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Articles 631 - 660 of 714

Full-Text Articles in Biology

Review Of Sexual Selection: Mate Choice And Courtship In Nature By James L. Gould And Carol Grant Gould, Marlene Zuk, Gita R. Kolluru, Kurt A. Mckean Dec 1997

Review Of Sexual Selection: Mate Choice And Courtship In Nature By James L. Gould And Carol Grant Gould, Marlene Zuk, Gita R. Kolluru, Kurt A. Mckean

Biological Sciences

No abstract provided.

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Sources Of Variability In The Column Photosynthetic Cross Section For Antarctic Coastal Waters, Mark A. Moline, Herve Claustre, Barbara B. Prezelin Nov 1997

Sources Of Variability In The Column Photosynthetic Cross Section For Antarctic Coastal Waters, Mark A. Moline, Herve Claustre, Barbara B. Prezelin

Biological Sciences

Using a highly resolved Long Term Ecological Research (LTER) database collected near Palmer Station, Antarctica, from 1991 to 1994, the variability in the column photosynthetic cross section (ψ*, m2 g Chl a -1) was analyzed. The relationship between the daily integrated primary production rates versus the product of surface irradiance (QPAR(0*)) and the integrated chlorophyll content (down to 0.1% QPAR(0*)) gave a ψ* value of 0.0695 m 2 g Chl a-1 (r2 = 0.85, p 2 g Chl a-1) with extreme values extending over a fiftyfold range (0.009-0.488 m 2 …

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Tree Root Response To Circling Root Barriers, Laurence R. Costello, Clyde L. Elmore, Scott J. Steinmaus Nov 1997

Tree Root Response To Circling Root Barriers, Laurence R. Costello, Clyde L. Elmore, Scott J. Steinmaus

Biological Sciences

Root system size and distribution were measured for Raywood ash (Fraxinus oxycarpa 'Raywood') and Lombardy poplar (Populus nigra 'Italica') planted with and without circling root barriers. Trees with circling barriers had fewer numbers of roots than controls (no barriers), but mean root diameters were similar. Root depth 30 cm outside barriers was greater for trees with barriers, but at 90 and 150 cm away, depth was equivalent to controls. Roots tended to grow toward the soil surface after growing under the barriers. No consistent differences in root response to any of the four types of barriers tested were …

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Isolation, Characterization, And Diversity Of Microorganisms From Amber, Raúl J. Cano Jul 1997

Isolation, Characterization, And Diversity Of Microorganisms From Amber, Raúl J. Cano

Biological Sciences

Retrieval of viable bacteria from fossil material dating from the Oligocene back to the Miocene opens the opportunity to study the evolution of prokaryotes through the evolution of their DNA, their physiology, and their ecology. This unique system in which ancient organisms and their genes may be compared directly, rather than by inference, with modern homologues is without precedent. Clearly, however, confirmation of the fossil origin of such isolates must be made in a manner that would allay reasonable skepticism. Present approaches of verification of authenticity of fossil DNA are either arbitrary or potentially unconvincing, because of their dependence on …

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Palmer Lter: Stable Interannual Successional Patterns Of Phytoplankton Communities In The Coastal Waters Off Palmer Station, Antarctica, Mark A. Moline, Barbara B. Prezelin, Oscar Schofield Jan 1997

Palmer Lter: Stable Interannual Successional Patterns Of Phytoplankton Communities In The Coastal Waters Off Palmer Station, Antarctica, Mark A. Moline, Barbara B. Prezelin, Oscar Schofield

Biological Sciences

No abstract provided.

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Review Of A Manual Of California Vegetation By J. Sawyer & T. Keeler-Wolf, David J. Keil Jan 1997

Review Of A Manual Of California Vegetation By J. Sawyer & T. Keeler-Wolf, David J. Keil

Biological Sciences

No abstract provided.

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Shortfin Mako, Isurus Oxyrinchus, Impaled By Blue Marlin, Makaira Nigricans (Teleostei: Istiophoridae), Harry L. Fierstine, Gregor M. Cailliet, Julie A. Neer Jan 1997

Shortfin Mako, Isurus Oxyrinchus, Impaled By Blue Marlin, Makaira Nigricans (Teleostei: Istiophoridae), Harry L. Fierstine, Gregor M. Cailliet, Julie A. Neer

Biological Sciences

No abstract provided.

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An Atlantic Blue Marlin, Makaira Nigricans, Impaled By Two Species Of Billfishes (Teleostei:Istiophoridae), Harry L. Fierstine Jan 1997

An Atlantic Blue Marlin, Makaira Nigricans, Impaled By Two Species Of Billfishes (Teleostei:Istiophoridae), Harry L. Fierstine

Biological Sciences

Billfishes (Istiophoridae and Xiphiidae) are notorious for driving their rostra into animate and inanimate objects, a behavior usually resulting in transverse fracture of the bill and leaving the distal segment embedded (Gudger, 1940; Frazier et aI., 1994). Some billfishes recover from this loss because there are records ofapparently healthy fish with missing rostra (Frazier et aI., 1994). Generally only one rostral fragment is found in each object, but multiple stabbings have been reported. For example, fragments of three swordfish bills were discovered in a whale during flensing (Jonsgard, 1962), several "marlin" spears were found impaled in bales of rubber that …

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Instar Susceptibility Of The Monarch Butterfly (Danaus Plexippus) To The Neogregarine Parasite, Ophryocystis Elektroscirrha, Kingston L. H. Leong, Michael A. Yoshimura, H. K. Kaya, H. Williams Jan 1997

Instar Susceptibility Of The Monarch Butterfly (Danaus Plexippus) To The Neogregarine Parasite, Ophryocystis Elektroscirrha, Kingston L. H. Leong, Michael A. Yoshimura, H. K. Kaya, H. Williams

Biological Sciences

The susceptibility of the monarch butterfly (Danaus plexippus) larvae to the neogregarine parasite, Ophryocystis elektroscirrha, was tested in the laboratory. Spore loads recovered from infected monarch butterflies were directly related to the inoculum level, larval stage of the host, and spore age. There was a linear relationship between spores ingested by first instar larvae and spore concentration. Larvae feeding on leaves treated with 0, 50, 500, 5000, or 50,000 spores averaged 0, 0, 193, 457, or 1,255 spores, respectively, on the abdomens of the adult butterflies. When first, third, and fifth instar larvae were given 14.5 spores/mg …

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Long-Term Monitoring And Analyses Of Physical Factors Regulating Variability In Coastal Antarctic Phytoplankton Biomass, In Situ Productivity And Taxonomic Composition Over Subseasonal, Seasonal And Interannual Time Scales, Mark A. Moline, Barbara B. Prezelin Dec 1996

Long-Term Monitoring And Analyses Of Physical Factors Regulating Variability In Coastal Antarctic Phytoplankton Biomass, In Situ Productivity And Taxonomic Composition Over Subseasonal, Seasonal And Interannual Time Scales, Mark A. Moline, Barbara B. Prezelin

Biological Sciences

A 3 yr high-resolution temporal data base related to phytoplankton dynamics was collected during the austral spring/summer periods of 1991 to 1994 in shelf waters adjacent to Palmer Station, Antarctica. Here, the data base is used (1) to quantify the variability in phytoplankton biomass, in situ productivity and taxonomic composition over subseasonal, seasonal and interannual time scales; (2) to elucidate environmental mechanisms controlling these temporal patterns; and (3) to ascertain which phytoplankton markers are most suitable for detecting longer-term (i.e. decadal) trends in phytoplankton dynamics in coastal waters of the Southern Ocean. The Long-Term Ecological Research (LTER) coastal study sites …

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High-Resolution Time-Series Data For 1991/1992 Primary Production And Related Parameters At A Palmer Lter Coastal Site: Implications For Modeling Carbon Fixation In The Southern Ocean, Mark A. Moline, Barbara B. Prezelin Nov 1996

High-Resolution Time-Series Data For 1991/1992 Primary Production And Related Parameters At A Palmer Lter Coastal Site: Implications For Modeling Carbon Fixation In The Southern Ocean, Mark A. Moline, Barbara B. Prezelin

Biological Sciences

Our goal was to provide a high-resolution temporal data base for modeling primary production in shelf waters adjacent to Palmer Station, Antarctica. Here, the resulting 1991/1992 data base is used to: (1) determine in situ productivity over a range of seasonal to subseasonal time scales; (2) identify time scales of significant variability in marine productivity during the peak growing season; (3) identify environmental, experimental and analytical factors that can significantly impact the accuracy of daily, weekly and seasonal productivity estimates; and (4) integrate our findings with previous studies of Antarctic coastal primary pro- duction. Data were gathered every 2–3 days …

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Genetic And Social Control Of Male Maturation In Phallichthys Quadripunctatus (Pisces: Poeciliidae), Gita R. Kolluru, David N. Reznick Nov 1996

Genetic And Social Control Of Male Maturation In Phallichthys Quadripunctatus (Pisces: Poeciliidae), Gita R. Kolluru, David N. Reznick

Biological Sciences

Age and size at maturity can have significant fitness consequences. Selection often favors early-maturing individuals because of their higher survival to maturity and greater relative contribution to population growth rate, but it may also favor delayed maturation if fitness increases with age or size at maturity. Males of several poeciliid fishes exhibit variation in age and size at maturity primarily controlled by a sex-linked gene called the P-locus. Wild-caught Phallichthys quadripunctatus males show a bimodal size distribution, which is often associated with a P-locus polymorphism in other poeciliids. We conducted two experiments to evaluate the inheritance of male age and …

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Azorhizobium Caulinodans Uses Both Cytochrome Bd (Quinol) And Cytochrome Cbb3 (Cytochrome C) Terminal Oxidases For Symbiotic N2 Fixation, Alexandre Kaminski, Christopher L. Kitts, Zachary Zimmerman, Robert A. Ludwig Oct 1996

Azorhizobium Caulinodans Uses Both Cytochrome Bd (Quinol) And Cytochrome Cbb3 (Cytochrome C) Terminal Oxidases For Symbiotic N2 Fixation, Alexandre Kaminski, Christopher L. Kitts, Zachary Zimmerman, Robert A. Ludwig

Biological Sciences

Azorhizobium caulinodans employs both cytochrome bd (cytbd; quinol oxidase) and cytcbb3 (cytc oxidase) as terminal oxidases in environments with very low O2 concentrations. To investigate physiological roles of these two terminal oxidases both in microaerobic culture and in symbiosis, knockout mutants were constructed. As evidenced by visible absorbance spectra taken from mutant bacteria carrying perfect gene replacements, both the cytbd- and cytcbb3- mutations were null alleles. In aerobic culture under 2% O2 atmosphere, Azorhizobium cytbd- and cytcbb3- single mutants both fixed N2 at 70 to 90% of wild-type rates; in root nodule symbiosis, both single mutants fixed N2 at 50% …

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Two Erroneous, Commonly Cited Examples Of "Swordfish" Piercing Wooden Ships, Harry L. Fierstine, Oliver Crimmen May 1996

Two Erroneous, Commonly Cited Examples Of "Swordfish" Piercing Wooden Ships, Harry L. Fierstine, Oliver Crimmen

Biological Sciences

No abstract provided.

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Use Of Rostral Characters For Identifying Adult Billfishes (Teleostei: Perciformes: Istiophoridae And Xiphiidae), Harry L. Fierstine, Nicole L. Voigt Feb 1996

Use Of Rostral Characters For Identifying Adult Billfishes (Teleostei: Perciformes: Istiophoridae And Xiphiidae), Harry L. Fierstine, Nicole L. Voigt

Biological Sciences

Seven species of the family Istiophoridae and Xiphias gladiu6 were identified using only features of their rostrum. In the Istiophoridae, two rostral regions were emphasized, one-fourth and one·half the distance between the distal tip and the orbital margin of the lateral ethmoid bone. Characters studied in each region were the depth and width of rostrum and height, width, and position of nutrient canals (as seen in cross-section). Characters studied without reference to region were the distribution of denticles on both dorsal and ventral surfaces of the bilI and position of the prenasal bone. In the Xiphiidae, the only characters studied …

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Trade-Offs In Parasitology, Evolution And Behavior, Marlene Zuk, M. J. Bryant, Gita R. Kolluru, V. Mirmovitch Feb 1996

Trade-Offs In Parasitology, Evolution And Behavior, Marlene Zuk, M. J. Bryant, Gita R. Kolluru, V. Mirmovitch

Biological Sciences

No abstract provided.

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Light-Saturated Primary Production In Antarctic Coastal Waters, Mark A. Moline, Barbara B. Prezelin, Herve Claustre Jan 1996

Light-Saturated Primary Production In Antarctic Coastal Waters, Mark A. Moline, Barbara B. Prezelin, Herve Claustre

Biological Sciences

No abstract provided.

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Temporal Dynamics Of Coastal Antarctic Phytoplankton: Environmental Driving Forces And Impact Of 1991/92 Summer Diatom Bloom On The Nutrient Regimes, Mark A. Moline, Barbara B. Prezelin, Oscar Schofield, Raymond C. Smith Jan 1996

Temporal Dynamics Of Coastal Antarctic Phytoplankton: Environmental Driving Forces And Impact Of 1991/92 Summer Diatom Bloom On The Nutrient Regimes, Mark A. Moline, Barbara B. Prezelin, Oscar Schofield, Raymond C. Smith

Biological Sciences

Within the Palmer Long Term Ecological Research Program (PAL-LTER), a suite of environmental data sets were collected at a nearshore station throughout the 1991/92 austral summer. Seasonal changes are presented in the context of phytoplankton community ecology. Subseasonal fluctuations in sea-ice coverage, freshwater inputs, as well as wind driven and advective processes disrupting stratified surface waters, appeared to be the major driving forces affecting the timing, duration and demise of local phytoplankton blooms. During a large diatom-dominated bloom (~30 mg chl a m-3), macronutrients were depleted to detection limits (NO3--3, PO4-3< 0.03 mmol m-3) …

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Effect Of Larval Swimming Duration On Success Of Metamorphosis And Size Of The Ancestrular Lophophore In Bugula Neritina (Bryozoa), Dean E. Wendt Jan 1996

Effect Of Larval Swimming Duration On Success Of Metamorphosis And Size Of The Ancestrular Lophophore In Bugula Neritina (Bryozoa), Dean E. Wendt

Biological Sciences

There is a growing realization that events during one portion of an organism's life cycle can have both subtle and dramatic effects on other stages in the life history. Lethal and sublethal effects associated with the duration of larval swimming in marine invertebrates were examined for the bryozoan Bugula neritina. Larvae were kept swimming up to a maximum of 28 h at 20{deg}C by exposure to continuous bright fluorescent illumination. At 4-h intervals, samples of 20-40 larvae were removed from bright illumination and were exposed to seawater containing 10 mM excess KCI, an inducer of metamorphosis in this species. …

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Analysing Ancient Dna, Raúl J. Cano Jan 1996

Analysing Ancient Dna, Raúl J. Cano

Biological Sciences

Much of what we know about extinct organisms comes from traits that are not preserved in the fossil record. Until recently, morphological analysis was the only tool available for scientists to determine relationships for extinct fossil organisms. We now know that ‘ancient’ DNA can be preserved in the remains of extinct organisms. By targeting specific gene sequences, it may be possible to deduce biochemical characteristics and through sequence comparisons, to estimate the extent of evolutionary divergence. By comparing the amount and type of these changes, one could estimate how quickly some DNA ‘evolves’ relative to other segments, or which genes …

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Pseudomonas Aeruginosa Strain Ma01 Aerobically Metabolizes The Aminodinitrotoluenes Produced By 2,4,6-Trinitrotoluene Nitro Group Reduction, Mark A. Alvarez, Christopher Kitts, James L. Botsford, Pat J. Unkefer Nov 1995

Pseudomonas Aeruginosa Strain Ma01 Aerobically Metabolizes The Aminodinitrotoluenes Produced By 2,4,6-Trinitrotoluene Nitro Group Reduction, Mark A. Alvarez, Christopher Kitts, James L. Botsford, Pat J. Unkefer

Biological Sciences

Many microbes reduce the nitro substituents of 2,4,6-trinitrotoluene (TNT), producing aminodinitrotoluenes (ADNTs). These compounds are recalcitrant to further breakdown and are acutely toxic. In a search for organisms capable of metabolizing ADNTs, a bacterial strain was isolated for the ability to use 2-aminobenzoate (anthranilate) as sole C-source. This isolate, Pseudomonas aeruginosa MAO1, metabolized TNT by first reducing one nitro group to form either 2-amino-4,6-dinitrotoluene (2ADNT) or 4 -amino-2,6-dinitrotoluene(4ADNT). However, strain MA01 was distinct from other TNT-reducing organisms in that it transformed these compounds into highly polar metabolites through an 02-dependent process. Strain MAOl was able to cometabolize TNT, 2ADNT, and …

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On The Dangers Of Interpopulational Transfers Of Monarch Butterflies, Lincoln P. Brower, Linda S. Fink, Andrew Van Zandt Brower, Kingston L. H. Leong, Karen Oberhauser, Sonia Altizer, Orley Taylor, Daniel Vickerman, William H. Calvert, Tonya Van Hook, Alfonso Alonso-Mejia, Stephen B. Malcolm, Denis F. Owen, Myron P. Zalucki Sep 1995

On The Dangers Of Interpopulational Transfers Of Monarch Butterflies, Lincoln P. Brower, Linda S. Fink, Andrew Van Zandt Brower, Kingston L. H. Leong, Karen Oberhauser, Sonia Altizer, Orley Taylor, Daniel Vickerman, William H. Calvert, Tonya Van Hook, Alfonso Alonso-Mejia, Stephen B. Malcolm, Denis F. Owen, Myron P. Zalucki

Biological Sciences

No abstract provided.

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Reply To Nylin, Wickman & Wiklund Regarding Sex Ratios Of California Overwintering Monarch Butterflies, Dennis F. Frey, Kingston L. H. Leong Feb 1995

Reply To Nylin, Wickman & Wiklund Regarding Sex Ratios Of California Overwintering Monarch Butterflies, Dennis F. Frey, Kingston L. H. Leong

Biological Sciences

No abstract provided.

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Statistical Analyses Of Environmental Predictors For Phytoplankton Photosynthetic Parameters And Productivity In An Antarctic Time Series Database, Mark A. Moline, Barbara B. Prezelin, Oscar Schofield Jan 1995

Statistical Analyses Of Environmental Predictors For Phytoplankton Photosynthetic Parameters And Productivity In An Antarctic Time Series Database, Mark A. Moline, Barbara B. Prezelin, Oscar Schofield

Biological Sciences

No abstract provided.

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Palmer Lter: Photoacclimation In A Coastal Phytoplankton Bloom, Oscar Schofield, Mark A. Moline, Barbara B. Prezelin Jan 1995

Palmer Lter: Photoacclimation In A Coastal Phytoplankton Bloom, Oscar Schofield, Mark A. Moline, Barbara B. Prezelin

Biological Sciences

No abstract provided.

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Induction Of Larval Settlement By Kcl In Three Species Of Bugula (Bryozoa), Dean E. Wendt, Robert M. Woollacott Jan 1995

Induction Of Larval Settlement By Kcl In Three Species Of Bugula (Bryozoa), Dean E. Wendt, Robert M. Woollacott

Biological Sciences

Elevation of the K+ concentration in seawater (added as KCl) induces larval settlement and metamorphosis in Bugula simplex, B. stolonifera, and B. turrita. All three of these bryozoan species have similar bell-shaped dose-response curves: 5 mM excess K+ is sufficient to increase settlement and metamorphosis significantly over seawater controls in all the species and optimal responses to excess K concentrations occur ations at 10-25 mM, 5-10 mM, and 10-15 mM for B. simplex, B. stolonifera, and B. turrita, respectively. Percent settlement in all three species is decreased at levels greater than 25 mniM excess …

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Isolation Of Three Hexahydro-1,3,5-Trinitro-1,3,5-Triazine- Degrading Species Of The Family Enterobacteriaceae From Nitramine Explosive-Contaminated Soil, Christopher Kitts, Daryl P. Cunningham, Pat J. Unkefer Dec 1994

Isolation Of Three Hexahydro-1,3,5-Trinitro-1,3,5-Triazine- Degrading Species Of The Family Enterobacteriaceae From Nitramine Explosive-Contaminated Soil, Christopher Kitts, Daryl P. Cunningham, Pat J. Unkefer

Biological Sciences

Three species of the family Enterobacteriaceae that biochemically reduced hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) were isolated from nitramine explosive-contaminated soil. Two isolates, identified as Morganella morganii and Providencia rettgeri, completely transformed both RDX and the nitroso-RDX reduction intermediates. The third isolate, identified as Citrobacter freundii, partially transformed RDX and generated high concentrations of nitroso-RDX intermediates. All three isolates produced 14CO2 from labeled RDX under O2-depleted culture conditions. While all three isolates transformed HMX, only M. morganii transformed HMX in the presence of RDX.

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Review Of Survival, Reproduction, And Behavior By J.R. Krebs And N.B. Davies, Marlene Zuk, Torgeir S. Johnsen, Gita R. Kolluru, Kurt A. Mckean, Bradd Schulke Sep 1994

Review Of Survival, Reproduction, And Behavior By J.R. Krebs And N.B. Davies, Marlene Zuk, Torgeir S. Johnsen, Gita R. Kolluru, Kurt A. Mckean, Bradd Schulke

Biological Sciences

No abstract provided.

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The Role Of Enzyme Activation State In Limiting Carbon Assimilation Under Variable Light Conditions, Gretchen F. Sassenrath-Cole, Robert W. Pearcy, Scott J. Steinmaus Aug 1994

The Role Of Enzyme Activation State In Limiting Carbon Assimilation Under Variable Light Conditions, Gretchen F. Sassenrath-Cole, Robert W. Pearcy, Scott J. Steinmaus

Biological Sciences

The mechanisms regulating transient photosynthesis by soybean (Glycine max) leaves were examined by comparing photosynthetic rates and carbon reduction cycle enzyme activities under flashing (saturating 1 s lightflecks separated by low photon flux density (PFD) periods of different durations) and continuous PFD. At the same mean PFD, the mean photosynthetic rates were reduced under flashing as compared to continuous light. However, as the duration of the low PFD period lengthened, the CO2 assimilation attributable to a lightfleck increased. This enhanced lightfleck CO2 assimilation was accounted for by a greater postillumination CO2 fixation occurring after the …

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Disparate Rates Of Molecular Evolution In Cospeciating Hosts And Parasites, M. S. Hafner, P. D. Sudman, F. X. Villablanca, T. A. Spradling, J. W. Demastes, S. A. Nadler Aug 1994

Disparate Rates Of Molecular Evolution In Cospeciating Hosts And Parasites, M. S. Hafner, P. D. Sudman, F. X. Villablanca, T. A. Spradling, J. W. Demastes, S. A. Nadler

Biological Sciences

DNA sequences for the gene encoding mitochondrial cytochrome oxidase I in a group of rodents (pocket gophers) and their ectoparasites (chewing lice) provide evidence for cospeciation and reveal different rates of molecular evolution in the hosts and their parasites. The overall rate of nucleotide substitution (both silent and replacement changes) is approximately three times higher in lice, and the rate of synonymous substitution (based on analysis of fourfold degenerate sites) is approximately an order of magnitude greater in lice. The difference in synonymous substitution rate between lice and gophers correlates with a difference of similar magnitude in generation times.

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