Basal metabolic rate (BMR), the sum of maintenance energy costs, represents a major component of the energy budgets of ectothermic vertebrates and varies between individuals within a species. Individual ectotherms are generally assumed to have a constant BMR at any given temperature. A strategy of flexibility in BMR might have evolved to cope with differing environmental conditions. Within-individual variation in BMR was examined in two fishes, juvenile Atlantic salmon Salmo salar and juvenile northern pike Esox lucius, whilst the effects of exercise and ration on BMR, maximum metabolic rate (MMR), enzyme levels and body composition were studied in detail for pike. In the first part of the study, measurements of BMR were made for first-summer Atlantic salmon parr at rest by respirometry. In 1996, initial measurements of BMR were made for 25 fish held in a stock tank. Fish were then allocated in small groups to channels to represent a change in environment and BMR re-measured after a period of several weeks. The procedure was repeated for 30 fish in the summer of 1997, when fish were given a reduced food ration. Variation in BMR in each experiment was analysed for individual fish, and for all fish using a linear mixed model. There were statistically significant differences in BMR values between the two times, the within-individual, between-time variation representing approximately ± 21% of BMR in 1996 and ± 28% of BMR in 1997. Reduced-rafion fish (1997) displayed a significant decrease in the mean elevation of the allometric scaling relationship between body mass and BMR between time periods. To further explore possible mechanisms for flexibility in BMR and relationships with MMR, juvenile pike were used. Initial measurements of BMR and MMR (following exhaustive exercise) were made and factorial metabolic scope calculated (MMR/BMR). Fish were then split into a high ration no-exercise group (n = 10), low ration no-exercise group (n = 10) and sustained exercise group (n = 13). Initial measurements were termed time 1, with subsequent measurements made after approximately 3 weeks (time 2) and 11 weeks (time 3). Exercised fish had a significantly larger MMR and scope following 3 weeks of sustained swimming. For all fish there were significant correlations between BMR and MMR at times 1 and 3 but not at time 2.After the oxygen measurements made at time 3 all fish were humanely killed. Maximal enzyme assays were performed on six tissues for each remaining fish (n = 30). Levels of each of two enzymes (citrate synthase, CS, and lactate dehydrogenase, LDH, measured in the direction of lactate oxidation) were found to be similar between treatment groups for respective tissues. Total CS activity levels and LDH levels were highest in the heart and red muscle. In general there was little difference in the relative organ masses of fish exposed to different treatments. It is concluded that in these two fish species with very different life styles, between- and within- individual variation in BMR (salmon & pike) and MMR (pike only) is apparent and that differences in ration and exercise influence individual physiology.

Ectotherms such as frogs must either function within environments with temperatures amenable to their physiological needs, or find means to reduce the impact of temperature on their activities. Recent studies on reptile and amphibian feeding have shown convergent use of elastic recoil to drive feeding movements, thereby decoupling temperature's effects on muscle from movement and allowing the animals to feed over broader temperature ranges. Rana pipiens specimens (n=5) were exposed to three ambient temperatures (10°, 15°, and 25° C) at which feeding behavior was imaged at 6000 Hz. The image sequences yielded detailed kinematic and dynamic information for jaw, tongue, and body movements, including velocity, acceleration, power, duration, and excursion. Previously published studies have examined feeding in ranid frogs; however, those studies employed slower frame rates that did not permit analysis of instantaneous accelerations and velocities, and depressor and jaw-tongue complex mass specific power outputs in Rana feeding have not yet been established. Specimens were dissected for morphological measurement and calculation of mass-specific dynamics relative to the m. depressor mandibulae and the center of mass of the jaw-tongue complex. Previous studies on tongue projection in Bufo terrestris have shown that the rapid jaw depression that inertially elongates the tongue relies on elasticity in the depressor muscles. Further, because this movement is elastically driven, it is less sensitive to temperature than a completely muscle-driven movement would be. Because Rana also feeds through inertial elongation of the tongue (as does Bufo, in which the mechanism is convergent), I hypothesized that Rana would demonstrate thermal insensitivity in its feeding kinematics and dynamics in a pattern similar to that documented in Bufo. Experimental results indicated that portions of the feeding cycle related to the initial, ballistic phase were at least moderately thermally insensitive. At all temperatures studied, Rana reached approximately half of the depressor mass-specific power of Bufo, demonstrating that Bufo's depressor mass-specific power output is not the minimum value necessary for inertial elongation. I further hypothesize that thermal independence and power output in excess of that achievable by muscle alone during the initial, ballistic mouth opening phase of feeding suggests the involvement of an elastic mechanism convergent with that of Bufo terrestris.

Understanding how climatic variation affects animal populations and communities is essential for addressing threats posed by climate change, especially in systems where impacts are projected to be high. We evaluated abundance dynamics of five common species of diurnal lizards over 25 years in a Sonoran Desert transition zone where precipitation decreased and temperature increased across time, and assessed hypotheses for the influence of climatic flux on spatiotemporal variation in abundances. We repeatedly surveyed lizards in spring and summer of each year at up to 32 sites, and used hierarchical mixture models to estimate detection probabilities, abundances, and population growth rates. Among terrestrial species, abundances of a short-lived, winter-spring breeder increased markedly by an estimated 2375285% across time, while two larger spring-summer breeders with higher thermal preferences declined by up to 64%. Abundances of two arboreal species that occupy shaded and thus sheltered microhabitats fluctuated but did not decline systematically. Abundances of all species increased with precipitation at short lag times (151.5 yrs) likely due to enhanced food availability, but often declined after periods of high precipitation at longer lag times (254 yrs) likely due to predation and other biotic pressures. Although rising maximum daily temperatures (Tmax) are expected to drive global declines of lizards, associations with Tmax were variable and weak for most species. Instead, abundances of all species declined with rising daily minimum temperatures, suggesting degradation of cool refugia imposed widespread metabolic or other costs. Our results suggest climate warming and drying are having major impacts on lizard communities by driving declines of species with traits that augment exposure to abiotic extremes and by modifying species interactions. The complexity of patterns we report indicate that evaluating and responding to the influence of climate change on biodiversity must consider a broad array of ecological processes.

Made available in DSpace on 2014-06-11T19:22:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-07-01Bitstream added on 2014-06-13T18:08:52Z : No. of bitstreams: 1 bovo_rp_me_sjrp.pdf: 510815 bytes, checksum: bcd7a1e15ce55c75992debce1daffe04 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Dada a importância da temperatura na maior parte dos processos biológicos, estudos sobre a termorregulação têm desempenhado importante papel no entendimento sobre a ecologia dos vertebrados ectotérmicos. Em serpentes, como em outros ectotérmicos, o controle da temperatura corpórea (Tc) é dependente da utilização de fontes externas de calor e principalmente de ajustes comportamentais, embora ajustes fisiológicos e morfológicos também ocorram. Em geral, esse controle é alcançado por meio da escolha de ambientes quentes ou frios, cuja disponibilidade pode variar ao longo do dia e das estações do ano. A termorregulação, portanto, constitui aspecto central da biologia das serpentes, as quais dedicam porção considerável de seu tempo e energia a essa atividade. Os objetivos do presente estudo foram documentar a variação sazonal e circadiana da temperatura corpórea da jararaca-ilhoa, Bothrops insularis, em seu ambiente natural, a Ilha da Queimada Grande (IQG), a fim de prover análise descritiva da Tc e do comportamento termorregulatório destes animais à luz dos custos e benefícios da regulação da Tc na região tropical; e entender como estes parâmetros são ditados/influenciados por fatores ambientais (temperatura local e de microhábitats, umidade relativa, precipitação, radiação solar, vento, características do substrato) e bióticos (tamanho dos indivíduos, sexo, estágio reprodutivo, estado digestivo). (1) As jararacas-ilhoa são usualmente termoconformadoras, embora consigam atingir a temperatura corpórea preferida em todas as estações do ano; (2) as temperaturas ambientais indicam que a IQG é um ambiente termicamente favorável para essas serpentes; (3) a Tc destes animais sofre forte influência da variação sazonal e circadiana da temperatura ambientel... / Given the pervasive effects of temperature on most biological processes, studies focusing on thermoregulation are pivotal to the understanding of ectotherm’s vertebrate ecology. In snakes, like other ectotherms, body temperature (Tb) control is dependent of external heat sources and based mainly on behavioral adjustments, although physiological and/or morphological adjustments can also occur. In general, such control is achieved through the choice of warm or cold environments, whose availability may vary along the days and/or seasons. Thus, thermoregulation can be regarded as a central aspect of snake biology, and these animals invest considerable time and energy into this activity. The aims of the present study were to document the seasonal and circadian variation in the Tb’s of the golden lancehead, Bothrops insularis, in its natural habitat, the Queimada Grande Island (QGI). We then used such database to provide a descriptive analysis of Tb variation and thermoregulatory behavior for this species in the light of the costs-benefits theory applied to a tropical region. Our second goal was to understand how body temperature is dictated/influenced by environmental (local and microhabitat temperatures, relative humidity, precipitation, solar radiation, wind, substrate characteristics) and biotic factors (individual size, sex, reproductive stage, digestive state). The main findings of the present study were: (1) Golden lanceheads can be regarded as being thermoconformers, although they do reach their preferred body temperature in all seasons; (2) environmental temperatures indicate that QGI has a high thermal quality, i.e., it is thermically suitable for the snakes; (3) Tb is strongly influenced by seasonal and diel variation of the environmental temperature; (4) B. insularis selected... (Complete abstract click electronic access below)

In this dissertation, I explored the effects of developmental hypoxia on heart contractility in three separate species of ectotherms: the common snapping turtle (Chelydra serpentina), the American alligator (Alligator mississippiensis), and the zebrafish (Danio rerio). I began with the common snapping turtle and tested whether the utilization of the sarcoplasmic reticulum was altered in response to developmental hypoxia. In the next two chapters, developmental hypoxia of the American alligator was explored studying how the cardiac tissue was affected, specifically in physiological stressors, sarcoplasmic reticulum utilization and sensitivity to pharmacological increases in contractility. The last chapter explored how zebrafish heart contractility was altered in response to chronic hypoxia from egg to adult. Findings from these chapters suggest that while developmental hypoxia did alter cardiac contractility, it did not alter the response of the heart to physiological stressors such as increased heart rate or under hypoxia. Overall, these findings contribute to increasing the current understanding of how developmental hypoxia alters the cardiovascular system but with an emphasis on the cardiac tissue level.

Resumo: Dada a importância da temperatura na maior parte dos processos biológicos, estudos sobre a termorregulação têm desempenhado importante papel no entendimento sobre a ecologia dos vertebrados ectotérmicos. Em serpentes, como em outros ectotérmicos, o controle da temperatura corpórea (Tc) é dependente da utilização de fontes externas de calor e principalmente de ajustes comportamentais, embora ajustes fisiológicos e morfológicos também ocorram. Em geral, esse controle é alcançado por meio da escolha de ambientes quentes ou frios, cuja disponibilidade pode variar ao longo do dia e das estações do ano. A termorregulação, portanto, constitui aspecto central da biologia das serpentes, as quais dedicam porção considerável de seu tempo e energia a essa atividade. Os objetivos do presente estudo foram documentar a variação sazonal e circadiana da temperatura corpórea da jararaca-ilhoa, Bothrops insularis, em seu ambiente natural, a Ilha da Queimada Grande (IQG), a fim de prover análise descritiva da Tc e do comportamento termorregulatório destes animais à luz dos custos e benefícios da regulação da Tc na região tropical; e entender como estes parâmetros são ditados/influenciados por fatores ambientais (temperatura local e de microhábitats, umidade relativa, precipitação, radiação solar, vento, características do substrato) e bióticos (tamanho dos indivíduos, sexo, estágio reprodutivo, estado digestivo). (1) As jararacas-ilhoa são usualmente termoconformadoras, embora consigam atingir a temperatura corpórea preferida em todas as estações do ano; (2) as temperaturas ambientais indicam que a IQG é um ambiente termicamente favorável para essas serpentes; (3) a Tc destes animais sofre forte influência da variação sazonal e circadiana da temperatura ambientel... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Given the pervasive effects of temperature on most biological processes, studies focusing on thermoregulation are pivotal to the understanding of ectotherm's vertebrate ecology. In snakes, like other ectotherms, body temperature (Tb) control is dependent of external heat sources and based mainly on behavioral adjustments, although physiological and/or morphological adjustments can also occur. In general, such control is achieved through the choice of warm or cold environments, whose availability may vary along the days and/or seasons. Thus, thermoregulation can be regarded as a central aspect of snake biology, and these animals invest considerable time and energy into this activity. The aims of the present study were to document the seasonal and circadian variation in the Tb's of the golden lancehead, Bothrops insularis, in its natural habitat, the Queimada Grande Island (QGI). We then used such database to provide a descriptive analysis of Tb variation and thermoregulatory behavior for this species in the light of the costs-benefits theory applied to a tropical region. Our second goal was to understand how body temperature is dictated/influenced by environmental (local and microhabitat temperatures, relative humidity, precipitation, solar radiation, wind, substrate characteristics) and biotic factors (individual size, sex, reproductive stage, digestive state). The main findings of the present study were: (1) Golden lanceheads can be regarded as being thermoconformers, although they do reach their preferred body temperature in all seasons; (2) environmental temperatures indicate that QGI has a high thermal quality, i.e., it is thermically suitable for the snakes; (3) Tb is strongly influenced by seasonal and diel variation of the environmental temperature; (4) B. insularis selected... (Complete abstract click electronic access below) / Orientador: Otavio Augusto Vuolo Marques / Coorientador: Denis Otávio Vieira de Andrade / Banca: Ricardo Jannini Sawaya / Banca: Carlos Arturo Navas / Mestre

Les changements climatiques ont un impact sur quasiment toutes formes de vie. Des augmentations des moyennes de température ainsi que desfluctuations peuvent causer un stress, particulièrement chez les ectothermes aquatiques sessiles tels que les moules d’eau douce. Cependant, certaines espèces semblent mieux faire face à ces températures stressantes que d’autres. La tolérance au stress thermique peut par exemple expliquer le succès de certaines espèces envahissantes. Il est connu que les mitochondries peuvent jouer un rôle clé dans l’établissement de la thermo-tolérance des ectothermes. Dans cette étude, nous avons visé à caractériser la thermo-tolérance mitochondriale chez des moules d’eau douce endémiques et invasives. À travers l’utilisation de la respirométrie à haute résolution, nous avons analysé la respiration mitochondriale de deux espèces de moules d’eau douce exposées à plusieurs températures différentes. Nous avons remarqué que la moule invasive Dreissena bugensis possédait un métabolisme mitochondrial moins thermo-tolérant que la moule endémique Elliptio complanata. Cette lacune au niveau de la tolérance a été liée à une dépression métabolique aérobique plus marquée à des températures élevées. Ces résultats pourraient potentiellement être associées avec les traits de caractéristiques de vie de ces espèces, car D. bugensis est plus adaptée à des environnements instables dans lesquels les pressions de sélection pour des adaptations de résistance sont réduites. Nos résultats s’ajoutent à la littérature grandissante qui caractérise le métabolisme mitochondrial de plusieurs espèces aquatiques face aux changements climatiques / Climate change is impacting many, if not all, forms of life. Increases in extreme temperature fluctuations and average temperatures can cause stress, particularly in aquatic sessile ectotherms such as freshwater mussels. However, some species seem to thrive more than others in face of temperature-related stressors. Thermal tolerance may for example explain invasive species success. It is also known that mitochondria can play a key role in setting an ectothermic species’ thermal tolerance. In this study, we aimed to characterize the mitochondrial thermo-tolerance in invasive and endemic freshwater mussels. With the use of high-resolution respirometry, we analyzed the mitochondrial respiration of two freshwater bivalve species exposed to a broad range of temperatures. We noticed that the invasive dreissenid Dreissena bugensis displayed a less thermo-tolerant mitochondrial metabolism than the endemic unionid Elliptio complanata. This lack of tolerance was linked with a more noticeable depression of aerobic metabolism at elevated temperatures. These findings may be associated with the life history traits of both species, as D. bugensis is more adapted to unstable habitats, where selection pressures for resistance adaptations are reduced. Our findings add to the growing body of literature characterizing the mitochondrial metabolism of many aquatic ectotherms in the context of climate change.