Hibernacula of bats in Mexico, the southernmost records of hibernation in North America.

Although Mexico holds the southernmost hibernating bats in North America, information on winter behavior and hibernacula microclimate use of temperate Mexican bats is limited. We studied hibernating bats at high altitudes (>1,000 m a.s.l.) in northern and central Mexico during 5 consecutive winters. Our aims were to document and describe the hibernacula, winter behavior (such as abundance and roost pattern), and microclimates (estimated as adjacent substrate temperature) of cave-hibernating bats in Mexico. We found 78 hibernacula and 6,089 torpid bats of 10 vespertilionid species, increasing by over 50% the number of cave-hibernating bat species and quadrupling the number of hibernacula for Mexico. Hibernacula were at altitudes between 1,049 and 3,633 m a.s.l., located in 3 mountain ranges, mainly in oak and conifer forests. Myotis velifer was the most common species, followed by Corynorhinus townsendii and C. mexicanus. We recorded the adjacent substrate temperatures from 9 species totaling 1,106 torpid bats and found differences in microclimate use among the 3 most common species. In general, abundance of torpid bats in our region of study was similar to those in the western United States, with aggregations of tens to a few hundred individuals per cave, and was lower than in the eastern United States where a cave may hold thousands of individuals. Knowledge of bat hibernation is crucial for developing conservation and management strategies on current conditions while accommodating environmental changes and other threats such as emerging diseases.

Aunque México tiene los murciélagos hibernantes más sureños en Norteamérica, la información sobre el comportamiento invernal y el uso de microclimas en los refugios de hibernación de los murciélagos templados mexicanos es limitada. Estudiamos a los murciélagos hibernantes en altitudes altas (>1000 msnm) en el norte y centro de México durante cinco inviernos consecutivos. Nuestros objetivos fueron documentar y describir las cuevas de hibernación, el comportamiento invernal (como la abundancia y patrón de percha), y el uso de microclimas (estimado como la temperatura del sustrato adyacente), de los murciélagos que hibernan en cuevas en México. Encontramos 78 cuevas de hibernación con 6089 murciélagos en torpor de 10 especies de vespertiliónidos, incrementando en más del 50% el número de especies de murciélagos que hibernan en cuevas y cuadriplicando el número de cuevas de hibernación para México. Las cuevas de hibernación estuvieron en elevaciones entre 1049 y 3633 msnm, localizadas en tres cadenas montañosas, principalmente en bosques de encinos y coníferas. Myotis velifer fue la especie más común, seguida por Corynorhinus townsendii y C. mexicanus. Reportamos las temperaturas del sustrato adyacente de 1106 murciélagos en torpor de nueve especies y encontramos diferencias en el uso de microclimas entre las tres especies más comunes. Aquí proveemos información relevante para especies de murciélagos templados en la ocurrencia más sureña de hibernación de murciélagos en Norteamérica. En general, la abundancia de murciélagos en torpor que encontramos fue similar a las del oeste de Estados Unidos, con agregaciones de decenas y algunos cientos de individuos por cueva; y fue menor que las del este de Estados Unidos, donde las cuevas pueden albergar miles de murciélagos. El conocimiento de la hibernación de murciélagos es crucial para el desarrollo de estrategias de conservación y manejo adecuadas en la actualidad y mientras se adaptan a los cambios ambientales y a otras amenazas tales como las enfermedades emergentes.

Climate change and population persistence in a hibernating marsupial.

Climate change has physiological consequences on organisms, ecosystems and human societies, surpassing the pace of organismal adaptation. Hibernating mammals are particularly vulnerable as winter survival is determined by short-term physiological changes triggered by temperature. In these animals, winter temperatures cannot surpass a certain threshold, above which hibernators arouse from torpor, increasing several fold their energy needs when food is unavailable. Here, we parameterized a numerical model predicting energy consumption in heterothermic species and modelled winter survival at different climate change scenarios. As a model species, we used the arboreal marsupial monito del monte (genus Dromiciops), which is recognized as one of the few South American hibernators. We modelled four climate change scenarios (from optimistic to pessimistic) based on IPCC projections, predicting that northern and coastal populations (Dromiciops bozinovici) will decline because the minimum number of cold days needed to survive the winter will not be attained. These populations are also the most affected by habitat fragmentation and changes in land use. Conversely, Andean and other highland populations, in cooler environments, are predicted to persist and thrive. Given the widespread presence of hibernating mammals around the world, models based on simple physiological parameters, such as this one, are becoming essential for predicting species responses to warming in the short term.

Modeling heterothermic fitness landscapes in a marsupial hibernator using changes in body composition.

Hibernation is an adaptive strategy that allows animals to enter a hypometabolic state, conserving energy and enhancing their fitness by surviving harsh environmental conditions. However, addressing the adaptive value of hibernation, at the individual level and in natural populations, has been challenging. Here, we applied a non-invasive technique, body composition analysis by quantitative magnetic resonance (qMR), to calculate energy savings by hibernation in a population of hibernating marsupials (Dromiciops gliroides). Using outdoor enclosures installed in a temperate rainforest, and measuring qMR periodically, we determined the amount of fat and lean mass consumed during a whole hibernation cycle. With this information, we estimated the daily energy expenditure of hibernation (DEEH) at the individual level and related to previous fat accumulation. Using model selection approaches and phenotypic selection analysis, we calculated linear (directional, ß), quadratic (stabilizing or disruptive, γ) and correlational (ρ) coefficients for DEEH and fat accumulation. We found significant, negative directional selection for DEEH (ßDEEH = - 0.58 ± 0.09), a positive value for fat accumulation (ßFAT = 0.34 ± 0.07), and positive correlational selection between both traits (ρDEEH × FAT = 0.24 ± 0.07). Then, individuals maximizing previous fat accumulation and minimizing DEEH were promoted by selection, which is visualized by a bi-variate selection surface estimated by generalized additive models. At the comparative level, results fall within the isometric allometry known for hibernation metabolic rate in mammals. Thus, by a combination of a non-invasive technique for body composition analysis and semi-natural enclosures, we were characterized the heterothermic fitness landscape in a semi-natural population of hibernators.

Energy and time optimization during exit from torpor in vertebrate endotherms.

Torpor is used in small sized birds and mammals as an energy conservation trait. Considerable effort has been put towards elucidating the mechanisms underlying its entry and maintenance, but little attention has been paid regarding the exit. Firstly, we demonstrate that the arousal phase has a stereotyped dynamic: there is a sharp increase in metabolic rate followed by an increase in body temperature and, then, a damped oscillation in body temperature and metabolism. Moreover, the metabolic peak is around two-fold greater than the corresponding euthermic resting metabolic rate. We then hypothesized that either time or energy could be crucial variables to this event and constructed a model from a collection of first principles of physiology, control engineering and thermodynamics. From the model, we show that the stereotyped pattern of the arousal is a solution to save both time and energy. We extended the analysis to the scaling of the use of torpor by endotherms and show that variables related to the control system of body temperature emerge as relevant to the arousal dynamics. In this sense, the stereotyped dynamics of the arousal phase necessitates a certain profile of these variables which is not maintained as body size increases.

Body Composition and Energy Savings by Hibernation: Lessons from the South American Marsupial Dromiciops gliroides.

AbstractHibernation (i.e., seasonal or multiday torpor) has been described in mammals from five continents and represents an important adaptation for energy economy. However, direct quantifications of energy savings by hibernation are challenging because of the complexities of estimating energy expenditure in the field. Here, we applied quantitative magnetic resonance to determine body fat and body composition in hibernating Dromiciops gliroides (monito del monte). During an experimental period of 31 d in winter, fat was significantly reduced by 5.72±0.45 g, and lean mass was significantly reduced by 2.05±0.14 g. This fat and lean mass consumption is equivalent to a daily energy expenditure of hibernation (DEEH) of 8.89±0.6 kJ d-1, representing 13.4% of basal metabolic rate, with a proportional contribution of fat and lean mass consumption to DEEH of 81% and 18%, respectively. During the deep heterothermic bouts of monitos, body temperature remained 0.41°C ± 0.2°C above ambient temperature, typical of hibernators. Animals shut down metabolism and passively cool down to a critical defended temperature of 5.0°C ± 0.1°C, where they begin thermoregulation in torpor. Using temperature data loggers, we obtained an empirical estimation of minimum thermal conductance of 3.37±0.19 J g-1 h-1 °C-1, which is 107% of the expectation by allometric equations. With this, we parameterized body temperature/ambient temperature time series to calculate torpor parameters and metabolic rates in euthermia and torpor. Whereas the acute metabolic fall in each torpor episode is about 96%, the energy saved by hibernation is 88% (compared with the DEE of active animals), which coincides with values from the literature at similar body mass. Thus, estimating body composition provides a simple method to measure the energy saved by hibernation in mammals.

Why bears hibernate? Redefining the scaling energetics of hibernation.

Hibernation is a natural state of suspended animation that many mammals experience and has been interpreted as an adaptive strategy for saving energy. However, the actual amount of savings that hibernation represents, and particularly its dependence on body mass (the 'scaling') has not been calculated properly. Here, we estimated the scaling of daily energy expenditure of hibernation (DEEH), covering a range of five orders of magnitude in mass. We found that DEEH scales isometrically with mass, which means that a gram of hibernating bat has a similar metabolism to that of a gram of bear, 20 000 times larger. Given that metabolic rate of active animals scales allometrically, the point where these scaling curves intersect with DEEH represents the mass where energy savings by hibernation are zero. For BMR, these zero savings are attained for a relatively small bear (approx. 75 kg). Calculated on a per cell basis, the cellular metabolic power of hibernation was estimated to be 1.3 × 10-12 ± 2.6 × 10-13 W cell-1, which is lower than the minimum metabolism of isolated mammalian cells. This supports the idea of the existence of a minimum metabolism that permits cells to survive under a combination of cold and hypoxia.

Seasonal changes in steroid and thyroid hormone content in shed skins of the tegu lizard Salvator merianae.

Sampling blood for endocrine analysis from some species may not be practical or ethical. Quantification of hormones extracted from nontypical sample types, such as keratinized tissues, offers a less invasive alternative to the traditional collection and analysis of blood. Here, we aimed to validate assays by using parallelism and accuracy tests for quantification of testosterone, corticosterone, progesterone, and triiodothyronine (T3) in shed skins of tegu lizards. We assessed whether hormone content of sheds varied across one year similar to what was previously detected in plasma samples. In addition, we aimed to identify the phase relationship between hormone levels of shed skin and plasma levels obtained from the same animals. High frequency of shedding occurred during the active season for tegus (spring/summer), while shedding ceased during hibernation (winter). All hormones measured in shed skins exhibited seasonal changes in concentration. Levels of testosterone in shed skins of male tegus correlated positively with plasma testosterone levels, while corticosterone in both males and females exhibited an inverse relationship between sample types for the same month of collection. An inverse relationship was found when accounting for a lag time of 3 and 4 months between sheds and plasma testosterone. These results indicate that endocrine content of sheds may be confounded by factors (i.e., seasons, environmental temperature, thermoregulatory behavior, among others) that affect frequency of molting, skin blood perfusion, and therefore hormone transfer from the bloodstream and deposition in sheds of squamates.

Spatial distribution and sample size to estimate Lycosa erythrognatha (Araneae: Lycosidae) population density overwintering / Distribuição espacial e tamanho de amostra para estimar a densidade populacional de Lycosa erythrognatha (Araneae: Lycosidae) durante o inverno

Lycosa erythrognatha Lucas, 1833 (Araneae: Lycosidae) is a predatory arthropod with potential for conservation biological control. In addition to being considered a bioindicator of environmental quality, this arthropod provides an important service for agriculture by reducing insect-pest populations. In this work we seek to understand how the plants Andropogon bicornis L., Saccharum angustifolium Nees and Eustachys retusa Lag (Poales: Poaceae) and their different clump sizes affect the population density, spatial distribution and determination of the minimum number of samples to estimate its population density during the winter. Among the evaluated host plants, S. angustifolium and A. bicornis presented higher population density than E. retusa, but we observed that the clump diameter significantly influences the population density and the minimum number of samples. We observed a gregarious behavior in plants of A. bicornis and E. retusa. For S. angustifolium, a uniform distribution was observed.(AU)

Lycosa erythrognatha Lucas, 1833 (Araneae: Lycosidae) é um artrópode predador com potencial para controle biológico de conservação. Além de ser considerado um bioindicador da qualidade ambiental, esse artrópode fornece um importante serviço para a agricultura, reduzindo as populações de insetos-praga. Neste trabalho buscamos entender como as plantas Andropogon bicornis L., Saccharum angustifolium Nees e Eustachys retusa Lag (Poales: Poaceae) e seus diferentes tamanhos de touceira afetam a densidade populacional, distribuição espacial e a determinação do número mínimo de amostras para estimar sua densidade populacional durante o inverno. Entre as plantas hospedeiras avaliadas, S. angustifolium e A. bicornis apresentaram maior densidade populacional que E. retusa, observamos que o diâmetro da touceira influencia significativamente a densidade populacional e o número mínimo de amostras. Observamos um comportamento gregário nas plantas de A. bicornis e E. retusa. Para S. angustifolium, uma distribuição uniforme foi observada.(AU)

Spatial distribution and sample size to estimate Lycosa erythrognatha (Araneae: Lycosidae) population density overwintering / Distribuição espacial e tamanho de amostra para estimar a densidade populacional de Lycosa erythrognatha (Araneae: Lycosidae) durante o inverno

Abstract Lycosa erythrognatha Lucas, 1833 (Araneae: Lycosidae) is a predatory arthropod with potential for conservation biological control. In addition to being considered a bioindicator of environmental quality, this arthropod provides an important service for agriculture by reducing insect-pest populations. In this work we seek to understand how the plants Andropogon bicornis L., Saccharum angustifolium Nees and Eustachys retusa Lag (Poales: Poaceae) and their different clump sizes affect the population density, spatial distribution and determination of the minimum number of samples to estimate its population density during the winter. Among the evaluated host plants, S. angustifolium and A. bicornis presented higher population density than E. retusa, but we observed that the clump diameter significantly influences the population density and the minimum number of samples. We observed a gregarious behavior in plants of A. bicornis and E. retusa. For S. angustifolium, a uniform distribution was observed.

Resumo Lycosa erythrognatha Lucas, 1833 (Araneae: Lycosidae) é um artrópode predador com potencial para controle biológico de conservação. Além de ser considerado um bioindicador da qualidade ambiental, esse artrópode fornece um importante serviço para a agricultura, reduzindo as populações de insetos-praga. Neste trabalho buscamos entender como as plantas Andropogon bicornis L., Saccharum angustifolium Nees e Eustachys retusa Lag (Poales: Poaceae) e seus diferentes tamanhos de touceira afetam a densidade populacional, distribuição espacial e a determinação do número mínimo de amostras para estimar sua densidade populacional durante o inverno. Entre as plantas hospedeiras avaliadas, S. angustifolium e A. bicornis apresentaram maior densidade populacional que E. retusa, observamos que o diâmetro da touceira influencia significativamente a densidade populacional e o número mínimo de amostras. Observamos um comportamento gregário nas plantas de A. bicornis e E. retusa. Para S. angustifolium, uma distribuição uniforme foi observada.

Skeletal muscle histidine-containing dipeptide contents are increased in freshwater turtles (C. picta bellii) with cold-acclimation.

Freshwater turtles found in higher latitudes can experience extreme challenges to acid-base homeostasis while overwintering, due to a combination of cold temperatures along with the potential for environmental hypoxia. Histidine-containing dipeptides (HCDs; carnosine, anserine and balenine) may facilitate pH regulation in response to these challenges, through their role as pH buffers. We measured the HCD content of three tissues (liver, cardiac and skeletal muscle) from the anoxia-tolerant painted turtle (C. picta bellii) acclimated to either 3 or 20 °C. HCDs were detected in all tissues, with the highest content shown in the skeletal muscle. Turtles acclimated to 3 °C had more HCD in their skeletal muscle than those acclimated to 20 °C (carnosine = 20.8 ± 4.5 vs 12.5 ± 5.9 mmol·kg DM-1; ES = 1.59 (95%CI: 0.16-3.00), P = 0.013). The higher HCD content shown in the skeletal muscle of the cold-acclimated turtles suggests a role in acid-base regulation in response to physiological challenges associated with living in the cold, with the increase possibly related to the temperature sensitivity of carnosine's dissociation constant.

Heterothermy as the Norm, Homeothermy as the Exception: Variable Torpor Patterns in the South American Marsupial Monito del Monte (Dromiciops gliroides).

Hibernation (i.e., multiday torpor) is considered an adaptive strategy of mammals to face seasonal environmental challenges such as food, cold, and/or water shortage. It has been considered functionally different from daily torpor, a physiological strategy to cope with unpredictable environments. However, recent studies have shown large variability in patterns of hibernation and daily torpor ("heterothermic responses"), especially in species from tropical and subtropical regions. The arboreal marsupial "monito del monte" (Dromiciops gliroides) is the last living representative of the order Microbiotheria and is known to express both short torpor episodes and also multiday torpor depending on environmental conditions. However, only limited laboratory experiments have documented these patterns in D. gliroides. Here, we combined laboratory and field experiments to characterize the heterothermic responses in this marsupial at extreme temperatures. We used intraperitoneal data loggers and simultaneous measurement of ambient and body temperatures (T A and T B, respectively) for analyzing variations in the thermal differential, in active and torpid animals. We also explored how this differential was affected by environmental variables (T A, natural photoperiod changes, food availability, and body mass changes), using mixed-effects generalized linear models. Our results suggest that: (1) individuals express short bouts of torpor, independently of T A and even during the reproductive period; (2) seasonal torpor also occurs in D. gliroides, with a maximum bout duration of 5 days and a mean defended T B of 3.6 ± 0.9°C (one individual controlled T B at 0.09°C, at sub-freezing T A); (3) the best model explaining torpor occurrence (Akaike information criteria weight = 0.59) discarded all predictor variables except for photoperiod and a photoperiod by food interaction. Altogether, these results confirm that this marsupial expresses a dynamic form of torpor that progresses from short torpor to hibernation as daylength shortens. These data add to a growing body of evidence characterizing tropical and sub-tropical heterothermy as a form of opportunistic torpor, expressed as daily or seasonal torpor depending on environmental conditions.

Spatial distribution and sample size to estimate Lycosa erythrognatha (Araneae: Lycosidae) population density overwintering

Abstract Lycosa erythrognatha Lucas, 1833 (Araneae: Lycosidae) is a predatory arthropod with potential for conservation biological control. In addition to being considered a bioindicator of environmental quality, this arthropod provides an important service for agriculture by reducing insect-pest populations. In this work we seek to understand how the plants Andropogon bicornis L., Saccharum angustifolium Nees and Eustachys retusa Lag (Poales: Poaceae) and their different clump sizes affect the population density, spatial distribution and determination of the minimum number of samples to estimate its population density during the winter. Among the evaluated host plants, S. angustifolium and A. bicornis presented higher population density than E. retusa, but we observed that the clump diameter significantly influences the population density and the minimum number of samples. We observed a gregarious behavior in plants of A. bicornis and E. retusa. For S. angustifolium, a uniform distribution was observed.

Resumo Lycosa erythrognatha Lucas, 1833 (Araneae: Lycosidae) é um artrópode predador com potencial para controle biológico de conservação. Além de ser considerado um bioindicador da qualidade ambiental, esse artrópode fornece um importante serviço para a agricultura, reduzindo as populações de insetos-praga. Neste trabalho buscamos entender como as plantas Andropogon bicornis L., Saccharum angustifolium Nees e Eustachys retusa Lag (Poales: Poaceae) e seus diferentes tamanhos de touceira afetam a densidade populacional, distribuição espacial e a determinação do número mínimo de amostras para estimar sua densidade populacional durante o inverno. Entre as plantas hospedeiras avaliadas, S. angustifolium e A. bicornis apresentaram maior densidade populacional que E. retusa, observamos que o diâmetro da touceira influencia significativamente a densidade populacional e o número mínimo de amostras. Observamos um comportamento gregário nas plantas de A. bicornis e E. retusa. Para S. angustifolium, uma distribuição uniforme foi observada.

Loss of developmental diapause as prerequisite for social evolution in bees.

Diapause is a physiological arrest of development ahead of adverse environmental conditions and is a critical phase of the life cycle of many insects. In bees, diapause has been reported in species from all seven taxonomic families. However, they exhibit a variety of diapause strategies. These different strategies are of particular interest since shifts in the phase of the insect life cycle in which diapause occurs have been hypothesized to promote the evolution of sociality. Here we provide a comprehensive evaluation of this hypothesis with phylogenetic analysis and ancestral state reconstruction (ASR) of the ecological and evolutionary factors associated with diapause phase. We find that social lifestyle, latitude and voltinism are significant predictors of the life stage in which diapause occurs. ASR revealed that the most recent common ancestor of all bees likely exhibited developmental diapause and shifts to adult, reproductive, or no diapause have occurred in the ancestors of lineages in which social behaviour has evolved. These results provide fresh insight regarding the role of diapause as a prerequisite for the evolution of sociality in bees.

A functional transcriptomic analysis in the relict marsupial Dromiciops gliroides reveals adaptive regulation of protective functions during hibernation.

The small South American marsupial, Dromiciops gliroides, known as the missing link between the American and the Australian marsupials, is one of the few South American mammals known to hibernate. Expressing both daily torpor and seasonal hibernation, this species may provide crucial information about the mechanisms and the evolutionary origins of marsupial hibernation. Here, we compared torpid and active individuals, applying high-throughput sequencing technologies (RNA-seq) to profile gene expression in three D. gliroides tissues and determine whether hibernation induces tissue-specific differential gene expression. We found 566 transcripts that were significantly up-regulated during hibernation (369 in brain, 147 in liver and 50 in skeletal muscle) and 339 that were down-regulated (225 in brain, 79 in liver and 35 in muscle). The proteins encoded by these differentially expressed genes orchestrate multiple metabolic changes during hibernation, such as inhibition of angiogenesis, prevention of muscle disuse atrophy, fuel switch from carbohydrate to lipid metabolism, protection against reactive oxygen species and repair of damaged DNA. According to the global enrichment analysis, brain cells seem to differentially regulate a complex array of biological functions (e.g., cold sensitivity, circadian perception, stress response), whereas liver and muscle cells prioritize fuel switch and heat production for rewarming. Interestingly, transcripts of thioredoxin-interacting protein (TXNIP), a potent antioxidant, were significantly over-expressed during torpor in all three tissues. These results suggest that marsupial hibernation is a controlled process where selected metabolic pathways show adaptive modulation that can help to maintain homeostasis and enhance cytoprotection in the hypometabolic state.

Dispersal behavior of yellowjacket (Vespula germanica) queens.

Understanding the factors that affect animal dispersal behavior is important from both fundamental and applied perspectives. Dispersal can have clear evolutionary and ecological consequences, but for nonnative insect pests, dispersal capacity can also help to explain invasion success. Vespula germanica is a social wasp that, in the last century, has successfully invaded several regions of the world, showing one of the highest spread rates reported for a nonnative insect. In contrast with nonsocial wasps, in social species, queens are responsible for population redistribution and spread, as workers are sterile. For V. germanica, it has been observed that queen flight is limited to 2 distinct periods: early autumn, when new queens leave the nest to mate and find sheltered places in which to hibernate, and spring when new colonies are founded. Our aim was to study the flight behavior of V. germanica queens by focusing on the different periods in which dispersal occurs, characterizing as well the potential contribution of queen flight (i.e., distance) to the observed geographical spread. Our results suggest that the distances flown by nonoverwintered queens is greater than that flown by overwintered individuals, suggesting that the main queen dispersal events would occur before queens enter hibernation. This could relate to a behavioral trait of the queens to avoid the inbreeding with related drones. Additionally, given the short distances flown and remarkable geographical spread observed, we provide evidence showing that queen dispersal by flight is likely to contribute proportionately less to population spread than human-aided factors.

Isquemia miocárdica: conceptos básicos, diagnóstico e implicaciones clínicas. Tercera parte / Myocardial ischemia: basic concepts, diagnosis and clinical implications. Part three

Resumen El término «cardiopatía isquémica¼ se refiere a la disfunción del ventrículo izquierdo secundaria a infarto del miocardio, miocardio isquémico viable o enfermedad coronaria severa documentada por arteriografía coronaria, la cual tiene un pobre pronóstico, con una supervivencia del 45% a 5 años. El tratamiento de la cardiopatía isquémica involucra la estimación de la viabilidad en el miocardio afectado para determinar si la revascularización puede generar una remodelación positiva que mejore la función del ventrículo izquierdo. Existen cuatro modalidades básicas usadas en la práctica clínica para calcular la viabilidad miocárdica: tomografía de emisión simple de positrones, tomografía por emisión de positrones, ecocardiograma estrés y resonancia magnética cardiaca. Hoy en día hay estudios que demuestran que la terapia médica mejora la función del ventrículo izquierdo en la cardiopatía isquémica, independiente de la presencia o no de viabilidad o de la revascularización miocárdica; por tanto es posible que otros factores como la cantidad de remodelado, los volúmenes del ventrículo izquierdo, la insuficiencia mitral y la fracción de eyección puedan afectar también los desenlaces. Se requiere definir de manera clara los estadios del remodelado ventricular izquierdo en los cuales la presencia de viabilidad es benéfica y las etapas en las que el remodelado es reversible con la revascularización miocárdica. En cuanto a los métodos para determinar la viabilidad, la resonancia magnética parece dar más respuestas al respecto, ya que puede aportar información adicional relacionada con dimensiones del ventrículo izquierdo, fracción de eyección, fibrosis miocárdica y anormalidades valvulares.

Abstract The term myocardial ischemia refers to a left ventricular dysfunction secondary to a myocardial infarction, viable ischemic myocardium or sever coronary disease documented by means of a coronary angiography, which has a poor prognosis, with five-year survival rate of 45%. Management of myocardial ischemia involves estimating viability of the affected myocardium in order to determine whether revascularization can generate a positive remodelling that improves left ventricle functioning. Four different basic modalities are used in clinical practice to assess myocardial viability: single-photon emission computed tomography, positron emission tomography, stress echocardiogram and cardiac magnetic resonance. Nowadays there are studies that have shown medical therapy improves left ventricle function in ischemic heart disease, regardless of the presence or not of the viability or the myocardial revascularization; therefore, it is possible that other factors such as the amount of remodelling, the left ventricle volumes, mitral insufficiency and ejection fraction could also afffect the outcomes. A clear definition of the left ventricle remodelling states where the presence of viability is beneficial and the stages where the remodelling is reversible with myocardial revascularization is required. With regards to methods for assessing viability, magnetic resonance seems to provide more answers, as it can give additional information related to the dimensions of the left ventricle, ejection fraction, myocardial fibrosis and valvular abnormalities.

Leptin levels, seasonality and thermal acclimation in the Microbiotherid marsupial Dromiciops gliroides: Does photoperiod play a role?

Mammals of the Neotropics are characterized by a marked annual cycle of activity, which is accompanied by several physiological changes at the levels of the whole organism, organs and tissues. The physiological characterization of these cycles is important, as it gives insight on the mechanisms by which animals adjust adaptively to seasonality. Here we studied the seasonal changes in blood biochemical parameters in the relict South American marsupial Dromiciops gliroides ("monito del monte" or "little mountain monkey"), under semi-natural conditions. We manipulated thermal conditions in order to characterize the effects of temperature and season on a battery of biochemical parameters, body mass and adiposity. Our results indicate that monitos experience an annual cycle in body mass and adiposity (measured as leptin levels), reaching a maximum in winter and a minimum in summer. Blood biochemistry confirms that the nutritional condition of animals is reduced in summer instead of winter (as generally reported). This was coincident with a reduction of several biochemical parameters in summer, such as betahydroxybutyrate, cholesterol, total protein concentration and globulins. Monitos seem to initiate winter preparation during autumn and reach maximum body reserves in winter. Hibernation lasts until spring, at which time they use fat reserves and become reproductively active. Sexual maturation during summer would be the strongest energetic bottleneck, which explains the reductions in body mass and other parameters in this season. Overall, this study suggests that monitos anticipate the cold season by a complex interaction of photoperiodic and thermal cues.

Spatial distribution and sample size to estimate Lycosa erythrognatha (Araneae: Lycosidae) population density overwintering

Abstract Lycosa erythrognatha Lucas, 1833 (Araneae: Lycosidae) is a predatory arthropod with potential for conservation biological control. In addition to being considered a bioindicator of environmental quality, this arthropod provides an important service for agriculture by reducing insect-pest populations. In this work we seek to understand how the plants Andropogon bicornis L., Saccharum angustifolium Nees and Eustachys retusa Lag (Poales: Poaceae) and their different clump sizes affect the population density, spatial distribution and determination of the minimum number of samples to estimate its population density during the winter. Among the evaluated host plants, S. angustifolium and A. bicornis presented higher population density than E. retusa, but we observed that the clump diameter significantly influences the population density and the minimum number of samples. We observed a gregarious behavior in plants of A. bicornis and E. retusa. For S. angustifolium, a uniform distribution was observed.

Resumo Lycosa erythrognatha Lucas, 1833 (Araneae: Lycosidae) é um artrópode predador com potencial para controle biológico de conservação. Além de ser considerado um bioindicador da qualidade ambiental, esse artrópode fornece um importante serviço para a agricultura, reduzindo as populações de insetos-praga. Neste trabalho buscamos entender como as plantas Andropogon bicornis L., Saccharum angustifolium Nees e Eustachys retusa Lag (Poales: Poaceae) e seus diferentes tamanhos de touceira afetam a densidade populacional, distribuição espacial e a determinação do número mínimo de amostras para estimar sua densidade populacional durante o inverno. Entre as plantas hospedeiras avaliadas, S. angustifolium e A. bicornis apresentaram maior densidade populacional que E. retusa, observamos que o diâmetro da touceira influencia significativamente a densidade populacional e o número mínimo de amostras. Observamos um comportamento gregário nas plantas de A. bicornis e E. retusa. Para S. angustifolium, uma distribuição uniforme foi observada.

Isquemia miocárdica: conceptos básicos, diagnóstico e implicaciones clínicas. Segunda parte / Myocardial ischemia: basic concepts, diagnosis and clinical implications. Part two

Resumen La isquemia miocárdica puede ser irreversible o reversible dependiendo de diferentes factores moleculares y fisiológicos. En la isquemia miocárdica irreversible se presentan tres tipos de muerte celular a nivel miocárdico: la necrosis, la apoptosis y la autofagia; mientras en la isquemia reversible la restauración de la función de los miocitos está determinada por factores como el restablecimiento temprano del flujo sanguíneo coronario y fenómenos de pre y posacondicionamiento isquémico. Conceptos como el miocardio aturdido (disfunción mecánica temporal luego de una lesión isquémica pero con flujo sanguíneo normal en ausencia de cualquier lesión irreversible) y el miocardio hibernante (región miocárdica viable, sin contractilidad) son formas quiescentes de la función cardiaca y explican un poco la capacidad del miocardio de restablecer su funcionamiento normal luego de un episodio de isquemia.

Abstract Myocardial ischemia can be irreversible or reversible depending on multiple molecular and physiological factors. In irreversible myocardial ischemia there are three types of cell death on a myocardial level: necrosis, apoptosis and autophagy; whereas in reversible ischemia the restoration of the myocytes is determined by factors such as early recovery of coronary blood flow and pre- and postischemic conditioning phenomena. Concepts such as stunned myocardium (temporary mechanical dysfunction following an ischemic episode but with normal blood flow and without irreversible damage) and hibernating myocardium (viable myocardial region without contractility) are quiescent forms of the cardiac function and explain the ability of the myocardium to resume its normal functioning after an ischemic episode.

Isquemia miocárdica: conceptos básicos, diagnóstico e implicaciones clínicas. Primera parte / Myocardial ischaemia: basic concepts, diagnosis and clinical implications

Resumen La isquemia miocárdica es el conjunto de una serie de fenómenos fisiológicos que se manifiesta por condiciones clínicas como isquemia silente, angina estable y síndromes corona-rios agudos. Diversos mecanismos de la regulación del flujo sanguíneo, la demanda miocárdica, la liberación de adenosina y la función del endotelio en las arterias coronarias son claves para mantener la irrigación miocárdica y han sido la base fisiológica para el desarrollo de pruebas de detección de isquemia como lo es el flujo de reserva fraccional, que hoy día hace parte de las recomendaciones de las guías.

Abstract Myocardial ischaemia as a whole is a series of physiological phenomena manifested by clinical conditions such as silent ischaemia, stable angina and acute coronary syndromes. Various blood flow regulation mechanisms, myocardial demand, adenosine release and endot-helial function in the coronary arteries are vital for maintaining myocardial irrigation, and have been the physiological basis for tests like fractional flow reserve, developed to detect ischaemia, that today forms part of the guideline recommendations.