Browsing by Author "Naya, Daniel E."

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    A new species of Melanophryniscus (Anura, bufonidae) from Uruguay
    (2008) Maneyro, Raul; Naya, Daniel E.; Baldo, Diego
    A new species of bufonid toad of the genus Melanopryniscus from northern Uruguay is described. It is included in the M. moreirae group and its external morphology is similar to Melanopryniscus sanmartini. Melanopryniscus sp. nov. is distinguished by having a light brown dorsal colorationa with six darker longitudinal glandular ridges on the dorsal surface of the body and the gular region uniformly black.
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    Gut size variation among Bufo spinulosus populations along an altitudinal (and dietary) gradient
    (2009) Naya, Daniel E.; Veloso, Claudio; Bozinovic, Francisco
    To date, digestive flexibility has been studied in dozens of vertebrate species. However, practically all of these works has ignored the importance of intraspecific physiological variability across populations inhabiting different habitats. Here, we compare the digestive tract gross morphology of three populations of the Andean toad (Bufo spinulosus), inhabiting along an altitudinal gradient and feeding on different food items. Results support a core prediction of digestive theory, i.e., intestinal length increases in parallel with the content of indigestible material in the natural diet. The present study suggest how variation in the abiotic environment associated with altitude (e.g., temperature, water availability, soil quality) can change biotic conditions (e.g., vegetation cover, prey availability), affect feeding behavior of individuals (e.g., width and composition of trophic niche), and, ultimately, individuals' digestive features (e.g., gut morphology).
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    Physiological and life-history plasticity in a harvestman species: contrasting laboratory with field data
    (2017) Naya, Daniel E.; Lardies Carrasco, Marco Antonio; Bozinovic Kuscevic, Francisco
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    Physiological flexibility in the Andean lizard Liolaemus bellii: seasonal changes in energy acquisition, storage and expenditure
    (2008) Naya, Daniel E.; Veloso, Claudio; Bozinovic, Francisco
    According to the "barrel model", an organism may be represented by a container, with input energy constraints (foraging, digestion, and absorption) symbolized by funnels connected in tandem, and energy outputs (maintenance, growth, and reproduction) symbolized by a series of spouts arranged in parallel. Animals can respond to changes in environmental conditions, through adjustments in the size of the funnels, the fluid stored inside the barrel, or the output flow through the spouts. In the present study, we investigate the interplay among these processes through the analysis of seasonal changes in organ size and metabolic rate in a lizard species (Liolaemus bellii) that inhabits extremely seasonal environments in the Andes range. We found that digestive organ size showed the greatest values during spring and summer, that is, during the foraging seasons. Energy reserves were larger during summer and autumn, and then decreased through winter and spring, which was correlated with overwintering maintenance and reproductive costs. Standard metabolic rate was greater during the high-activity seasons (spring and summer), but this increase was only noticeable at higher environmental temperatures. The ability of many lizard species to reduce their maintenance cost during the cold months of the year, beyond what is expected from temperature decrease, is probably related to their success in coping with highly fluctuating environments. Here, we demonstrate that this ability is correlated with high physiological flexibility, which allows animals to adjust energy acquisition, storing and expenditure processes according to current environmental conditions.
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    Seasonal changes in digestive enzymes in five bird species
    (2018) Ramirez Otarola, Natalia; Naya, Daniel E.; Sabat, Pablo
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    Seasonal Flexibility in Organ Size in the Andean Lizard Liolaemus moradoensis
    (2010) Naya, Daniel E.; Veloso, Claudio; Sabat, Pablo; Bozinovic, Francisco
    The understanding of animal functioning in fluctuating environments is a major goal of physiological and evolutionary ecology. In temperate terrestrial habitats, one of the most pervasive changes in environmental conditions is that associated with the seasonal change along the year. In this study, we describe the pattern of seasonal variation in the size of nine internal organs in the lizard Liolaemus moradoensis from the Andes Mountains of Central Chile. We observed that the size of digestive organs was greater during summer in comparison to other seasons. Dry masses of liver and fat bodies reached maximum values during summer and minimum during spring. We suspect that lowest spring values are related with build-up costs of energetically expensive organs (e.g., digestive, muscle mass) at the end of the hibernation period. Dry mass of the heart and lungs did not show a clear pattern of variation, suggesting that cardiac and pulmonary performance were maintained throughout the year. The dry mass of kidneys was greater during winter than during summer, a result observed in other hibernating lizards but for which there is no clear explanation. Finally, the dry mass of testes showed a maximum value during autumn and a progressive reduction toward summer, indicating that reproduction occurs during autumn. When represented in a bivariate space, acquisition (digestive), distribution (heart, lungs and kidneys), storage (liver and fat bodies), and expenditure (testes) organs generate four clusters. In general terms, observed seasonal pattern of change in organ size is in agreement with those reported for other lizard species that inhabit highly fluctuating environments. J. Morphol. 271:1440-1445, 2010. (C) 2010 Wiley-Liss, Inc.
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    Seasonal Flexibility of Organ Mass and Intestinal Function for the Andean Lizard Liolaemus nigroviridis
    (2009) Naya, Daniel E.; Veloso, Claudio; Sabat, Pablo; Bozinovic, Francisco
    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 digestive enzymes (trehalase, maltase, and aminopeptidase-N) hydrolytic activities, dry masses of digestive organs and liver, and energy reserve (dry mass of fat bodies and tail energy density) were greater during summer than during winter months. By contrast, dry mass of the kidneys, lungs, heart, and gonads were greater during winter (though significance was reach only for the last two organs). In summary, obtained results reinforce the idea that hibernation is connected with phenotypic adjustments at different organizational levels, which in turn, potentially affects rates of energy acquisition and expenditure, organisms' fitness, and, ultimately, ecological and evolutionary success of species living in highly seasonal environments. We suggest that, owing to the pressing need to explain and predict the impact of climatic change on the biota, more studies destined to determine the levels and limits of physiological flexibility are necessary. J. Exp. Zool. 311A:270-277, 2009. (C) 2009 Wiley-Liss, Inc.
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    The effect of diet quality on physiological and life-history traits in the harvestman Pachylus paesslerik
    (PERGAMON-ELSEVIER SCIENCE LTD, 2007) Naya, Daniel E.; Lardies, Marco A.; Bozinovic, Francisco
    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 in harvestmen natural habitat. As proxy variables of the energy expenditure process, we quantified standard metabolic rate (maintenance), changes in body mass (somatic condition), and fecundity (reproduction). We found that animals consuming the protein-rich diet were able to increase both their body condition and fecundity. However, the increment in these two life-history traits was correlated with higher maintenance costs. In contrast, the carbohydrate-rich diet did not provide enough specific nutrients for reproductive events, although it may have allowed animals to survive for a long time. Thus, according to the quality of the diet available in the environment, harvestman females can adopt different life-history strategies correlated with phenotypic adjustments at anatomical and physiological levels. In the Mediterranean region, spatial and temporal changes in food quality are typical, so greater phenotypic flexibility is expected to cope with this kind of environmental variation. (c) 2006 Elsevier Ltd. All rights reserved.
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    The effect of short- and long-term fasting on digestive and metabolic flexibility in the Andean toad, Bufo spinulosus
    (2009) Naya, Daniel E.; Veloso, Claudio; Sabat, Pablo; Bozinovic, Francisco
    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 to evaluate changes of whole organism structure and physiology still are scarce, which is particularly true for amphibians that hibernate on land. Accordingly, in the Andean toad (Bufo spinulosus), we investigated the effect of short-term fasting and hibernation on the hydrolytic activity of digestive enzymes, histology of the small intestine, gross morphology of digestive and other internal organs and standard metabolic rate. Based on the pattern of size variation, internal organs may be grouped into those that were affected by both season and feeding condition (small intestine, stomach and liver), those that were only affected by season (fat bodies), those that were only affected by feeding condition (kidneys) and, finally, those that did not change between the three groups (large intestine, heart and lungs). Hydrolytic activity of maltase, trehalase and aminopeptidase-N followed the same pattern of variation (feeding>fasting>hibernating toads), although the change for the latter enzyme was less noticeable than for the disaccharidases. Enzymatic adjustments were correlated with changes in small intestine histology: villus and enterocyte height increased from hibernating to fasting and more markedly from fasting to feeding toads. Metabolic rate decreased during hibernation to 7.8% (at 5 degrees C) and 13.6% (at 15 degrees C) of summer values, which is one of the highest metabolic depressions reported for any ectothermic vertebrate. Our results suggest that amphibian persistence in highly seasonal environments is related to a large capacity of phenotypic flexibility at different organisational levels; an ability that may be related to the extensive ranges of temporal existence and geographic distribution of these vertebrates.
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    Thermal tolerances in rodents: species that evolved in cold climates exhibit a wider thermoneutral zone
    (2014) Bozinovic, Francisco; Ferri-Yanez, Francisco; Naya, Hugo; Araujo, Miguel B.; Naya, Daniel E.
    Background: Thermal constraints are often invoked to explain animal distributions. Maximum temperatures are less variable in different biomes around the globe than are minimum temperatures. Considerable information is available for mammals about basal metabolic rate and thermal conductance.