Physiology, environmental change, and anuran conservation

This paper reviews diverse ways in which the emerging discipline of conservation physiology may contribute to the conservation of anuran amphibians. We first present a summary of the goals of conservation physiology. Then, we review five specific sources of environmental change that are known to affect anurans: introduced pathogens (highlighting the case of chytridiomycosis) and exotic species, pollutants, habitat fragmentation, and global climate change. We discuss these types of environmental change in the context of how and why altered environments may become stressing to anurans and cause population declines. We also discuss synergism among variables that may worsen the effect of environmental alterations, and emphasize the importance of conservation physiology for Brazilian anurans

Paracellular Absorption: A Bat Breaks the Mammal Paradigm

Bats tend to have less intestinal tissue than comparably sized nonflying mammals. The corresponding reduction in intestinal volume and hence mass of digesta carried is advantageous because the costs of flight increase with load carried and because take-off and maneuverability are diminished at heavier masses. Water soluble compounds, such as glucose and amino acids, are absorbed in the small intestine mainly via two pathways, the transporter-mediated transcellular and the passive, paracellular pathways. Using the microchiropteran bat Artibeus literatus (mean mass 80.6±3.7 g), we tested the predictions that absorption of water-soluble compounds that are not actively transported would be extensive as a compensatory mechanism for relatively less intestinal tissue, and would decline with increasing molecular mass in accord with sieve-like paracellular absorption. Using a standard pharmacokinetic technique, we fed, or injected intraperitonealy the metabolically inert carbohydrates L-rhamnose (molecular mass = 164 Da) and cellobiose (molecular mass = 342 Da) which are absorbed only by paracellular transport, and 3-O-methyl-D-glucose (3OMD-glucose) which is absorbed via both mediated (active) and paracellular transport. As predicted, the bioavailability of paracellular probes declined with increasing molecular mass (rhamnose, 90±11%; cellobiose, 10±3%, n = 8) and was significantly higher in bats than has been reported for laboratory rats and other mammals. In addition, absorption of 3OMD-glucose was high (96±11%). We estimated that the bats rely on passive, paracellular absorption for more than 70% of their total glucose absorption, much more than in non-flying mammals. Although possibly compensating for less intestinal tissue, a high intestinal permeability that permits passive absorption might be less selective than a carrier-mediated system for nutrient absorption and might permit toxins to be absorbed from plant and animal material in the intestinal lumen

Tight junctions: from simple barriers to multifunctional molecular gates

Epithelia and endothelia separate different tissue compartments and protect multicellular organisms from the outside world. This requires the formation of tight junctions, selective gates that control paracellular diffusion of ions and solutes. Tight junctions also form the border between the apical and basolateral plasma-membrane domains and are linked to the machinery that controls apicobasal polarization. Additionally, signalling networks that guide diverse cell behaviours and functions are connected to tight junctions, transmitting information to and from the cytoskeleton, nucleus and different cell adhesion complexes. Recent advances have broadened our understanding of the molecular architecture and cellular functions of tight junctions

Aspects of metabolic physiology and locomotor performance in anuran amphibians: implications of habitat fragmentation

Diversos aspectos metabólicos e comportamentais possuem uma estreita relação com as condições do ambiente, havendo um compromisso entre as condições naturais e a dinâmica de modificações sobre os organismos. Devido ao grande índice de degradação ambiental proveniente da atividade humana nos últimos tempos, populações de anfíbios têm sido particularmente mais afetadas devido a sua alta sensibilidade a alterações ambientais. Em uma paisagem fragmentada, a manutenção de metapopulações viáveis é um importante fator a persistência das populações. Dentro deste contexto, este estudo propõe investigar as relações entre a fragmentação florestal e habilidade das algumas espécies de anuros para se deslocar entre os fragmentos, ou entre estes e corpos d\'água. Assim, realizamos comparações, fisiológicas e comportamentais intra e interespecífica de espécies de anuros residentes em paisagens contínuas e fragmentadas em duas localidades da Floresta Atlântica, com base em suas características morfológicas. De acordo com nossos resultados, as diferenças ambientais entre as paisagens estão relacionadas com as diferenças morfofisiológicas entre as espécies.In the last few decades, human activity has changed environmental condition, resulting in amphibian populations decline all around the world. In this study we analyze the relationships between forest fragmentation and the ability of some frog species to move between forest fragments or between fragments and breeding sites. Our study focus relies on anuran locomotor performance and supporting physiology, and the relationship between these traits and resistance to forest fragmentation. We compare morphological, physiological and behavioral traits between populations of anurans species living in different landscapes (continuous or fragmented) of two sites in the Atlantic Forest. According to our data, differences in environmental conditions of landscape are related to morpho-physiological traits. This relationship, however, depends on the site of the Atlantic Forest and also varies between species

Resposta fenotípica integrada do morcego frugívoro Artibeus lituratus (Chiroptera, phyllostomidae) frente à redução da qualidade da dieta

Apesar das inúmeras vantagens da endotermia, os animais endotérmicos necessitam do constante aporte de energia. As variações na qualidade da dieta são tidas como um dos principais agentes seletivos envolvidos na evolução de padrões comportamentais, morfológicos e fisiológicos de endotérmicos. O presente trabalho procurou analisar os mecanismos ingestórios e digestórios utilizados por Artibeus lituratus quando deparado com a queda na qualidade da dieta, e seus efeitos sobre o metabolismo basal (TMB) e a capacidade termogênica (CT). Após 7, 30 e 90 dias de aclimatação a dietas artificiais com diferentes teores de fibras, foram quantificadas a eficiência digestória, a TMB, a CT, a condição corpórea e massa dos órgãos viscerais. A. lituratus sob dieta de baixa qualidade apresentaram maiores digestibilidade de matéria seca e energia, com um maior aporte de energia metabolizável ingerida. No entanto, nenhuma alteração foi observada nos órgãos viscerais, com exceção dos rins. A hipertrofia desse órgão pode ter sido conseqüência da maior ingestão de proteínas. A ausência de flexibilidade fenotípica na massa dos órgãos pode ser devida a uma combinação de fatores, incluindo o uso de ajustes comportamentais (produção de ejetas) e/ou a utilização de reservas energéticas. A TMB e a CT apresentaram-se maiores para os morcegos sob dieta de baixa qualidade. Como não houve alteração na massa dos órgãos em função da qualidade da dieta, e tampouco correlação entre massa dos órgãos e TMB, os mecanismos responsáveis pelo maior gasto energético basal de morcegos expostos à dieta de baixa qualidade são incertos, mas podem estar relacionados a uma maior atividade enzimática dos órgãos viscerais. A maior CT de morcegos expostos à dieta de baixa qualidade não pode ser explicada pelo modelo clássico da capacidade aeróbica. A CT foi influenciada...Although endothermy has innumerous advantages, endothermic animals need constant energy ingestion. Variations on diet composition are among the most important selective determinant factors of behavior, morphologic and physiologic aspects of evolution of endothermic animals. In spite of the numerous advantages of endothermy, such animals require constant energy income. This study aims to analyze ingestion and digestion mechanisms employed by Artibeus lituratus when facing a decrease in food quality, and the influence of this on its basal metabolism (BMR) and thermogenic capacity (TC). Past 7, 30 and 90 days of acclimation to diets containing different fiber concentrations, we quantified the digestive efficiency, BMR and TC of the bats, and also recorded their body condition and visceral organs masses. The species presented higher dry matter and energy digestibility, and also high metabolizable energy intake under low quality diet condition, but there were no observed morphological alterations on their internal organs, with the exception of their kidneys, which were unusually increased. This could have been due to higher protein ingestion. The lack of phenotypic variation in the visceral mass could have been caused by a myriad of factors, including behavioral adjustments (i.e. ejecta production), or utilization of energetic reserves. There was an increase of the BMR and TC of bats under low quality food conditions. As there were no alterations on the internal organs mass neither any detected correlation between this mass and the BMR of the bats, perhaps the greater energy expenses responsible mechanisms could be involved with a greater enzymatic activity of the internal organs. The observed greater TC of the bats fed on low quality food is not explainable through the classical aerobic capacity model. TC was influenced by fat mass, independently of diet quality and acclimation time. However... (Complete abstract click electronic access below)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Comparison of fractional absorption of nonactively transported, water soluble compounds by intact small mammals.

1<p>compound was cellobiose whereas other studies used lactulose.</p

Summary statistics on parameters for bi-exponential fit of plasma concentrations from injection/elimination experiments shown in Figure 1.

<p>The model was <i>C_t</i> = A e^−αt+B e^−βt.</p><p>Mean concentrations for each probe (based on measurements in 8 bats) were fit to the model.</p

Cumulative intestinal absorption of carbohydrates after oral administration.

<p>The cumulative absorption as a function of time since ingestion of 3-O-methyl-D-glucose (3OMD-glucose; unfilled circles, solid line), cellobiose (unfilled triangle, dashed line) and L-rhamnose (unfilled square, dotted line).</p