bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular interactions of victorin and oats
Authors: Navarre D. A. , Lorang J. M. , Moore D. L. , Wolpert T. J.
Published: May 2008

We have been investigating a disease called victoria blight of oats, which is caused by the fungus Cochliobolus victoriae. The fungus is pathogenic because of its ability to produce the host-selective toxin, victorin. Victorin is composed of a group of structurally related cyclized pentapeptides. The most abundant component of victorin in culture filtrates, victorin C, has a molecular weight of 814 and is composed of glyoxylic acid, 5,5-dichloroleucine, threo-β-hydroxylysine, erythro-β-hydroxyleucine, α-amino-β-chloroacrylic acid, and 2-alanyl-3,5-dihydroxy-⌂2-cyclopentenone-1. Sensitivity to victorin, and thus, susceptibility to the fungus, is controlled by a dominant allele at the Vb locus. Furthermore, the Vb gene is either closely linked or identical to the Pc-2 gene, which confers resistance to the crown rust pathogen Puccinia coronata. Thus, it is anticipated that identification of the product of the Vb gene, a putative toxin receptor, will simultaneously identify the product of the Pc-2 rust resistance gene. We have identified two proteins, referred to as victorin binding proteins (VBP), which bind biologically active, radiolabelled victorin in vivo. One protein, a 100-kDa VBP, binds victorin in vivo only in toxin-sensitive, susceptible genotypes. The other VBP, a 15-kDa protein, binds victorin in vivo in both susceptible and resistant genotypes. We have isolated and characterized the 100-kDa VBP and have recently identified, in vitro, a 15-kDa VBP. Both of these proteins are components of the multienzyme complex, glycine decarboxylase. Current investigations center on the role of this enzyme complex in toxin sensitivity. Key words: victorin, oats, toxin, glycine decarboxylase, resistance, susceptibility.
Differential expression of defense-related genes in arbuscular mycorrhiza
Authors: Lambais Marcio R. , Mehdy Mona C.
Published: May 2008

Differential expression of plant defense related genes may contribute to the control of arbuscular mycorrhiza growth and development. The expression of chitinases, β-1, 3-glucanases, and genes involved in the biosynthesis of isoflavonoid phytoalexins has been studied in these symbiotic associations. Relative to noninfected roots, mycorrhizal roots showed a transient induction of endochitinase activities followed by suppression, under low and high P conditions. The suppression was attenuated under high P. Differential reductions in the steady-state level of mRNAs encoding a basic and an acidic endochitinase was observed. Suppression of β-1, 3-glucanase activities, two glucanase mRNAs, and chalcone isomerase mRNA levels was also observed. In situ localization of several defense-related mRNAs showed a predominant accumulation in the vascular cylinder of mycorrhizal and noninfected roots, under both P conditions. The levels of these mRNAs were systemically suppressed in arbuscular mycorrhizae (AM). Additionally, the accumulation of mRNAs encoding an acidic endochitinase and a β-1, 3-endoglucanase was enhanced in and around cells containing arbuscules, under high and low P conditions, respectively. The differential regulation of defense-related genes may contribute to the observed pattern of intraradical fungal growth. A hypothetical model for the functional roles and regulation of endochitinases and β-1, 3-endoglucanases in arbuscular mycorrhiza is proposed. Key words: arbuscular mycorrhiza, differential gene expression, plant defense genes, chitinases, β-1, 3-glucanases, phosphate.
Morphological data, molecular data, and total evidence in phylogenetic analysis
Authors: Tehler Anders
Published: May 2008

Two data sets, one morphological and one molecular, for ascolocular fungi have been analysed separately for taxonomic congruence and in combination for total evidence. Data were analysed with cladistic parsimony, the total support test, and the congruence test. The morphological data set comprised 15 characters and four species, Arthonia radiata, Dendrographa leucophaea, Lecanactis abietina, and Schismatomma pericleum (Arthoniales). The molecular data include the same species and comprised sequence data with 21 informative sites from approximately half of the 18S ribosomal RNA gene. The morphological phylogeny is corroborated by the molecular phylogeny with regard to relationships of Arthonia radiata, Schismatomma pericleum, and Dendrographa leucophaea. But in the molecular phylogeny Lecanactis abietina is placed as a sister species to the former three species. In the phylogeny inferred from morphological data Lecanactis abietina and Dendrographa leucophaea constitute a sister pair with Schismatomma pericleum followed by Arthonia radiata as subsequent sister taxa. The consensus obtained from the taxonomic congruence method was fully collapsed and uninformative. The combined morphological and molecular data in total evidence produced one most parsimonious cladogram. In total evidence Lecanactis abietina is placed as sister species to Schismatomma pericleum and Dendrographa leucophaea all with Arthonia radiata as sister species. The most resolved and phylogenetically informative hypothesis was obtained from cladistic parsimony analysis using total evidence. A review of congruence between morphological and molecular data in determining gross relationships within the Eumycota and Ascomycetes is also given. Key words: Ascomycetes, Arthoniales, phylogeny, cladistics, taxonomic congruence, total evidence, 18SrDNA.
Biogeography and fungal systematics
Authors: Lichtwardt Robert W.
Published: May 2008

Almost all mycogeographic studies to date have dealt with fungi that are directly or indirectly associated with plants; very few have been concerned with fungal associates of insects or other animals. Some widespread species of Trichomycetes (Zygomycota), all of which live in arthropod guts, are useful subjects for biogeographic studies, and such an approach can be used in some instances to distinguish between long-distance dispersal and vicariance events. Evidence for the presumed antiquity of certain trichomycete species is provided using specific examples of Eccrinales and Asellariales in marine Isopoda, and Harpellales in lotic larvae of Chironomidae and Plecoptera. These examples indicate that speciation of the fungi is more conservative than that of their hosts. Thirty-two isolates of Smittium culisetae cultured from different continents and from several families of dipteran hosts had almost no variation in their isozyme patterns, which suggests a degree of evolutionary stasis in that species. Historical mycogeography, though it requires some basic knowledge of the taxonomy of fungal groups, adds a spacial component to phylogenetic systematics as well as a more realistic time scale than phylogeny alone can provide. Mycogeography can also be used to reassess and develop new phylogenies for some fungal species. Key words: biogeography, fungi, Harpellales, insects, isopods, Trichomycetes.
How natural should anamorph genera be?
Authors: Gams W.
Published: May 2008

The taxonomy of anamorphic fungi has always been artificial, as a concession to the practical needs of identifying and naming important organisms, because of insufficient characters indicative of a more natural classification. Integration of anamorph taxa into a teleomorph classification is best served by retaining anamorph names for fungi that have no teleomorph fructification. Proposals to split more or less heterogeneous anamorph genera such as Aspergillus, Fusarium, Acremonium, Verticillium, and Gliocladium into more natural units have prompted this assay. While subdivision of these genera can be defended only partly, some nematophagous genera with affinities to Arthrobotrys or Monacrosporium are considered for lumping, to achieve a more natural classification. This raises the question of to what extent anamorph genera can be delimited naturally and how far they must reflect teleomorph associations. A consistent application of natural genus concepts for anamorphic fungi, even if that were possible, would completely upset nomenclature. While the segregation of morphologically divergent, obviously unrelated taxa from an anamorph genus is defendable, some admittedly deviating taxa (different teleomorphs) should be tolerated in somewhat artificial genera for the sake of identification. Conversely, lumping all anamorphs associated with one teleomorph genus into one genus is not supported when the criteria used for identification clearly favour splitting; otherwise it would render identification according to morphological criteria impossible. Therefore classification of anamorph genera cannot aim at genera that adequately reflect natural relationships and the most convenient generic delimitation must be considered for individual cases. Key words: anamorph, teleomorph, classification, nomenclature, Deuteromycetes, pleomorphism.
Phylogenetic perspectives on basidiomycete systematics: evidence from the 18S rRNA gene
Authors: Swann Eric C. , Taylor John W.
Published: May 2008

Basidiomycete systematics has a history of dramatic change with the introduction of new forms of information. We present a new class level taxonomy for basidiomycetes consisting of the Urediniomycetes emend., Ustilaginomycetes, and Hymenomycetes. The primary source of characters for this analysis is the 18S rRNA gene. Other characters such as cellular carbohydrate composition, major ubiquinone system, 5S rRNA sequence, basidium morphology, and septum and spindle pole body ultrastructure are considered. Comparison of the new class system to other basidiomycete taxonomies is made. Use of 18S sequence to test the monophyly of an order is made in an examination of the Filobasidiales. Key words: basidiomycetes, molecular systematics, taxonomy, Filobasidiales, basidiomycetous yeasts.
Heat shock proteins and human pathogens
Authors: Burnie J. P.
Published: May 2008

Recent years have seen the identification of heat shock protein 90 (HSP90) as one of sthe key immunodominant antigens in systemic fungal infection. In disseminated candidiasis, patients seroconvert when they recover from the infection. In a mouse model of infection, human, mouse, and human recombinant antibody all showed a degree of protection. HSP90 is also immunodominant in patients with an aspergilloma, allergic bronchopulmonary aspergillosis, and invasive aspergillosis who mount an antibody response. This paper argues the case for immunotherapy with antibody in treating these serious infections. Key words: heat shock protein 90, invasive candidiasis, invasive aspergillosis, immunotherapy.
Antigens ofAspergillus fumigatusexpressed during infection
Authors: Debeaupuis Jean-Paul , Sarfati Jacqueline , Kobayashi Hidemitsu , Boucias Drion G. , Beauvais Anne , Paris Sophie , Latgé Jean-Paul , Gumowski Pierre , Monod Michel
Published: May 2008

Aspergillus fumigatus secretes an array of antigenic molecules in vitro and in vivo. Recent progresses have been made in the characterization and standardization of A. fumigatus antigens useful for the serodiagnosis of aspergillosis. The chymotrypsin antigen has been purified and can be utilized for the diagnosis of aspergillosis occurring in patients with an immunocompetent B cell population. In the case of immunosuppressed patients suffering from invasive aspergillosis, new methods have been developed to detect the galactofuran containing antigen in the serum. The chemical configuration of this molecule is now known. In contrast to their potential in diagnosis, very little progress has been made on the study of the biochemical and pathoimmunological role of these antigens during the infection process. Two reasons can be advanced for this lack of understanding of the virulence determinants. First of all, antigens studied have been produced in vitro in a dextrose rich medium where pH reaches a value below 5 at maximal growth. These culture conditions are very different from the nutritional environment of the lung, which is a protein-based medium with a slightly basic pH. Antigens expressed under these nutritional conditions are very different from the ones detected in vitro. Second, A. fumigatus is an opportunistic fungus which is characterized by a multifactorial virulence. Gene disruption strategy is not adequate to discriminate the role of a factor in the virulence of the fungus. In contrast, as shown by the studies on two toxins of A. fumigatus, a direct effect of an antigen can be seen directly when several fungal molecules are tested in conjunction on host cells. Key words: Aspergillus fumigatus, antigen, invasive aspergillosis, galactomannan, protease.
Possible roles of wall hydrolases in the morphogenesis ofCoccidioides immitis
Authors: Cole Garry T. , Pishko Elizabeth J. , Seshan Kalpathi R.
Published: May 2008

We have used the human respiratory pathogen, Coccidioides immitis, as an experimental model to explore possible interrelationships of wall-associated hydrolases, cell growth, and reproduction. Preliminary evidence has been presented that suggests that certain wall hydrolases (glucanase, chitinase) may play key roles in cell development in this systemic pathogen. Initial differentiation of the parasitic cells from cylindrical arthroconidia involves a period of isotropic growth and results in formation of a multinucleate spherule (approximately 60 μm diameter). An endo-1,3-β-glucanase that may participate in this diametric growth phase has been isolated. Two distinct chitinase genes (cts1, cts2) have been isolated from C. immitis and shown to be members of different classes of this wall hydrolase. The class I chitinase (CTS2) demonstrates homology to a reported endochitinase of Saccharomyces cerevisiae that has been shown to be essential for yeast daughter cell release. CTS2 may play a pivotal role in isotropic growth, as well as differentiation and release of endospores from maternal spherules. In the absence of specific gene disruption and transformation experiments, these data are still circumstantial evidence for the functions of wall hydrolases in C. immitis development. However, we suggest our results provide further support for the concept that wall hydrolases represent rational molecular targets for future development of novel antifungal agents. Key words: Coccidioides, cell wall, β-glucanase, chitinase, morphogenesis.
The structure of chitinases and prospects for structure-based drug design
Authors: Robertus Jon D. , Hart P. John , Monzingo Arthur F. , Marcotte Edward , Hollis Thomas
Published: May 2008

Many fungi, including pathogenic strains, require proper chitin metabolism to assure normal cell wall replication. Chitinase hydrolyzes chitin; inhibition of endogenous chitinases or application of extracellular chitinases can disrupt fungal division. It is possible that chitinase inhibitors could be used as antifungal agents. We have solved the X-ray structure of a class II chitinase from barley and proposed a mechanism of action. The enzyme has a structural core similar to lysozyme and probably acts in a similar catalytic manner. The enzyme structure can, in principle, be used to identify small molecules that will bind avidly to the active site and act as inhibitors. Those inhibitors that embody transition state geometry are likely to be particularly effective. Key words: chitinase, mechanism of action, drug design.
Recognition of endothelial cells byCandida albicans: role of complement-binding proteins
Authors: Calderone Richard A.
Published: May 2008

Candida albicans, a commensal of humans, can cause either mucosal or systemic infections. The virulence properties of the organism include cell-surface adhesins that recognize ligands of host cells. Hyphal forms of the organism possess a 60-kDa mannoprotein that recognizes a variety of host-cell ligands including the complement C3 conversion products, C3bi and C3d. In addition, a protein of similar molecular mass also binds to endothelial extracellular matrix proteins such as laminin and fibronectin. While the 60-kDa protein is associated with the cell surface of hyphal forms of the organism, a protein of 50 kDa with similar ligand-binding activities is associated with the plasma membrane of blastoconidia. This protein cross reacts with antibodies to the 60-kDa protein. Isolation of the gene(s) encoding these cell-surface proteins is underway using both a human B-lymphocyte CR2 gene fragment or oligonucleotides based upon peptide sequence to screen libraries of C. albicans. Mutants of the organism with reduced expression of either C3d or C3bi-binding activity have been isolated. These strains are less virulent and also less adherent in vitro. Studies are currently underway to define the contribution of these proteins to the virulence of the organism. Key words: adherence, complement receptor, mannoprotein, virulence, ligand recognition.
Molecular targets for new antifungal drugs
Authors: Perfect John R.
Published: May 2008

Fungal infections in man and animals have a significant impact on health. However, there are only a few antifungal agents available for treatment of invasive mycoses. Further understanding of fungal molecular pathogenesis in collaboration with biochemistry and molecular modeling strategies should be able to develop new selective fungicidal agents. An example of this approach is Cryptococcus neoformans, which is reviewed in this discussion, as a model system for identification of antifungal molecular targets. Key words: antifungals, fungi, treatment, cryptococcosis, molecular biology, targets.
Dynamics of fungal pathogens in host plant tissues
Authors: Takenaka Shigehito
Published: May 2008

To develop efficient control measures against fungal plant pathogens, the dynamics of host plant colonization during disease development and the interactions among fungi within host plant tissues need to be clarified. These studies require accurate quantitative estimation of specific fungal biomass in plant tissues. This has been approached by direct-microscopic methods, cultural methods, chemical determinations of fungal components, serological methods, and molecular methods. Among these methods, serological and molecular methods provide rapid, specific, and sensitive quantitative measures of fungal biomass in host plant tissues. Therefore, studies on fungal dynamics of host plant colonization using these two methods are presented. Some examples of species interactions among pathogenic fungi within host plants, such as synergism and competition, are reviewed and the usefulness of serological and molecular methods for studies on these interactions is presented. These quantitative methods will provide helpful information for understanding the ecology of plant pathogenic fungi, such as the dynamics of host plant colonization and species interactions. Key words: quantitative methods, fungal biomass, ELISA, PCR, fungal colonization, species interaction.
Molecular analysis of ectomycorrhizal fungal communities
Authors: Egger Keith N.
Published: May 2008

Despite advances in mycorrhizal identification, the goal of elucidating the structure and development of mycorrhizal communities remains elusive. Fruit body production can be sporadic, morphological typing of mycorrhizae is subject to variation with environmental conditions or host, and cultural studies are labor intensive and miss fungi that cannot be isolated. Molecular techniques for identification of fungal symbionts can supplement these techniques and offer an approach that is rapid, is independent of environmental variation, and can be applied directly to large numbers of samples. Molecular approaches to mycorrhizal community analysis attempt to distinguish taxonomic groups so they can be monitored and their interactions studied. Initial characterization of community structure involves enzymatic amplification of DNA directly from mycorrhizal roots using fungus-specific primers, followed by restriction endonuclease digestion to produce taxon-specific restriction fragment patterns. Comparison of these patterns with those obtained from fungal fruit bodies or reference cultures facilitates identification of fungal symbionts. Phylogenetic relationships of fungi that cannot be matched to reference isolates can be inferred by sequencing enzymatically amplified DNA. Future directions that will result from molecular approaches include development of sampling strategies, resolution of species complexes, field observations of host specificity, elucidation of the dynamics of replacement processes (succession), and determination of the role of dispersal in community development. As additional techniques are developed for population analysis, resolution of questions related to genetic structure, variation, and gene flow will become feasible. Key words: molecular ecology, fungal community structure, PCR.
Crayfish Productivity, Allochthony, and Basin Morphometry
Authors: Jones P. D. , Momot W. T.
Published: May 2008

West Lost Lake has a higher production of the crayfish, Orconectes virilis, than does nearby North Twin Lake. The basis for the higher carrying capacity of West Lost Lake lies in its steeper basin slope which extends more of its littoral leaf fall distribution to the deeper waters where the social dominance of males forces the female adults to reside. As a result there is a greater available supply of allochthonous food provided for the female brood stock in West Lost Lake. Even though attached egg production per female breeder is the same in both lakes, more hatchlings are produced in West Lost because it has a greater density of nursery area provided by larger beds of Carex aquatilis var. substricta. Because the survival rate of crayfish throughout life is not different in the two lakes, the higher production in West Lost is attributed to a greater carrying capacity for both young and adults.Key words: crayfish production, basin morphometry, allochthonous import, Orconectes virilis
Determinants of Diet of Brook Trout (Salvelinus fontinalis) in a Mountain Stream
Authors: Allan J. David
Published: May 2008

Feeding rates, time of feeding, and prey choice of brook trout (Salvelinus fontinalis) were studied in Cement Creek, Colorado, in 1975–77. On each of five dates from early June to late September, I collected trout at intervals over a 24-h period, along with samples of invertebrate drift and benthos. Although substantial individual variation was observed in time of feeding and prey choice, feeding during the day appeared to predominate. The period of peak feeding shifted from 18:00–22:00 in June–July to earlier hours in August–September. The average number of prey per predator declined over the season and trout relied more heavily on terrestrial forms as aquatic taxa became more rare. The weight of food eaten per day was ~3–4 × the average amount observed per stomach.The numerical abundance of prey in the diet was significantly correlated with abundance of prey in the drift. Except for a few trout which ingested large, rare prey, this was also true for prey composition by biomass. Large taxa tended to be consistently overrepresented in trout diet and small taxa underrepresented. Several prey species shifted from underrepresentation in trout diets to overrepresentation as they grew in size. Abundance and size of prey, along with individual specialization by trout presumably as a result of experience, are suggested as primary determinants of trout diet.Key words: brook trout, Salvelinus fontinalis; stream, predator-prey, aquatic insects
Analysis of Chlorophyll a in Sediments by High-Pressure Liquid Chromatography
Authors: Brown Lewis M. , Hargrave Barry T. , MacKinnon Michael D.
Published: May 2008

We have developed a method that uses high-pressure liquid chromatography (HPLC) with fluorometric detector for the determination of concentrations of chlorophylls a and b and their pheophytins in sediments. A reversed-phase column allowed direct injection of extracts prepared in the conventional manner (90% acetone or other solvent mixtures containing water). Concentrations of chlorophyll a in acetone estimated by a spectrophotometric method (using the acidification ratio) agreed with those estimated by HPLC. Chlorophyll a concentrations in sediments estimated by fluorometry were sometimes quite different from those estimated by HPLC or spectrophotometry. Estimates of concentrations of chlorophyll b and pheophytins a and b can be made by the HPLC method even in the presence of degradation products other than pheophytins that would interfere with the determination by spectrophotometry or fluorometry. The method is sensitive, rapid (14 min per sample), probably compatible with a variety of solvent mixtures, and can be automated for processing large numbers of samples.Key words: chlorophyll a, chlorophyll b, pheophytins, high-pressure liquid chromatography, sediments, algae, epipelic, biomass, primary productivity, suspended particulate matter
Anadromous Arctic Char, Salvelinus alpinus, Penetrating Southward on the Norwegian Coast
Authors: Jensen John Willas
Published: May 2008

Anadromous Arctic char, Salvelinus alpinus, have been limited on the Norwegian coast to areas north of 65°N. In 1967 anadromous char invaded the river Granvinelv in the Hardangerfjord at 60°N, and have given rise to a dense population of stationary freshwater char in the lake Granvinvatn. During 1978–79 anadromous char spread to several rivers at the head of the fjord. Events assumed to have taken place during the melting-off phase of the last glacial period are recurring. The Hardangerfjord is colder than the outside coastal waters and will very probably function as a subarea of the char. The available data indicates that an average coastal water temperature of 14 °C at 4–5 m depth is limiting the anadromous char to the south on the Norwegian coast. Continuous water masses colder than 13.6 °C could have permitted the southward penetration of anadromous char to the Hardangerfjord in 1964, but the char may also have escaped from a hatchery in the vicinity of the fjord. Landlocked char of a river entering the head of the Hardangerfjord evidently do not possess the capacity to give rise to an anadromous population.Key words: Salvelinus alpinus, anadromous char, distribution area, southward penetration, temperature barrier
Radiotracer Experiments on Phosphorus Uptake and Release by Limnetic Microzooplankton
Authors: Taylor W. D. , Lean D. R. S.
Published: May 2008

When carrier-free 32PO4 is added to lakewater, the planktonic ciliated protozoan Strombidium viride gradually becomes labeled over at least 30 h. The label enters S. viride primarily by the ingestion of labeled particles 0.2–1.0 μm in size; direct uptake of phosphate or uptake of larger particles (≥5 μm) is relatively slight or absent. When labeled S. viride are transferred to unlabeled lake water, they lose 32P by a discontinuous process, presumed to be defecation, plus a relatively slow, continuous process. The latter is assumed to be equivalent to what is usually termed excretion for crustacean zooplankton, and is equivalent to a turnover time for the animal's phosphorus content of many hours. Results of release experiments with the rotifer Keratella cochlearis are quantitatively similar, but defecation was a much larger part of the total. Excretion was similar in turnover time to that for S. viride. The soluble phosphorus released by both species was characterized as primarily phosphate using gel filtration. These results do not support the conventional view that microzooplankton regenerate dissolved phosphorus much more rapidly for their biomass than larger crustacean zooplankton.Key words: phosphorus uptake, phosphorus release, microzooplankton, Strombidium viride, Keratella cochlearis
Lampetra macrostoma, a New Species of Freshwater Parasitic Lamprey from the West Coast of Canada
Authors: Beamish Richard J.
Published: May 2008

Lampetra macrostoma n.sp., a freshwater parasitic lamprey, is distinguished from related species L. tridentata, L. lethophaga, L. folletti, L. minima, and L. similis by its parasitic habit and very large disc. Other characters distinguishing the species from L. tridentata are its longer prebranchial length, large eye, weakly pigmented velar tentacles, and its ability to remain in freshwater. The recently metamorphosed form readily survives in freshwater and probably is non-anadromous even though it can survive in salt water. The new species has been discovered in two lakes on Vancouver Island, British Columbia, Canada, where it attacks large numbers of resident salmonids. Because of its ability to survive and feed in freshwater, it poses a definite threat to freshwater fishes.Key words: lamprey, new species, non-anadromous lamprey, salmonid parasitism
Energetics of Sablefish, Anoplopoma fimbria, under Laboratory Conditions
Authors: Sullivan Kathleen M. , Smith Jr. Kenneth L.
Published: May 2008

We measured respiration, growth, ingestion, and excretion rates for sablefish, Anoplopoma fimbria, collected off southern California at a depth of 500 m and maintained in the laboratory. We also measured the water, protein, and lipid content of white skeletal muscle in both laboratory-held and field fish. Sablefish fed a large ration (14% of wet body weight) every 7–10 d showed growth rates two to three times higher than known growth rates for field fish. On a reduced ration (4% of wet body weight) sablefish grew at rates similar to field fish, but white muscle composition varied significantly from field fish. Oxygen consumption rates under constant temperature conditions showed a decrease in the weight-specific oxygen consumption rates with increase in body weight, ranging from routine metabolic rates of 195.8 mg O2∙kg−1∙h−1 for a 0.25-kg fish to 60.8 mg O2∙kg−1∙h−1 for a 2.78-kg fish. Based on measurements of respiration and excretion, sablefish were estimated to have 162 d of energy stored in the body lipids and did not show signs of starvation stress with food deprivation up to 6 mo in the laboratory. Energy allocation shows very slow growth rates, low conversion efficiencies, and low metabolic rates as adjustments made to large, infrequent meals.Key words: physiological responses, benthopelagic fish, growth, metabolic rate, respiration, excretion
Solution to the "Char Problem" based on Arctic Char (Salvelinus alpinus) in Norway
Authors: Nordeng Hans
Published: May 2008

Rearing and transplantation experiments demonstrate that three coexisting forms of Arctic char Salvelinus alpinus (anadromous, small and large freshwater residents) belong to the same gene pool. The parr of each form segregate into all three forms. Single individuals may manifest all three forms during their lifetime, successively attaining the appearance and spawning color of each form. Males mature at a younger age and smaller size than females. Hence, in char populations featuring two or more forms, males dominate in the early maturing form and females in the late maturing form. Char populations that feature only one form (sex ratio 1:1) seem to be established through natural selection for age at sexual maturity. Segregation during the young stage depends upon their genetic constitution and access to food. Offspring of the small resident parents produced more resident individuals and fewer smolts than did offspring of anadromous parents. An increased amount of food increases the resident fraction and reduces the fraction of anadromous char. It is demonstrated that the potential for anadromy exists in populations of char in the southern nonanadromous area, and that one reason for resident behavior in the smolt may be infection of the ureter fluke Phyllodistomum conostomum Olsson.
Reaction of Bottlenose Dolphins, Tursiops truncatus, to a Controlled Oil Spill
Authors: Smith T. G. , Geraci J. R. , St. Aubin D. J.
Published: May 2008

Three captive bottlenose dolphins, Tursiops truncatus, were observed in an ocean pen measuring 14 × 11 m, divided into three equal areas by oil-containment booms. Each dolphin was placed in the pen alone for 4 d with no oil present, and 2 d with dark-colored mineral oil in one of the areas. We noted their area of surfacing, underwater movements, dive times, and reactions. After a few brief contacts with the oil, dolphins completely avoided surfacing in the slick. The oil also acted as a temporary barrier restricting their underwater movement.
Toxicity of Trace Metal Mixtures to American Flagfish (Jordanella floridae) in Soft, Acidic Water and Implications for Cultural Acidification
Authors: Hutchinson N. J. , Sprague J. B.
Published: May 2008

Laboratory exposures over 1.3 generations showed that trace metal mixtures played a dominant role in the reproductive failure of American flagfish (Jordanella floridae) in soft (6.0 mg∙L−1as CaCO3total hardness), acidified (pH 5.8) water. This finding may also apply for native fish species inhabiting culturally acidified waters. Reproductive failure was complete when pH 5.8 water contained a mixture of Al, Mn, Fe, Ni, Zn, Cu, and Pb at 57% of the concentrations found in acidified waters (or 0.57 ALC). Fry died within 6 d of exposure, adults transferred into the treatment ceased spawning, and hatching of transferred eggs was reduced. The onset of steady spawning activity was delayed by addition of smaller amounts (0.09–0.27 ALC) of metals, but reductions in size of juvenile fish did not persist to maturity. At pH 5.8 with no metals, no effects on any stage of the life cycle were observed. Subsequent testing of fry showed that lethality of a mixture of Al, Zn, and Cu was equivalent to that of all seven metals. The threshold acute LC50 for flagfish fry at pH 5.8 occurred with the simultaneous presence of Al, Zn, and Cu at 29, 5, and 2.3 μg∙L−1, respectively, or with 95 μg Al∙L−1alone. Future research on trace metal stress in culturally acidified waters should consider Zn and Cu, in addition to Al.
Comparison of Methods for Estimating Annual Productivity of the Copepods Acartia hudsonica and Eurytemora herdmani in Passamaquoddy Bay, New Brunswick
Authors: Middlebrook Ken , Roff John C.
Published: May 2008

Annual productivity of the copepods Acartia hudsonica and Eurytemora herdmani was estimated over a 12-mo period at three sites in Passamaquoddy Bay, New Brunswick. The sites were chosen to represent the range of habitats present in the bay. Samples were collected in vertical hauls of a 64-μm-mesh plankton net. Annual productivity was estimated by three methods. Estimates by the temperature–biomass method were 578–677 kJ∙m−2∙yr−1 for A. hudsonica and 63–173 kJ∙m−2∙yr−1 for E. herdmani. Both the mass-specific and cohort P/B methods yielded productivity estimates comparable with those calculated by the temperature–biomass method for E. herdmani. Acartia hudsonica estimates by the P/B methods were lower. We suspect that the cause of this discrepancy is the incorporation of periods of diapause and nonmaximal growth in estimating a mean biomass value for A. hudsonica. Other temporally abundant copepods observed in the bay included Tortanus discaudatus, Temora longicornis, Pseudocalanus sp., Oithona similis, and Centropages typicus. Total copepod productivity, assuming productivity by the rare species to be proportional to their relative numeric contribution, was estimated to be 800–850 kJ∙m−2∙yr−1. Through comparison of these estimates with previously published estimates, we suggest that copepod productivity in coastal areas may be similar over broad geographic areas.
Direct and Indirect Effects of Arsenic on the Survival and Fecundity of Estuarine Zooplankton
Authors: Sanders James G.
Published: May 2008

Estuarine Zooplankton are resistant to relatively high concentrations of arsenate, up to 100 μg∙L−1, and are not likely to be impacted directly in natural systems. Indirect impacts, however, can be much more severe. Natural phytoplankton communities are significantly inhibited by low levels of arsenate, altering species composition and succession of dominant species, affecting normal predator–prey relationships, and greatly reducing zooplankton grazing, survival, and reproductive success. Thus, an initial prediction of insignificant pollutant impact based upon direct effects would be erroneous. Both potential direct and indirect impacts and the significance of pollutant-induced changes at one trophic level to species at higher levels must be determined for aquatic systems if reliable predictions concerning pollutant impacts are to be generated.
Capelin (Mallotus villosus) Spawning on the Southeast Shoal: Influence of Physical Factors Past and Present
Authors: Carscadden J. E. , Frank K. T. , Miller D. S.
Published: May 2008

Co-occurrence of beach- and offshore bottom-spawning populations of capelin (Mallotus villosus) in the Northwest Atlantic appears to be unusual. To explain the evolution of bottom-spawning in the offshore spawning population on the Southeast Shoal, we examined relevant substrate, water temperature, and biological data. Published data indicate that the Southeast Shoal was not glaciated during the Wisconsin glaciation (about 20 000 yr ago) and was above sea level. As the glaciers melted, this area was a surf zone before it became inundated. This suggests that this stock was once a beach-spawning stock and supports our hypothesis that substrate is the ultimate factor affecting spawning location. Analysis of 7 yr of distribution, maturity, and bottom temperature data showed that the variation in the final spawning location was not large and spawning occurred where bottom temperatures exceeded approximately 2 °C. We conclude that bottom temperature is a proximate factor influencing the final spawning location. Physical data for other areas of the Grand Banks indicate that only the Southeast Shoal has favourable substrate, bottom temperatures and environmental factors subsequent to spawning to allow the long-term survival of a capelin population.
A Conceptual Model for the Estimation of the Sensitivity of Black Fly Larvae to Bacillus thuringiensis var. israelensis
Authors: Morin Antoine , Back Christian , Boisvert Jacques , Peters Robert H.
Published: May 2008

Results from bioassays of a commercial formulation of Bacillus thuringiensis var. israelensis (Teknar HP-D) are combined with an empirical model of the feeding rate of larvae of a target species of black fly (Simulium venustum/verecundum) to develop a model relating the mortality of larvae to the amount of formulation ingested per unit mass of larvae (specific ingested dose). LD50 of Teknar HP-D was about 1 μg wet mass of Teknar per milligram dry mass of larvae, and independent of size of the larvae and seston concentration. Compared with standard assay analysis relating the mortality to the dose (milligrams per litre times seconds), the proposed model allowed more precise and replicable estimation of the effective dose. Reanalysis of published data on the potency of another Bti formulation (Teknar WDC), confirmed the superiority of the proposed model over the standard procedure. Susceptibility of larvae to particulate larvicides is mainly a function of the larval feeding rate. In addition to size of the larvae, temperature, and seston concentration, analysis of the model reveals that the length of the contact period and the variability of feeding rates among individual larvae are important factors determining the mortality rate following treatments.
Implications of Streamflow Variability and Predictability for Lotic Community Structure: A Regional Analysis of Streamflow Patterns
Authors: Poff N. LeRoy , Ward J. V.
Published: May 2008

Long-term discharge records (17–81 yr) of 78 streams from across the continental United States were analyzed to develop a general quantitative characterization of streamflow variability and predictability. Based on (1) overall flow variability, (2) flood regime patterns, and (3) extent of intermittency, 11 summary statistics were derived from the entire record for each stream. Using a nonhierarchical clustering technique, nine stream types were identified: harsh intermittent, intermittent flashy, intermittent runoff, perennial flashy, perennial runoff, snowmelt, snow + rain, winter rain, and mesic groundwater. Stream groups separated primarily on combined measures of intermittency, flood frequency, flood predictability, and overall flow predictability, and they showed reasonable geographic affiliation. A conceptual model that incorporates the nine stream clusters in a hierarchical structure is presented. Also, the positions of the 78 streams in a continuous three-dimensional flow space illustrate the wide range of ecologically important hydrologic variability that can constrain ecological and evolutionary processes in streams. Long-term daily streamflow records are a rich source of information with which to evaluate temporal and spatial patterns of lotic environments across many physiographic and ecographic regions. Relative positions of streams in flow space provide a conceptual framework for evaluating a priori the relative importance of abiotic and biotic factors in regulating population and community processes and patterns.
Multiple-Frequency Acoustic Backscattering and Zooplankton Aggregations in the Inner Scotian Shelf Basins
Authors: Cochrane N. A. , Sameoto D. , Herman A. W. , Neilson J.
Published: May 2008

Acoustic backscatter observations at 12, 50, and 200 kHz in the inner Scotian Shelf basins reveal large populations of silver hake (Merluccius bilinearis) and its principal prey, the euphausiid Meganyctiphanes norvegica. Multichannel sonar colour imagery facilitates separation of fish from euphausiids and delineation of their separate diurnal migration patterns. Silver hake acoustic abundances are consistent with midwater trawl sampling. Acoustic column densities for mature M. norvegica of approximately 1000/m2 exceed net sampling column densities by over 1 order of magnitude indicating strong net avoidance. Numerical simulation of euphausiid backscattering using a fluid cylinder model and natural distribution of scatterer orientations yields an approximate 20 log L target strength length dependence and little frequency domain dependence in the "geometric" scattering regime. Quantitative interpretation of euphausiid scattering in situ must account for randomness in their orientations.
Food Consumption and Bioenergetics of Young-of-the-Year Walleye (Stizostedion vitreum vitreum): Model Predictions and Population Density Effects
Authors: Fox Michael G.
Published: May 2008

I compared in situ growth and food consumption estimates of young-of-the-year walleye (Stizostedion vitreum vitreum) reared at three different densities in outdoor ponds with predictions of a bioenergetic model for walleye (KitcheH et al. 1977. Res. Board Can. j. Fish. 34: 1922–1935), and used the model to determine whether fish population density affects growth efficiency or metabolism. Maximal walleye growth rate was adequately predicted by model simulations. Consumption estimates were 40% lower than predicted, but predictions were improved when the respiration equation of Minton and McLean (1982. Can. J. Fish. Aquat. Sci. 39: 1396–1403) was substituted in the model. There was no evidence that juvenile walleye have higher consumption or respiration rates than those predicted by allometric models based on larger fish. Walleye in low-density ponds had a higher growth efficiency and active metabolic rate than those reared at lower densities, but the difference was not statistically significant.
Population Dynamics and Food Habits of Bluegill (Lepomis macrochirus) in a Thermally Stressed Reservoir
Authors: Taylor Barbara E. , Aho John M. , Mahoney Diane L. , Estes Ruth A.
Published: May 2008

Bluegill (Lepomis macrochirus) is the dominant fish species in a 67-ha cooling reservoir for a nuclear reactor on the Savannah River Site in South Carolina. Mortality and breeding season of bluegill were strongly influenced by reactor operations, which often produced temperatures of 40–60 °C in portions of the reservoir. Late spring and summer reactor operations caused ~ 90% mortality of bluegill. This mortality was largely associated with reactor restarts. Survivors occupied small thermal refuges in coves. Elevated fall and winter temperatures allowed an extended breeding season, although extremely high summer temperatures appeared to inhibit breeding. Bluegill depended primarily on benthic food resources, including dipterans and microcrustaceans. Despite the great variation in environmental conditions and diets, body condition of surviving bluegill was nearly constant between April 1985 and January 1986. Factors that contribute to the success of bluegill in this system include high thermal tolerance, broad diets, and an ability to breed when thermal conditions are appropriate, regardless of season.
Bacterioplankton Density and Activity in Benthic Nepheloid Layers of Lake Michigan and Lake Superior
Authors: Hicks Randall E. , Owen Christopher J.
Published: May 2008

Benthic nepheloid layers were observed in Lake Michigan and Lake Superior during July 1988 using the Johnson-Sea-Link II submersible. A particularly well-defined benthic nepheloid layer was present in Whitefish Bay, Lake Superior, where particle concentrations increased 10 times over the bottom 30 m. Bacterial abundance, however, increased only 1.5 times in the same depth interval and a maximum of only 16% 1 m above the sediment in both lakes when the sediment boundary layer was deliberately resuspended. Bacterial abundance was greater in Lake Michigan than in Lake Superior. Bacterioplankton abundance and the frequency of dividing cells were both related to temperature and organic carbon concentrations. The range of individual cell volumes (0.024–0.042 μm3) was similar in both lakes, regardless of depth. Less than 5% of the heterotrophic bacteria were actively dividing and only 2.0–3.4% of the bacterioplankton in the epilimnion and hypolimnion were synthetically active in both lakes. Bacterioplankton doubling times, estimated from field measurements of the frequency of dividing cells, increased from 29 h at 5 m to > 230 h at 310 m in the Caribou Basin of Lake Superior. The abundance, cell size, and activity of heterotrophic bacterioplankton in the deep hypolimnia of Lake Michigan and Lake Superior were unaffected by the presence of a benthic nepheloid layer.
Survival and Growth of Atlantic Salmon (Salmo salar) Fry Stocked at Varying Densities in the White River, Vermont
Authors: Whalen K. G. , LaBar G. W.
Published: May 2008

Survival and growth of unfed Atlantic salmon (Salmo salar) fry stocked at varying densities (12, 25, 50, and 75 fry∙100 m−2) was evaluated in the White River, a tributary of the Connecticut River in Vermont, using a randomized complete block design. Fry to age-0 parr survival was inversely related to fry stocking density and, in most sampling sections, no significant increases in age-0 parr density were attained by stocking at rates ≥50 fry∙100 m−2. Most age-0 parr ranged in length between 65 and 80 mm; no significant differences in mean age-0 parr length were detected among stocking densities. Greatest age-0 parr production efficiency may be attained by stocking at densities <50 fry∙100 m−2. However, the density of age-0 parr produced from stocking at 12 fry∙100 m−2 may be insufficient to achieve carrying capacity of age-1 parr.