Francisco Bozinovic

RESUMEN La selección natural actúa sobre los individuos, en este sentido predecir las respuestas que estos tendrán frente a los cambios ambientales y el éxito del individuo al momento de enfrentarse a estos resulta sumamente complejo, ya que involucra aspectos genéticos, fisiológicos y la interacción del organismo con su ambiente. El estudio efecto del cambio climático en organismos ha sido ampliamente desarrollado en las últimas décadas, estos se han focalizado en evaluar los efectos de (i) el aumento de la temperatura media y (ii) el efecto del aumento de la variabilidad térmica a largo plazo en algún parámetro de la adecuación biológica o desempeño de los individuos. Sin embargo, de acuerdo a nuestro conocimiento, son pocos los estudios que han evaluado el impacto de los eventos de extremos térmicos, que se encuentran dentro de las proyecciones de cambio climático.A raíz de esto, decidimos evaluar en una población natural de la mosca de la fruta, los efectos de los eventos térmic...

Objective: To test for an effect of isomorphy on development rate under different experimental thermal environments. Methods: In three different thermal environments, we studied the following characters as response variables during development: metabolic rate, body mass, and body length. We used as our study model the terrestrial isopod Armadillidium vulgare during the first 14 weeks of development. Conclusions: Our results suggest that although metabolic rate and body mass may depend on the internal state of individuals, body length may present an isomorphic response. This would be evidence that a non-adaptive interpretation could explain developmental patterns and thus highlight the importance of avoiding the frequent use of unsupported adaptive explanations in evolutionary ecology.

SUMMARY Hibernation in ectothermic animals was historically considered as a simple cold-induced torpor state resulting from the inability to maintain a high body temperature at low ambient temperatures. During the last decades this vision changed and nowadays there is a myriad of studies showing that hibernation implies different adjustments at the genetic, molecular, biochemical and cellular levels. However, studies oriented

One of the most fundamental questions in organismal ecology is how animals work in a continuously changing environment. In order to contribute to the current understanding of this question, this study evaluated seasonal changes in digestive enzymes activities, organs size, and energy reserves in Liolaemus nigroviridis, a medium-size lizard that inhabit extreme environments in the Andes range. We found that

The balance between energy acquisition and expenditure is critical to the survival and reproductive success of animals. Here we investigate the long-term effects of diet quality on physiological and life-history flexibility in the harvestman, Pachylus paessleri. We used cow meal as a protein-rich diet and potatoes as a carbohydrate-rich diet in order to reproduce two extreme conditions regarding food quality

Bile acids (BAs) regulate energy expenditure by activating G-protein Coupled Bile Acid Receptor Gpbar1/TGR5 by cAMP-dependent mechanisms. Cholecystectomy (XGB) increases BAs recirculation rates resulting in increased tissue exposure to BAs during the light phase of the diurnal cycle in mice. We aimed to determine: 1) the effects of XGB on basal metabolic rate (BMR) and 2) the roles of TGR5 on XGB-dependent changes in BMR. BMR was determined by indirect calorimetry in wild type and Tgr5 deficient (Tgr5-/-) male mice. Bile flow and BAs secretion rates were measured by surgical diversion of biliary duct. Biliary BAs and cholesterol were quantified by enzymatic methods. BAs serum concentration and specific composition was determined by liquid chromatography/tandem mass spectrometry. Gene expression was determined by qPCR analysis. XGB increased biliary BAs and cholesterol secretion rates, and elevated serum BAs concentration in wild type and Tgr5-/- mice during the light phase of the diurnal cycle. BMR was ~25% higher in cholecystectomized wild type mice (p <0.02), whereas no changes were detected in cholecystectomized Tgr5-/- mice compared to wild-type animals. XGB increases BMR by TGR5-dependent mechanisms in mice.

Rodents from arid and semiarid environments live under conditions where the spatial and temporal availability of water is limited. Octodon degus is a South-American desert-dwelling rodent inhabiting arid and semiarid habitats of central and northern Chile. Its survival depends on morphological, physiological and behavioral adaptations that allow water conservation. This rodent has a high urine concentrating ability, high capacity of

... RTEWL) presentó una variación significativa entre las especies de Cinclodes, siendo mayor para las especies de agua dulce C. oustaleti y C ... permit desert birds to cope with desert conditions, by allowing more efficient water conservation (Dawson 1982, Williams 1996, McNab ...

... changes in digestive enzymatic activity in the small Chilean marsupial Thylamys elegans: intestinal disaccharidases PABLO SABAT y ... diferencias en la abundancia de frutos (RO Bustamante, co-municación personal) e insectos (López-Calleja & Díaz-Barraza 1991(1 ...

... Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile FRANCISCO BOZINOVIC2 Departamento ... resident breeder on large parts of North America, leaving in winter to migrate ... southern Florida, where some juveniles were found during most winters, and from ...

Defense against natural aggressors, such as bacterial infections, requires both energy and an immune-cellular response. However, the question as to how these two components are interconnected in small endotherms by means of the host diet remains only poorly understood. Here, we tested in laboratory mice whether dietary proteins and carbohydrates can modulate the interplay between energy expenditure, food intake and the innate and adaptive immune response when confronting a bacterial challenge (Bacillus Calmette-Guérin, BCG). We observed that mice fed with a high protein diet (HP) developed a better immune response associated to increased numbers of circulating monocytes. In addition, HP diet directly influenced the peripheral blood proportions of both T and B lymphocytes even before the BCG challenge. Interestingly, animals that developed this type of immune response after BCG challenge showed an increased rate of metabolism and food consumption before being challenged. Thus, HP diet induced in non-challenged animals a similar energy expenditure and food intake described by BCG-treated mice. These data suggest that a high amount of proteins in diet can modify the energetic and nutrient dynamic in the host causing a better immune reaction against a microbial challenge.

Mammals exposed to low temperatures increase their metabolic rate to maintain constant body temperature and thus compensate for heat loss. This high and costly energetic demand can be mitigated through thermoregulatory behavior such as social grouping or huddling, which helps to decrease metabolic rate as function of the numbers of individuals grouped. Sustained low temperatures in endothermic animals produce changes over time in rates of energy expenditure, by means of phenotypic plasticity. However, the putative modulating effect that huddling exerts on the flexibility of the basal metabolic rate (BMR) due to thermal acclimation remains unknown. We determined BMR values in Octodon degus, an endemic Chilean rodent, after being acclimated to either 15 or 30°C during 60 days, both alone and in groups of three and five individuals. At 15°C, BMR of huddling individuals was 40% lower than that of animals housed alone. Moreover, infrared thermography revealed a significant increase in local surface temperatures in huddled animals. Furthermore, individual thermal conductance was lower in individuals acclimated to 15°C than to 30°C, but no differences were observed between single and grouped animals. Our results indicate that huddling prevents an increase in BMR when animals are acclimated to cold conditions and that this effect is proportional to the number of animals grouped.