bluuebunny/crossref_metadata_2025 huggingface dataset:
Basic Fibroblast Growth Factor Protects against Rotenone-Induced Dopaminergic Cell Death through Activation of Extracellular Signal-Regulated Kinases 1/2 and Phosphatidylinositol-3 Kinase Pathways
Authors: Hsuan Shih-Ling , Klintworth Heather M. , Xia Zhengui
Published: April 2006

Administration of rotenone to rats reproduces many features of Parkinson’s disease, including dopaminergic neuron degeneration, and provides a useful model to study the pathogenesis of Parkinson’s disease. However, the cell death mechanisms induced by rotenone and potential neuroprotective mechanisms against rotenone are not well defined. Here we report that rotenone-induced apoptosis in human dopaminergic SH-SY5Y cells is attenuated by pretreatment with several growth factors, most notably basic fibroblast growth factor (bFGF). bFGF activated both extracellular signal-regulated kinase 1/2 (ERK1/2) and phosphatidylinositol-3 kinase (PI3-kinase) pathways in SH-SY5Y cells. Ectopic activation of ERK1/2 or PI3-kinase protected against rotenone, whereas inhibition of either pathway attenuated bFGF protection. Reducing the expression of the proapoptotic protein Bcl-2-associated death protein (BAD) by small interfering RNA rendered SH-SY5Y cells resistant to rotenone, implicating BAD in rotenone-induced cell death. Interestingly, bFGF induced a long-lasting phosphorylation of BAD at serine 112, suggesting BAD inactivation through the ERK1/2 signaling pathway. Moreover, primary cultured dopaminergic neurons from mesencephalon were more sensitive to rotenone-induced cell death than nondopaminergic neurons in the same culture. The loss of dopaminergic neurons was blocked by bFGF, an inhibition dependent on ERK1/2 and PI3-kinase signaling. These data suggest that rotenone-induced dopaminergic cell death requires BAD and identify bFGF and its activation of ERK1/2 and PI3-kinase signaling pathways as novel intervention strategies to block cell death in the rotenone model of Parkinson’s disease.
Interaction of Kv3 Potassium Channels and Resurgent Sodium Current Influences the Rate of Spontaneous Firing of Purkinje Neurons
Authors: Akemann Walther , Knöpfel Thomas
Published: April 2006

Purkinje neurons spontaneously generate action potentials in the absence of synaptic drive and thereby exert a tonic, yet plastic, input to their target cells in the deep cerebellar nuclei. Purkinje neurons express two ionic currents with biophysical properties that are specialized for high-frequency firing: resurgent sodium currents and potassium currents mediated by Kv3.3. How these ionic currents determine the intrinsic activity of Purkinje neurons has only partially been understood. Purkinje neurons from mutant mice lacking Kv3.3 have a reduced rate of spontaneous firing. Dynamic-clamp recordings demonstrated that normal firing rates are rescued by inserting artificial Kv3 currents into Kv3.3 knock-out Purkinje neurons. Numerical simulations indicated that Kv3.3 increases the spontaneous firing rate via cooperation with resurgent sodium currents. We conclude that the rate of spontaneous action potential firing of Purkinje neurons is controlled by the interaction of Kv3.3 potassium currents and resurgent sodium currents.
Selling Viagra
Authors: Irvine Janice M.
Published: April 2006

Advertisers face a paradox: Anxieties about sex and masculinity fuel consumer demand for Viagra, yet these same anxieties may stigmatize it.
The Modern Offal Eaters
Authors: strong jeremy
Published: April 2006

This paper considers the manner in which offal is discussed and figured in contemporary cookery books and television programmes in Britain and North America. Arguing that offal has become largely the preserve of an affluent culinary cognoscenti, it uses and adapts the ideas of Pierre Bourdieu to examine the value of offal in terms of the status its preparation and consumption may confer. The role of key opinion formers in effecting this transformation is charted, as is the process by which less economically-favoured consumers have been distanced from offal and primary foodstuffs generally.
Being in Two Spaces at Once
Authors: Wasson Christina
Published: April 2006

This article examines the meetings of virtual teams in a corporate workplace. I explore how these meetings are different from the face‐to‐face meetings that have historically been analyzed by linguistic anthropologists. In particular, I investigate the ramifications of team membersability to participate in two interactional spaces at the same time. Goffman s writings are used to develop an analytical framework that accommodates the new possibilities and constraints afforded to participants in virtual meetings. The development of a transcription system to visually represent these encounters is also described as an integral part of the analysis process. This research contributes to an emerging focus in linguistic anthropology on technology‐mediated communication.
Responses to Selection for Partial Resistance to Crown Rust in Oat
Authors: Long Jin , Holland James B. , Munkvold Gary P. , Jannink Jean‐Luc
Published: April 2006

Crown rust, caused by the fungal pathogen, Puccinia coronata Corda var. avenae W.P. Fraser Ledingham, reduces kernel quality and grain yield in oat (Avena sativa L.). Partial resistance is considered to be a durable form of rust resistance. This study sought to evaluate the feasibility of simultaneously improving partial resistance to crown rust, grain yield, and seed weight in an oat population, and to estimate predicted and realized heritabilities for area under disease progress curve (AUDPC) and genetic correlations between AUDPC and agronomic traits in both crown rust‐inoculated and fungicide‐treated plots. A single cycle of selection for partial resistance to crown rust was performed. The initial (C0) and selected (C1) generations were evaluated in a field experiment in 2001 and 2002 at two Iowa locations. Selection on an index increased the levels of crown rust resistance, grain yield, and seed weight in crown rust−inoculated plots, and seed weight in fungicide‐treated plots. However, the change for the grain yield in fungicide‐treated plots was not significant. In both C0 and C1 populations, AUDPC was highly heritable (H = 0.77 and 0.78 respectively), and was favorably correlated with grain yield, seed weight, and test weight measured in inoculated plots. Realized heritabilities for all traits except grain yield under fungicide treatment were consistent with predicted heritabilities. Our results suggested that index selection could increase levels of crown rust resistance, grain yield, and seed weight simultaneously.
On the Necessity of Violation
Authors: Lebel Jean-Jacques
Published: April 2006

We must also be capable of setting ourselves above morality; not with the uneasy rigidity of the man who constantly fears to lose his footing and fall, but with the practised ease of one who can float, disport himself above it! And how should we achieve this without art, without the madman's aid? … And as long as you are in any way ashamed of yourself, you cannot possibly be of our number.

Nietzsche (Die Fröbliche Wissenschaft)

The middle-class hero, product of Western culture, still dreams of seeing his moral sense triumphant over all rebellions. This mediocrity has a bête noire—free art. He thinks that he, personally, is being attacked by the transformations which young artists claim to be bringing into his life as well as to their own.
The Old and the New in Brazilian Cinema
Authors: Viany Alex
Published: April 2006

The first stirrings of the Cinema Nôvo movement were in the early 1950's, when some young filmmakers began to protest the expensive imitations of Hollywood and cheap musical comedies (chanchadas) that made up the traditional Brazilian cinema. This protest found an immediate echo among young film critics.

In 1952, Italian neo-realism was the main inspiration of my first film, Agulha no palheiro (Needle in a Haystack), for which Nelson Pereira dos Santos served as assistant director. Neo-realism dominated dos Santos’ own first two films, Rio, 40 grans (Rio, 40 Degrees), 1955, and Rio, zona none (Rio, Northern District), 1957, as well as his production of Roberto Santos’ O grande momenta (The Great Moment) in 1958. From 1958 to 1962, there was a series of experimental short films.

The name of the movement, Cinema Nôvo, appeared for the first time around 1959-60, but even then it was as fluid and undefined as that of the French nouvelle vague.
Kinesics and Performance
Authors: Schechner Richard , Mintz Cynthia
Published: April 2006

At least as far back as Darwin's The Expression of the Emotions in Man and Animals(1872) scientists have studied analogic (as distinct from digital) modes of communication. Clearly all artists other than writers are technicians of the analogic.

Analogic codification constitutes a series of symbols that in their proportions and relations are similar to the thing, idea, or event for which they stand. […] Such a form of codification deals with continuous functions, unlike digital codification, which deals with discrete step intervals. […] The principles of analogic codification as contrasted with digital codification have a central importance to students of human behavior that is still perhaps insufficiently understood. The use of words, whether in speech or writing, has certain limitations akin to those of digital computers: words remain identifying or typifying symbols that lack the impelling immediacy of analogic devices.
Two Manifestos: The Influence of Italian Futurism in Russia
Authors: Deák František
Published: April 2006

From the very beginning of the Futurist movement in Italy in 1909, Russian artists, poets, and critics were well informed about the movement's manifestos and general development. Strong schools of Futurist poetry and painting quickly came into being. By 1913, Russian Futurism was already in full force. In that year, on December 2 and 3, the first Futurist theatre productions took place: Vladimir Mayakovsky's Vladimir Mayakovsky and Alexander Kruchenykh's Victory Over the Sun (T52). However, Mayakovsky and Kruchenykh were not familiar with the first Futurist manifesto devoted to theatre: the Variety Theatre Manifesto (September 29, 1913). Their plays and productions were influenced by general Futurist principles, rather than a specific theatrical theory.
Developmental Approaches to Theatre
Authors: Hindman James
Published: April 2006

The primary focus of both theatre and therapy is the same: human behavior. Dramatic action generally stems from a movement toward or an avoidance of change in behavior—the same process that characterizes a dynamic therapy. The actor and the director confront human action in the text of the drama. In the development of a score for performance, they adapt immediate and ongoing behavior to this action. Behavior is suggested, represented, experienced; the entire range of human response is available as a source for creation and discovery in performance. The function of criticism and acting training is to provide systems to analyze patterns of action—in the text and in the related experience of the performer. Traditional analysis has nearly always been external, treating behavior as an artifact that can be schematized, predicted, fixed, kept in a limbo between past and present.
Greek Resistance Theatre in World War II
Authors: Myrsiades Linda Suny
Published: April 2006

The Greek resistance movement, supported and directed by EAM (Ethnikon Apeleftherotikon Metopon—the National Liberation Front) in the mountains of Greece under the German occupation of World War II, spawned a popular resistance theatre that schooled itself among the people and brought a measure of political enlightenment to peasants in the mountain villages, who had small exposure to theatre. Those who went to market saw some Karaghiozis—Greek shadow puppet theatre—and those who attended religious festivals occasionally saw Lenten plays. Secular theatre was sometimes performed in tents in provincial villages and refugee settlements.

Because, in the beginning, artists would not come into the mountains to write songs for the struggle or to dramatize events, the andartes, or mountain fighters, began to write and perform. Their intention initially was to familiarize the people with their work and to develop friendly territories in which they could operate freely.
The Ramlila of Ramnagar [India]
Authors: Schechner Richard , Hess Linda
Published: April 2006

Ramlila is a cycle play lasting ten to thirty-two days performed annually outdoors in the Hindi speaking region of north India. Its season is around the Dasarha holidays in September-October. The performance is based on Tulsidas’ late 16th-century epic poem Ramacaritamanas (RCM), a Hindi version of Valmiki's Sanskrit Ramayana. Although thousands of Ramlilas are performed, we shall describe only one—the 31-day cycle of Ramnagar across the Ganga River from Varanasi (Benares or Kasi). Due to the patronage of the Maharaja of Benares who resides in Ramnagar this Ramlila is the most extensive, best performed, and draws the largest audiences of any. It developed its present shape during the early and mid 19th-century. The whole subject of Ramlila is vast, touching on themes of pilgrimage, bhakti (devotional worship), Hindu ideas of reincarnation, the nature of a mixed oral-literate culture of immense sophistication, relationship between government, Maharaja, and ordinary people.
Teatr Loh, Indonesia, 1977-8
Authors: Taymor Julie
Published: April 2006

The idea to develop Teatr Loh came after I had already lived in Indonesia two years. For many reasons I was dissatisfied with the process of developing my previous work, Jalannya Salju, in Java. My intention was to bring the best of my tradition with me in collaboration with artists here. Teatr Loh, by Indonesian standards, was a very small group. During the first few months we were five Balinese, one Sundanese, two East Javanese, a Central Javanese, a Frenchman and two Americans. A few of the people had worked with me on the previous production. Pak Tempo was a key figure in rounding up the other Balinese members. He is a fine topeng performer from Tampaksiring, who had toured to Europe and Shiraz. It was a surprise that he joined our group because he was in his 50's, and it meant leaving behind in the village his wife, six children and numerous grandchildren.
Stuart Sherman's Singular Spectacles
Authors: Scott Trudy
Published: April 2006

Through visual idea-music, retinally heard, seeing and thinking become duplicate metaphors for a languageworld whose actions and objects remain unnamed.

Stuart Sherman

At one time, Stuart Sherman was writing a great deal. To begin the process, he would open a book, choose a word and write. The initial word might be eliminated eventually, no longer needed, but the accumulated associations would have provided ample material for a story. He felt the use of a visual stimulus prevented preconceived notions about the work from hindering the flow of Ideas. In those days, he was also making abstract line drawings, word pictures, of everyday objects: a tree, sunlight, a waterfall. However, the two-dimensionality of the drawings and the writing began to give him the sense of increasing alienation from “animate” things. As a result, he now performs pieces that he considers visual abstract language about the relations between objects; he calls the work “Spectacles.”
Developmental and Environmental History of the Dismal Swamp
Authors: Whitehead Donald R.
Published: April 2006

Pollen analysis of several cores from the Dismal Swamp in southeastern Virginia have indicated that the swamp is a relatively young feature, having begun to develop along drainage lows as recently as the late—glacial. Formation of extensive fresh—water marshes along streams appears to have been brought about by general water—table changes controlled by the post glacial rise of sea level. As the sea continued to rise, marsh development proceeded inland and fine—grained organic sediments began to accumulate. By 6,000 years B.P. approximately 50% of Dismal Swamp area had been mantled by fine—grained peat deposits. From 6,000 to 3,500 B. P. peat accumulation continued, but at an appreciably lower rate. The corresponds both to the hypsithermal interval and to a distinct slackening in the rate of sea—level rise. By 3,500 B.P. peat had mantled virtually all of the interfluves and "islands" within the swamp. The pollen diagrams suggest a gradual change from boreal spruce—pine forests during the full—glacial, to somewhat less boreal pine—spruce during the early late—glacial, to hardwood forests containing many species characteristic of the present northern hardwoods forests during the latter portion of the late—glacial, to hardwood—dominated forests containing species now found in southeastern Virginia during the early postglacial. Although precise vegetational and environmental reconstructions are not possible, this general sequence suggests a unidirectional climatic amelioration from conditions comparable to those in northern New England during the full—glacial to a climate comparable to the present by 8,000 years B.P. The climate may have been warmer and drier during the hypsithermal, but the observed changes could just as easily be a result of a slackening in the rate of sea—level rise. The cypress—gum forests that have characterized the Dismal Swamp for the past 3,500 years have been variable both spatially and temporally. These variations doubtless reflect local differences in water table, peat depth, fires, wind throws, and a variety of human disturbances. The origin of Lake Drummond remains an enigma. It is a young feature of the swamp, apparently originating only 4,000 years ago. It is not the last vestige of an earlier open—water phase of the swamp.
The Foraging Specializations of Individual Bumblebees
Authors: Heinrich Bernd
Published: April 2006

Bumblebees of any one species in Maine forage for pollen and/or nectar from a large variety of morphologically diverse flowers, but individuals have limited foraging repertoires at any one time. Unspecialized individuals were sometimes unsuccessful in extracting nectar and/or pollen from highly rewarding flowers. In any one area with a variety of concurrently blooming plants, the bumblebees had apparent species preferences. Superimposed on the species preferences were individual preferences. Individuals had primary foraging specialties (their majors) and secondary specialities (their minors). Minors were often bridges to new majors. Queens in Maine necessarily have several successive majors during their lifetime since the blooming time of the plants they utilize are brief relative to their life—span as foragers. However, the blooming time of most plants available to Bombus fervidus workers are long relative to their lifetime. Switching was rarely observed in these bees, even in some individuals observed daily for up to 1 mo at the same foraging area containing other plant species in bloom that were highly attractive to other individuals of the same bumblebee species. On a per flower basis, those flowers producing the most food rewards generally had the largest number of bees majoring from them, and the food rewards available were roughly comparable between different kinds of flowers, regardless of their differences in rates of nectar production. Specializing was usually preceded by sampling a variety of rewarding as well as nonrewarding flowers. When the flowers from which bees were majoring in an area were experimentally removed many of the bees sampled flowers of other concurrently blooming plants, but they generally did not switch to flowers from which the food rewards were being depleted by specialists, unless these were experimentally fortified with syrup. Upon finding superior food rewards in enriched blossoms, they switched immediately. Flower—specificity is related to site—specificity. Many bees shared the same foraging area, but different individual bees at the same site utilized the flowers of different plant species. When the foraging area contained landmarks, the bees visited clumps of flowers in a sequence (foraging path) that was generally repeated several times on the same foraging trip when the foraging site was small. The foraging behavior of bumblebees is discussed from a comparative standpoint with other bees and in relation to food distribution and availability in the environment.
Community Structure: A Neutral Model Analysis
Authors: Caswell Hal
Published: April 2006

The relation of community structure to community function is the subject of much ecological theorizing. Three approaches to the problem, based on cybernetics, control theory, and niche theory, can be identified. They concur in giving biological interactions a major role in the determination of community structure in general, and species diversity in particular. To examine this body of theory, I use a "neutral" model for community development, a model which eliminates completely the biological interactions in question. Comparison of the patterns of community structure resulting from this model with the structure of natural communities provides an estimate of the effect of the biotic interactions. This can then be compared to the theoretically predicted effects. The neutral model used was originally developed in population genetics. In the context in which it is used here, it describes the stochastic development of a set of noninteracting populations, which colonize a community, persist temporarily, and eventually become extinct. The model predicts the form of the distribution of relative abundances and of species area curves, and sample values of species diversity. Comparisons of the model's predictions with actual community structure are made across what are taken to be gradients in the importance of biological interaction (successional vs. climax communities, high variation vs. low variation environments, the temperate zone vs. the tropics), using data on birds, fish, trees and insects. The results clearly contradict some of the theories of community structure. In those situations where biological interactions are predicted to generate the greatest increase in species diversity, the neutral model analysis shows that diversity is in fact significantly lower than would be expected in the absence of such interactions. Some implications of these findings for community theory are discussed.
The Coevolution of Pine Squirrels (Tamiasciurus) and Conifers
Authors: Smith Christopher C.
Published: April 2006

Field observations of discriminatory feeding behavior of squirrels indicate that in the process of maximizing their own feeding efficiency squirrels act as selective agents on several characteristics of plant reproduction. Calorimetric measurements of the energy content of plant reproductive organs confirm the evolutionary effects of discriminatory feeding by squirrels. The reproductive characteristics of conifers which are affected include several details of cone anatomy, the number of seeds per cone, the time at which cones shed their seeds, the thickness of seed coats, and annual fluctuations in the size of cone crops. A prolonged evolutionary interaction between rodent—like, arboreal mammals and the reproductive organs of the modern genera in the family Pinaceae is consistent with the fossil record. A general analysis of selective pressure influencing terrestrial plant reproduction indicates that seed eaters could have a marked influence on the evolution of plant reproduction. Among the interrelated selective pressures that influence the coevolution of conifers and squirrels, the physical environment is the independent variable. The effect of one predator feeding on two species of prey is the divergent evolution of defense mechanisms in the two prey species. However, one species of predator can cause convergent evolution in the pattern of variation in the production of prey, which may also be considered a defense mechanism.
Dynamics of High and Low Populations of the Limpet, Acmaea scabra (Gould)
Authors: Sutherland John P.
Published: April 2006

The dynamics of naturally occurring high (zone 1) and low (zone 2) populations of the limpet, Acmaea scabra, were investigated on Bodega Head in Sonoma County, California. Populations at different intertidal heights can be considered separate because migration between levels is precluded by the homing behavior of A. scabra. Each population was investigated by means of 400—cm2 quadrats containing marked individuals; the quadrats were censused approximately every 2 months and yielded information on density, size distribution, dispersion, recruitment, growth, and mortality. Samples were collected from each population approximately every 2 weeks to determine the seasonal pattern of reproduction and changes in size—specific weights. In zone 1 the probable pattern of food availability was distinctly seasonal because of the interaction of tides and climate. Growth and reproduction in this zone were also seasonal, probably increasing and decreasing with the food supply. Seasonal changes in size—specific weights were correlated with the reproductive cycle. Dispersion in zone 1 was always contagious. Recruitment was lower in zone 1, resulting in lower densities and a lower rate of mortality. Annual growth was greater in zone 1 because of the lower densities; consequently limpets in zone 1 were larger and biomass was greater than in zone 2. The population in zone 1 was susceptible to density—independent (catastrophic) mortality and corresponds to a population on the "edge" of the species' range. In zone 2 food was probably more constantly available because this zone was submerged more regularly and to a greater extent than zone 1. As a result there were more constant rates of growth and reproduction, and since reproduction was less variable, there were no seasonal changes in size—specific weights. Dispersion in zone 2 was random or, occasionally, uniform. Recruitment was higher in zone 2 resulting in higher densities and a higher mortality rate. Annual growth was lower because of the higher densities; consequently limpets in zone 2 were smaller and biomass was lower than in zone 1. The population in zone 2 was less susceptible to density—independent (catastrophic) mortality and corresponds to a population in the "center" of the species' range. Zone 2 is the "center" of the species' range, yet individual performance was poor because of the high densities; the probability of dying was high, growth rates were low, and the animals remained small. In both zones competition for food limited biomass, but lack of food did not cause mortality, i.e., regulate density.
Vegetation of the Big Horn Mountains, Wyoming, in Relation to Substrate and Climate
Authors: Despain Don G.
Published: April 2006

The vegetation of the Big Horn Mountains is typical of the Central Rocky Mountain region; a lower Juniperus osteosperma zone is followed by Pinus ponderosa, Pseudotsuga menziesii, Pinus contorta, and Picea engelmannii—Abies lasiocarpa zones. Rock or geologic substrate type has a strong influence on forest vegetation. On sedimentary areas forests cover less that 50% of the area and are composed of Pseudotsuga menziesii or Picea engelmannii—Abies lasiocarpa. On granitic substrates forests cover over 80% of the surface and are composed chiefly of Pinus contorta with Picea engelmannii—Abies lasiocarpa at higher elevations. Populus tremuloides is present but unimportant as a vegetation type. Most of the rainfall comes during March, April, and May; precipitation is less than 30 mm per month during summer. Thus soil—water relationships are important in determining vegetation pattern. Precipitation comes from the east, which allows forest vegetation to reach lower elevations on the east than on the west slope.
Periphyton Dynamics in Laboratory Streams: A Simulation Model and Its Implications
Authors: McIntire C. David
Published: April 2006

A simple and an expanded model of periphyton dynamics in lotic environments are described. The simple model includes one level variable, the biomass of the periphyton assemblage, and four rate variables: primary production, community respiration, and two export fractions. In the expanded model three level variables and eight rate variables are added to the simple model to introduce the effects of allochthonous organic matter and grazing activities by an aquatic snail. In general, computer output from the expanded model supports the hypothesis that the relatively low biomasses of periphyton observed in the small streams of western Oregon are the result of grazing activities by aquatic animals, high silt loads during the fall and winter months, and the effects of a dense canopy of terrestrial vegetation on light penetration. Furthermore, the model indicates that it is bioenergetically feasible for a periphyton biomass of about 10 g m—2 ash—free dry weight to support a consumer biomass of 150 g m—2 or more if the productive capacity of the system is sufficient. The simulation models provided an analytical way of synthesizing the results of a number of experiments with periphyton assemblages, identified weaknesses in the experimental data, and provided insights into the dynamics of periphyton assemblages that could not be obtained by intuition alone or by examining the results of individual experiments.
Biomass Turnover, Respiration, and Interpopulation Variation in the Stream Limpet Ferrissia rivularis (Say)
Authors: Burky Albert J.
Published: April 2006

The stream limpet Ferrissia rivularis, which occurs extensively in North America and is ubiquitous in streams of upper New York State, was studied from two distinct populations, one located in the Canandaigua Outlet at Alloway, N. Y. (AL) and the other in Black Creek at Cleveland, N. Y. (BC). These environments differ substantially, that at AL being the more eutrophic. At BC there is one generation per year, but at AL there are two generations per year and more rapid growth rates. Thirteen months is the adult life span for BC limpets, whereas at AL 11 and 3 months are normal for spring and summer adults respectively. At BC 8.4 eggs per limpet are laid, and 34.8 eggs per limpet are laid by spring adults at AL. Biomass and egg production are assessed as total carbon (equivalent to calorific measures) and expressed as biomass—turnover rates (growth and egg production). Egg—production rates can be double those for growth at AL; at BC egg—production rates are usually less than those for growth. This is partly a consequence of greater primary productivity at AL, but may also reflect implied genetic differences. Limpets at BC build up carbon during late summer and early fall; an increase in the C:N ratio (to 4.8) indicates an accumulation of storage compounds. During the winter (lower temperature, solar input, and primary productivity) the C:N ratio decreases, and during spring breeding there is a more marked loss of carbon associated with egg laying. In field—acclimated BC animals, respiration is lowest during the winter; during the spring, respiratory rate is closely correlated with temperature and egg—laying intensity. Oxygen—consumption measurements at 10° and 20°C for all seasons reveal that these limpets show reverse acclimation at low temperature (qualitative and quantitative downward adjustment of metabolism). This acclimation pattern is accompanied by a decrease in Q10 (3.3 to 2.1) which can act to dampen the effects of winter temperature fluctuations. Energy balance (respiration, growth, egg production) is expressed as rates of carbon turnover for the population at BC. Respiration rates are greatest during the summer and spring and reflect increased assimilation due to growth or reproduction or both. The total carbon turnover per year is approximately 1.25 g/m2. Data on energy balance emphasize the adaptive importance of reverse acclimation at times of low energy input.
Thermoregulation and Adaptation to Temperature in Dragonflies (Odonata: Anisoptera)
Authors: May Michael L.
Published: April 2006

Several of Anisoptera maintain their body temperature more constant than ambient temperature. Species that spend most of their active period on perches (perchers) and make only short flights thermoregulate heliothermically, primarily by means of postural adjustments. Some of the species that fly continuously (fliers) are endothermic regulators during flight. They control body temperature by: (1) controlling metabolic heat production by alternately using gliding or powered flight; (2) controlling heat loss by altering circulation between thorax and abdomen. Small fliers are unable to regulate well because they are subject to high rates of convective heat loss. Cooling constants, as defined by Newton's law of cooling, are related to thoracic weight by a negative power function over a wide size range. Cooling constants are higher in live dragonflies than in dead ones, a difference that is accentuated at high ambient temperatures. High cooling constants at high temperatures probably result from increased rates of circulation. Most fliers, and some large perchers, are able to elevate their body temperature by "wing—whirring." In some species the rate of heat production apparently varies in response to ambient temperature. The body temperature at which flight begins after warm—up is positively correlated with body weight, probably because wing loading increases with increasing body size. The maximum voluntarily tolerated temperature and the threshold of heat torpor of several species were determined. Both parameters are correlated with habitat. The minimum temperature at which flight is possible is positively correlated with body weight and is slightly higher in tropical dragonflies than in temperate zone species. Body temperature is probably more variable relative to air temperature in tropical than in temperate zone species. The ability of dragonflies to maintain a relatively constant body temperature is determined primarily by climate, body size, and behavior.
Feeding Relationships among Species of Notropis (Pisces: Cyprinidae) in a Wisconsin Stream
Authors: Mendelson Jon
Published: April 2006

The relationship between spatial preference and diet in four species of the genus Notropis (Pisces: Cyprinidae) was investigated in Roxbury Creek, a small stream in southern Wisconsin. Characteristic spatial distributions for each species were determined from frequency of catch in unbaited minnow traps set at varying heights and locations in the pools of the stream. Data for the year 1966—67 indicate that two species, Notropis atherinoides and N. spilopterus are common in midwater. Notropis dorsalis is most frequently found near the bottom and shows a strong preference for the upstream edge of pools Notropis stramineus is also found most often near the bottom but within the pools themselves. The spatial distributions of aquatic invertebrates, the major prey of Notropis in the pools of Roxbury Creek, were also investigated. Data gathered from drift and bottom samples taken in eight sampling periods during 1970—71 suggest a separation between the relatively sedentary bottom fauna, composed of oligochaetes, isopods, several genera of chironomids, tipulids, and trichopterans; and the drift fauna, composed of copepods, chironomids of the subfamily Orthocladiinae, ephemeropterans, and terrestrial anthropods. Certain genera, including the ubiquitous Gammarus were found commonly in both drift and benthic samples. Indices of similarity between pool benthos and drift ranged between 7% and 59%. Data on food habits of Notropis gathered from stomach content analysis of fishes collected over the same period indicate that 73% of the invertebrate genera present are utilized by Notropis species in Roxbury Creek. Considerable overlap exists in the invertebrate genera chosen by the four species (69%—84%), and strong overall correlations between species are found in the importance of various orders of aquatic invertebrates in the diet. Differences in food habits relate principally to differences in space utilization. Midwater species tend to feed on drifting chironomids, copepods, terrestrials, and other animals found in the water column. Bottom—dwelling fishes feed on benthic genera of chironomids, tipulids, oligochaetes, and other organisms found commonly in pool substrates. It is concluded that spatial rather than taxonomic considerations are the chief determinants of prey selection in these four species, and that this pattern of resource subdivision acts to reduce competition in sympatric, syntopic populations of these fishes. Data from other Wisconsin Streams, from aquarium observations, and from literature review suggest that multispecific assemblages of mutually responsive species like the ones in Roxbury Creek are common in Notropis.
Stability in Relation to Nutrient Enrichment in Arthropod Consumers of Old‐Field Successional Ecosystems
Authors: Hurd Lawrence E. , Wolf Larry L.
Published: April 2006

Two adjacent, abandoned hayfields in central New York State were subjected to nutrient enrichment perturbation by means of a single application of 10—10—10 N, P, K fertilizer early in the growing season of 1970. Aboveground arthropod herbivores and carnivores were monitored with respect to net productivity (dB/dt) and diversity for one growing season (1970) in the younger field (6 yr old), and for two growing seasons (1970 and 1971) in the older field (17 and 18 yr old). Sampling of arthropods was done with a gasoline—powered suction sampler between 1200 and 1600 h, twice weekly. Stability of the old—field arthropods was defined as resistance to change imposed by external (fertilizer) perturbation and was measured in terms of (1) magnitude (amplitude of deflection from ground state, (2) rate of initial response to perturbation, and (3) rate of damping or return to ground state. The degree of deflection from ground state was determined by comparing fertilized (treated) plots with unfertilized (control) plots in each field. During the first growing season the older, more species—rich field was less stable with respect to magnitude and rate of productivity deflection than the younger, less species—rich field at both arthropod consumer levels. In addition, the magnitude of productivity deflection from ground state was lower in the carnivore level than in the herbivore trophic level. By the second growing season, the productivity of the arthropod consumers in the treated plots of the older field had not yet returned to control levels. The productivity of arthropod herbivores in the older field exhibited a relatively lower magnitude of response in 1971 than in 1970, while the arthropod carnivores in the older field exhibited a significantly greater difference from ground state in 1971 than in 1970. It was concluded that (1) the magnitude of deflection caused by the enrichment perturbation was decreased up the trophic levels from the herbivore to the carnivore level, (2) the rate of response to perturbation decreased up the trophic levels, and (3) although in control plots diversity increased and productivity decreased with increasing successional age for both trophic levels, stability was not positively related to either higher diversity or to increasing age in either consumer trophic level in this old—field successional ecosystem.
Models for Age‐Specific Interactions in a Periodic Environment
Authors: Oster G. , Takahashi Y.
Published: April 2006

In 1954 Hutchinson and Slobodkin suggested that populations can be viewed as feedback systems that could resonate in response to environmental fluctuation with a frequency of approximately one generation time. In this paper we pursue this observation by constructing several mathematical models based on the demographic equations governing population age structure. The existence of this and several other effects of ecological importance are investigated for populations coupled by age—specific interactions.
The Response of Two Salt Marsh Molluscs, Littorina irrorata and Geukensia demissa, to Field Manipulations of Density and Spartina Litter
Authors: Stiven Alan E. , Kuenzler Edward J.
Published: April 2006

There is little research on processes limiting macroconsumer species in salt marshes. We investigated the significance of competition for space and food resources in three North Carolina salt marshes by altering densities of the molluscs Littorina irrorata and Geukensia demissa, and by manipulating Spartina litter. Morality and weight gain were the two principal responses measured. Enclosures (7.5 m2) were used to contain Littorina and marsh grass. Molluscan densities and Spartina litter levels were one—half, control, and double control levels. The field experiments ran from February 1975 through March 1977. The overall mortality and growth patterns of both species were similar within each marsh, but differed among marshes. The molluscs exhibited high mortality and slow growth in Tar Landing marsh, high mortality and rapid growth in Causeway marsh, and low mortality and slow growth in Calico marsh (enriched by sewage effluent). In Tar Landing survival and weight gain in both species were reduced by crowding. Increasing Spartina litter produced significant weight gain of medium—sized Littorina and small Geukensia. In Causeway marsh crowding decreased Littorina and Geukensia growth rates, but increased mortality only in the mussel population. Litter manipulations primarily affected weight gain in Littorina and mortality in Geukensia. In the enriched Calico marsh crowding depressed Geukensia survivorship and Littorina weight gain. Only in the mussel population was weight gain enhanced (1st yr only) by the addition of Spartina litter. We conclude that competition for food is an important limiting process, particularly for larger Littorina in Tar Landing marsh. In Causeway marsh competition for space appears more significant. In Calico marsh space limitation in Littorina populations and competition for food resources in Geukensia appear to be the principal processes. Variation in these competition—limiting mechanisms between two distant marsh consumers, a grazer and a filter feeder, may represent different procedures for dealing with the variable resource levels existing among salt marshes.
Organization of Contiguous Communities of Amphibians and Reptiles in Thailand
Authors: Inger Robert F. , Colwell Robert K.
Published: April 2006

In adjacent areas of broadleaf evergreen forest, deciduous dipterocarp forest, and agricultural land in northeastern Thailand, >4,000 individuals of 105 species of reptiles and amphibians were systematically collected. The position of capture of each individual was recorded in terms of a complex microhabitat code. The 3 environments differ substantially in pattern of human disturbance, in vegetation structure, and in range and predictability of temperature and total evaporation, the evergreen forest having the most buffered climate near the ground. Of the 3 environments studied, the evergreen forest has the most diverse and distinct herpetofauna, and the largest percentage of autochthonous species. The evergreen forest community has more southern or tropical affinities, while the deciduous forest community has more northern affinities. Analysis of the use of microhabitat categories by coexisting species reveals significant differences, even among the most similar sets of species. Differences in species richness among the three communities are not explained by differences in microhabitat diversity, mean niche breadth, or mean niche overlap. However, an ith nearest neighbor analysis of the dispersion of niche centers in resource space reveals closer packing and larger and more distinct guilds in the evergreen forest: the environment richest in species and the most predictable in climate. Both a graphical treatment and an analysis of sets of species grouped a priori according to their general natural history confirm the existence of larger and significantly tighter guilds in the evergreen forest. It is suggested that unpredictable environments tend to prevent the formation of distinct guilds, while the greater species richness of more predictable environments may be a function of guild formation.
Dominance and Diversity Maintenance in an Oceanic Ecosystem
Authors: McGowan John A. , Walker Patricia W.
Published: April 2006

Disturbance—perturbation, dispersal—reaction, and contemporaneous disequilibrium are similar theories used to explain the maintenance of species diversity in communities. These theories explicitly predict that in patches, on certain time—space scales, there should be substantial shifts in the order of species dominance. There is good evidence that these theories may explain species coexistence in terrestrial and marine systems of sessile organisms. We have tested this set of theories in a mobile pelagic system by examining the order of dominance of copepod species in samples separated in time and space, collected from °30 min to 16 yr apart, and from hundreds of metres to thousands of kilometres apart. We could not detect significant changes among the samples in rank order or in percent similarity of species abundance on any time scale, or on any space scale up to °800 km, either when all 175 species or when only the 30 most abundant were considered. There was small—scale, mesoscale, seasonal, and interannual heterogeneity in physical properties during the time we made our measurements. Although the theories are satisfactory explanations of diversity maintenance in sessile systems, our results fail to validate them in our mobile pelagic system. Because there were episodes of significant physical variability and because of the long—term species equilibrium and constancy of dominance, we believe our highly diverse community to be resilient and robust, rather than fragile. The regulatory forces are strong and almost certainly biological, rather than physical, but we cannot identify them.
Structure and Function of the Zooplankton Community of Mirror Lake, New Hampshire
Authors: Makarewicz Joseph C. , Likens Gene E.
Published: April 2006

An intensive study of the zooplankton community of Mirror Lake, New Hampshire, was undertaken over a 3—yr period. Our objectives in the lake study have included measurements of a number of attributes of the zooplankton community that integrate structure and function at the ecosystem level; among these are dispersion, biomass, productivity, respiration, and nutrient cycling. Eight species of rotifers and 3 species of cladocerans were successfully cultured. Generation time for planktonic rotifers was °8—10 days (17°C). The effect of higher food levels on rotifers was to shorten generation time and to increase brood size. In cladocerans, high food levels caused an increase in length and brood size. A curvilinear relationship existed between zooplankton community respiration and temperature in Mirror Lake. Mean monthly zooplankton community respiration ranged from 96.0 kg C/ha/mo in June of 1969 to a low of 20.5 kg C/ha/mo in April of 1970. Over a 3—yr period, respiration was 79.9% of assimilation. The 0 to 4.5—m strata (°epilimnion) contributed 68.5% and 46.5% of the annual zooplankton production and biomass. Zooplankton community production ranged from 22.3 kg C/ha/yr to 29.3 kg C/ha/yr with a 3—yr mean of 25.2 kg C/ha/yr. The annual zooplankton biomass ranged from 1.4 to 2.6 kg C/ha with a 3—yr mean of 2.0 kg C/ha. A linear relationship was found to exist between net phytoplankton and zooplankton production in various lakes of the world. Ecological efficiency apparently increases with the trophic status of the lake. It is recommended that the term ecological efficiency be refined to include both autochthonous and allochthonous inputs of reduced carbon into the lake. Rotifers assume a major role in intrasystem nutrient cycling and energy transfer within the lake ecosystem. Of the total amount of P incorporated into the organic matter of zooplankton community each year, 33.5% is assimilated in rotifer tissue. The annual turnover rate of P by rotifers is 30.9 and is high compared to crustaceans (10.1). Copepods comprise 55.4% of the total zooplankton biomass. However, the copepods, with their slow growth over an entire year, represent only 19.3% of the zooplankton production, while rotifers account for 39.8% of the zooplankton production annually in Mirror Lake. Also, evidence is presented that rotifers play a major role in energy transfer in lakes of varying trophic status (oligotrophic to eutrophic).