Browsing by Author "Novoa, FF"

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Does thermal history affect metabolic plasticity?
    (2001) Rezende, EL; Silva-Durán, I; Novoa, FF; Rosenmann, M
    (1) The aim of this study was to understand the effects of thermal history in metabolic features such as maximum (MMR) and basal (BMR) metabolic rates, as well as in metabolic plasticity, considered as the total variation of MMR and BMR during the acclimation period, (2) We studied three species of the genus Phyllotis, from different thermal environments, in an altitudinal gradient from sea level to 3800 m.a.s.l. Animals were acclimated to contrasting temperatures of 5 and 30 degreesC. To determine the metabolic flexibility, MMR was measured at intervals of 6 days during the acclimation period, while BMR values were obtained at the end of acclimations. Aerobic scope and the rates of change of MMR were estimated in all populations. (3) High- and low-altitude rodents did not show differences in BMR. However, both upper and lower limits of MMR, as well as aerobic scope, were significantly different between high- and low-altitude species, indicating similar ranges of metabolic plasticity. On the other hand, the rates of change of MMR were similar in all populations. (4) Our results indicate that thermal history has a profound effect on the individuals' thermogenic capacity, probably in both phylogenetic and ontogenetic levels. Low-altitude species could not increase MMR to the same levels as high-altitude species, while the later were unable to decrease MMR to achieve the values of the low-altitude species. (C) 2001 Elsevier Science Ltd. All rights reserved.
  • No Thumbnail Available
    Item
    Intraspecific differences in metabolic rate of Chroeomys olivaceus (Rodentia: Muridae)
    (2005) Novoa, FF; Rivera-Hutinel, A; Rosenmann, M; Sabat, P
    Studies of metabolic capacities in rodents have been largely Studied at an inter-specific levels, but physiological capacities of populations belonging to the same species have received lesser attention. Here we studied the maximum and basal metabolic rates Of two Populations of the rodent Chroeomys olivaceus dwelling in habitats with contrasting temperature and rainfall regimes, and to test if differences ill metabolic capacities are due to local adaptation or acclimatization effect. After four weeks of acclimation to 25 and 10 degrees C, the BMR arid MMR were determined in individuals from the northern population of Caleta Loa, and the southern population of La Picada. Individuals front 'La Picada' Population were heavier than those from Caleta Loa. MMR and BMR exhibited higher values in cold acclimated animals compared with warm-acclimated animals. Besides, BMR, but not MMR, was lower in Caleta Loa individuals, in spite of the acclimation treatment. Hence, the differences in the metabolic capacities and the response to acclimation of C. olivaceus populations appear to be an evolutionary response to the environmental cues.
  • No Thumbnail Available
    Item
    Modulating factors of the energetic effectiveness of huddling in small mammals
    (1998) Canals, M; Rosenmann, M; Novoa, FF; Bozinovic, F
    Huddling is effective in decreasing metabolic rate permitting energy saving. However, this decrease varies among different species depending on physical, physiological and behavioral characteristics of the huddled individuals. Following a general model we analyzed the effects of ambient temperature, thermal conductance and ontogeny on the huddling effectiveness (energy saving level from huddling behaviour) in white mice Mas musculus. Also, we studied the effects of thermal conductance by using the Sigmodontine Abrothrix andinus as a model organism. To put our results in a general context we analyzed literature data of huddling of several species of rodents at different temperatures. No effects of temperature and thermal conductance was detected. However, based on literature data, we found that at temperatures lower or near thermoneutrality the huddling effectiveness decrease. Also, the huddling effectiveness depends on the stage of development. Temperature probably affects the intensity of huddling, while changes in huddling effectiveness at early stages of development are likely consequences of structural (morphological) changes during the ontogeny. In this sense, it appears that the capacity to change the body form is and individual structural constraint which is extended to the huddling group.
  • No Thumbnail Available
    Item
    Passerines versus nonpasserines
    (2002) Rezende, EL; Swanson, DL; Novoa, FF; Bozinovic, F
    We analyzed and compared the scaling of both basal and maximal thermogenic metabolic rates in passerine and nonpasserine birds using conventional and phylogenetic methods. In spite of the presumed adaptive importance of both metabolic traits, few studies concerning both their relationships and their ecological and evolutionary constraints have been conducted. We found no statistical differences in the scaling of maximal metabolic rate between passerines and nonpasserines; hence, we suggest the use of a single allometric regression for this trait in birds. In addition, basal and maximal metabolic rates were indeed correlated after removing the effects of body mass and phylogeny. The apparent generality of this correlation within both birds and mammals reinforces the need for general ecological and physiological explanations for the evolution of endothermy.