Fecal calcium levels of bird nestlings as a potential indicator of species-specific metal sensitivity.

Sensitivity of bird species to environmental metal pollution varies but there is currently no general framework to predict species-specific sensitivity. Such information would be valuable from a conservation point-of-view. Calcium (Ca) has antagonistic effects on metal toxicity and studies with some common model species show that low dietary and circulating calcium (Ca) levels indicate higher sensitivity to harmful effects of toxic metals. Here we measured fecal Ca and five other macroelement (potassium K, magnesium Mg, sodium Na, phosphorus P, sulphur S) concentrations as proxies for dietary levels in 66 bird species to better understand their interspecific variation and potential use as an indicator of metal sensitivity in a wider range of species (the main analyses include 39 species). We found marked interspecific differences in fecal Ca concentration, which correlated positively with Mg and negatively with Na, P and S levels. Lowest Ca concentrations were found in insectivorous species and especially aerial foragers, such as swifts (Apodidae) and swallows (Hirundinidae). Instead, ground foraging species like starlings (Sturnidae), sparrows (Passeridae), cranes (Gruidae) and larks (Alaudidae) showed relatively high fecal Ca levels. Independent of phylogeny, insectivorous diet and aerial foraging seem to indicate low Ca levels and potential sensitivity to toxic metals. Our results, together with information published on fecal Ca levels and toxic metal impacts, suggest that fecal Ca levels are a promising new tool to evaluate potential metal-sensitivity of birds, and we encourage gathering such information in other bird species. Information on the effects of metals on breeding parameters in a wider range of bird species would also help in ranking species by their sensitivity to metal pollution.

A review on exposure and effects of arsenic in passerine birds.

Arsenic (As) is a metalloid of high concern because of its toxic effects for plants and animals. However, it is hard to find information on this metalloid in passerines. This review presents a comprehensive overview of As exposure and effects in birds, and more particularly in passerines, as a result of an extensive search of the literature available. Internal tissues are the most frequently analyzed matrices for As determination in passerines (37.5% of the reviewed studies used internal tissues), followed by feathers and eggs (32.5% each), feces (27.5%), and finally blood (15%). A clear tendency is found in recent years to the use of non-destructive samples. Most studies on As concentrations in passerines have been done in great tit (Parus major; 50%), followed by pied flycatcher (Ficedula hypoleuca; 22.5%). Some factors such as diet and migratory status are crucial on the interspecific differences in As exposure. More studies are needed to elucidate if intraspecific factors like age or gender affect As concentrations in different tissues. The literature review shows that studies on As concentrations in passerines have been done mainly in the United States (30%), followed by Belgium (22.5%), and Finland (20%), making evident the scarce or even lack of information in some countries, so we recommend further research in order to overcome the data gap, particularly in the southern hemisphere. Studies on humans, laboratory animals and birds have found a wide range of effects on different organ systems when they are exposed to different forms of As. This review shows that few field studies on As exposure and effects in passerines have been done, and all of them are correlative so far. Arsenic manipulation experiments on passerines are recommended to explore the adverse effects of As in free-living populations at similar levels to those occurring in the environment. CAPSULE: This review summarizes the most interesting published studies on As exposure and effects in passerines.

A microplate adaptation of the thiobarbituric acid reactive substances assay to determine lipid peroxidation fluorometrically in small sample volumes / Una adaptación de microplacas del ensayo de sustancias reactivas del ácido tiobarbitúrico para determinar la peroxidación lipídica fluorométricamente en pequeños volúmenes de muestra

A simple, fast, reproducible and low-cost assay for thiobarbituric acid reactive substances (TBARS) has been adapted for use with a microplate spectrofluorometer. The technique allows rapid analysis of multiple samples and requires a very small sample volume (50 μl of red cell homogenates from passerine birds at protein concentrations of 3.4-8.9 mg/ml in this study), what is of special interest for biomonitoring studies working with small-sized animals from which a limited amount of sample can be obtained. The TBARS test involves the reaction of thiobarbituric acid (TBA) with malondialdehyde (MDA) under heating (90°C), leading to the formation of products that can be measured fluorometrically using black 384-well plates at excitation/emission wavelength of 532/553 nm. The concentrations of peroxidized lipids in samples were determined by extrapolation from a MDA standard curve. Two different excitation/emission combinations (532/553 and 530/550 nm) were used and both pairs were suitable for this technique. Intra- and inter-plate variability was < 20% and a good linearity of the standard curve was observed (R2 > 0.99). The research use of this microplate adaptation of the TBARS assay will provide further data and understanding of lipid peroxidation reducing the limitation of small sample volumen (AU)

El presente trabajo adapta un ensayo sencillo, rápido, reproducible y económico de sustancias reactivas al ácido tiobarbitúrico (TBARS) para su uso en espectrofluorómetro para microplacas. La técnica permite un análisis rápido de múltiples muestras y requiere un mínimo volumen de muestra (50 μl de un homogeneizado de eritrocitos de aves paseriformes a una concentración proteica de 3.4-8.9 mg/ml en este estudio), lo cual resulta de especial interés en estudios de biomonitorización que trabajan con animales de pequeño tamaño de los que se puede obtener una cantidad de muestra limitada. El ensayo TBARS consiste en la reacción del ácido tiobarbitúrico (TBA) con malondialdehído (MDA) en condiciones de calor (90°C), formando productos que pueden medirse fluorométricamente usando microplacas negras de 384 pocillos a 532/553 nm de excitación/emisión. La concentración de peróxidos lipídicos en la muestra se determinó por extrapolación de una curva de MDA. Se utilizaron dos combinaciones diferentes de excitación/emisión (532/553 and 530/550 nm) y ambas fueron apropiadas para la técnica. La variabilidad intra- e inter-placa fue <20% y se observó una buena linealidad de la curva estándar (R2 >0.99). El uso científico de la adaptación a microplaca del ensayo TBARS proporcionará más datos y comprensión sobre la peroxidación lipídica reduciendo la limitación que supone los pequeños volúmenes de muestra (AU)