bluuebunny/crossref_metadata_2025 huggingface dataset:
Disruption of a Nonribosomal Peptide Synthetase in
Aspergillus fumigatus
Eliminates Gliotoxin Production
Authors: Cramer Robert A. , Gamcsik Michael P. , Brooking Rhea M. , Najvar Laura K. , Kirkpatrick William R. , Patterson Thomas F. , Balibar Carl J. , Graybill John R. , Perfect John R. , Abraham Soman N. , Steinbach William J.
Published: June 2006

The fungal secondary metabolite gliotoxin produced by
Aspergillus fumigatus
has been hypothesized to be important in the development of invasive aspergillosis. In this study, we addressed this hypothesis by disrupting a nonribosomal peptide synthetase (NRPS) (encoded by
gliP
) predicted to be involved in gliotoxin production. Mutants with a disrupted
gliP
locus failed to produce gliotoxin, which confirmed the role of the NRPS encoded by
gliP
in gliotoxin biosynthesis. We found no morphological, developmental, or physiological defects in Δ
gliP
mutant strains. In addition, disruption of
gliP
resulted in down regulation of gene expression in the gliotoxin biosynthesis gene cluster, which was restored with addition of exogenous gliotoxin. This interesting result suggests a role for gliotoxin in regulating its own production. Culture filtrates from the Δ
gliP
mutant were unable to inhibit ionomycin-dependent degranulation of mast cells, suggesting a role for gliotoxin in suppressing mast cell degranulation and possibly in disease development. However, the Δ
gliP
mutant did not have an impact on survival or tissue burden in a murine inhalational model of invasive aspergillosis. This result suggests that gliotoxin is not required for virulence in an immunosuppressed host with an invasive pulmonary infection.
Identification of the Major Spliceosomal RNAs in
Dictyostelium discoideum
Reveals Developmentally Regulated U2 Variants and Polyadenylated snRNAs
Authors: Hinas Andrea , Larsson Pontus , Avesson Lotta , Kirsebom Leif A. , Virtanen Anders , Söderbom Fredrik
Published: June 2006

Most eukaryotic mRNAs depend upon precise removal of introns by the spliceosome, a complex of RNAs and proteins. Splicing of pre-mRNA is known to take place in
Dictyostelium discoideum
, and we previously isolated the U2 spliceosomal RNA experimentally. In this study, we identified the remaining major spliceosomal RNAs in
Dictyostelium
by a bioinformatical approach. Expression was verified from 17 small nuclear RNA (snRNA) genes. All these genes are preceded by a putative noncoding RNA gene promoter. Immunoprecipitation showed that snRNAs U1, U2, U4, and U5, but not U6, carry the conserved trimethylated 5′ cap structure. A number of divergent U2 species are expressed in
Dictyostelium
. These RNAs carry the U2 RNA hallmark sequence and structure motifs but have an additional predicted stem-loop structure at the 5′ end. Surprisingly, and in contrast to the other spliceosomal RNAs in this study, the new U2 variants were enriched in the cytoplasm and were developmentally regulated. Furthermore, all of the snRNAs could also be detected as polyadenylated species, and polyadenylated U1 RNA was demonstrated to be located in the cytoplasm.
Genetic diversity and distribution ofSarracenia purpurea(Sarraceniaceae) in the western Lake Superior basin
Authors: Karberg Jennifer M. , Gale Margaret R.
Published: June 2006

Restoring plant populations requires an understanding of plant morphological adaptation to site locations and population genetic diversity and relatedness. This study examined the genetic and morphological diversity of Sarracenia purpurea L. within the natural fragmentation of western Lake Superior. Populations of S. purpurea were compared among three locations: Isle Royale National Park, the Keweenaw Peninsula, Michigan, USA, and Sleeping Giant Provincial Park, Ontario, Canada. Analysis of genetic and demographic data showed Canadian populations to be less robust with smaller plant sizes. Canadian populations were also slightly distinct genetically. Overall genetic diversity appears moderate (H = 0.30–0.36) and populations genetically similar. Analysis of molecular variance showed only 3.83% of variation among the three locations (p = 0.0049). Fragmentation did not have a distinguishable effect on genetic diversity and morphological characters but the limestone bedrock geology of the Canadian region may be starting to influence plant morphology and genetic differentiation. This indicates that restoration can take place within the western basin of Lake Superior using a variety of seed sources but regional geology may influence observed plant morphology.
Cryptic characteristics distinguish diploid and triploid varieties of Pteris fauriei (Pteridaceae)
Authors: Huang Yao-Moan , Chou Hsueh-Mei , Hsieh Tsung-Hsin , Wang Jenn-Che , Chiou Wen-Liang
Published: June 2006

There are two varieties of Pteris fauriei Hieron. in Taiwan: P. fauriei var. fauriei and P. fauriei var. minor Hieron. Their mature sporophytes are virtually indistinguishable based on gross morphology. To better understand these two varieties and the differences between them, and to determine whether they are based on different ploidies, we examined and compared the sporophytes and gametophytes of both varieties in detail. Each variety exhibited distinct, constant cryptic characteristics and cytotype. Based on the diameter of spores from type specimens, we confirmed that P. fauriei var. minor is diploid and that P. fauriei var. fauriei is triploid. Diploid sporophytes produced 64-spore sporangia. Their haploid gametophytes produced archegonia and antheridia containing 64 sperm each. Gametophytes cultured for 10 weeks formed sexual sporophytes, the first fronds of which lacked midribs. Triploid sporophytes produced 32-spore sporangia. Triploid spores were significantly larger in diameter than haploid spores. Triploid gametophytes did not produce archegonia but did produce 32-sperm antheridia, which were significantly larger in diameter than antheridia produced by haploid gametophytes. The life span of triploid gametophytes was 4 weeks shorter than that of haploid gametophytes. After 6 weeks in culture, apomictic triploid sporophytes arose directly from gametophyte cells. Each of their first fronds had three pinnae and a midrib. These data are useful for delimiting P. fauriei var. fauriei and P. fauriei var. minor.
Feeding impact of Lygus lineolaris (Heteroptera: Miridae) on Vitis vinifera: a behavioural and histological study
Authors: Fleury Dominique , Paré Josiane , Vincent Charles , Mauffette Yves
Published: June 2006

Nymphs and adults of the tarnished plant bug ( Lygus lineolaris (Palisot de Beauvois)) feeding on grapevine were videorecorded in the laboratory to determine the short-term impact of feeding punctures at various phenological stages. Feeding behaviour was significantly different between nymphs and adults in the number of punctures but not in the feeding time spent. Observations by light and scanning electron microscopy showed that, from phenological stages B (bud burst) to F (visible cluster), feeding did not cause plant damage and injuries did not impact the meristems, which were coated with viscous or filamentous pectin. During phenological stages H (florets separated) and I (flowering), feeding was restricted to nectar glands, and as there is no functional relationship between nectaries and ovaries, feeding had no impact on normal development of ovaries. In later phenological stages J (berry set) to L (cluster closure, berry touch), most damage was on the pedicels of berries. Pedicels attacked at the next phenological stage show no evidence of injuries. Grapevine appears to tolerate punctual feeding made by this insect; damage is minimal and berry production is not threatened.
Molecular evidence for the systematic positions of two enigmatic mosses: Pterogonidium pulchellum (Sematophyllaceae, Musci) and Piloecium pseudorufescens (Myuriaceae, Musci)
Authors: Chang Ying , Khiong Chan Woon , Graham Sean W. , Tan Benito C.
Published: June 2006

The systematic position of Pterogonidium pulchellum (W.J. Hooker) Muell. Hal. in the Sematophyllaceae and Piloecium pseudorufescens (Hampe) Muell. Hal. in the Myuriaceae is reexamined with new evidence derived from rbcL gene sequences. A total of 18 taxa from Sematophyllaceae, Hypnaceae, Myuriaceae, and Hookeriaceae were included, 11 of which were newly sequenced for the rbcL gene. Analyses were done using maximum parsimony, maximum likelihood (TrN + Γ + I model and GTR + Γ + I model), and Bayesian inference (GTR + Γ + I model). The results show that Pterogonidium pulchellum has a closer relationship with members of Hypnaceae than with Sematophyllaceae, while Piloecium pseudorufescens forms a clade with the Sematophyllaceae in all phylogenetic analyses, with robust branch support. Two SOWH tests were carried out and the results show that it is not appropriate to classify Pterogonidium pulchellum in Sematophyllaceae and it is also not appropriate to classify Piloecium pseudorufescens in Myuriaceae.
Stand age influence on litter mass ofPinus nigraplantations on dolomite hills in Hungary
Authors: Cseresnyés Imre , Csontos Péter , Bózsing Erika
Published: June 2006

In Hungary, plantations of Pinus nigra Arn. (Austrian pine) involve large areas of dolomite rock grasslands and have caused the impoverishment or local extinction of the original flora. In addition to these conservation concerns, an important economic problem is the flammability of these forests. Fire risk depends on the amount of accumulated flammable organic components. Thus, the purpose of our research was to quantify the mass of litter accumulated in Austrian pine stands and to examine the correlation between litter mass, stand age, and slope aspect. Forty-eight sampling sites were selected with stand ages ranging from 21 to 108 years. Stands represented four age classes and three exposure types. At each sampling site, litter mass was determined in the following three fractions: needles, branches, and cones. The litter fractions showed their maximum quantities in age class 61–80 years (needles = 17 560 kg/ha, branches = 2764 kg/ha, and cones = 2960 kg/ha). For the needle litter, a significant increase with age was detected through the age classes of 21–40, 41–60, and 61–80 years, and then a significant decrease occurred in stands above 80 years. In the case of branch litter, the age-dependent increase was again significant to its maximum quantity, but the decrease in old stands proved to be insignificant. With cone litter, age dependence could not be detected. Exposure of the stands had no effect on the quantities of the three litter fractions. The amount of accumulated litter of Austrian pine stands many times exceed the litter quantity of the rock grasslands (the original vegetation prior to afforestation). Furthermore, it is two or three times higher than the amount of litter reported from native zonal forests of Hungary. Therefore, the Austrian pine stands are subjected to an increased risk of fire, especially in age class 61–80 years.
The parasitic ascomyceteMniaecia jungermanniaeinduces the formation of giant perichaetia and apogamous sporophytes in leafy liverworts
Authors: Pressel Silvia , Duckett Jeffrey G
Published: June 2006

To test the hypothesis that the apothecia of Mniaecia jungermanniae (Nees ex Fr.) Boud. growing on stems of the liverwort Cephalozia bicuspidata (L.) Dumort. might be the perfect stage of an ascomycete fungus forming a symbiotic association with swollen rhizoids in a liverwort, we grew both axenically and resynthesized the association. Contrary to our expectation, Mniaecia remained extracellular, but induced, on Cephalozia , the formation of giant perichaetia containing supernumerary archegonia followed by parthenogenetic and apogamous sporophytes. This is the first report of these latter two features in liverworts. By analogy with apogamy and apospory in mosses and pteridophytes that are induced by media supplemented with organic nutrients and growth regulators, we suggest that the abnormal structures in Cephalozia resulted from substances produced by Mniaecia. Giant perichaetia and abnormal perianths were also observed on wild colonies of Cephalozia, Diplophyllum , and Scapania heavily infected with Mniaecia. Apart from local depression of perianth formation in the wild, this parasitic fungus appears to cause no long-term damage to its hosts.
Impacts of Lythrum salicaria invasion on plant community and soil properties in two wetlands in central New York, USA
Authors: Mahaney Wendy M. , Smemo Kurt A. , Yavitt Joseph B.
Published: June 2006

While the spread of the exotic Lythrum salicaria L. across wetlands in North America is thought to negatively affect the performance and diversity of native species, the actual impacts of L. salicaria invasion on community dynamics and ecosystem properties are not well understood. To determine whether L. salicaria affects community aboveground biomass, native species biomass, or soil properties, we studied two common situations in central New York State where L. salicaria invaded (i) an abandoned agricultural field and (ii) a relatively pristine wetland with low species diversity. In the agricultural site, nearly monospecific stands of L. salicaria and Phalaris arundinacea L. had nearly identical shoot mass (approx. 850 g·m–2) but divergent soil characteristics. Inorganic nitrogen was significantly higher under L. salicaria than under P. arundinacea. The low-diversity site is dominated by Carex lacustris Willd., with distinct areas codominated by either L. salicaria or Typha latifolia L. In this site, we found that areas with a codominant species had significantly more total aboveground biomass than those dominated by C. lacustris, suggesting that L. salicaria invasion does not significantly lower native species biomass. However, most soil nutrient levels did not differ among vegetation zones, indicating that species composition changes did not alter soil properties in the short term. This study supports a growing literature suggesting that L. salicaria invasion may not negatively impact relatively pristine wetlands as previously believed.
Size-dependent reproductive effort in Amaranthus retroflexus: the influence of planting density and sowing date
Authors: Wang Tianhui , Zhou Daowei , Wang Ping , Zhang Hongxiang
Published: June 2006

Size-dependent reproductive effort is an important component of plant fitness. The responses of reproductive effort to environmental factors in Amaranthus retroflexus L. were measured in two experiments. A wide range of selection pressures were generated by manipulating the sowing date (29 April, 23 May, 18 June, and 14 July) and planting density (13.4, 36, 121, and 441 plants·m–2). Allometric analysis between reproductive biomass and vegetative biomass across treatments showed that reproductive effort increased with size in response to different planting densities but decreased with size in sowing dates experiment. The allometric exponent between treatments was not influenced by planting densities but had significant variation with sowing date. Total branch length could explain most of the variation of reproductive accumulation and allocation in planting density experiments. For the plants with different sowing dates, total branch length was the main determinant of reproductive biomass, while reproductive effort mainly depended on the number of primary branches per unit stem mass. Architectural constraints with size result in size-dependent reproduction. Size-dependent reproduction in A. retroflexus was influenced by available resources and environmental conditions through the mechanisms of self-regulation of architectural traits.
Ribosomal protein gene regulation: what about plants?
Authors: McIntosh Kerri B. , Bonham-Smith Peta C.
Published: June 2006

The ribosome is an intricate ribonucleoprotein complex with a multitude of protein constituents present in equimolar amounts. Coordination of the synthesis of these ribosomal proteins (r-proteins) presents a major challenge to the cell. Although most r-proteins are highly conserved, the mechanisms by which r-protein gene expression is regulated often differ widely among species. While the primary regulatory mechanisms coordinating r-protein synthesis in bacteria, yeast, and animals have been identified, the mechanisms governing the coordination of plant r-protein expression remain largely unexplored. In addition, plants are unique among eukaryotes in carrying multiple (often more than two) functional genes encoding each r-protein, which substantially complicates coordinate expression. A survey of the current knowledge regarding coordinated systems of r-protein gene expression in different model organisms suggests that vertebrate r-protein gene regulation provides a valuable comparison for plants.
Competition ofScleroconidioma sphagnicolawith fungi decomposing spruce litter needles
Authors: Koukol O. , Mrnka L. , Kulhánková A. , Vosátka M.
Published: June 2006

This study addressed competition of Scleroconidioma sphagnicola Tsuneda, Currah & Thormann with saprotrophic ascomycetes and basidiomycetes. We isolated this fungus, previously considered as a preferentially necrotrophic parasite of moss, from spruce needle litter. Competition of Scleroconidioma sphagnicola was simulated with strains of the autochthonous litter colonizers Ceuthospora pinastri (Fr.) Höhn., Chalara longipes (Preus) Cooke, Setulipes androsaceus (L.) Antonín ( Marasmius androsaceus (L.) Fr.), and Mollisia minutella (Sacc.) Rehm and the wood-decaying fungus Hypholoma fasciculare (Huds.) Quél. Pairings were performed on agar plates with two types of low-nutrient medium made from spruce litter needles. Reisolation on nutritionally rich agar medium following the competition revealed that Sleroconidioma sphagnicola was mostly successfully reisolated even though apparently being replaced by the mycelium of other fungi. It formed strongly melanised mycelium and microsclerotia that seem to be responsible for its resistance to fungal competition. All tested strains of needle litter colonizers were outcompeted by Hypholoma fasciculare. Enzymatic screening aimed at semiquantitative assay of polyphenol oxidase, peroxidase, and tyrosinace revealed that Scleroconidioma sphagnicola, together with other strains, was able to produce polyphenol oxidase and peroxidase on various nutritional media. Activity of tyrosinase was detected only for Hypholoma fasciculare. Previous records of Scleroconidioma sphagnicola from moss, wood, and our isolations from spruce litter suggest that this species possesses an ability to occupy a wide spectrum of niches.
DNA barcoding in land plants: evaluation of rbcL in a multigene tiered approach
Authors: Newmaster S.G. , Fazekas A.J. , Ragupathy S.
Published: June 2006

DNA barcoding based on the mitochondrial cytochrome c oxidase 1 (cox1) sequence is being employed for diverse groups of animals with demonstrated success in species identification and new species discovery. Applying barcoding systems to land plants will be a more challenging task as plant genome substitution rates are considerably lower than those observed in animal mitochondria, suggesting that a much greater amount of sequence data from multiple loci will be required to barcode plants. In the absence of an obvious well-characterized plant locus that meets all the necessary criteria, a key first step will be identifying candidate regions with the most potential. To meet the challenges with land plants, we are proposing the adoption of a tiered approach wherein highly variable loci are nested under a core barcoding gene. Analysis of over 10 000 rbcL sequences from GenBank demonstrate that this locus could serve well as the core region, with sufficient variation to discriminate among species in approximately 85% of congeneric pair-wise comparisons. Use of a secondary locus can be implemented when required and can vary from group to group if necessary. The implementation of a barcoding tool has multiple academic and practical applications. It will speed routine identifications and the detection of alien species, advance ecological and taxonomic inquiry, permit fast and accurate forensic analysis of plant fragments, and can function as an additional layer of quality control in the food industry.
UPb constraints on the thermotectonic evolution of the Vernon antiform and the age of the Aberdeen gneiss complex, southeastern Canadian Cordillera
Authors: Glombick P , Thompson R I , Erdmer P , Heaman L , Friedman R M , Villeneuve M , Daughtry K L
Published: June 2006

The Aberdeen gneiss complex is composed of complexly deformed migmatitic orthogneiss and paragneiss situated within the core of the Vernon antiform, a structure defined by a series of subparallel reflectors visible at upper to middle crustal depths (618 km) in seismic reflection data from the Vernon area of the Shuswap metamorphic complex. The Vernon antiform and the Aberdeen gneiss complex lie within the footwall of the gently west dipping (top to the west) Kalamalka Lake shear zone. Migmatitic gneiss exposed within the antiform records evidence (recorded as age domains in complexly zoned zircon grains) of three metamorphic events, occurring at 155150, 90, and 6651 Ma. The timing of magmatic events within the antiform includes emplacement of diorite at ~232 Ma, tonalite at ~151 Ma, granodiorite at 102 Ma, and monzonite at 52 Ma. Middle to Late Jurassic metamorphism resulted in widespread migmatization. Early Tertiary metamorphism (6651 Ma) was coeval with the emplacement of granitic rocks and exhumation typical of other areas of the Shuswap metamorphic complex. Highly deformed orthogneiss situated within the hanging wall of the Kalamalka Lake shear zone, comprising the superstructure, was emplaced at ~171 Ma. Ductile deformation had ceased by 162 Ma. The complex metamorphic and magmatic evolution of the Vernon antiform, which is similar to other areas of the southern Canadian Cordillera including the Nicola horst, Mount Lytton  Eagle plutonic complex, Cariboo Mountains, and Mica Creek area, may reflect episodic tectonic activity at the plate margin.
Ovummuridae (calcareous microfossils) from a Late Devonian ramp: their distribution, preservation potential, and paleoecological significance
Authors: MacNeil Alex J , Jones Brian
Published: June 2006

Enigmatic calcareous microfossils that belong to the Ovummuridae Munnecke, Servais, and Vachard, 2000 are present in ten cores through the upper part of the Escarpment Formation and Alexandra Formation in the Hay River area of the Northwest Territories, Canada. These Late Devonian (Frasnian) siliciclastic, mixed carbonatesiliciclastic, and carbonate ramp deposits accumulated on the western margin of Laurussia. Finding ovummurids in these deposits is significant because it provides the first formal documentation that these microorganisms existed in the Devonian and confirms that the stratigraphic range of the family extends from the Lower Silurian to Upper Permian. The microfossils, which are of unknown biological affinity, include Minourella gotlandica, previously known only from Silurian strata, Ovummurus duoportius, and Minourella cameroni sp. nov. The preservation potential of these microfossils was markedly enhanced by thick cement overgrowths, akin to the syntaxial overgrowths that are common on Paleozoic crinoid fragments. The distribution of ovummurids in these ramp deposits is significant because it demonstrates that ovummurids were capable of inhabiting turbid, likely nutrient-enriched marine environments, with significant siliciclastic influx, that were unsuitable for most other carbonate-secreting organisms in the Paleozoic.
Provenance of fossiliferous clasts in Carboniferous conglomerate, Isle Madame, southern Cape Breton Island, Nova Scotia
Authors: Boucot Arthur J , Landing Ed , Boyce W Douglas , Barr Sandra M , White Chris E
Published: June 2006

Fossiliferous clasts occur in Carboniferous conglomerate in the Horton Group on western Isle Madame and in the Mabou Group on eastern Isle Madame. Most of the clasts (21 of 23 examined) are calcareous siltstone and sandstone that contain Silurian  Lower Devonian faunas comparable to those in the Arisaig area, northern mainland Nova Scotia, although the lithologies are coarser grained and less calcareous than those of the Arisaig section. These middle Paleozoic faunas are well constrained to the Silurian (uppermost Llandovery through Pridoli) and lowest Devonian and are characteristic of those known from shallow siliciclastic-dominated platforms of the Avalon microcontinent in Wales and England. The remaining two clasts have abundant inarticulate brachiopod shells that indicate provenance from Middle Cambrian proximal marine facies on the Avalonian marginal platform. No clasts were found that are likely to have been derived from the Torbrook Formation, and thus from the Meguma terrane in southwestern Nova Scotia, as has been previously reported. The association of relatively large, reworked fossiliferous clasts in Carboniferous conglomerate on Isle Madame suggests local derivation from lower and middle Paleozoic units not presently exposed, although probably present as subcrop under the Carboniferous units, in southwestern Cape Breton Island and adjacent mainland Nova Scotia.
Assessing anadromy of brook char (Salvelinus fontinalis) using scale microchemistry
Authors: Courtemanche David A , Whoriskey, Jr. Frederick G , Bujold Valerie , Curry R Allen
Published: June 2006

Brook char (Salvelinus fontinalis) exist in both freshwater and anadromous forms, often in sympatry, the ecology of the latter being poorly understood. As strontium (Sr) can substitute to calcium (Ca) and as its concentration in seawater is higher than in freshwater, scale circulii laid down during seawater exposure should be enriched in Sr, allowing precise identification of residence patterns in freshwater and seawater. We attempted to document movements of anadromous brook char using wavelength-dispersive X-ray electron microscopy on individual circulii of sagittally sectioned scales. Body scales of brook char experimentally transferred between freshwater and seawater had elevated Sr/Ca ratios in regions laid down during exposure to seawater. Wild anadromous brook char body scales had consistently higher Sr/Ca ratios than river-resident form. However, in both experimental and wild brook char, Sr/Ca ratios in the scale circulii from freshwater periods showed elevated Sr/Ca ratios after seawater exposure, suggesting whole-scale Sr enrichment associated with exposure to seawater. Although whole-scale elemental composition revealed whether a fish has ever resided in a marine environment, analysis of Sr patterns at the level of individual circulii did not allow resolution of fine-scale patterns of these movements in brook char.
Predation, competition, and the recovery of overexploited fish stocks in marine reserves
Authors: Baskett Marissa L , Yoklavich Mary , Love Milton S
Published: June 2006

Community interactions alter the management actions necessary to recover overfished species using marine reserves. For example, in communities where a larger species preys on their juveniles' competitors, overfishing of the larger species may cause prey population expansion; subsequent increased competition for the juveniles of the over fished species may impede its recovery within reserves. We explore the implications of such community interactions for reserve design with a model of a subtidal rockfish (genus Sebastes) system from the Northeast Pacific Ocean within a no-take reserve. Ignoring community interactions, the model predicts that a reserve large enough for internal recruitment to counterbalance mortality will allow recovery of the overfished species. However, after incorporating community interactions, the model predicts that two alternative stable states exist: one where the overfished species dominates and one where the prey dominates. In the community model, the ability of an overfished system to recover to the equilibrium where the overfished species dominates after reserve establishment depends on the initial densities of both species, and a larger reserve is required for recovery to be possible.
Physiological and energetic correlates of en route mortality for abnormally early migrating adult sockeye salmon (Oncorhynchus nerka) in the Thompson River, British Columbia
Authors: Young Jeffery L , Hinch Scott G , Cooke Steven J , Crossin Glenn T , Patterson David A , Farrell Anthony P , Kraak Glen Van Der , Lotto Andrew G , Lister Andrea , Healey Michael C , English Karl K
Published: June 2006

Since 1995, large segments of the late-run sockeye salmon (Oncorhynchus nerka) stock complex from the Fraser River, British Columbia, Canada, have been initiating spawning migrations several weeks earlier than normal. Most aberrant migrants die before spawning. To evaluate the mechanisms underlying the mortality, we intercepted late-run sockeye salmon of the AdamsShuswap stock complex halfway along their freshwater migration (i.e., in the Thompson River Canyon situated 270 km from the Fraser estuary), nonlethally assessed physiological and energetic status, and tracked individuals using gastrically inserted radio transmitters. Aberrant migrants that resumed their migration but failed to reach the spawning grounds had lower gross somatic energy, higher average migration ground speeds, higher plasma osmolality, and higher levels of plasma reproductive hormones than those that reached the spawning grounds. Fish surgically fitted with electromyogram radio transmitters did not continue their migration and fell downstream. These fish displayed excessive bleeding during transmitter implantation, an unusual phenomenon that likely contributed to the fish's inability to resume migration. Blood clotting time decreased steadily throughout the migration period. Collectively, these data implicate a combination of energy depletion, premature reproductive development, and blood loss from wounds as potential contributors to mortality in early migrating late-run sockeye.
Incorporating parameter uncertainty into evaluation of spawning habitat limitations on Chinook salmon (Oncorhynchus tshawytscha) populations
Authors: Beechie Timothy J , Greene Correigh M , Holsinger Lisa , Beamer Eric M
Published: June 2006

Incorporating parameter uncertainty into a Monte Carlo procedure for estimating spawning habitat capacity helped determine that spawning habitat availability is unlikely to limit recovery of six populations of Chinook salmon (Oncorhynchus tshawytscha) in Puget Sound. Spawner capacity estimates spanned up to four orders of magnitude, yet there was virtually no overlap of distributions of capacity estimates with distributions of current spawner abundance (<0.2% overlap), except for the Suiattle River population (51% overlap). Empirical distributions of input parameters contained several important sources of uncertainty, insuring reasonably wide distributions of capacity estimates. The most defensible ranges of input parameters tended to produce conservative capacity estimates, indicating that increased model accuracy would only strengthen our conclusion that spawning habitat is not a constraint on these populations. There are insufficient data with which to develop parameter distributions that better represent historical capacity, which would certainly be higher than our estimates. Our results suggest that factors other than spawning capacity limit population size and that recovery efforts for Skagit River Chinook salmon need not focus on spawning habitat restoration.
Species identity and aqueous calcium concentrations as determinants of calcium concentrations of freshwater crustacean zooplankton
Authors: Jeziorski Adam , Yan Norman D
Published: June 2006

Calcium (Ca) is a major component of the crustacean zooplankton carapace. As crustacean zooplankton obtain most of their Ca from lake water, taxa with high Ca demands may be negatively affected if environmental Ca concentrations fall below thresholds necessary for adequate Ca uptake rates. Currently, Ca concentrations are falling in many soft-water lakes with a history of acid deposition, both within Canada and globally. Hence, there is a need to identify species with high Ca demands. We analyzed Ca concentrations of eight crustacean zooplankton taxa from nine lakes spanning a 0.435 mg·L1 Ca gradient. Our objectives were to determine (i) if both species identity and lake Ca concentrations are determinants of zooplankton Ca concentration and (ii) if zooplankton Ca concentration varies seasonally. Large differences in Ca concentrations were observed among taxa. Levels in Daphnia sp. ranged from 2% to 8% of dry body weight, whereas levels in copepods and non-daphniid cladocera were much lower at 0.2%0.4%. Seasonal variation in zooplankton Ca concentration was negligible, but positive correlations with lake Ca concentration were detected, with up to twofold differences in Ca concentration between lakes in three of the eight species. Species identity was the most important determinant of crustacean zooplankton Ca concentration.
Factors influencing the distribution of chironomids in lakes distributed along a latitudinal gradient in northwestern Quebec, Canada
Authors: Larocque Isabelle , Pienitz Reinhard , Rolland Nicolas
Published: June 2006

The effect of 33 environmental variables on the distribution of chironomids was studied in 60 lakes of northwestern Quebec (Canada). A detrended canonical correspondence analysis detected linearity in the chironomid assemblages, thus redundancy analysis was used to identify the variables affecting the chironomid communities. Lake depth, dissolved organic carbon (DOC), mean August air temperature, and surface water temperature were the four variables that best explained the distribution of chironomids. Partial least squares analysis was used to develop new inference models. Among models, the one for mean August air temperature had the highest coefficient of determination (r[Formula: see text] = 0.67) and the lowest root mean square error of prediction (= 1.17 °C). The results indicated that for downcore temperature reconstructions, it might be hard to dissociate the combined effects of temperature, DOC, and depth. Changes in taxa such as Heterotrissocladius brundini-type, Heterotrissocladius subpilosus-type, Heterotrissocladius grimshawi-type, Micropsectra radialis-type, Tanytarsus lugens-type, and Microtendipes can be attributed to changes in lake depth and (or) temperature. Changes in Heterotanytarsus, Dicrotendipes, Cryptotendipes, and Cryptochironomus might be attributed to shifts in temperature and DOC. Relationships among temperature, DOC, and lake depth should be studied in a "neo-ecology" design to better understand their impact on chironomid assemblage composition.
Comment on "Fishing and the impact of marine reserves in a variable environment"
Authors: Holland Daniel S , Stokes T Kevin
Published: June 2006

Rodwell and Roberts (Can. J. Fish. Aquat. Sci. 61: 20532068 (2004)) use a discrete time simulation model to investigate the impact of marine reserves on catch and biomass levels in a fishery regulated by total catch quotas. They show that the probability of achieving various probabilistic biomass reference point targets is greater with reserves than without reserves under equal nonreserve exploitation rates. However, they compare management performance on the basis of exploitation rates of the nonreserve biomass rather than average yields (i.e., not using the same overall exploitation rate for the population as a whole). What Rodwell and Roberts fail to show is that with their model all of the reference point targets can be achieved with a higher level of catch without a reserve than with a reserve. For any given level of mean catch at or below maximum sustainable yield, management without a marine reserve leads to a higher average biomass and lower variation in catch than management with a reserve. In summary, the specific model and parameters used by Rodwell and Roberts fail to show any comparative advantage of marine reserves in a quota-managed fishery.
Genetic structure in relation to movements in wild European grayling (Thymallus thymallus) in three Norwegian rivers
Authors: Heggenes Jan , Qvenild Tore , Stamford Michael D , Taylor Eric B
Published: June 2006

The relationship among genetic structure, movements, and barriers was studied in European grayling (Thymallus thymallus). Gene flow is closely related to movement patterns, and genetic differentiation may be negatively correlated with movement. Grayling movements in the Glomma River (8149 tagged) and the neighboring Trysilelva River (4070 tagged) were different among sampling sites. Most individuals were stationary (±0.5 km), but some individuals moved long distances (≤153 km). The movement data indicated potential for gene flow between the two upstream sampling sites in the Glomma River and between the two midstream sites in the Trysilelva River. Allele frequencies at seven microsatellite loci indicated pairwise differentiation across sampling sites. Genetic structuring was generally consistent with the observed movement pattern. Isolation-by-linear-distance or number of potential barriers (dams, lakes) was not significant among sites within streams or among sites within the two southern streams. They were significant, however, if two outlying northern populations in the Pasvik River were included. Our results suggest that although grayling may move long distances, they also exhibit genetic structuring within large continuous river systems. Fish movement, often the result of flexible and adaptive behavioral strategies, is the ecological mechanism for gene flow. Movements may be the adaptive link explaining how environmental conditions affect genetic structuring.
Influence of suspended mussel lines on the biogeochemical fluxes in adjacent water in the Îles-de-la-Madeleine (Quebec, Canada)
Authors: Richard Marion , Archambault Philippe , Thouzeau Gérard , Desrosiers Gaston
Published: June 2006

Oxygen consumption and nutrient fluxes were measured in 80 L enclosures containing water, 1- or 2-year-old mussels, or 1- or 2-year-old line sections (mussels plus associated fauna  organic matter complex: AFOM) in August and September 2003 in the Îles-de-la-Madeleine. Mussel lines acted as nutrient sources and oxygen sinks in adjacent water. The magnitude of fluxes at the mussel line interface depended on the nutrient (NH4 >> Si(OH)4, PO4 > NO3 > NO2). Mussel metabolism contributed greatly to O2 consumption and NH4 and PO4 releases. Mussel influence was greater in stressful periods. The AFOM complex mainly contributed to NO3, NO2, and Si(OH)4 fluxes. These fluxes could originate from organic matter decomposition rather than from associated faunal metabolism. The influence of AFOM depended on its composition and thus on line immersion time. Mussel lines by ammonia releases could be a factor of reduction of N limitation in the water column. Mussel line should be integrated as a new interface of biogeochemical exchanges in environmental carrying capacity studies.
A decision analysis of flow management experiments for Columbia River mountain whitefish (Prosopium williamsoni) management
Authors: Alexander Clint AD , Peters Calvin N , Marmorek David R , Higgins Paul
Published: June 2006

High spawning flows from Hugh Keenleyside Dam (HKD) on the Columbia River results in dewatering of eggs in mountain whitefish (Prosopium williamsoni) populations, but the ultimate effect on adult abundance depends on the shape of the egg-to-adult recruitment curve. Our decision analysis assessed the benefits of alternative flow experiments while accounting for uncertainties in this relationship and in flows in the Columbia and Kootenay rivers. The value of experimenting depended on the true recruitment relationship, how we quantified experimental benefits, and experimental design. With current uncertainty, the optimal HKD spawning flow (out of 11 alternative flows) was 1699.2 m3·s1. Spawning flows below 1699.2 m3·s1 did not improve egg survival because lower flows rendered high-quality spawning habitat unavailable and increased scour mortality. Two experimental designs, both with higher precision monitoring, had a high probability of detecting the true recruitment curve at reasonable cost. Information from these experiments suggested an optimal spawning flow of 1699.2 m3·s1 if adult abundance were sensitive to egg mortality or 1982.4 m3·s1 if the population were insensitive.
Assessing possible thermal rearing restrictions for juvenile coho salmon (Oncorhynchus kisutch) through thermal infrared imaging and in-stream monitoring, Redwood Creek, California
Authors: Madej M A , Currens C , Ozaki V , Yee J , Anderson D G
Published: June 2006

We quantified patterns in stream temperature in a northern coastal California river using thermal infrared (TIR) imaging and in-stream monitoring and related temperature patterns to the historical and present distributions of juvenile coho salmon (Oncorhynchus kisutch). In Redwood Creek, California, water temperature increased from the headwaters to about 60 km downstream, then gradually decreased over the next 40 km as the river approaches the Pacific Ocean. Despite the lack of fish migration barriers, juvenile coho are currently only observed in the downstream-most 20 km, whereas historically they were found in 90 km of river channel. Maximum daily temperatures and duration of elevated stream temperatures were not significantly different in the headwater and downstream reaches but were significantly higher in the 50 km long intervening reach, where maximum weekly maximum temperatures ranged from 23 to 27 °C. An increase in stream temperatures in the middle basin during the last three decades as a result of channel aggradation, widening, and the removal of large riparian conifers may play an important role in restricting juvenile coho to one-fifth of their historical range.
Population structure and divergence using microsatellite and gene locus markers in Chinook salmon (Oncorhynchus tshawytscha) populations
Authors: Heath Daniel D , Shrimpton J Mark , Hepburn Russell I , Jamieson Sara K , Brode Sarah K , Docker Margaret F
Published: June 2006

Using different classes of genetic markers can provide insight into the role of selection, as well as a broader context for identifying population differentiation. We used nine microsatellite loci and polymorphisms at eight gene loci (major histocompatibility complex (MHC) classes I and II, growth hormones 1 and 2, transferrin, and immunoglobin heavy-chain) to determine population structure in six coastal populations (Vancouver Island, VI) and five interior populations (Fraser River, FR) of Chinook salmon (Oncorhynchus tshawytscha) in British Columbia, Canada. FSTand [Formula: see text] values for specific VI gene loci were significantly higher than those for the FR and VI microsatellite loci or the FR gene loci. Pairwise microsatellite FSTvalues were correlated with geographic distance across regions, but not using the gene locus marker data. Neighbor-joining cluster analyses showed one VI population as particularly divergent based on the gene locus data, while the VI and FR microsatellite locus and the FR gene locus analyses yielded no anomalous population divergence. The VI MHC class II marker FSTvalues were exceptionally high, indicative of probable directional selection acting on MHC class II. Our results are consistent with local adaptation in Chinook salmon, but the nature of the local adaptation likely differs among regions.
Pure spatial and spatially structured environmental variables explain Skistodiaptomus copepod range limits in the northeastern USA
Authors: Thum Ryan A , Stemberger Richard S
Published: June 2006

We assessed the ability of present-day environmental factors to explain the nonoverlapping range boundaries of Skistodiaptomus copepods in the northeastern USA. Variance partitioning using partial canonical correspondence analysis (CCA) attributed 21% of the variance in species occurrences to spatial location, 20% to spatially structured environmental variation, and 12% to environmental factors that are not spatially structured. Discriminant function analysis (DFA) aided our interpretation of the variance in species' occurrences attributed to spatially structured environmental variation. Skistodiaptomus pallidus lakes were discriminated from Skistodiaptomus oregonensis and Skistodiaptomus pygmaeus lakes along a productivity gradient, with S. pallidus occurring in more productive lakes. In contrast, S. oregonensis and S. pygmaeus lakes were environmentally similar. Thus, a large portion of the spatially structured variation in the variance-partitioning analysis most likely reflected the shared correlations between the spatial locations and environmental conditions of S. pallidus lakes. Taken together, the results from CCA and DFA analyses suggested that S. pallidus' range boundary is controlled by environmental factors (lake productivity), while the range boundaries for S. oregonensis and S. pygmaeus were related more to their biogeographic histories than to present-day environments. We discuss alternative explanations for range limits that are independent of environmental conditions.
Electronion interactions for trapped highly charged Ge ions
Authors: Machtoub G , López-Urrutia J.R. Crespo , Zhang X , Tawara H
Published: June 2006

A theoretical simulation of complex K X-ray spectra including those from dielectronic recombination and excitation processes is presented for trapped highly charged germanium ions ( Geq+, q = 2730) interacting with a dense electron beam. We carried out numerical calculations of transition rates, level energies, transition wavelengths, resonance and collision strengths, and satellite intensity factors. Analytical results related to cross sections of B- through He-like Ge ions were obtained as well. The simulated spectra, including the contribution from different charge states of Ge27+Ge30+, show good overall agreement over a wide electron energy range with the available X-ray measurements from the Heidelberg electron beam ion trap (EBIT). We have also predicted the electron impact excitation cross-section ratios for different transitions of Ge29+ and Ge30+ ions. It should be emphasized that the present analysis can also provide new information and clues of possible temperature measurements for EBIT and other plasma diagnostics.PACS No.: 32.30.Rj
The asymptotic iteration method for the angular spheroidal eigenvalues with arbitrary complex size parameter c
Authors: Barakat T , Abodayeh K , Abdallah B , Al-Dossary O M
Published: June 2006

The asymptotic iteration method is applied to calculate the angular spheroidal eigenvalues [Formula: see text] (c) with arbitrary complex size parameter c. It is shown that the numerical results obtained for [Formula: see text] (c) are all in excellent agreement with the available published data over the full range of parameter values [Formula: see text] m, and c. Some representative values of [Formula: see text] (c) for large real c are also given.PACS No.: 02.70.c.
The Uehling correction to the energy levels in a pionic atom
Authors: Karshenboim S G , Korzinin E Yu. , Ivanov V G
Published: June 2006

We consider a correction to energy levels in a pionic atom induced by the Uehling potential, i.e., by a free electron vacuum-polarization loop. The calculation is performed for circular states (l = n1). The result is obtained in a closed analytic form as a function of Zα and the pion-to-electron mass ratio. Certain asymptotics of the result are also presented.PACS Nos.: 12.20.Ds, 36.10.Gv
The Bargmann-Wigner equations in spherical space
Authors: McKeon D.G.C. , Sherry T N
Published: June 2006

The BargmannWigner formalism is adapted to spherical surfaces embedded in three to eleven dimensions. This is demonstrated to generate wave equations in spherical space for a variety of antisymmetric tensor fields. Some of these equations are gauge invariant for particular values of the parameters characterizing them. For spheres embedded in three, four, and five dimensions, this gauge invariance can be generalized so as to become non-Abelian. This non-Abelian gauge invariance is shown to be a property of second-order models for two index antisymmetric tensor fields in any number of dimensions. The O(3) model is quantized and the two-point function is shown to vanish at the one-loop order.PACS No.: 11.30j