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In this review, we summarize the energetic and physiological correlates of prey handling and ingestion in lizards and snakes. There were marked differences in the magnitude of aerobic metabolism during prey handling and ingestion between these two groups, although they show a similar pattern of variation as a function of relative prey mass. For lizards, the magnitude of aerobic metabolism during prey handling and ingestion also varied as a function of morphological specializations for a particular habitat, prey type, and behavior. For snakes, interspecific differences in aerobic metabolism during prey handling seem to be correlated with adaptations for prey capture (venom injection vs. constriction). During ingestion by snakes, differences in aerobic metabolism might be due to differences in cranial morphology, although allometric effects might be a potentially confounded effect. Anaerobic metabolism is used for prey handling and ingestion, but its relative contribution to total ATP production seems to be more pronounced in snakes than in lizards. The energetic costs of prey handling and ingestion are trivial for both groups and cannot be used to predict patterns of prey-size selection. For lizards, it seems that morphological and ecological factors set the constraints on prey handling and ingestion. For snakes, besides these two factors, the capacity of the cardio-respiratory system may also be an important factor constraining the capacity for prey handling and ingestion.

Summary Aside from the pervasive effects of body mass, much controversy exists as to what factors account for interspecific variation in basal metabolic rates (BMR) of mammals; however, both diet and phylogeny have been strongly implicated. We examined variation in BMR within the New World bat family Phyllostomidae, which shows the largest diversity of food habits among mammalian families, including frugivorous, nectarivorous, insectivorous, carnivorous and blood-eating species. For 27 species, diet was taken from the literature and BMR was either measured on animals captured in Brazil or extracted from the literature. Conventional (nonphylogenetic) analysis of covariance (ANCOVA), with body mass as the covariate, was first used to test the effects of diet on BMR. In this analysis, which assumes that all species evolved simultaneously from a single ancestor (i.e., a “star” phylogeny), diet exerted a strong effect on mass-independent BMR: nectarivorous bats showed higher mass-independent BMR than other bats feeding on fruits, insects or blood. In phylogenetic ANCOVAs via Monte Carlo computer simulation, which assume that species are part of a branching hierarchical phylogeny, no statistically significant effect of diet on BMR was observed. Hence, results of the nonphylogenetic analysis were misleading because the critical values for testing the effect of diet were underestimated. However, in this sample of bats, diet is perfectly confounded with phylogeny, because the four dietary categories represent four separate subclades, which greatly reduces statistical power to detect a diet (= subclade) effect. But even if diet did appear to exert an influence on BMR in this sample of bats, it would not be logically possible to separate this effect from the possibility that the dietary categories differ for some other reason (i.e., another synapomorphy of one or more of the subclades). Examples such as this highlight the importance of considering phylogenetic relationships when designing new comparative studies, as well as when analyzing existing data sets. We also discuss some possible reasons why BMR may not coadapt with diet.

Marine Biological Laboratory University of Copenhagen, Strandpromenaden 5, DK-3000, Helsingor

Body temperatures and thermoregulatory behaviour of the teiid lizard Ameiva ameiva inhabiting the edge and the understory were studied in Central Amazonian forests. Despite of differences in the thermal profile of the habitats, the mean body temperature was the same for active lizards observed at the edge or inside the forest, where only slight peculiarities in thermoregulatory behaviour were observed. A. ameiva is capable of maintaining body temperature significantly above microhabitat temperature.

The scaling of oxygen uptake was measured along the ontogeny, in the neotropical pitviper Bothrops moojeni . Allometric relationship between oxygen uptake and body mass, quantified for juveniles, sub-adults and adults, showed the same mass coefficient and exponent. The uniformity of mass constants along ontogeny suggests that B. moojeni is energetically homomorphic. Variation in mass seem to be the sole determinant of oxygen uptake, and structural modifications have no effect on the metabolic rate. Applications of the homomorphism principle to assess variations in mass coefficient and exponent for intraspecific analysis of metabolism in reptiles are discussed. B. moojeni had an oxygen consumption in the range reported for viperids, but lower than that for colubrid snakes of similar size. Possible causative reasons for this pattern is discussed.

We studied how food abundance and consumption regulates torpor use and internal organ size in the Chilean mouse-opossum Thylamys elegans (Dielphidae), a small nocturnal marsupial, endemic in southern South America. We predicted that exposure to food rations at or above the minimum energy levels necessary for maintenance would not lead to any signs of torpor, while reducing food supply to energy levels below maintenance would lead to marked increases in frequency, duration and depth of torpor bouts. We also analyzed the relationship between food availability and internal organ mass. We predicted a positive relationship between food availability and internal organ size once the effect of body size is removed. Animals were randomly assigned to one of two groups and fed either 70, 100 or 130% of their daily energy requirement (DER). We found a positive and significant correlation between %DER and body temperature, and also between %DER and minimum body temperature. In contrast, for torpor frequency, duration and depth, we found a significant negative correlation with %DER. Finally, we found a significant positive correlation between the %DER and small intestine and ceacum dry mass. We demonstrate that when food availability is limited, T. elegans has the capacity to reduce their maintenance cost by two different mechanisms, that is, increasing the use of torpor and reducing organ mass.

Jararhagin is a metalloproteinase from Bothrops jararaca responsible for hemorrhage, inflammation, necrosis and edema. Effects of low doses of the toxin were analyzed on the energy metabolism of mice as well as its physiological implications. Measures of O2 consumption (VO2) were quantified after 4 and 24 h of the jararhagin administration during four weeks. Hematocrit and histology of the lungs were also analyzed after the end of the treatment. Results showed that animals that received subcutaneous doses of jararhagin had significant increase in VO2 from second (120 ng) and third weeks (60 ng) after 4 and 24 h, comparing to control, as well as in the number of erythrocytes after four weeks. Histology of the lungs showed interstitial edema within the alveolar septum. Results suggest that the jararhagin toxin caused an increase in VO2 and edema of intra-alveolar septum. The increase of the erythrocytes could be a physiological response to adjust the higher necessity of oxygen, due to diffusional abnormalities caused by the edema. Thus, low doses of jararhagin promote endothelial edema which lead to changes in several physiological conditions.

In this article, we review intraspecific studies of basal metabolic rate (BMR) that address the correlation between diet quality and BMR. The "food-habit hypothesis" stands as one of the most striking and often-mentioned interspecific patterns to emerge from studies of endothermic energetics. Our main emphasis is the explicit empirical comparison of predictions derived from interspecific studies with data gathered from within-species studies in order to explore the mechanisms and functional significance of the putative adaptive responses encapsulated by the food-habit hypothesis. We suggest that, in addition to concentrating on the relationship among diet quality, internal morphology, and BMR, new studies should also attempt to unravel alternative mechanisms that shape the interaction between diet and BMR, such as enzymatic plasticity, and the use of energy-saving mechanisms, such as torpor. Another avenue for future study is the measurement of the effects of diet quality on other components of the energy budget, such as maximum thermogenic and sustainable metabolic rates. It is possible that the effects of diet quality operate on such components rather than directly on BMR, which might then push or pull along changes in these traits. Results from intraspecific studies suggest that the factors responsible for the association between diet and BMR at an ecological timescale might not be the same as those that promoted the evolution of this correlation. Further analyses should consider how much of a role the proximate and ultimate processes have played in the evolution of BMR.

Made available in DSpace on 2013-08-28T14:09:23Z (GMT). No. of bitstreams: 1 WOS000260469400021.pdf: 175101 bytes, checksum: b45cf5b0e56cc91f5b1735363893830e (MD5) Made available in DSpace on 2013-09-30T18:50:15Z (GMT). No. of bitstreams: 2 WOS000260469400021.pdf: 175101 bytes, checksum: b45cf5b0e56cc91f5b1735363893830e (MD5) WOS000260469400021.pdf.txt: 52494 bytes, checksum: a66f2082bbf35077b651f7ab8d0c2489 (MD5) Previous issue date: 2008-01-09 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T14:00:15Z No. of bitstreams: 2 WOS000260469400021.pdf: 175101 bytes, checksum: b45cf5b0e56cc91f5b1735363893830e (MD5) WOS000260469400021.pdf.txt: 52494 bytes, checksum: a66f2082bbf35077b651f7ab8d0c2489 (MD5) Made available in DSpace on 2014-05-20T14:00:15Z (GMT). No. of bitstreams: 2 WOS000260469400021.pdf: 175101 bytes, checksum: b45cf5b0e56cc91f5b1735363893830e (MD5) WOS000260469400021.pdf.txt: 52494 bytes, checksum: a66f2082bbf35077b651f7ab8d0c2489 (MD5) Previous issue date: 2008-01-09 National Science Foundation (NSF) - USA Agencia Nacional de Promoción Científica y Tecnológica (ANPCYT) Universidad Nacional de San Luis (Argentina) Max McGraw Wildlife Foundation 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. Univ Nacl San Luis, CONICET, Fac Ciencias Humanas, Lab Biol Prof E Caviedes Codelia, San Luis, Argentina Univ Nacl San Luis, Dept Bioquim & Ciencias Biol, San Luis, Argentina Univ Wisconsin Madison, Dept Wildlife Ecol, Madison, WI USA Univ Nacl San Luis, Fac Ciencias Human, Area Psicobiol, San Luis, Argentina Univ Estadual Paulista, Inst Biocien, Dept Zool, São Paulo, Brazil Univ Estadual Paulista, Inst Biocien, Dept Zool, São Paulo, Brazil NSF: IBN-0216709 NSF(USA): IOS-0615678 UNSL (Argentina): 25561 Universidad Nacional de San Luis (Argentina): 22Q751

Departamento de Zoologia Institute de Biociencias Universidade Estadual Paulista, C. P. 199, CEP 33506-900, Rio Claro, SP