Artículos científicos

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Glyphosate Use in Forest Plantations
(2010) Kogan, Marcelo; Alister, Claudio
Under Chilean conditions the lack of weed control at forest tree establishment results in an average of at least 60% less biomass accumulation during the first year of growth of radiate pine or eucaliptus, and glyphosate offers a series of advantages in forestry weed management because its activity in both herbaceous weed groups, monocots and dicots, as well as annuals, biennials and perennials. Also, its efficacy in woody undesirable vegetation makes glyphosate a very important herbicide that can be applied to control herbaceous and woody weeds as pre-planting and during the second or third years of trees growth as strip applications. The aim of this review is to discuss the main uses of glyphosate in reforestation worldwide, during the first 2 yr after tree establishment, as broadcast application over the top of the forest trees and the most important factors that could affect glyphosate efficacy as a forest herbicide, like weed growth stage, application technique, volume and water quality, rainfastness, dew effect and the use of extra adjuvant with formulated glyphosate.
Evaluation Of Risk Factors In Agriculture: An Application Of The Analytical Hierarchical Process (AHP) Methodology
(2011) Toledo, Roger; Engler, Alejandra; Ahumada, Víctor
Risk in the agricultural sector has multiple dimensions or factors and prioritization of these can support decision making. On the other hand, knowing the importance of these risk factors for distinct agricultural activities and how they vary according to geographic zone constitutes relevant information for agricultural development. The objective of this study was to prioritize risk factors that are highly relevant for farmers in Central South Chile. The multicriteria Analytical Hierarchical Process (AHP) methodology was used to define a decision structure with four risk factors or criteria: climate, price and direct cost variability, human factor, and commercialization. In general, results obtained showed that there are no important imbalances in the weightings of different risk factors. Price and cost variability was the most important factor (0.30) whereas climate was the least important (0.20). It also confirmed that there are spatial differences in the weightings obtained for the distinct risk factors which determine distinct risk levels for the respective agricultural activities according to geographic region.
Using penoxsulam ALS inhibitor as a broad-spectrum herbicide in Chilean rice
(2011) Kogan, Marcelo; Gómez, Patricio; Fischer, Albert; Alister, Claudio
The continuously-flooded rice production system in Chile has selected highly competitive aquatic weeds selection capable ofreducing paddy yields by 25 to 50%. Penoxsulam is a broad-spectrum triazolopyrimidine (ALS inhibitor) commercially introduced in Chile in 2006, where Alisma plantago aquatica hads already evolved resistance to sulfonylurea herbicides (SU). Several field trials with water seeded rice were conducted during 2003 and 2004 in Chile to determine efficacy, timing of application, spectrum of control, and control of SU-resistant A. plantago aquatica with the herbicide penoxsulam, either in single applications or in sequence with other herbicides. Penoxsulam was applied a) 12 days after seeding (DAS) into the water (IW), b) in postemergence after draining the water from field (ADW) at 35 DAS or c) IW followed by ADW applications of MCPA, cyhalofop, bentazon, or triclopyr. Penoxsulam was tested at 20, 30, and 40 g a.i. ha-1. Comparisons were made with recommended rates of other IW treatments (metsulfuron, bensulfuron and cyclosulfomuron) and sequential applications of molinate (IW) followed by ADW applications of MCPA, cyhalofop, bentazon, or triclopyr. One IW penoxsulam application was sufficient to achieve broad-spectrum control: Echinochloa spp. (100% control), A.plantago-aquatica (80 to 100%), Schoenoplectus mucronatus (50 to 80%), and Cyperus difformis (80 to 100%). Rice yields in penoxsulam-treated plots were 30 to 56% higher than in the untreated controls. Yields with penoxsulam IW (all rates) were similar (P>0.05) to those obtained using molinate (IW) followed by ADW applications of bentazon or MCPA. Although penoxsulam is an ALS inhibitor, it controlled A. plantago-aquatica resistant to metsulfuron and bensulfuron.
Endoparasites of the kodkod, Oncifelis guigna (Carnivora, Felidae) in Chile
(2011) González-Acuña, Daniel; Moreno, Lucila; Ardiles, Karen; Flores, Marcelo; Duclos, Melanie; Kinsella, Mike
Effects of physicochemical soil properties of five agricultural soils on herbicide soil adsorption and leaching
(2011) Alister, Claudio; Araya, Manuel; Kogan, Marcelo
Once pesticides reach the soil, there are several factors that affect their soil behavior. To identify the principal soil and herbicide properties that control their adsorption and leaching, a study of five Chilean agricultural and forest soils was performed. Simazine, diuron, terbuthylazine and MCPA were applied to the top of 45-cm tall by 12-cm diameter disturbed soil columns, filled with either an Andisol, Ultisol, Entisol or one of two Inceptisol soils. After herbicide applications, each lysimeter received 24 mm of simulated rain every 24 hours for five days. Once water percolation stopped, the lysimeters were divided into five sections and herbicide concentrations were quantified using High Pressure Liquid Chromatography. Relationships between soil physicochemical properties, herbicide sorption (adsorption and desorption) and herbicide leaching were determined. All herbicides exhibited the least depth reached from the Andisol soil (10 cm) and the highest from the Ultisol soil (45 cm). The principal soil property that affected herbicide adsorption was the soil organic carbon content, specifically the fulvic acid-humins fraction. Soil leaching was related to the inverse of soil adsorption (1/Kd), cation exchange capacity, humic substances content and herbicide pKa. These results suggest that it is possible to develop simple quantitative models to predict the soil-leaching properties of pesticides.
Adsorption and desorption variability of four herbicides used in paddy rice production
(2011-01) Alister, Claudio A.; Araya, Manuel A.; Kogan, Marcelo
This investigation was performed to determine the effect of physicochemical soil properties on penoxsulam, molinate, bentazon, and MCPA adsorption-desorption processes. Four soils from Melozal (35° 43' S; 71° 41' W), Parral (36° 08' S; 71° 52' W), San Carlos (36° 24' S; 71° 57' W), and Panimavida (35° 44' S; 71° 24' W) were utilized. Herbicide adsorption reached equilibrium after 4 h in all soils. The Freundlich L-type isotherm described the adsorption process, which showed a high affinity between herbicides and sorption sites mainly because of hydrophobic and H-bonds interaction. Penoxsulam showed the highest adsorption coefficients (4.23 ± 0.72 to 10.69 ± 1.58 mL g⁻¹) and were related to soil pH. Molinate showed K(d) values between 1.72 ± 0.01 and 2.3 ± 0.01 mL g⁻¹ and were related to soil pH and organic matter, specifically to the amount of humic substances. Bentazon had a high relationship with pH and humic substances and its K(d) values were the lowest, ranging from 0.11 ± 0.01 to 0.42 ± 0.01 mL g⁻¹. MCPA K(d) ranged from 0.14 ± 0.02 to 2.72 ± 0.01 mL g⁻¹, however its adsorption was related to humic acids and clay content. According to these results, the soil factors that could explain the sorption process of the studied herbicides under paddy rice soil conditions, were principally humic substances and soil pH. Considering the sorption variability observed in this study and the potential risk for groundwater contamination, it is necessary to develop weed rice management strategies that limit use of herbicides that exhibit low soil adsorption in areas with predisposing conditions to soil leaching.
Water and sediment dynamics of penoxsulam and molinate in paddy fields: field and lysimeter studies
(2011-07-15) Kogan, Marcelo; Araya, Manuel; Alister, Claudio
BACKGROUND: In Chile, rice is cultivated under water-seeded and continuously flooded conditions. Because herbicide dynamics in paddy fields and non-flooded fields is different, 3 year experiments were performed to study the dissipation of molinate and penoxsulam in water and sediment. RESULTS: In field experiments, both herbicides dissipated by 45–55% from the initial applied amounts during the first 6 h after application in all crop seasons; in lysimeter experiments, dissipation amounts were approximately 10% for penoxsulam and 16% for molinate. Penoxsulam field water DT50 values varied from 1.28 to 1.96 days during the three study seasons, and DT90 values from 4.07 to 6.22 days. Molinate field water DT50 values varied from 0.89 to 1.73 days, and DT90 values from 2.82 to 5.48 days. Sediment residues were determined 2 days after herbicide application into the paddy water, and maximum concentrations were found 4–8 days after application. In sediment, DT50 values varied from 20.20 to 27.66 days for penoxsulam and from 15.02 to 29.83 days for molinate. CONCLUSIONS: Results showed that penoxsulam and molinate losses under paddy conditions are dissipated rapidly from the water and then dissipate slowly from the sediment. Penoxsulam and molinate field water dissipation was facilitated by paddy water motion created by the wind. Sediment
Simazine transport in undisturbed soils from a vineyard at the Casablanca valley, Chile
(2013-01-20) Suárez, Francisco; Guzmán, Edwin; Muñoz, José F.; Bachmann, Jaime; Ortiz, Cristian; Alister, Claudio; Kogan, Marcelo
Simazine is a soil-active herbicide that has been applied worldwide in agricultural soils, being the second most commonly detected herbicide in groundwater and surface waters. Although its use has been restricted in many countries of Europe, it is still applied in many locations around the world in orchards, vineyards and forestry. Therefore, it is important to study its fate and transport in the environment. This paper investigates simazine transport in undisturbed bare soils from a vineyard at the Casablanca valley, Chile. In the study site, shallow groundwater tables (<1.0 m depth) and high simazine levels (>15 μg L−1) in the groundwater were observed and thus, there is potential for simazine to be transported further away through the saturated zone. The soils from the study site were characterized and the hydrodynamic transport parameters were determined. Column leaching experiments showed that the two-site chemical non-equilibrium model correctly represented simazine transport. It was found that 36.3% of the adsorption sites achieve instantaneous equilibrium and that the first-order kinetic rate of the non-equilibrium sites was 6.2 × 10−3 h−1. Hydrus 2D was used to predict the transport of simazine in the study site under natural field conditions. Simulation results showed that simazine concentrations at depths shallower than 2.1 m are above the maximum contaminant level of 4 μg L−1 (defined by the U.S. Environmental Protection Agency). The timing of herbicide application was found to be important on simazine leaching and the main processes involved in simazine transport were degradation and adsorption, which accounted for 95.78 and 4.19% of the simulated mass of pesticide, respectively. A qualitative agreement in the timing and magnitude of simazine concentration was obtained between the simulations and the field data. Therefore, the model utilized in this investigation can be used to predict simazine transport and is a valuable tool to assess agricultural practices to minimize environmental impacts of simazine.
Competitive Strategies and Growth of Neighbouring Bromus valdivianus Phil. and Lolium perenne L. Plants Under Water Restriction
(2013-05) López, F.; Kemp, P. D.; Dörner, J.; Descalzi, C. A.; Balocchi, O. A.; García, S.
Often perennial pastures have to tolerate soil water restriction during summer, which can affect the relative abundance of the most desired species. In the south of Chile, Bromus valdivianus and Lolium perenne are preferred species. The competitiveness of B. valdivianus and L. perenne was evaluated when sown in pots in a glasshouse as monocultures or a mix (50/50 %) with restricted water availability. The water restriction treatments were as follows: 80–85 % field capacity (FC), 45–50 % FC and 20–25 % FC, maintained for 1196 growing degree days. For both species, dry matter (DM) accumulated per plant and per pot decreased similarly with increasing water restriction, but at tiller level, resource allocation differed, for B. valdivianus root growth was accentuated over aerial development, but this was less so for L. perenne. The foliage mass per tiller for B. valdivianus decreased relatively more than that for L. perenne with increasing water restriction. As monocultures, B. valdivianus produced larger tillers than L. perenne, such that B. valdivianus tillers had 2.2 times greater lamina mass, 3.6 times more leaf area and 2.5 times greater root mass than those of L. perenne. However, L. perenne produced a larger number of smaller tillers that enabled foliage, root and total mass at plant level, to be similar to that of B. valdivianus. Within the mixed pasture, L. perenne tiller density increased compared with when grown as a monoculture, but not for B. valdivianus. The results of the study suggested that L. perenne and B. valdivianus have differences in growth strategies that allow them to survive under environmental stress and competition. Competitiveness increased for L. perenne aboveground without water restriction and that for B. valdivianus increased belowground as water restriction was increased.
Quantifying effects of irrigation and soil water content on electricalpotentials in grapevines (Vitis vinifera) using multivariate statisticalmethods
(2014-05-20) Gil, Pilar M.; Saavedra, Jorge; Schaffer, Bruce; Navarro, Rosa; Fuentealba, Claudia
Several studies have shown that physiological responses in plants, including fruit crops, are associated with changes in electrical potentials (EP), but it is often difficult to statistically quantify these responses. This study tested the effects of irrigation on EP in grapevines (Vitis vinifera), taking into account vapor pressure deficit (VPD) and position of electrodes along the stem by using multivariate analytical methods and a suite of statistical pretreatments. In two separate experiments, plants were exposed to one of two irrigation treatments in a greenhouse: (T1) irrigation once per day (Experiment 1), or no irrigation (Experiment 2); or (T2) irrigation three times or twice per day (Experiments 1 and 2, respectively). In each experiment, EP at three positions along the stem, soil (potting medium) water content, and VPD were continuously measured. In Experiment 2, stomatal conductance (gs) and stem water potential (SWP) were also measured for plants in each irrigation treatment as indicators of plant water status. Data were analyzed by Principal Component Analysis (PCA) to determine the effects of irrigation treatment on EP and difference in EP between pairs of electrodes (ΔEP) at various locations along the stem. Data were also analyzed by partial least squares (PLS) analysis to determine if EP or ΔEP could be used as predictors of changes in soil water content due to different irrigation treatments. Significant differences in soil water content due to irrigation treatments could be readily detected by difference in EP or ΔEP using PCA with Orthogonal Signal Correction pre-processing. Also, PLS showed that differences in soil moisture can be predicted by EP and/or ΔEP measurements at specific locations along the stem. Thus, the use of multivariate statistical methods was effective for relating EP and ΔEP measurements in grapevines to soil moisture due to differences in irrigation.
Role of the spinal TrkB-NMDA receptor link in the BDNF-induced long-lasting mechanical hyperalgesia in the rat: A behavioural study
(2017) Marcos, José L.; Galleguillos, D.; Pelissier, T.; Hernández, A.; Velásquez, L.; Villanueva, L.; Constandil, L.
Background: Intrathecal/intracisternal BDNF in rodents produces longlasting hyperalgesia/allodynia, which implies BDNF plays a role in the establishment and maintenance of central sensitization. Both selfregeneration of endogenous BDNF and neuroplastic modifications of spinal NMDA receptors downstream TrkB signalling could be involved in such enduring hyperalgesia. We investigated to what extent BDNF by itself could participate in the generation and maintenance of mechanical hyperalgesia using pharmacological tools. Methods: We studied sensitivity of mechanical hyperalgesia induced by a single intrathecal (i.t.) injection of BDNF (3 ng/10 lL i.t.) administered at time zero, for: (1) chronic NMDA receptor inhibition with subcutaneously implanted 7-day delivery osmotic pumps loaded with ketamine; (2) TrkB receptor inhibition with intraperitoneal (i.p.) cyclotraxine-B; and (3) chronic glial inhibition with repeated propentofylline i.t. injections. Nociceptive threshold to paw pressure, tested on days -3, 0, 3, 7, 10 and 14, was used as the index of central sensitization. Locomotor patterns and food and water consumption were assessed with LABORAS. Results: Chronic ketamine prevented the mechanical hyperalgesia induced by BDNF, without affecting locomotion and food and water consumption. After pump depletion, a late hyperalgesic response to paw pressure stimulation emerged, which can be lastingly antagonized by cyclotraxine-B. Chronic propentofylline treatment irreversibly suppressed BDNF-induced hyperalgesia. Conclusion: Activation of NMDA receptors downstream to TrkB signalling is essential for behavioural expression of the mechanical hyperalgesia induced by intrathecal BDNF. However, maintenance of the hyperalgesia depends mainly from self-regenerating glial BDNF rather than from a NMDA receptor-dependent form of neuroplasticity. Significance: Intrathecal BDNF induces long-lasting central sensitization via a glial-likely BDNF self-regenerating mechanism, whose behavioural expression depends on downstream activation of NMDA receptors. This knowledge suggests that TrkB antagonists could represent an interesting lead for the development of novel therapeutic strategies for some chronic pain conditions.
Evaluation of sustainability and the impact of the agriculture styles of the chilean coastal dry lands
(2017) González Ulibarry, Paco; García Elizalde, Pedro; Gastó Corderch, Juan; De Kartzow Garcia, Alejandro; Obando-Ulloa, Javier Mauricio
Agriculture has been progressing continuously, from the use of free natural resources to the fossil fuels as energy sources. Even though agriculture depends mainly on ecosystem resources and services, its development has been apparently centered only on yield, not considering neither the ecological value of the negative externalities nor the decapitalization of the resources that influence sustainability. Thus, the information on the evaluation of the sustainability on different agriculture styles is scarce or almost null. This investigation evaluates the sustainability in different agriculture styles (intensive horticulture, traditional farm and self-sustaining horticulture) established in Hualqui (Region of Biobío, Chile), through the energy flows present on each style to measure the impact generated on the land. The results revealed that the self-sustaining horticulture style showed a higher sustainability compared to the traditional farm and intensive horticulture style. These results can contribute to the public, policies to reorient the action strategy to encourage the sustainability in the different agriculture styles.
Pyrrolizidine alkaloid toxicosis and hepatic encephalopathy in horses in Easter Island, Chile
(2018) Lohse, Jorge C.; Paredes, Enrique; González, Carlos M.; Koene, Marc; Magged, Mahmoud
A group of horses died in Easter Island following anorexia, weight loss and neurological signs. Similar cases have occurred since the introduction of a plant containing pirrolizidine alkaloid to the island. This study describes the grazing behaviour of the horses and the potential correlation with the development of these horses clinical signs.
Quercetin Prevents Diastolic Dysfunction Induced by a High-Cholesterol Diet: Role of Oxidative Stress and Bioenergetics in Hyperglycemic Rats
(2018) Castillo, Rodrigo L.; Herrera, Emilio A.; Gonzalez-Candia, Alejandro; Reyes-Farias, Marjorie; de la Jara, Nicole; Peña, Juan Pedro; Carrasco-Pozo, Catalina
Alterations in cardiac energy metabolism play a key role in the pathogenesis of diabetic cardiomyopathy. Hypercholesterolemia associated with bioenergetic impairment and oxidative stress has not been well characterized in the cardiac function under glycemic control deficiency conditions. This work aimed to determine the cardioprotective effects of quercetin (QUE) against the damage induced by a high-cholesterol (HC) diet in hyperglycemic rats, addressing intracellular antioxidant mechanisms and bioenergetics. Quercetin reduced HC-induced alterations in the lipid profile and glycemia in rats. In addition, QUE attenuated cardiac diastolic dysfunction (increased E:A ratio), prevented cardiac cholesterol accumulation, and reduced the increase in HC-induced myocyte density. Moreover, QUE reduced HC-induced oxidative stress by preventing the decrease in GSH/GSSG ratio, Nrf2 nuclear translocation, HO-1 expression, and antioxidant enzymatic activity. Quercetin also counteracted HCinduced bioenergetic impairment, preventing a reduction in ATP levels and alterations in PGC-1α, UCP2, and PPARγ expression. In conclusion, the mechanisms that support the cardioprotective effect of QUE in rats with HC might be mediated by the upregulation of antioxidant mechanisms and improved bioenergetics on the heart. Targeting bioenergetics with QUE can be used as a pharmacological approach to modulate structural and functional changes of the heart under hypercholesterolemic and hyperglycemic conditions.
Efectos de Aceites Esenciales de Lavanda y Eucalipto en el Control de la Varroasis de Apis melifera
(2018) Marcos, J.; Ahumada, M.; Cadavid, A.; Bañares, G.; Silva, C.
Las abejas como polinizadores participan en la economía global y su aporte ha sido estimado entre 235 y 285 billones de US$ al año. (Lautenbach, et al., 2012) Actualmente se ha informado el debilitamiento general de las abejas melíferas, representado por pérdidas de colonias, elevando la preocupación pública, encareciendo el manejo de las colonias de abejas y aumentando los costos de los servicios de polinización (Calderone, 2012). El ácaro Varroa destructor se considera un impulsor crucial de esta difícil situación mundial de colonias de de abejas (Le Conte, et al., 2010). Los métodos actuales utilizados para controlarlo, son la aplicación de acaricidas piretroides (fluvalinate) y organofosforados (coumaphos) que inicialmente fueron altamente efectivos, pero el uso frecuente de estos ha llevado al desarrollo de la resistencia de los ácaros (Milani, 1999). Los aceites esenciales (AE) ofrecen una alternativa generalmente más barata y segura para el hombre y las abejas (Isman 2000). Son clasificados como suplementos alimenticios y seguros para consumo humano (Quarles, 1996). Los AE, pueden alterar el comportamiento, el crecimiento y desarrollo, la ecdisis, el apareamiento y la oviposición de los insectos (Khater, 2011). La actividad insecticida de los componentes de los AE de lavanda y eucalipto ha sido relacionada con la inhibición de la acetilcolinesterasa y como agonista octopaminergico respectivamente. (Rattan, 2010). El AE de eucaliptus es efectivo en reducir la población de varroa, (Principal, et al., 2004) El objetivo fue determinar el efecto de los AE de lavanda y eucalipto para el control de la varroasis en condiciones de campo.
Determinación del Efecto de Tres Concetraciones de Aceite Esencial de Eucalipto, para el Control Ecológico de la Varroasis en Colmenas en Producción, en Los Molles, Región de Valparaíso, Chile
(2018) Ahumada, M.; Marcos, José L.; Bañares, G.
La varroasis es producida por ácaros de la especie Varroa destructor, un ectoparásito que desde hace décadas, ha generado graves problemas a la producción apícola nacional y mundial. El año 1992 se diagnosticó por primera vez en Chile, con carácter de emergencia sanitaria (FIA, 2009). Existen distintas opciones terapéuticas químicas alopáticas para su control, como por ejemplo flumetrina, fluvalinato, amitraz, etc., pero desencadenan efectos tóxicos sobre el sistema nervioso de las abejas, reduciendo el rendimiento de aprendizaje en los insectos (Tan et al., 2013). También el uso y abuso de estos acaricidas ha generado resistencia de Varroa a dichos productos (Moreno, 2006). Los productos alternativos más interesantes son los aceites esenciales de timol y eucalipto, y los ácidos orgánicos oxálico y fórmico (Jaume, 2003). Según Principal et al. (2004), el aceite esencial de eucalipto es efectivo en reducir la población de Varroa, y su acción fue más evidente a las 36 h post tratamiento. La actividad insecticida del aceite esencial de eucalipto ha sido descrita como agonista del receptor de octopamina (Rattan, 2010). Los aceites esenciales de plantas presentan una buena eficacia en el control de Varroa, una mínima residualidad en la miel y no dañan a las abejas (Schmidt et al., 2008). El objetivo de este trabajo fue determinar los efectos de tres concentraciones del aceite esencial de eucalipto como tratamiento ecológico contra la varroasis en colmenas en producción.
High-Fat-Diet-Induced Obesity Produces Spontaneous Ventricular Arrhythmias and Increases the Activity of Ryanodine Receptors in Mice
(2018) Sánchez, Gina; Araneda, Felipe; Peña, Juan Pedro; Finkelstein, José Pablo; Riquelme, Jaime A.; Montecinos, Luis; Barrientos, Genaro; Llanos, Paola; Pedrozo, Zully; Said, Matilde; Bull, Ricardo; Donoso, Paulina
Ventricular arrhythmias are a common cause of sudden cardiac death, and their occurrence is higher in obese subjects. Abnormal gating of ryanodine receptors (RyR2), the calcium release channels of the sarcoplasmic reticulum, can produce ventricular arrhythmias. Since obesity promotes oxidative stress and RyR2 are redox-sensitive channels, we investigated whether the RyR2 activity was altered in obese mice. Mice fed a high fat diet (HFD) became obese after eight weeks and exhibited a significant increase in the occurrence of ventricular arrhythmias. Single RyR2 channels isolated from the hearts of obese mice were more active in planar bilayers than those isolated from the hearts of the control mice. At the molecular level, RyR2 channels from HFD-fed mice had substantially fewer free thiol residues, suggesting that redox modifications were responsible for the higher activity. Apocynin, provided in the drinking water, completely prevented the appearance of ventricular arrhythmias in HFD-fed mice, and normalized the activity and content of the free thiol residues of the protein. HFD increased the expression of NOX4, an isoform of NADPH oxidase, in the heart. Our results suggest that HFD increases the activity of RyR2 channels via a redox-dependent mechanism, favoring the appearance of ventricular arrhythmias.
Reporte de Caso: Primer Caso de Pearsonema spp. en Felino Doméstico de Chile
(2018) Sanhueza, Vicente; Melo, T.; Weinborn, Romy M.
En Chile no han sido reportados casos de Pearsonema spp (Capillaria spp) en caninos o felinos domésticos, sólo se han descrito en cánidos silvestres (Jiménez et al., 2012). En cuanto a la literatura internacional existen artículos publicados, tanto en animales silvestres (Studzińska et al., 2015) como en caninos y felinos domésticos (Henrique, 2014). Sin embargo, se reconoce como una infección relativamente poco común y asintomática para ambas especies (Studzińska et al., 2015; Del-angel-caraza et al., 2018).
Aproximaciones a la deserción universitaria en Chile
(2018) Arancibia Carvajal, Rosa; Trigueros Cervantes, Carmen
La educación universitaria vespertina, en Chile, ha presentado en los últimos años, un acentuado crecimiento en su matrícula. Sin embargo, la interrupción de los estudios de quienes estudian en este horario de 19 a 23 horas (vespertino) ha sobrepasado la cifra promedio de deserción del sistema universitario chileno. Estos estudiantes se caracterizan por combinar responsabilidades familiares, laborales y académicas, presentando mayores niveles de deserción que los estudiantes que ingresan a la modalidad universitaria diurna, debido a las particularidades y situaciones que les rodean. En este contexto, esta investigación se propuso indagar sobre los factores que intervienen en las decisiones de abandono de los estudiantes universitarios con características no tradicionales, que asisten a programas de estudios vespertinos. Metodológicamente se optó por un diseño de investigación cualitativo de tipo exploratorio debido a la escasa investigación en la temática en el país. Para ello, se realizaron entrevistas semiestructuradas a diez estudiantes desertores vespertinos. Una vez sistematizada la información, se obtuvo cuatro dimensiones emergentes de análisis, que sintetizaron las lógicas y significados que intervienen en el fenómeno que afecta a este grupo específico. Los hallazgos sobre la decisión de abandono de los estudiantes vespertinos de características no tradicionales dan cuenta de los siguientes factores, según relevancia, condiciones y características personales, capital y desempeño académico, imprevistos y circunstancias adversas y experiencias con la oferta institucional.
Matching global and regional distribution models of the recluse spider Loxosceles rufescens: to what extent do these reflect niche conservatism?
(2018) Taucare Ríos, A.; Nentwig, W.; Bizama, G.; Bustamante, R.
The Mediterranean recluse spider, Loxosceles rufescens (Dufour, 1820) (Araneae: Sicariidae) is a cosmopolitan spider that has been introduced in many parts of the world. Its bite can be dangerous to humans. However, the potential distribution of this alien species, which is able to spread fairly quickly with human aid, is completely unknown. Using a combination of global and regional niche models, it is possible to analyse the spread of this species in relation to environmental conditions. This analysis found that the successful spreading of this species varies according to the region invaded. The majority of populations in Asia are stable and show niche conservatism, whereas in North America this spider is expected to be less successful in occupying niches that differ from those in its native region and that do not support its synanthropic way of living.

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