Libellulidae) and its relationship to the host's age
Authors: Smith Bruce P. , Cook Wanda J.
Published: May 2008

Numbers of larval Arrenurus sp. and Limnochares americana Lundblad mites, parasitic on adult males in a population of Leucorrhinia frigida Hagen, were found to be negatively correlated. The two mite species did differ in their seasonality, but a strong negative covariance remained even when analyses were run separately on data grouped by day. When dragonflies were separated into tenerals and sexually mature males, almost all newly emerged males were heavily parasitized by Arrenurus sp. and rarely parasitized by L. americana, whereas males holding reproductive territories were almost always heavily parasitized by L. americana but carried reduced loads of Arrenurus sp. When territorial males were subdivided dependent on presence or absence of Arrenurus sp., the dragonflies with Arrenurus were significantly less heavily parasitized than those without Arrenurus sp. Through the above partitioning of data, plus recapture of previously marked dragonflies, it was established that the negative covariance between mite taxa reflects the differences in host discovery: Arrenurus sp. attaches to dragonflies during the host's emergence from the water, whereas L. americana attaches to males while they defend reproductive territories at the water's margin. We conclude that the age-correlated differences in infestation of dragonflies by mites could be a valuable method for determining relative age within odonate populations.
Growth and body size in Blanding's turtles (Emydoidea blandingi): relationships to reproduction
Authors: Congdon Justin D. , Loben Sels Richard C. van
Published: May 2008

Growth and reproduction in Blanding's turtles (Emydoidea blandingi) were studied in southeastern Michigan from 1975 through 1988. Average body sizes of both sexes of adults were similar; however, shapes of males were different from those of females. The average size of a group of females with a mean minimum age of 47 years was not significantly different from a younger group with a mean age of 21 years. Clutch size ranged from 3 to 19 ([Formula: see text], N = 280) eggs over 11 years. Clutch wet mass ranged from 60.4 to 183.4 g ([Formula: see text], N = 17), and relative clutch mass of nine females averaged 0.12. Clutch size, and to a lesser degree egg size, showed a significant positive relationship with body size, but not with age of females. Hatchlings averaged 31.0 mm in plastron length, 35.3 mm in carapace length, and 9.2 g in body wet mass. Differences in juvenile growth rates and age at sexual maturity appear to be the major cause of variation in body size of adult Blanding's turtles and the related reproductive output per clutch.