bluuebunny/crossref_metadata_2025 huggingface dataset:
Global genetic resources forAgaricusbreeding and cultivation
Authors: Kerrigan Richard W.
Published: May 2008

Until recently the natural history and resource status of the button mushroom Agaricus bisporus has been but poorly known. At present, five and perhaps six genetically distinctive, reproductively isolated populations of this species from western North America, Europe, and western Asia have been located, sampled, and partially characterized. Morphology, diversity, reproductive syndrome, and other economically important traits vary among these populations. Other populations may exist in northern and central Africa and in Australia. Available evidence suggests that the studied populations are ancient. However, probably through cultivation, European germ plasm has invaded the three known North American populations and has already displaced a large portion of the indigenous coastal Californian population; the trend is less advanced in Alberta and the California desert. The recovery of diverse wild germ plasm of this mushroom, still in its infancy, is likely to become increasingly difficult. The value of these genetic resources, the threats that confront them, and appropriate responses by the mushroom industry are discussed. Hypotheses about the outcomes of heterokaryon somatogamy and the concept of the individual in this species are presented. The term metagenotype is coined to describe the ancestral or consensus genotype of a multigenerational intramictic lineage group. Key words: Agaricus bisporus, genetic resources, biodiversity, breeding, population structure, resource management.
Biodegradation of lignin
Authors: Reid Ian D.
Published: May 2008

Lignin is an aromatic polymer forming up to 30% of woody plant tissues, providing rigidity and resistance to biological attack. Because it is insoluble, chemically complex, and lacking in hydrolysable linkages, lignin is a difficult substrate for enzymatic depolymerization. Certain fungi, mostly basidiomycetes, are the only organisms able to extensively biodegrade it; white-rot fungi can completely mineralize lignin, whereas brown-rot fungi merely modify lignin while removing the carbohydrates in wood. Several oxidative and reductive extracellular enzymes (lignin peroxidase, manganese peroxidase, laccase, and cellobiose:quinone oxidoreductase) have been isolated from ligninolytic fungi; the role of these enzymes in lignin biodegradation is being intensively studied. Enzymatic combustion, a process wherein enzymes generate reactive intermediates, but do not directly control the reactions leading to lignin breakdown, has been proposed as the mechanism of lignin biodegradation. The economic consequences of lignin biodegradation include wood decay and the biogeochemical cycling of woody biomass. Efforts are being made to harness the delignifying abilities of white-rot fungi to aid wood and straw pulping and pulp bleaching. These fungi can also be used to degrade a variety of pollutants in wastewaters and soils, to increase the digestibility of lignocellulosics, and possibly to bioconvert lignins to higher value products. Key words: delignification, white-rot fungi, biobleaching, lignin peroxidase, manganese peroxidase, laccase.
Bioconversion of cereal straw into mushroom compost
Authors: Straatsma Gerben , Olijnsma Tineke W. , Gerrits Jan P. G. , Griensven Leo J. L. D. Van , Samson Robert A. , Op Den Camp Huub J. M.
Published: May 2008

Agaricus bisporus mushrooms are cultivated on straw compost prepared in the sequence phase I and phase II. Phase I is a process at 70–80 °C for several days up to 2 weeks. Phase II is a controlled process at 45 °C for 6 days. In phase II the thermophilic fungus Scytalidium thermophilum becomes abundant. Its density in finished compost is correlated with the yield of mushrooms. It stimulates the growth rate of mushroom mycelium. Scytalidium thermophilum was inoculated in batches of 1 tonne of pasteurized compost for experimental phase II. Mushroom yields on these composts were twice those of controls (pasteurized, not inoculated). This indicated that S. thermophilum is important for the conversion of straw to compost. The essential actions for mushroom crop productivity of high temperatures during phase I and of S. thermophilum during phase II are unclear. Key words: Agaricus bisporus, button mushroom, Scytalidium thermophilum, solid-state fermentation, processing, review.
Gene regulation in the white–opaque transition ofCandida albicans
Authors: Soll David R. , Srikantha Thyagarajan , Morrow Brian , Chandrasekhar Anand , Schröppel Klaus , Lockhart Shawn
Published: May 2008

Most strains of Candida albicans switch frequently and reversibly among a number of different phenotypes distinguishable by colony morphology. Previous experiments indicated that switching involved differential gene expression. Using the white–opaque transition as a model switching system, we have cloned two opaque-specific genes, PEP1 and OP4, and one white specific gene, WH11. Differential transcription of these genes suggested that switching involves the coordinate regulation of batteries of unlinked phase-specific genes. It has been demonstrated that the frequency of integration at phase specific loci is a function of the transcriptional state of the phase-specific genes. In addition, a functional dissection of the 5′-upstream region of the WH11 gene has identified two major domains containing cis-acting regulatory sequences that are involved in phase-specific transcription. Gel retardation experiments provide evidence for white phase-specific trans-acting factors which form complexes with both domains. The regulation of the switching event is discussed. Key words: Candida albicans, phenotypic switching, white–opaque transition, phase-specific genes, integrative transformation, promoter regions, WH11 gene.
Regulation of fungal extracellular proteases and their role in mammalian pathogenesis
Authors: Hensel Michael , Tang Christoph M. , Arst Jr. Herbert N. , Holden David W.
Published: May 2008

Fungal infection in the immunocompromised host is a problem of increasing importance. The virulence determinants of Aspergillus fumigatus, the major agent of invasive aspergillosis, and of Candida albicans, causing candidiasis, are not well characterized. For both pathogens, the involvement of extracellular proteases in pathogenesis is discussed. The use of gene disruption techniques to inactivate the A. fumigatus alkaline protease and metalloprotease genes has led to the firm conclusion that neither of these enzymes has a significant role in virulence. The diploid nature of C. albicans (necessitating sequential inactivation of both alleles for gene disruption studies) and the presence of a multigene family encoding secreted aspartyl proteases has hampered progress in understanding the role of proteases in virulence. We discuss the involvement of wide-domain regulators in the control of protease production and give an example of how one of these regulators (encoded by the areA gene) has been used in virulence studies. Key words: Aspergillus, Candida, proteases, gene regulation.
Function and chromosomal location of theCochliobolus heterostrophus TOX1locus
Authors: Turgeon B. G. , Kodama M. , Yang G. , Rose M.S. , Lu S.W. , Yoder O.C.
Published: May 2008

Conventional genetic analyses have firmly established that the difference in virulence between race T and O of the corn pathogen Cochliobolus heterostrophus is determined by a single genetic locus called Tox1, which also controls production of T-toxin, a polyketide specifically toxic to corn with Texas male sterile (T) cytoplasm. More recently, molecular genetic analyses have revealed that Tox1 is not a single gene but rather at least two genetic loci situated on two different chromosomes. DNA at both of these loci is required for the biosynthesis of T-toxin and for the high virulence of race T to corn carrying T-cytoplasm. One of the loci encodes a polyketide synthase that is necessary for the assembly of the T-toxin molecule. Key words: polyketide, restriction enzyme mediated integration (REMI), host-specific toxin, corn, fungus, virulence.
The secreted proteases of pathogenic species of Aspergillus and their possible role in virulence
Authors: Monod Michel , Jaton-Ogay Katia , Fatih Abdelouahad , Paris Sophie , Latgé Jean-Paul
Published: May 2008

The species of Aspergillus secrete aspartic, serine and metalloproteases. The role of secreted proteases in virulence were investigated with A. fumigatus which is the species the most frequently found in patients with aspergillosis. A mutant of A. fumigatus deficient in proteolytic activity at neutral pH in vitro, was constructed and tested for pathogenicity in a murine model. No difference in pathogenicity was observed between the wild type strain and the mutants, suggesting that the proteases secreted at neutral pH are not essential for the invasion of the lung tissues by the fungus. Key words: proteases, Aspergillus, virulence.
Characterization of a cell-surface antigen isolated from the plant pathogen Phytophthora parasitica var. nicotianae
Authors: Séjalon N. , Dargent R. , Villalba F. , Bottin A. , Rickauer M. , Esquerré-Tugayé M. T.
Published: May 2008

The genus Phytophthora contains several species that are pathogenic to plants. Phytophthora parasitica var. nicotianae is the causal agent of the black shank disease of tobacco. From this fungus we have isolated and purified to homogeneity a 34-kDa glycoprotein (GP34) that elicits defence responses in tobacco. Among other features, this glycoprotein contains the rare amino acid hydroxyproline. Antibodies against GP34 permitted us to study its localization in vitro and in planta. Ultrastructural cytochemistry using immunogold labelling shows that GP34 is present in the cell wall into which it is secreted by vesicles when the fungus is grown on synthetic medium. In zoospores, labelling precedes and is strictly associated with the formation of a new cell wall. At early stages of infection of tobacco, only a faint labelling of the mycelium is observed. Later on it is enhanced in the incompatible interaction between the fungus and a resistant host cultivar. Key words: cell wall, elicitor, hydroxyproline, Phytophthora, tobacco.
Aspergillusproteinases and their interactions with host tissues
Authors: Rhodes Judith C.
Published: May 2008

Invasive aspergillosis is a life-threatening infection that is caused primarily by the species Aspergillus fumigatus and A. flavus, both of which are highly angioinvasive. From this observation, interest has focused on proteinases produced by these organisms and their possible roles in the pathogenesis of infection. Both species produce alkaline serine proteinases (ALP) and metalloproteinases during the course of infection based on immunohistochemistry of experimental lesions and serologic response of patients. These enzymes can be shown to degrade numerous biologically relevant targets, including elastin, collagen, laminin, fibrinogen, and iC3b. Physicochemical properties, immunoreactivities, and amino acid sequences of the ALP of A. fumigatus and A. flavus show that these two enzymes are closely related. The metalloproteinases, however, appear to represent members of a small family of similar enzymes. Finally, although studies using conventionally produced mutants support roles for these hydrolases as virulence factors in aspergillosis, similar studies using strains of A. fumigatus in which the enzymatic activity has been ablated through gene disruption do not reveal differences in virulence between the wild-type strains and the mutants. Key words: aspergillosis, proteinase, pathogenesis.
Molecular signals during the early stages of alfalfa anthracnose
Authors: Dickman Martin B. , Buhr T. L. , Warwar V. , Truesdell G. M. , Huang C. X.
Published: May 2008

Colletotrichum trifolii causes anthracnose disease of alfalfa (Medicago sativa). Fungal perception and response to host signals are likely to be crucial in determining whether successful infection occurs. Our research is based on two premises: (i) that early recognition events result in specific responses and these responses determine whether disease occurs and (ii) recognition involves signal exchange between host and pathogen. We have taken two approaches to study this interaction. One is to isolate "important" genes by methods that make no assumption about their products and then to use molecular characterization (e.g., sequence, expression pattern) to identify the biochemical processes involved. Alternatively, known biochemical entities (genes) that function in signal transduction in other organisms are used as heterologous probes or primers. These molecules are then manipulated to determine functional relevance to the host–pathogen. Data is presented from the later approach and we show that calmodulin, protein kinase C, and a novel protein kinase are specifically expressed during the early stages of infection. Key words: protein kinase, calmodulin, fungal infection, host–parasite interaction, fungal gene expression.
Immunity in histoplasmosis: identification of protective immunogens fromHistoplasma capsulatum
Authors: Deepe Jr. George S.
Published: May 2008

The complexities of the protective immune response to Histoplasma capsulatum remain poorly understood. It is clear that an interaction between antigen-reactive T cells and macrophages is essential for successful resolution of infection. The primary focus in our laboratory is to identify the antigens from this fungus that stimulate T cells to mediate growth inhibition of H. capsulatum. We describe herein the results of studies that centered on the identification of two antigens that trigger T-cell proliferation and can confer protective immunity. These antigens potentially can be used to generate a vaccine against this pathogenic fungus. Key words: histoplasmosis, T cells, antigens, protective immunity, HIS-62.
Fungi and the evolution of growth form
Authors: Andrews John H.
Published: May 2008

Fungi belong to the modular class of organisms characterized by an iterative, indeterminate mode of growth; internal age structure; localized rather than generalized senescence; cellular totipotency; and passive rather than active mobility. Growth form in the fungi therefore reflects their absorptive, sessile lifestyle. Aggregation/differentation of a few basic cell types gives rise to multicellular complexes associated with foraging, reproductive, survival, or dispersal activities. The morphological plasticity of fungi is analogous to but surpasses that of other modular creatures such as the benthic invertebrates and plants. For instance, in response to environmental signals, fungi can vary the timing, extent, and mode of differentiation; interconvert among different growth forms; and decouple the sexual and asexual phases of the life cycle. Evolutionary determinants of their form are phylogenetic constraint, adaptation, developmental constraint, ecophenotypic factors, and chance. Physiological determinants of their form relate primarily to morphogenesis of the cell wall and include the cytoskeleton and cytosis. Key words: morphology, morphogenesis, shape, allometry, modular, evolutionary.
Episodic selection as a force in fungal microevolution, with special reference to clonal speciation and hybrid introgression
Authors: Brasier C. M.
Published: May 2008

Episodic selection encompasses any sudden environmental disturbance likely to lead to a significant alteration in a species' population structure. Such disturbances include geographical transposition, a change in substrate availability, exposure to a new host or a new vector, climate change, and pollution stress. Today, such events may often be brought about by man. Their role in the promotion of fungal microevolution is discussed. In some circumstances, episodic selection may result in the emergence of a highly fitted clone from an originally heterogeneous population, and sustained disturbance may lead to clonal speciation. Clonal speciation accompanied by loss of sexual function, whether under episodic selection or under less intensive but analagous environmental conditions, could account for the origin of many of today's imperfect taxa (Deuteromycotina). Geographical transposition, a special form of episodic selection, can lead to hybridization between previously allopatric species. This may result in modifications to existing species via the acquisition of new loci or cytoplasmic elements, in the production of new taxa via secondary speciation, or in the emergence of hybrid swarms. Episodic selection will also favour survival of novel genotypes by providing new habitats for exploitation, so encouraging novel evolutionary development. Key words: episodic selection, fungal speciation, hybridization, introgression.
Fungal interactions in food fermentations
Authors: Nout M. J. R.
Published: May 2008

Fermented foods are of importance worldwide. Most are prepared under nonsterile conditions using mixed cultures, either deliberately or unavoidably. Fungal mixed cultures show interactive relations at various levels. In this paper, inhibitory effects among fungi owing to competition, formation of organic acids, toxic proteins, and mycotoxins are discussed. In addition, fungi show inhibitory effects towards bacteria and vice versa, through pH changes, and excretion of organic acids, antibiotics, peptides, etc. Stimulatory interactions among fungi and between fungi and bacteria relate mainly to carbon and nitrogen metabolism, and they play an important role in the inherent stability of mixed-culture systems maintained by enrichment techniques. Better understanding of natural mixed-culture fermentations has evolved into the development of the concept of cocultivation employing compatible microbial strains of complementary metabolic ability. Especially in the area of direct conversion of complex carbohydrates (e.g., starch, inulin, or lignocellulosic matter into ethanol), cocultivation has much to offer. Genetic modification of starter organisms offers opportunities to improve, for example, their ability to degrade substrate with a minimum of catabolite repression, and produce final products of superior quality. This is illustrated by recent recombinant DNA constructs for alcoholic fermentations. Key words: food, fungi, interaction, inhibition, stimulation, cocultivation.
Forest endophytes: pattern and process
Authors: Carroll George
Published: May 2008

Studies on taxonomy, distribution, and possible function have dominated the literature on forest endophytes since these fungi were first noted. Endophyte distributions have been described at a variety of scales ranging from those at a landscape level to those at the finest scales of resolution within a single leaf or patch of bark. At a landscape level, distribution patterns seem to be determined by host specificity, liquid precipitation, canopy cover, and geographic continuity or disjunctness. At the level of the individual stand or tree, height in the crown may become important. At the level of individual branch systems, age of substrate appears the most important factor. At a microscopic scale, tissue specificity, leaf topography, and phenology of the infection process with respect to leaf development all play a role. Endophytic fungi have seldom been found to cause widespread disease in trees; furthermore, their age-specific infection frequencies in conifer needles show continuous increases with needle age, in contrast to needle pathogens in which infections are largely confined to young needles. Endophytes are usually viewed as protective mutualists acting against herbivorous insects and pathogenic fungi. Proof of mutualism requires not only that endophytes be present in tissues under attack and their presence be correlated with, for example, increased insect mortality, but that inoculation experiments and comparisons with uninoculated plant tissues also be done. Such experiments often show no differences between treatment and control plants, results that may be related to unsuccessful inoculation of the endophyte. Such results may also be rooted in an inability to reproduce the biological complexity present in natural forest stands. Multiple infections of single leaves may lead to synergistic interactions of toxins produced by endophytes. Insect herbivores have evolved behavioral responses to the presence of endophytes, and protective mutualism by endophytes may occur only intermittently. Key words: endophyte, distribution, mutualism, gall midge, toxins, coevolution.
Fungi with heteroxenous life histories
Authors: Malloch David
Published: May 2008

Heteroxenous (multiple host) life histories are characteristic of many groups of parasitic protista and animals, including Zoomastigina, Apicomplexa, Mesozoa, Platyhelminthes, Nematoda, Acanthocephala, Pentastomida, and Arthropoda. Parasitic fungi, including the Chytridiomycota and the Dikaryomycota (ascomycetes and basidiomycetes), may also have heteroxenous life histories and have many features in common with parasites from other groups. In spite of many conceptual similarities, the study of parasitic fungi has occurred in isolation, resulting in the creation of a separate vocabulary and literature. Many of the concepts developed by zoologists are useful to mycologists and allow examination of parasitic fungi from new perspectives. These new perspectives reveal that heteroxenous fungi are not only similar to heteroxenous protistans and animals but that they also have unique characteristics of their own. Chief among these is a high level of endocyclic asexual reproduction, a phenomenon promoting exponential increases of infections in definitive host populations. Heteroxeny appears to have a number of benefits including (i) increased lifetime reproductive success, (ii) increased transmission efficiency (iii) enhanced effectiveness in colonizing ephemeral or periodically appearing hosts and hosts occurring in low population densities, (iv) maintenance or enhancement of overdispersed frequency distributions in host populations, and (v) enhancement of genetic exchange through multiple dispersal events. Key words: fungi, heteroxenous, parasite, life histories.
Mutualistic and parasitic interactions betweenPhorbiaflies andEpichloe: convergence between a fungus and entomophilous angiosperms
Authors: Bultman Thomas L.
Published: May 2008

During egg laying, Phorbia flies transport spermatia between individuals of their heterothallic fungal host Epichloe. Flies provide a service ecologically analogous to pollination. As a guide for studying the ecology and evolution of this unusual fungus – insect interaction, I propose that it has converged with angiosperm – entomophilous insect systems in general, and more specifically with highly coevolved pollinating seed parasite – angiosperm systems. I document similarities with insect pollination systems in general that include primary dependence by Epichloe on animal vectors, a color change of the fruiting structure following cross-fertilization, rewards provided to animal vectors, and exploitation by third party species that use rewards offered by the fungus but provide no payment for the rewards. Furthermore, the fungus – insect interaction shows several similarities with coevolved pollinating parasite systems. First, the interaction contains a mix of mutualism and parasitism with the net effect being positive for both partners. Second, flies display a specific behavior that ensures cross-fertilization of Epichloe. Third, the interaction is symbiotic and appears species specific and obligate for the interactants. Under the convergent evolution hypothesis, I discuss selection pressures that could have operated to produce ecologically analogous interactions among distantly related taxa of insect pollinated angiosperms and Epichloe. Key words: convergent evolution, Epichloe, mutualism, parasitism, Phorbia, pollination.
The significance of grazing on fungi in nutrient cycling
Authors: McGonigle Terence P.
Published: May 2008

Excretion of N by fungal grazers is not the dominant process by which N is released in nutrient cycling: it accounts for one eighth or less of total net N mineralization. Fungivores comprise between 21 and 76% of the fauna biomass. Other fauna, as well as fungi and bacteria, all participate in the mineralization process. Microcosm studies have shown fungal grazing can promote release of N, but immobilization by concomitant microbe production can occur in tandem with that release. Studies using field applications of biocides have had inconsistent outcomes. Fungivores contribute to nutrient cycling by the combined action of comminution, mixing, and dispersal of inoculum, which promote microbial activity. Passage through the Collembola gut has been estimated to have the capacity to bring about a 42-fold increase in nitrate concentration from food to faeces, which on an ecosystem scale could conceivably translate into a doubling of levels of nitrate. Recent laboratory work has shown that fungivores may prefer the thinner mycorrhizal hyphae that occur some distance away from the more coarse mycorrhizal hyphae in the rhizoplane. Where this occurs, grazing can be expected to have only a small impact on the effectiveness of mycorrhizal fungi for the promotion of plant nutrient absorption in the field. Key words: fungivores, fauna, soil, litter, mineralization, mycorrhizal effectiveness.
Spatial development of populations of a decomposer fungus, Mycena galopus
Authors: Frankland Juliet C. , Poskitt Jan M. , Howard Doreen M.
Published: May 2008

Past and recent research on the distribution of the vegetative mycelium and basidiomes of Mycena galopus in a Picea sitchensis plantation is reviewed as an example of a litter-decomposing member of the Basidiomycotina, occupying a spatially continuous resource that is replenished throughout the year. Using a variety of methods, the mycelia were found to be concentrated in the F1 horizon and the basidiomes produced nonrandomly in aggregations or arcs around the trees. Evidence was obtained of rapid dikaryotisation of homokaryons and of the ability to outbreed with a strain from Quercus woodland. The dikaryotic mycelia (genets) were up to 2.5 m in diameter, perennial or renewable mycelium occupying longstanding positions. A hierarchy of causal factors, including a competing saprotroph, a mycophagous collembolan, and variations in soil properties around tree boles, is discussed. Examination of relationships between NH4+-N content, moisture, or pH of the litter and distance from a tree or relative positions of basidiomes showed that there was significantly (P < 0.01) more NH4+-N at the arc position than the average for positions either side and a tendency for pH to reach maximum values in this region. The arc system with mycelium at its centre is contrasted with typical free and tethered fairy rings. Key words: Basidiomycotina, saprotrophs, Picea, tree litter, competition, fairy rings.
Windows of opportunity in desert ecosystems: their implications to fungal community development
Authors: Zak John C. , Sinsabaugh Robert , MacKay William P.
Published: May 2008

At the ecosystem level, all fungal activity in arid and semiarid systems is water regulated. However, as the observation scale is changed to allow for finer resolution of moisture effects, one finds that fungal community development in deserts may be influenced by either the temporal patterning of moisture pulses, or biotic factors that extend the benefits of moisture windows. When selected biocides were applied to the root region of a desert bunchgrass, Erioneuron pulchellum, to reduce microarthropod and nematode densities, fungal species numbers associated with the root surface were not altered. The temporal pattern in species numbers apparently reflect large scale seasonal responses of the fungi, microfauna, and plants to yearly differences in the occurrences of moisture windows. For wood on the soil surface, moisture windows of short duration coupled with high temperatures restrict fungal species composition in this habitat resulting in a lack of turnover in the dominant fungal species on surface wood. However, when wood was placed in the more amenable environment of a woodrat midden, patterns of fungal community development differed significantly from that observed for wood on the soil surface. These studies indicate that our understanding of the roles of fungi in the functioning of desert ecosystems is biased because the scale at which we usually make observations is too large to account for abiotic and biotic influences on fungal activity and community development. Moreover, we have to realize that the occurrence of favorable habitats for fungi in arid systems varies considerably in space and time. One consequence of the high spatial and temporal heterogeneity in favorable habitats is that functional diversity among fungi may be greater than would be predicted based solely on abiotic considerations. Key words: deserts, environmental heterogeneity, functional diversity, scale, wood.
Factors Governing Clutch Size in Two Species of Diaptomus (Copepoda: Calanoida)
Authors: Chow-Fraser Patricia , Maly Edward J.
Published: May 2008

We conducted a synoptic survey of 11 nonstratifying takes in eastern Quebec to investigate the relative importance of water temperature, food concentration ([Chl a]), female prosome length, copepod density (population and community densities), and mate availability (sex ratio and density of males) in determining the clutch size of two freshwater copepods, Diaptomus minutus and D. oregonensis. Multiple regression analyses indicated that 60% of the variation in clutch size of D. minutus could be accounted for by temperature and [Chl a] (n = 33; P = 0.0001), while 80% of the variation in the D. oregonensis data (n = 11; P = 0.0017) was explained by temperature and prosome length. Addition of other variables to either model did not significantly reduce the residual variation. We also investigated the effect of interspecific interaction on the egg-bearing potential of D. minutus and found some evidence that animals in sympatry may have lower clutch size than those in allopatry when temperature and food concentration were held constant. By using an independent measure of food and mate availability, we confirmed that clutch size decreased significantly in relation to food limitation for both species, but was unaffected by mate limitation for either.
Concentrations of Inorganic Elements and Fatty Acids in Geographic Populations of the Spot Prawn Pandalus platyceros
Authors: Whyte J. N. C. , Boutillier J. A.
Published: May 2008

Inorganic elements and fatty acids were quantified in body segments of different size classes of the spot prawn Pandalus platyceros collected from various locations in British Columbia. Substantial differences in concentration of elements occurred in different body segments of the spot prawn, with the exoskeleton accumulating the highest number of quantifiable elements. Comparison of elements in abdomen carapace and tissue from immature males, mature males, and females indicated no correlation between element concentration and size, age, or sex of the spot prawn. Fatty acid profiles were similar for all body parts, except the hepatopancreas, and of the major fatty acids, only the content of 18:1n9 increased significantly with age of the spot prawn. Fatty acids and elements in the abdomen tissue of spot prawns from different locations were not significantly different and indicated similarity of diet irrespective of location. The concentrations of elements absorbed into the carapace of female spot prawns from separate geographic locations were substantially different, suggesting incorporation from elements in the ambient seawater, rather than uptake from diet, or any genetic variability associated with element metabolism in the spot prawn. The levels obtained for metallic elements in the spot prawn provide a measure against which future environmental impact could be assessed.
Modèle énergétique uniboite de la croissance des huîtres (Crassostrea gigas) dans le bassin de Marennes-Oléron
Authors: Bacher C. , Héral M. , Deslous-Paoli J. M. , Razet D.
Published: May 2008

The growth of oysters (Crassostrea gigas) is modeled in order to study the trophic capacity of the Bay of Marennes-Oléron. Total seston and amount of protids, lipids, and carbohydrates converted to energy are the environmental factors taken into account. Time series of these variables are derived during 2 yr with a daily time step from a linear regression including the tidal velocity, the height of the water column, and the wind velocity. A model of the energetic budget based on assimilation and respiration terms and depending on the previous time series is run to simulate the individual growth of an oyster. The knowledge of the number of oysters, the flow of water entering the bay, and the volume of the bay allows us then to estimate that 7% of the available energy is used by the population. The number of individuals is given theoretical values to show that the impact of the amount of oysters on the growth of an individual is nonnegligible. The trophic capacity of the bay is then defined and it is pointed out that more information may be expected from a model coupling the transport of particulate matter and the growth of oysters.
Role of Fat Stores in the Maturation of Male Atlantic Salmon (Salmo salar) Parr
Authors: Rowe D. K. , Thorpe J. E. , Shanks A. M.
Published: May 2008

We provide evidence that in male Atlantic salmon (Salmo salar) parr, maturation is suppressed when mesenteric fat fails to exceed an undefined level by May. In nonmaturing parr the postwinter increase in total lipids began in May, while the mesenteric store started filling in June. However, in male parr which would have matured, total lipids started increasing a month earlier, in April, and the mesenteric store started filling in May. Consequently, maturing male parr had significantly more mesenteric fat than nonmaturing fish by June. Mesenteric fat is needed for maturation. Levels continued to increase in nonmaturing parr during autumn months, but had declined in maturing parr by September. This depletion of mesenteric fat in maturing males coincided with increases in the gonadosomatic index from 0.05 to 10% and with reductions in both feeding and growth. Fasting during spring months delayed increases in total lipids and fat accumulation into the mesenteric store until June and suppressed maturation rates of male parr. The internal decision to suppress maturation is therefore dependent on mesenteric fat levels increasing in May. However, this requires the prior replenishment of other stores in April. A model is proposed to explain the physiological link between fat accumulation during spring and the initiation of maturation.
A Method of Separating Offspring from Farmed and Wild Atlantic Salmon (Salmo salar) based on Different Ratios of Optical Isomers of Astaxanthin
Authors: Lura Harald , Saegrov Harald
Published: May 2008

A method of separating eggs and alevins from wild and farmed Atlantic salmon (Salmo salar) is described, using high-performance liquid chromatography (HPLC) to trace optical isomers of astaxanthin commonly occurring in the diet of both wild and farmed salmon. The proportions of isomers in eggs and alevins of farmed salmon, fed synthetic astaxanthin, differ highly from those of wild fish. The method can be used as a tool to determine the spawning success of escaped farmed female Atlantic salmon.
Effects of Moose Browsing on Decomposition Rates of Birch Leaf Litter in a Subarctic Stream
Authors: Irons III John G. , Bryant John P. , Oswood Mark W.
Published: May 2008

Leaves from birch trees previously browsed by moose differed from leaves from unbrowsed trees in food quality for stream detritivores in an Alaskan subarctic stream. Leaves from previously browsed plants decomposed faster. Effects of browsing were tested by collecting leaves from previously browsed and unbrowsed trees and measuring loss of mass over time in an Alaskan subarctic stream. The browsing history of birch trees was associated with increased leaching rate of tannin, foliar nitrogen concentration, and rate of mass loss. All three factors were higher for leaves from trees previously browsed than for unbrowsed ones. Faster loss of tannin through leaching and higher foliar nitrogen concentration apparently caused birch detritus to be processed more rapidly by stream biota, potentially increasing secondary production of stream consumers. Hence, moose browsing was associated with important changes in the food quality of birch leaf litter, Sinking terrestrial herbivory and aquatic food webs.
Herring Recruitment in Maine Coastal Waters: An Ecological Model
Authors: Campbell Daniel E. , Graham Joseph J.
Published: May 2008

An ecological model of larval herring survival in Maine coastal waters demonstrated, quantitatively, that herring recruitment is the result of a complex interaction of many processes, no one of which is truly dominant. Herring larval abundance measured on a series of spring cruises from 1965 to 1973 was used to estimate survival. Two-year-old recruitment to the Maine sardine fishery was established in the larval stage in some years, but not until the brit stage in other years. A sensitivity analysis of the model showed that food supply in winter and autumn and the quantity and distribution of spawning were primary factors controlling recruitment in years when the larval stage was critical. Density-dependent predation on brit by opportunistic pelagic and demersal predators was proposed as a mechanism determining recruitment in years of high larval herring survival. In the model, the Maine coast was divided into four spatial sectors of different area and characteristics. The western coastal waters from the headlands to the 100-m isobath made the largest contribution to recruitment in most years. Maine herring management regulations that limit fishing on spawning aggregations of herring should increase larval herring survival along the Maine coast in most years.
Pigment Preservation in Lake Sediments: A Comparison of Sedimentary Environments in Trout Lake, Wisconsin
Authors: Hurley James P. , Armstrong David E.
Published: May 2008

Fluxes and concentrations of a phorbins and major algal carotenoids were quantified in sediment trap material and sediment cores from two basins of Trout Lake, Wisconsin (TrDH and TrAB). The basins were chosen to contrast the influence of oxygen content at the sediment–water interface (TrDH, oxic and TrAB, reducing), sediment accumulation rate, and focusing. Pigment diagenesis occurred in both basins, but transformations and destruction were more extensive in TrDH. Although untransformed chlorophyll a was the major phorbin deposited at the sediment surface of both basins (51–64 mol%), pigment destruction, coupled with transition to pheophytin, accounted for substantial losses, especially in oxic TrDH sediments. Fucoxanthin, peridinin, and diadinoxanthin, despite representing > 70% of the deposited carotenoid flux, were substantially degraded or transformed in both basins. However, preservation was relatively high for secondary carotenoids, such as diatoxanthin and β-carotene, and for a major cryptomonad pigment, alloxanthin. Residual profiles in sediments show that pigment sedimentation from the epilimnion and accumulation in the permanent sediments are not directly related and that diagenesis must be considered in interpreting sedimentary pigments.
A New Method of Estimating Gillnet Selectivity, with an Example for Spotted Seatrout, Cynocion nehulosus
Authors: Helser Thomas E. , Condrey Richard E. , Geaghan James P.
Published: May 2008

This study proposes a new method of estimating the selectivity of gill nets. Using data on the distribution of fish lengths from the catches of various meshes in an experimental gill net, a system of m equations and n unknown coefficients is simultaneously solved describing the functional relationship of the moments from an assumed mathematical model across mesh size and size-class of fish. The solution to the model is a response surface describing the probability of capture of fish of size-class j in mesh i. This new method is applied to spotted seatrout (Cynocion nehulosus) in coastal Louisiana and used to estimate the relative abundance of the various size-classes of fish in the population. We suggest that this approach for estimating gillnet selectivity has several advantages over other methods: it is very flexible in terms of choosing a mathematical model which would best represent the data; it takes full advantage of the empirical data allowing catch information, nij, to contribute to the final solution both as a function of mesh size and size-class; and it offers simplicity and elegance in its overall iterative least squares approach and is tractable in terms of assessing the reliability of the parameters and model used.
Lake Trout (Salvelinus namaycush) Control of Snail Density and Size Distribution in an Arctic Lake
Authors: Merrick Glenn W. , Hershey Anne E. , McDonald Michael E.
Published: May 2008

In arctic Alaskan lakes the density and size distribution of the snail Lymnaea elodes appear to be greatly affected by the presence or absence of lake trout (Salvelinus namaycush). Snail densities were much lower and size distributions depressed in lakes where trout were present. During the summer of 1986, lake trout were introduced into an arctic lake to test the effects of their predation on the dominant snail Lymnaea elodes. During July and early August, snail densities in the experimental lake remained stable in the deepwater areas of the lake, but increased significantly in the deepwater areas of an adjacent, troutless control lake, probably due to snail migration from the lake periphery in the absence of predation pressure. These experimental results suggest that the observed pattern of snail distribution and size in lakes containing trout is due to Sake trout predation.
Groundfish Exploitation Rates Based on Life History Parameters
Authors: Clark William G.
Published: May 2008

The problem considered is how to choose a fixed exploitation rate that will provide a high yield at low risk, when the investigator has no knowledge of the yield curve or the spawner–recruit relationship of the stock. Commonly employed expedients are F0.1 and F = M, but these have little empirical or theoretical support. Calculations made with a range of life history parameter values typical of demersal fish and a range of realistic spawner-recruit relationships show that yield will be at least 75% of maximum sustainable yield so long as the spawning biomass is maintained in the range of about 20–60% of the unfished level, regardless of the form of the spawner–recruit relationship. A relative spawning biomass in this range can be achieved by choosing a fishing mortality rate that will reduce the spawning biomass per recruit to about 35% of the unfished level. This is the level of fishing mortality that maximizes the minimum yield among all of the spawner–recruit relationships considered ("maximin yield" rate, Fmmy). The actual value so calculated depends on the relative timing of growth, maturity, and recruitment to the fishery. In practice, Fmmy appears to be very close to F0.1 except where recruitment and maturity schedules do not coincide.
Spatial Stability of Cutthroat Trout (Oncorhynchus clarki) in a Small, Coastal Stream
Authors: Heggenes Jan , Northcote Thomas G. , Peter Armin
Published: May 2008

Spatial stability and local movement of a cutthroat trout (Oncorhynchus clarki) population were studied from winter to late summer in a small, coastal stream. The majority of the population was static and resided within a home range < 22 m2, while a small fraction of the fish apparently was more mobile. Local movement was very restricted; 32.4% of the individually marked cutthroat were recaptured within 1 m of their original capture and marking site, and 48% remained within 3 m of that site. Only 17.9% of the fish moved more than 50 m. This behaviour was stable during winter, spring, and summer and may be of adaptive significance. Fish occupying pool areas moved considerably less than fish occupying shallow habitats, indicating that pool dwellers were dominant fish.
An Electrophoretic Study of Spanish Sardine Suggests a Single Predominant Species in the Eastern Gulf of Mexico, Sardinella aurita
Authors: Wilson Jr. Raymond R. , Alberdi Jr. Peter D.
Published: May 2008

Specimens of Sardinella obtained from four sites around Florida, USA, were compared electrophoretically with 41 Brazilian specimens at between 36 and 41 presumptive genetic loci in an attempt to determine whether two electrophoretically distinct species of Spanish sardine are present in the eastern Gulf of Mexico. The study found no electrophoretic evidence for two species either in Florida waters or in waters off of Brazil, with both areas predominantly, if not exclusively, represented by S. aurita Valenciennes. Very low polymorphism in S. aurita hindered extensive comparisons of allelic frequencies between Florida and Brazilian specimens; however, significant differences among allele frequencies were detected between Florida populations although not between Florida and Brazilian populations.
Population and Community Patterns of Invertebrate Drift in an Unregulated Coastal Plain River
Authors: Benke Arthur C. , Parsons Keith A. , Dhar Sunita M.
Published: May 2008

Drifting invertebrates were sampled monthly during postdusk hours for 2 yr in the Ogeechee River, a sixth-order river in the southeastern United States. Drift quantities were among the highest reported in the literature, with mean biomass varying from 2.41 to 2.46 mg dry mass/m3between years and mean density from 20.4 to 22.8 individuals/m3. Major contributors to drift biomass were Ephemeroptera (30.3%), Coleoptera (25.1%), Plecoptera (16.6%), and Trichoptera (14.5%). Taxon-specific seasonal patterns of drift biomass for several mayflies (Ephemerellidae and Isonychia) and the dominant stonefly (Perlesta placida) resulted in biomass peaks in winter – early spring. Caddisflies (mostly Hydropsychidae and Chimarra) and beetles (Elmidae and Gyrinidae) complemented the mayfly–stonefly pattern with highest values in late spring – summer. These seasonal patterns coincided with standing stock biomass patterns on submerged wood (snags), their preferred habitat. Drift values were about 5.7 times higher in the Ogeechee than in another Coastal Plain river having only one fifth the amount of snags, suggesting a relationship between habitat abundance and drift. Percentages of snag-dwelling insects found in drift were substantially higher (0.1 to > 1%) than is generally found for smaller streams, indicating drift distances and times much greater than previously shown.
Feeding of Atlantic Cod (Gadus morhua) at Low Temperatures
Authors: Waiwood K. G. , Smith S. J. , Petersen M. R.
Published: May 2008

Satiation level, feeding frequency and maximum meal size of Atlantic cod (Gadus morhua) fed frozen shrimp (Pandalus montagui) were determined at temperatures of 1, 4, and 8 °C. Satiation level was predicted by a statistical model which separated the occurrence of feeding from the amount ingested. Decreased consumption of food at low temperatures was found to be primarily a function of decreased feeding frequency rather than decreased meal size. On a daily basis, cod ate 87, 77, and 54% of the time on average at 8, 4, and 1 °C, respectively. The average meal size, calculated over feeding days only, was directly related to the size of the fish and not to temperature. However, the maximum meal size was smaller, particularly for the larger fish at low temperatures.