Biology of growth of Hoplias aff. malabaricus (Bloch, 1794) in a shallow pampean lake Argentina

The trahira Hoplias aff. malabaricus is a top predator in pampean shallow lakes and is highly appreciated by recreational anglers and artisanal fishermen. Trahira growth from Yalca shallow lake was determined by lepidological analysis and age validated by marginal increment. When growth was fitted to the von Bertalanffy model, annual classes exhibited a bimodal pattern as a result of the presence of spring and summer annual cohorts associated with a three month spawning season, each period in turn showing different growth patterns. The trahira population-age structure at Yalca shallow lake showed a truncated profile with very low numbers of large adults and few individuals older than three to four years, thus producing an unbalanced length-structure population. Growth parameters and growth performance were similar to the corresponding parameters estimated for other shallow pampean lakes of the region, but strongly diverged from the data for those populations inhabiting subtropical and tropical environments. Such differences could be accounted for by dissimilarity in metabolic rates associated with thermal differences accompanying seasonal variability among latitudes as well as by the development of adaptive physiologic and demographic responses to cope with the high thermal amplitude and hydrologic instability observed in pampean lakes.A traíra Hoplias aff. malabaricus é um predador de topo encontrado em lagoas rasas nos Pampas, muito apreciada nas pescas comerciais e esportivas. O crescimento da traíra no lago Yalca foi determinado através de análises lepidológicas, validadas a partir do incremento marginal. O crescimento foi ajustado ao modelo de von Bertalanffy, sendo que as classes de tamanho anuais apresentaram padrão bimodal devido à presença de coortes de primavera e verão, associadas à uma longa estação reprodutiva com diferentes padrões de crescimento. A estrutura etária da traíra do lago Yalca apresentou um perfil truncado, com um número pequeno de adultos de maior porte e poucos indivíduos com mais de três ou quatro anos, produzindo uma estrutura em tamanho desbalanceada. Os parâmetros e a performance de crescimento foram similares aos estimados para outros lagos rasos da região, mas fortemente divergentes de populações encontradas em ambientes tropicais e subtropicais. Tais diferenças podem estar relacionadas à diferentes taxas metabólicas associadas à variação térmica sazonal entre latitudes e ao desenvolvimento de respostas adaptativas fisiológicas e demográficas em resposta aos padrões termais altamente variáveis e instabilidade hidrológica observados nos lagos da região dos Pampas.Fil: Balboni, Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Colautti, Dario César. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Baigún, Claudio Rafael M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); Argentin

Propagule pressure: A null model for biological invasions.

I begin with a review of recent attempts to identify characteristics of species \u27invasiveness\u27 (i.e., the ability to invade) and habitat \u27invasibility\u27 (i.e., the susceptibility to invasion), and find little support for an emerging consensus on species- or habitat-specific characteristics. Moreover, I find that few studies consider hypotheses based on the concept of \u27propagule pressure\u27 (i.e., introduction effort), despite its potential as a confounding factor. Another barrier to generalizations may be the divergent use of operationally important terms like \u27invasive\u27, \u27naturalized\u27, or \u27nuisance\u27. I therefore introduce a framework that conceptualizes biological invasions as a series of obligatory stages. This stage-based framework can aid in identifying characteristics that are confounded by \u27propagule biases\u27 (i.e., non-random variation in introduction effort), and can serve as common ground for an operational lexicon. I use this framework to investigate the enemy release hypothesis (ERH), which relates invasion success of a host species with the number of co-occurring enemies. (Abstract shortened by UMI.)Dept. of Biological Sciences. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2003 .C655. Source: Masters Abstracts International, Volume: 42-05, page: 1610. Advisers: Hugh J. MacIsaac; Daniel D. Heath. Thesis (M.Sc.)--University of Windsor (Canada), 2003

La Constitución de 1826 como antecedente y fuente de la Constitución Nacional

Fil: Colautti, Carlos Eduardo. Universidad de Buenos Aires. Facultad de Derecho. Cátedra Derecho Constitucional. Buenos Aires, Argentin

The Natuzzi Group and the Bari-Matera (Italy) upholstered furniture district. A case study of internationalisation in a traditional industry

The case-study focuses on the strategies adopted by the Natuzzi Group, world leader of the upholstered furniture sector, located in the Bari-Matera district (Southern Italy), to face increasing global competition and on their effects. In particular we consider the modes and determinants of productive internationalisation, carried out since 2000 by Natuzzi in China, Brazil and Romania to produce middle-low end products. By improving the competitiveness of the price-sensitive segment, the strategy contributed to the successful expansion of the Group until 2002. However, high range products, manufactured in Italy, record decreasing sales especially on the US market, despite the companys efforts in R&D and marketing and its investments in information technology. Moreover, due to Natuzzi's considerable weight in the district, the Groups performance impacts on the network of subcontracting firms, where a restructuring process is underway, raising questions about the evolution of the district.Internationalisation, Industrial District, Subcontracting

A Molecule‐Based Single‐Photon Source Applied in Quantum Radiometry

Single photon sources (SPSs) based on quantum emitters hold promise in quantum radiometry as metrology standard for photon fluxes at the low light level. Ideally this requires control over the photon flux in a wide dynamic range, sub-Poissonian photon statistics and narrow-band emission spectrum. In this work, a monochromatic single-photon source based on an organic dye molecule is presented, whose photon flux is traceably measured to be adjustable between 144 000 and 1320 000 photons per second at a wavelength of (785.6 +/- 0.1) nm, corresponding to an optical radiant flux between 36.5 fW and 334 fW. The high purity of the single-photon stream is verified, with a second-order autocorrelation function at zero time delay below 0.1 throughout the whole range. Featuring an appropriate combination of emission properties, the molecular SPS shows here application in the calibration of a silicon Single-Photon Avalanche Detector (SPAD) against a low-noise analog silicon photodiode traceable to the primary standard for optical radiant flux (i.e. the cryogenic radiometer). Due to the narrow bandwidth of the source, corrections to the SPAD detection efficiency arising from the spectral power distribution are negligible. With this major advantage, the developed device may finally realize a low-photon-flux standard source for quantum radiometry

Avances en el desarrollo del cultivo de la mojarra (Cheirodon interruptus) como alternativa a la explotación de poblaciones silvestres

Fil: Maiztegui, Tomás. IIB-INTECH. Instituto Biotecnológico Chascomús. UNSAM; ArgentinaFil: Campanella, Daniela. IIB-INTECH. Instituto Biotecnológico Chascomús. UNSAM; ArgentinaFil: Colautti, Darío César. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin

Age and growth of Pseudoplatystoma corruscans (Siluriformes: Pimelodidae) at the confluence of the Paraná and Paraguay rivers

The age and growth of Pseudoplatystoma corruscans, is analyzed on specimens landed in Puerto Antequera, Province of Chaco, Argentina. The study is based on length frequency distribution of 1192 individuals and growth marks of 293 pectoral spines. Previously to age assignation based on spines readings, we performed analyses that ruled out age-associated resorption of rings and corroborated the annual periodicity of mark formation. The average sizes of the radius of each ring were obtained, and the total length of fish were back-calculated to the time of the ring formation, by the regression model fitted between the total radius of the spines to the respective sizes of each fish. Such data showed a good fitting to growth models of von Bertalanffy, Gompertz and logistic for both sexes separately. Results indicate that the study of the species growth must be carried out for each sex separately and that the fishing regulations must consider this characteristic of the species since the current management guidelines could be promoting differential capture by sexes.Fil: Balboni, Leandro. Ministerio de Agricultura, Ganadería, Pesca y Alimento; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vargas, Facundo. Gobierno de la Provincia de Chaco. Ministerio de Planificación Ambiente e Innovación Tecnológica; ArgentinaFil: Colautti, Dario César. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Limnología "Dr. Raúl A. Ringuelet". Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología; Argentin

A potential biocide for control of the golden mussel, Limnoperna fortunei

We assessed to response of larvae of the golden mussel (Limnoperna fortunei) to different concentrations of a quaternary ammonium polymer (Bulab 6002 ®) in order to estimate its effectiveness in controlling this invasive mussel. Mussels were collected along the coast of the Rio de la Plata, Argentina, and were tested in two laboratory trials. The estimated median lethal concentration for these 24-h exposures were 9.6 mg/L and 4, 6 mg/L, indicating that this biocide may be suitable as a control agent for this mussel.Facultad de Ciencias Naturales y MuseoInstituto de Limnología "Dr. Raul A. Ringuelet