1,720,968 research outputs found
Neuston: A relevant trophic resource for apple snails?
No full textApple snails are known for the strong impacts they provoke in wetlands and aquatic crops by their macrophytophagous habits. Interestingly, they are able to persist after they have eradicated most palatable aquatic macrophytes in the invaded wetlands. Pedal surface collecting is a distinctive mechanism that apple snails use to capture materials in the water surface. We were interested in knowing the relevance of neuston, the organisms associated with the air-water interface, as an alternative trophic resource. Using the invasive Pomacea canaliculata as a model, our experiments with simulated trophic resources in the laboratory showed that neuston is highly consumed even in the presence of abundant palatable macrophytes. P. canaliculata was able to grow efficiently using neuston as an alternative trophic resource both under laboratory and natural conditions. Neuston probably plays a relevant role specially when other trophic resources are inedible or absent or have been depleted by apple snails. Pedal surface collecting probably evolved in apple snails as an adaptation to cope with fluctuating trophic resources.Fil: Saveanu, Lucía. Universidad Nacional del Sur. Departamento de Agronomia. Laboratorio de Ecologia; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico Bahia Blanca. Instituto de Ciencias Biologicas y Biomedicas del Sur; ArgentinaFil: Martín, Pablo Rafael. Universidad Nacional del Sur. Departamento de Biologia, Bioquimica y Farmacia. Laboratorio de Ecologia; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico Bahia Blanca. Instituto de Ciencias Biologicas y Biomedicas del Sur; Argentin
Pedal surface collecting as an alternative feeding mechanism of the invasive apple snail Pomacea canaliculata (Caenogastropoda: Ampullariidae)
Get PDFApple snails are freshwater gastropods with highly diverse feeding mechanisms (shredding, scraping and collecting) to exploit diverse food sources. Pomacea canaliculata is listed among the world´s 100 worst invaders, mainly due to its effects on aquatic crops and submersed macrophytes through shredding, its main feeding mechanism. In one of the alternative mechanisms, the snails obtain material from the water surface through a funnel formed by the anterior part of the foot, here termed pedal surface collecting (PSC). Our aims were to study the potential trophic spectrum of PSC and the effects of snail size and sex, density of food particles and particle size on efficiency of this feeding mechanism under laboratory conditions. We also explored occurrence and daily fluctuations in the field. Pomacea canaliculata snails were able to capture different food types irrespective of their physical nature (liquid, organic particles and biofilms) and size, although not all of them could be ingested. PSC was performed only when food was available on the surface by snails from the whole size range tested (3?52.8 mm shell length), although it was less frequent in snails <10 mm. The amount of food captured by unit mass decreased with animal size, but is partially compensated by a corresponding increase in frequency and duration of PSC. The specific capture rate increased, and the time spent forming pedal funnels decreased, with food density, but no effects of particle size were observed. In the field, PSC was observed only occasionally during the day, but showed a marked increase after sunset, and was observed even when submerged macrophytes and associated periphyton were abundant. The wide trophic spectrum, the high and adaptable capture rates and the wide size tolerance likely allow P. canaliculata to take advantage of highly variable and unpredictable food resources present on the water surface, thereby contributing to the invasion success of the species.Fil: Saveanu, Lucía. Universidad Nacional del Sur. Departamento de Biologia, Bioquimica y Farmacia. Laboratorio de Ecologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahia Blanca; ArgentinaFil: Martín, Pablo Rafael. Universidad Nacional del Sur. Departamento de Biologia, Bioquimica y Farmacia. Laboratorio de Ecologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahia Blanca; Argentin
Flowering phenology of Ulmus pumila (Ulmaceae) in Bahía Blanca city (Argentina)
Get PDFLa fenología es el estudio de los fenómenos periódicos que ocurren en los seres vivos y sus relaciones con condiciones ambientales como luz, temperatura, humedad, etc. Los objetivos de este trabajo fueron describir las fases fenológicas durante la floración de Ulmus pumila L. para la ciudad de Bahía Blanca y relacionar la floración con datos meteorológicos de temperaturas mínimas y máximas. Durante dos períodos de floración (julio a septiembre, de 2007 y de 2008) se realizaron observaciones fenológicas semanales de ejemplares de U. pumila presentes en el arbolado urbano de la ciudad. La floración se observó en los meses de julio y agosto, registrándose la máxima floración el 23 y el 7 de agosto de 2007 y 2008, respectivamente. Durante la floración del año 2007 la cantidad de flores registradas y la duración de la fase de floración fueron superiores a lo ocurrido en 2008. Estos resultados ayudan a conocer la dinámica de floración de U. pumila en la ciudad de Bahía Blanca, y a largo plazo contribuirá a la interpretación de los cambios climáticos de la región y a una mejor prevención de las alergias.Phenology is the study of predictably oc- curring biological events and their relatio- nship to environmental conditions as light, temperature, humidity, etc. The aims of this study were to describe flowering phenological phases of Ulmus pumila L. in Bahía Blanca city and relate flowering stage with weather data of minimum and maximum tempera- tures. During two flowering seasons (July to September, 2007 and 2008) phenological observations were carried out weekly in U. pumila plants present in the urban flora. Flo- wering stage was recorded in July and August, recording the highest flowering on 23 and 7 of August in 2007 and 2008, respectively. During 2007 flowering season, the number of flowers recorded and the open flowering stage duration were higher than 2008. These results help to understand the dynamics of flowering U. pumila in the city of Bahia Blanca; in the long term they will contribute to the understanding of climate change in the region and improve prevention of allergiesFil: Saveanu, Lucía. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; ArgentinaFil: Murray, María Gabriela. Universidad Nacional del Sur. Departamento de Biologia, Bioquimica y Farmacia. Laboratorio de Ecologia; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico Bahia Blanca. Instituto de Ciencias Biologicas y Biomedicas del Sur; Argentin
An invader's peculiar trophic behavior: diel fluctuations and environmental drivers
No full textThe trophic ecology of the invasive apple snail Pomacea canaliculata was intensely investigated because of the impacts of its grazing on aquatic vegetation, including crops. However, this freshwater snail also gathers food from the water surface using a pedal funnel, a distinctive trophic behavior called pedal surface collecting. We investigated the diel fluctuations of this trophic behavior through four whole-day field observations in a stream. We recorded the lowest pedal funnel frequencies during light hours and the highest after sunset, a pattern similar to that of general activity. We evaluated through laboratory experiments the influence of water temperature and velocity, photoperiod and a possible endogenous rhythm on this behavior. Pedal funnels are formed within the whole temperature range in which this snail is active. The highest pedal funnel formation rates were recorded at 30 °C, but the food captured was the same regardless of temperature. Pedal funnels were not observed at water velocities above 0.12 m? s-1 but below this limit the rate and time spent in funnels remained constant with velocity. Despite the time of day, pedal funnels were scarce under constant artificial light, ruling out an endogenous rhythm. Both in the laboratory and in the stream, the highest levels of pedal funnels were observed during dark periods, probably a strategy to avoid detection by visual predators. Pedal surface collecting on floating matter could represent an additional impact of invasive apple snails on freshwater ecosystems but it could also be used for the specific delivery of molluscicides against them.Fil: Saveanu, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ecología; Argentina. Universidad Nacional del Sur. Departamento de Matemática; ArgentinaFil: Martín, Pablo Rafael. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Laboratorio de Ecología; Argentin
Carrion consumption and its importance in a freshwater trophic generalist: the invasive apple snail Pomacea canaliculata
Get PDFTrophic flexibility is a relevant trait in the potential for organisms to establish widely,maintain high abundances, and spread post-invasion. Pomacea canaliculata is an apple snail that feeds primarily on aquatic macrophytes, although it also consumes other trophic resources that likely play an important role in its persistence and contribute to its impacts in invaded wetlands. We studied the ingestion rates P. canaliculata on carrion and its subsequent effects on growth, and we performed field and laboratory experiments to study the mechanism of carrion detection. We observed P. canaliculata snails of all sizes feeding on carrion. The specific ingestion rates of carrion decreased with snail size and were twenty times lower than when feeding only on lettuce. The growth rates of snails feeding only on carrion were 15-30% higher than those of fasting snails and 30% of those snails feeding on lettuce or lettuce and carrion. We found no evidence of distant chemoreception of carrion. The importance of carrion for P. canaliculata is mostly as an alternative resource when its preferred food is absent, and not a complementary resource that could enhance growth. Nevertheless, the ability of P. canaliculata to profit from carrion may help to explain its potential to establish widely and to have impacts on aquatic vegetation.Fil: Saveanu, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; ArgentinaFil: Manara, Enzo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; ArgentinaFil: Martín, Pablo Rafael. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; Argentin
Effects of Ingestion of Lithic Particles on Growth of the Apple Snail Pomacea canaliculata (Caenogastropoda, Ampullariidae)
Get PDFLithic particles are a common feature in the digestive tract of freshwater snails. Their role in the digestive processes has been demonstrated in some microphytophagous and detritivorous species, as they enhance growth, assimilation and reproduction. It has been suggested that they could have the same function in Pomacea canaliculata, a macrophytophagous apple snail with powerful jaws and radula, a strongly muscular and cuticularized gizzard and high levels of enzymatic activity. Our aims were to investigate the occurrence of lithic elements in the digestive tract of P. canaliculata snails from natural populations through the analyses of digestive contents, as well as the effect of size and availability of lithic particles on growth and growth efficiency through laboratory experiments. Lithic particles are very common in the digestive tract of P. canaliculata from natural populations and from laboratory aquaria if they are available in the immediate environment. Such particles are not retained or concentrated differentially in the stomach and they are apparently totally lost in less than four weeks if the supply is interrupted. The frequency of plant material and lithic particles increases from mouth to anus indicating that the retention time increases in the same way. Sand and plant material frequently co-occur in the intestine and in the stomach indicating that both are ingested together. Ground marble had negative effects on the growth of P. canaliculata probably due to the sharp edges and pointed ends of these particles. The availability of natural lithic particles (sand) had a positive effect on growth and also a synergic interaction with the availability of food. The growth efficiency was 25.2% higher when sand was available than when it was absent. These effects were more marked in juvenile females than in juvenile males. Our results indicate that growth rates may be underestimated under laboratory conditions if lithic particles are not supplied regularly and that their presence should be standardized to allow reliable comparisons between studies. Our results also indicate that the effects of food availability and plant palatability on the growth of P. canaliculata may be modulated by the presence of lithic particles and this may in turn affect the outcome of interactions between apple snails, other snails and macrophytes.Fil: Manara, Enzo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; ArgentinaFil: Saveanu, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; ArgentinaFil: Martín, Pablo Rafael. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; Argentin
Egg cannibalism in pomacea canaliculata (caenogastropoda, ampullariidae) from Southern Pampas: an alternative trophic strategy?
Get PDFPomacea canaliculata is a freshwater gastropod native to southern South America and is listed among the world?s 100 worst invaders. Diverse food sources can be exploited by this apple snail, including snails with gelatinous and subaquatic egg masses. Records of ingestion of their own egg masses (egg cannibalism), which are aerial and calcareous, have only been anecdotal in P. canaliculata. Our aims were to study egg cannibalism in a natural population and also under laboratory conditions. In a stream population from Southern Pampas we recorded P. canaliculata attacking their own fresh egg masses which had been naturally submerged by an increase in water level. In addition, when we artificially submerged fresh and old egg masses in a field experiment, we observed several snails readily attacking both. In the laboratory we also observed the capture by pedal surface collecting of floating remains of egg masses. In laboratory trials juveniles fed on eggs reached larger sizes than starved snails but smaller than those fed on lettuce; adult snails also eat eggs but their growth rates were not affected by the food regime. Pomacea canaliculata eggs present defensive and anti-nutritive compounds that apparently dissuade almost all potential predators, but this snail did not appear to be negatively affected when feeds on its own eggs. The ingestion of egg remains and submerged egg masses is probably more frequent than previously considered in P. canaliculata, which may take advantage of using these alternative food resources when others are scarce.Fil: Saveanu, Lucía. Universidad Nacional del Sur; ArgentinaFil: Martín, Pablo Rafael. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico Bahia Blanca. Instituto de Ciencias Biologicas y Biomedicas del Sur; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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