Living with voracious roommates: Factors that explain isotopic niche variation in a mixed colony of insectivorous bats.

Theory predicts that in resource-limited environments, coexisting species may overlap their niche dimensions but must differ in at least one to avoid competitive exclusion. Specifically, it has been suggested that the coexistence of competing species within a guild, could be sustained with mechanisms of resource partitioning, such as segregation along a trophic dimension. Among the most gregarious mammals are bats, which present diversification in their diet based on habitat choice and body size. Despite differences that could explain specialization in prey selection, there are insufficient studies that explore food overlap in mixed bat colonies and the factors that determine the selection of prey, both at intra- and inter-specific levels. To fill this gap, we analyzed the isotope signal (δ13C and δ15N) in feces collected in a mixed colony of Tadarida brasiliensis and Myotis chiloensis. To understand how several factors could influence these isotopic signals, intrinsic explanatory variables were analyzed, including body mass, body length, age, and sex. Also, extrinsic variables were analyzed, including monthly temporality and moonlight intensity. Our findings support age-dependent specialization in M. chiloensis, with a significant role of moonlight intensity and sex on δ15N. In T. brasiliensis, we identified a significant effect of size, sex, and ear length on δ15N. Our analysis indicates that both species of bats experience diverse degrees of overlap through austral summer months, affected by several factors that explain the variability in their fecal isotopic signals.

The effects of urban thermal heterogeneity and feather coloration on oxidative stress and metabolism of pigeons (Columba livia).

Urbanization stands out as a significant anthropogenic factor, exerting selective pressures on ecosystems and biotic components. A notable outcome of urbanization is thermal heterogeneity where the emergence of Urban Heat Islands is characterized by elevated air and surface temperatures compared to adjacent rural areas. Investigating the influence of thermal heterogeneity on urban animals could offer insights into how temperature variations can lead to phenotypic shifts. Urban pigeons (Columba livia) serve as an excellent model for studying urban thermal effects, given the melanism variations, which are associated with the pleiotropy of the melanocortin system. To examine the development of physiological plasticity in response to urban thermal variations, we conducted a study on pigeons in Santiago, Chile, during the rainy season. We assessed the influence of habitat on physiological traits related to metabolism and antioxidant capacities, which are theoretically affected by feather coloration. Our findings reveal that variations in melanism significantly impact pigeon physiology, affecting both antioxidant capacities and the mitochondrial activity of red blood cells. It was found that higher urban temperatures, from both the current sampling month and the prior sampling month (from CRU TS dataset), were negatively and strongly associated with lower antioxidant and metabolic activities. This suggests that elevated urban temperatures likely benefit the energetic budgets of pigeon populations and mitigate the negative effects of oxidative metabolism, with differential effects depending on feather colorations.

Primer Consenso Chileno de Grupo de Estudio de Tuberculosis Ocular / First Chilean Consensus Document of the Ocular Tuberculosis Study Group

INTRODUCCIÓN: El tratamiento de la tuberculosis (TB) ocular es un tema que genera controversia en el mundo. Para el correcto manejo de estos pacientes, es necesario el desarrollo de guías que consideren la epidemiología de la TB ocular en cada nación. El objetivo de este consenso fue discutir de forma interdisciplinaria la epidemiología, fisiopatología, clínica, diagnóstico, estudio y tratamiento de los pacientes con TB ocular, para establecer un algoritmo de tratamiento y proponer qué pacientes deben ser tratados en Chile y con qué tratamiento. Además, se establecieron acuerdos para efectuar quimioprofilaxis de los pacientes con TB latente que tienen indicación de tratamiento inmunosupresor por enfermedades inflamatorias oculares.

The treatment of ocular tuberculosis (TB) remains controversial worldwide. The development of guidelines for ocular TB can facilitate the approach and management of these patients. These guidelines should be developed regionally, considering the local TB epidemiology. The objectives of this consensus are: to initiate an interdisciplinary discussion about the epidemiology, pathophysiology, clinical presentation, diagnosis, workup and treatment of patients with ocular TB, to establish a treatment algorithm and define which patients should be treated in Chile and how and, to analyze and discuss the published data regarding chemoprophylaxis for patients with latent TB who need to start immunosuppressive treatment due to inflammatory ocular conditions.

Are levels of digestive enzyme activity related to the natural diet in passerine birds?

Digestive capabilities, such as the rates nutrient hydrolysis and absorption, may affect energy intake and ultimately feeding behavior. In birds, a high diversity in gut biochemical capabilities seems to support the existence of a correlation between the morphology and physiology of the intestinal tract and chemical features of the natural diet. However, studies correlating the activity of digestive enzymes and the feeding habits at an evolutionary scale are scarce. We investigated the effect of dietary habits on the digestive physiological characteristics of eight species of passerine birds from Central Chile. The Order Passeriformes is a speciose group with a broad dietary spectrum that includes omnivorous, granivorous and insectivorous species. We measured the activity of three enzymes: maltase, sucrase and aminopeptidase-N. Using an autocorrelation analysis to remove the phylogenetic effect, we found that dietary habits had no effect on enzymatic activity. However, we found that granivorous and omnivorous species had higher levels of disaccharidase activities and insectivores had the lowest. The major difference in enzymatic activity found at the inter-specific level, compared to the reported lower magnitude of enzyme modulation owing to dietary acclimation, suggests that these differences to some extent have a genetic basis. However, the lack of a clear association between diet categories and gut physiology suggested us that dietary categorizations do not always reflect the chemical composition of the ingested food.

Symmorphosis in the proximal pathway for oxygen in the leaf-eared mouse Phyllotis darwini

In this report, we explore the matching of structures to functional needs by comparing previously reported data of maximal oxygen consumption and the development of the lung in the leaf-eared mouse Phyllotis darwini in warm and cold environments. We discuss whether the state of structural design is commensurate with functional needs from regulated morphogenesis as predicted by the hypothesis of symmorphosis. We found a close match between respiratory structures and functional needs during postnatal development, expressed as safety factors close to unity. However, in the adult stage the safety factors were greater than two, which suggests that adult animals acquired a structure greater than that required considering their maximum capacities. A high safety factor in the respiratory system of adult mice may be a consequence of the symmorphosis that operates during ontogeny and does not necessarily support a rejection of this hypothesis.

Interplay between the morphometry of the lungs and the mode of locomotion in birds and mammals

We studied the lung diffusion parameters of two species of birds and two species of mammals to explore how structural and functional features may be paralleled by differences in life style or phylogenetic origin. We used two fast-flying species (one mammal and one bird), one running mammal and one bird species that flies only occasionally as models. The harmonic mean thickness of the air-blood barrier was very thin in the species we studied. An exception was the Chilean tinamou Notoprocta perdicaria, which only flies occasionally. It showed an air-blood barrier as thick as that of flightless Galliformes. We found that the respiratory surface density was significantly greater in flying species compared to running species. The estimated values for the oxygen diffusion capacity, DtO2 follow the same pattern: the highest values were obtained in the flying species, the bat and the eared dove. The lowest value was in N. perdicaria. Our findings suggest that the studied species show refinements in their morphometric lung parameters commensurate to their energetic requirements as dictated by their mode of locomotion, rather than their phylogenetic origin. The air-blood barrier appears to be thin in most birds and small mammals, except those with low energetic requirements such as the Chilean tinamou. In the species we studied, the respiratory surface density appears to be the factor most responsive to the energetic requirements of flight

Determinación de grosor de primer y segundo Flap, mediante paquimetría intraoperatoria / Determination of thickness of the first and second flap using intraoperative pachymetry

Objetivo: Determinar grosor del 1er y 2º flap, y sus factores predictivos, para el microquerátomo Hansatome en LASIK. Método: En 130 ojos operados (32 ojos con procedimiento bilateral) se registra AV pre y postoperatoria, queratometría paquimetría pre y postoperatoria y determina el grosor del flap para cada ojo. En los casos bilaterales se compara el grosor del primer flap con el segundo. Se correlacionan los factores preoperatorios con el grosor del primer flap. Resultados: El grosor promedio del primer flap fue 131µm (61-180; DS 25,9) y para los bilaterales el grosor del segundo flap fue 109 µm (49-164; DS 26,82) (p< 0,05). El flap fue menor a 160 µm sobre el 90 por ciento de los casos. El grosor se correlacionó mejor con la paquimetría preoperatoria (r = 0,36). Conclusiones: El microquerátomo HansatomeTM obtiene flaps más delgados a lo esperado, y menores aún con el 2º corte y en córneas más delgadas.

Pielonefritis aguda complicada durante el embarazo / Complicated acute pyelonephritis during pregnancy

Se presentan dos casos de pielonefritis aguda complicada. El primero de ellos evolucionó con un Síndrome de Distress respiratorio del adulto; el segundo inicialmente simuló un cuadro de abdomen agudo, evolucionando también con algún grado de compromiso respiratorio.

In this oportunity we analize two cases of acute pyelonephritis during pregnancy that happened in the Hospital Barros Luco, the first case got complicated with an adult respiratory distress syndrome, the second case inicially was diagnosed as an acute abdomen, and throughout its evolution got complicated as well with a respiratory compromise.