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Search Results: 1 - 10 of 463542 matches for " PATRICIO A; NAVARRETE "
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Variación ambiental y patrones di etarios del erizo negro Tetrapygus niger en costas intermareales rocosas del norte de Chile
NAVARRETE,ARTURO H; CAMUS,PATRICIO A; OPAZO,L. FELIPE;
Revista chilena de historia natural , 2008, DOI: 10.4067/S0716-078X2008000300001
Abstract: the role and impact of herbivores on rocky intertidal food webs could be more complex and diverse than previously considered, particularly in the case of larger and more abundant consumers such as the black urchin tetrapygus niger (molina) in the coast of chile. in this context, we analyzed the variation in diet richness and composition of the black urchin in four rocky intertidal communities over a 1,000 km stretch of coast in northern chile, sampled seasonally between the austral winter of 2004 and spring of 2005. the 2004-2005 el ni?o event took place during the study, and we incorporated its potential effects to this evaluation. for each community and season, we measured the abundance of species present in 45 quadrants (0.25 m2) distributed between five permanent blocks, collecting about 10 individuals of t. niger to measure their body size (dry biomass and maximum diameter) and to determine the number, identity and occurrence frequency of dietary items in their gastric tract. we collected a total of 251 urchin individuals, which consumed 89 items of algae (64 %) and invertebrates (36 %; including other herbivores). a significant inverse relationship between the number of ingested animal items and body size suggests that t. niger changes its diet throughout the ontogeny. dietary niche breadth was high but tended to decrease toward lower latitudes. the spectrum and occurrence frequency of dietary items were not significantly different among communities, despite their marked differences in upwelling intensity. similarly, we did not find clear relationships between the natural abundance of resources and their frequency in the diet of t. niger, highlighting the green alga ulva rígida which was the most frequently consumed item in all communities although not the most abundant in the field. however, the dietary richness of t. niger showed a significant negative relation with sea surface temperature, and was significantly lower throughout the el ni?o period. our data
Variación ambiental y patrones di etarios del erizo negro Tetrapygus niger en costas intermareales rocosas del norte de Chile Environmental variation and dietary patterns of the black urchin Tetrapygus niger in rocky intertidal shores of northern Chile
ARTURO H NAVARRETE,PATRICIO A CAMUS,L. FELIPE OPAZO
Revista chilena de historia natural , 2008,
Abstract: El rol e impacto de los herbívoros en la trama trófica de comunidades intermareales rocosas podría ser más diverso y complejo de lo considerado hasta ahora, particularmente en el caso de consumidores de mayor tama o y abundancia como el erizo negro Tetrapygus niger (Molina) en la costa de Chile. En este contexto, analizamos la variación en riqueza y composición de la dieta de T. niger en cuatro comunidades intermareales rocosas del norte de Chile, distribuidas en 1.000 km de costa, y muestreadas estacionalmente entre invierno 2004 y primavera 2005. Durante el estudio ocurrió el evento El Ni o 2004-2005 cuyo efecto potencial fue incorporado en esta evaluación. En cada comunidad y estación se evaluó la abundancia de las especies presentes en 45 cuadrantes (0,25 m2) distribuidos en cinco bloques permanentes, recolectando cerca de 10 individuos de T. niger a los que se midió su biomasa y longitud, determinando el número, identidad y frecuencia de ocurrencia de ítemes en su contenido gástrico. Colectamos un total de 251 individuos de T. niger, que en conjunto consumieron 89 ítemes de algas (64 %) e invertebrados (36 %; incluyendo otros herbívoros). Una relación inversa significativa entre el tama o corporal y el número de ítemes animales ingeridos sugiere que T. niger varía su dieta durante la ontogenia. La amplitud de nicho dietario fue alta y tendió a disminuir hacia latitudes menores. Globalmente, el espectro y frecuencia de ocurrencia de ítemes dietarios no fueron significativamente distintos entre comunidades, pese a marcadas diferencias en intensidad de surgencia entre ellas. Similarmente, no hubo relación clara entre la oferta ambiental de recursos y su frecuencia en la dieta de T. niger, destacando la clorófita Ulva rígida que fue el ítem consumido con más frecuencia en cada comunidad pero no el más abundante en terreno. Sin embargo, la riqueza dietaria de T. niger se relacionó negativa y significativamente con la temperatura superficial del mar, y fue significativamente menor en todo el período de El Ni o 2004-2005. Nuestros datos sugieren que T. niger es un generalista polífago cuyos patrones de consumo son fuertemente modulados por la fluctuación térmica ambiental. Además, hipotetizamos que T. niger puede usar estrategias oportunistas y selectivas sobre distintos recursos, y que su conectividad y posición trófica serían más complejas que las de un simple consumidor primario. The role and impact of herbivores on rocky intertidal food webs could be more complex and diverse than previously considered, particularly in the case of larger and more abunda
Caracterización trófica del placóforo intermareal Enoplochiton niger en el norte de Chile: variación ambiental y patrones dietarios a nivel local y region
SANHUEZA,ALVARO G; NAVARRETE,ARTURO H; OPAZO,L. FELIPE; CAMUS,PATRICIO A;
Revista chilena de historia natural , 2008, DOI: 10.4067/S0716-078X2008000400007
Abstract: the role and impact of herbivores on rocky intertidal food webs could be more complex and diverse than previously considered, particularly in the case of larger and more abundant consumers such as the placophoran mollusc enoplochiton niger. this species is one of the largest (up to 20 cm) and ecologically most important grazers on rocky shores of northern chile, but also one of the lesser known species in trophic terms. this work presents an assessment of the dietary patterns of e. niger in four communities of northern chile, distributed along 1,000 km of coastline and sampled seasonally from winter 2004 to autumn 2006. the analysis included the relationship of its diet with physical and biological factors, and particularly the potential effect of the 2004-2005 el ni?o event that occurred during the study period. at a regional level, the dietary spectrum of e. niger comprised a total of 98 food resources (60 algal ítems and 38 invertebrate ítems), and the most important ítems were sessile organisms of encrusting and layer-forming growth habits. e. niger exhibited a very high niche breadth at both local and regional levels (ranging from 20.7 to 28.0; levins' index), and its dietary richness at the individual level was independent from its body size. both the number of dietary ítems consumed per individual and the taxonomic composition of the diet did not show statistical differences among communities, but they were significantly different between the el ni?o and non-el ni?o periods. there was no clear relationship between the dietary patterns of e. niger and the contrasting levels of upwelling intensity among the communities studied. the results show that e. niger is a generalist polyphagous consumer, and a potential omnivore, which could have a high level of impact on space occupancy patterns in the intertidal community.
Trophic ecology of the chiton Acanthopleura echinata on Chilean rocky shores
CAMUS,PATRICIO A; NAVARRETE,ARTURO H; SANHUEZA,áLVARO G; OPAZO,L. FELIPE;
Revista chilena de historia natural , 2012, DOI: 10.4067/S0716-078X2012000100010
Abstract: polyplacophorans are common herbivores on rocky shores, but basic aspects of their ecology remain scarcely studied and their role within communities could be more complex than previously considered. such is the case of acanthopleura echinata (barnes), one of the largest and most conspicuous chitons in the world, and at the same time, one of the least known intertidal species in the southeastern pacific. to improve the basic ecological knowledge of this potentially important intertidal consumer, we studied the diet of a. echinata and its variation among sites of varying levels of coastal upwelling spread over 1000 km along the coast of northern chile. a seasonal evaluation of diet, body size distribution and density at sites expected to vary in overall nutrient loadings, benthic algal productivity and sea surface temperature, allowed us to examine plasticity in acantholeura diet and body size. overall, a. echinata consumed 85 items of algae (64.7 %, mainly fleshy and calcified encrusting thalli) and invertebrates (35.3 %, mainly barnacles). diet was always dominated by encrusting corallines, although the proportion of algae increased with body size suggesting an ontogenetic variation in feeding habits. although the number and occurrence frequency of dietary items varied significantly in time and space, there were no consistent seasonal patterns and the dominant items in the diet remained the same at all places. the density of a. echinata showed no significant spatial variation, but its body size and diet breadth correlated positively among sites and both tended to increase with latitude. our results show that a. echinata is a generalist, polyphagous consumer with a high potential for affecting the space-occupancy dynamics in the intertidal system, and also that among site variation in diet bears no simple relationship with variation in sea surface temperature and upwelling intensity.
Caracterización trófica del placóforo intermareal Enoplochiton niger en el norte de Chile: variación ambiental y patrones dietarios a nivel local y region Trophic characterization of the intertidal placophoran Enoplochiton niger in northern Chile: environmental variation and dietary patterns at local and regional levels
ALVARO G SANHUEZA,ARTURO H NAVARRETE,L. FELIPE OPAZO,PATRICIO A CAMUS
Revista chilena de historia natural , 2008,
Abstract: El rol e impacto de los herbívoros en la trama trófica de comunidades intermareales rocosas podría ser más diverso y complejo de lo considerado hasta ahora, particularmente en el caso de consumidores de mayor tama o y abundancia como el molusco placóforo Enoplochiton niger. Esta especie es uno de los pastoreadores de mayor tama o (hasta 20 cm) e importancia ecológica en las costas rocosas del norte de Chile, pero también una de las especies menos conocidas en términos tróficos. Este trabajo presenta una evaluación de los patrones dietarios de E. niger en cuatro comunidades del norte de Chile, distribuidas en 1.000 km de costa y muestreadas estacionalmente entre invierno 2004 y oto o 2006. Además se analizó la relación de su dieta con factores biológicos y físicos, incluyendo el efecto potencial del evento El Ni o 2004-2005 ocurrido durante el período de estudio. A nivel regional, el espectro dietario de E. niger abarcó un total de 98 recursos (60 ítemes algales y 38 ítemes invertebrados), y los ítemes más importantes fueron organismos sésiles con formas de crecimiento incrustante o en capa. E. niger mostró una gran amplitud de nicho tanto a nivel regional como local (rango: 20,7-28,0; índice de Levins), con una riqueza dietaria a nivel individual independiente del tama o corporal. Tanto el número de ítemes dietarios consumidos por individuo como la composición taxonómica de la dieta no mostraron diferencias significativas entre comunidades, pero variaron significativamente entre el período asociado al evento El Ni o y el período posterior. No hubo ninguna relación clara entre los patrones dietarios de E. niger y los niveles contrastantes de intensidad de surgencia entre las comunidades estudiadas. Los resultados muestran que E. niger es un consumidor generalista y polífago, y un potencial omnívoro, el cual podría tener un alto impacto sobre los patrones de ocupación de espacio en la comunidad intermareal. The role and impact of herbivores on rocky intertidal food webs could be more complex and diverse than previously considered, particularly in the case of larger and more abundant consumers such as the placophoran mollusc Enoplochiton niger. This species is one of the largest (up to 20 cm) and ecologically most important grazers on rocky shores of northern Chile, but also one of the lesser known species in trophic terms. This work presents an assessment of the dietary patterns of E. niger in four communities of northern Chile, distributed along 1,000 km of coastline and sampled seasonally from winter 2004 to autumn 2006. The analysis included the relatio
Trophic ecology of the chiton Acanthopleura echinata on Chilean rocky shores Ecología trófica del chitón Acanthopleura echinata en costas rocosas de Chile
PATRICIO A CAMUS,ARTURO H NAVARRETE,áLVARO G SANHUEZA,L. FELIPE OPAZO
Revista chilena de historia natural , 2012,
Abstract: Polyplacophorans are common herbivores on rocky shores, but basic aspects of their ecology remain scarcely studied and their role within communities could be more complex than previously considered. Such is the case of Acanthopleura echinata (Barnes), one of the largest and most conspicuous chitons in the world, and at the same time, one of the least known intertidal species in the southeastern Pacific. To improve the basic ecological knowledge of this potentially important intertidal consumer, we studied the diet of A. echinata and its variation among sites of varying levels of coastal upwelling spread over 1000 km along the coast of northern Chile. A seasonal evaluation of diet, body size distribution and density at sites expected to vary in overall nutrient loadings, benthic algal productivity and sea surface temperature, allowed us to examine plasticity in Acantholeura diet and body size. Overall, A. echinata consumed 85 items of algae (64.7 %, mainly fleshy and calcified encrusting thalli) and invertebrates (35.3 %, mainly barnacles). Diet was always dominated by encrusting corallines, although the proportion of algae increased with body size suggesting an ontogenetic variation in feeding habits. Although the number and occurrence frequency of dietary items varied significantly in time and space, there were no consistent seasonal patterns and the dominant items in the diet remained the same at all places. The density of A. echinata showed no significant spatial variation, but its body size and diet breadth correlated positively among sites and both tended to increase with latitude. Our results show that A. echinata is a generalist, polyphagous consumer with a high potential for affecting the space-occupancy dynamics in the intertidal system, and also that among site variation in diet bears no simple relationship with variation in sea surface temperature and upwelling intensity. Los poliplacóforos son herbívoros comunes en costas rocosas, pero los aspectos básicos de su ecología han sido escasamente estudiados y su rol trófico dentro de las comunidades podría ser más complejo de lo considerado hasta ahora. Tal es el caso de Acanthopleura echinata (Barnes), uno de los chitones más grandes y conspicuos en el mundo, pero a la vez una de las especies intermareales menos conocidas del Pacífico sudeste. A fin de mejorar el conocimiento ecológico básico de este consumidor intermareal potencialmente importante, estudiamos la dieta de A. echinata y su variación entre sitios con distintos niveles de surgencia costera distribuidos a través de 1000 km en la cost
Unexpected diastereotopic behaviour in the 1H NMR spectrum of 1,4-dihydropyridine derivatives triggered by chiral and prochiral centres
Argüello DaSilva, Jacqueline;Saitz Barría, Claudio;Jullian, Carolina;Navarrete, Patricio;Nú?ez Vergara, Luis;Squella, Juan A.;
Journal of the Brazilian Chemical Society , 2005, DOI: 10.1590/S0103-50532005000100018
Abstract: 1,4-dihydropyridine derivatives constitute an important pharmacological group for the treatment of cardiovascular diseases. we have synthesised a series 4-(5'-nitro-2'-furyl)-1,4-dihydropyridine derivatives, which were characterised by 1h-nmr. we have found that carboethoxy groups at the c-3 and c-5 on the 1,4-dihydropyridine ring show a much more complex signal in the 1h nmr spectra, either when c-4 is a pseudo-prochiral or a chiral centre.
Diversity, dynamics and biogeography of Chilean benthic nearshore ecosystems: an overview and guidelines for conservation
FERNANDEZ,MIRIAM; JARAMILLO,EDUARDO; MARQUET,PABLO A; MORENO,CARLOS A; NAVARRETE,SERGIO A; OJEDA,F. PATRICIO; VALDOVINOS,CLAUDIO R; VASQUEZ,JULIO A;
Revista chilena de historia natural , 2000, DOI: 10.4067/S0716-078X2000000400021
Abstract: despite chile has been one of the pioneering countries in studies of human impact on marine communities, and despite the enormous economic and social significance that the marine environment has for the country, the development of marine conservation programs and the scientific basis for sustainability has not kept pace, with the exploitation rate of marine fisheries and the increasing use of the coast for other purposes. although we think that the establishment of any conservation policies along the vast coastline of chile must be based on a multitude of approaches and considerations, scientific, biological, and ecological principles should guide much of these efforts. in this paper, we attempt to present a general overview of the current knowledge about the ecology and biogeography of nearshore systems in chile. based on the most relevant existing information, our goals are to: 1) identify major biogeographic and ecological features of nearshore ecosystems, and the obvious gaps in information, 2) identify the most harmful human activities impacting the structure and dynamics of these systems, and 3) suggest the possible use of indicators to assess the conservational status of different environments along the coast. this overview shows, on one side, the geographic areas of deficitary knowledge on nearshore environments that are critical for future marine conservation and management plans, and on the other, the availability of high quality information for other geographic areas along the coast. regarding the taxonomy and large-scale patterns of species distribution, important gaps in information were detected, however no big changes in the total number of species are expected in the future. there are few large-scale patterns of species distribution are reported in the literature, and in this contribution, but more work needs to be done, particularly for some taxa, to identify areas of high species diversity as well as areas which possess unique characteristics in te
On the one pot syntheses of chromeno[4,3-b]pyridine-3-carboxylate and chromeno[3,4-c]pyridine-3-carboxylate and dihydropyridines
Navarrete-Encina, Patricio A.;Salazar, Ricardo;Vega-Retter, Christian;Pérez, Karina;Squella, Juan A.;Nu?ez-Vergara, Luis J.;
Journal of the Brazilian Chemical Society , 2010, DOI: 10.1590/S0103-50532010000300003
Abstract: substituted chromenos, dihydropyridines and pyridines have been important in the syntheses of compounds having interesting pharmacological properties. therefore, we found of interest to synthesize chromenopyridines and chromenodihydropyridines (i.e., fused chromeno and dihydropyridine or pyridine rings) to further study their biological activity. here, we propose one-pot syntheses for substituted ethyl-2,4-dimethyl-5-oxo-5h-chromeno[4,3-b]pyridine-3-carboxylates, ethyl-2,4-dimethyl-5-oxo-5h-chromeno[3,4-c]pyridine-3-carboxylates and their respective 1,4-dihydropyridines based on a modified hantzsch pyridine synthesis using 2-hydroxyaryl aldehydes, with electron withdrawing and electron donating groups on the phenyl ring, as starting reactants. sixteen compounds were synthesized by the described method and fully characterized. an average yield of 37% was obtained for the different derivatives.
Julia Uceda: una voz olvidada
María Teresa Navarrete Navarrete
Perífrasis : Revista de Literatura, Teoría y Crítica , 2010,
Abstract: El artículo analiza las posibles causas que han propiciado la desatención del estudio de la obra de Julia Uceda dentro de la historiografía literaria espa ola. Para ello, se reconstruye la producción literaria de Julia Uceda analizando antologías dedicadas a los poetas de la generación del 50, revistas literarias y entrevistas. Esta revisión se realizará teniendo en cuenta que la obra literaria de Julia Uceda es producto de las corrientes artísticas y de la sociedad del momento.The article explores the causes of the oblivion of Julia Uceda’s work in the Spanish Literary Studies. Following the analysis of Spanish poets of the 1950’s anthology, literary reviews and interviews, the article reconstructs the Julia Uceda’s works, concluding that there is a close relationship between life, work, literature surrounding and society.
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