The bluefin tuna have a variety of distinctive anatomical and physiological adaptations that enhance performance. However, our understanding of bluefin tuna physiology is limited by the logistical difficulties of studying these large pelagic fish. This thesis examines some aspects of the metabolic physiology of the southern bluefin tuna. It provides insight into the high-performance, high-energy demand physiology of bluefin. It also examines the metabolic physiology of the mulloway, another important aquaculture species for which physiological information is currently limited. 1. Routine metabolic rate (RMR) of southern bluefin tuna (SBT) (Thunnus maccoyii), the largest tuna specimens studied so far (body mass = 19.6 kg (± 1.9 SE)) was measured in a large (250,000 l) flexible polypropylene respirometer “mesocosm respirometer”. Mean mass-specific RMR was 460 mg kg⁻¹ h⁻¹ (± 34.9) at a mean water temperature of 19°C. When total RMR is added to published values of other tuna species at equivalent swimming speeds, there is a strong allometeric relationship with body mass (654 • Mb ⁰·⁹ ⁵, R ² = 0.97). This demonstrates that interspecific RMR of tuna scale with respect to body mass similar to that of other teleosts, but is approximately 5-fold higher than the standard metabolic rate (SMR) of other active teleost species. 2. This study reports on the first measurements of the metabolic cost of food digestion and assimilation (specific dynamic action, SDA) of a tuna species. Oxygen consumption (MO₂) and swimming velocity of southern bluefin tuna (SBT) (Thunnus maccoyii) were elevated for periods between 20-45 h (longest for the largest rations) post-ingestion of sardines (Sardinops sagax). It is suggested that the purpose of increased swimming velocity was to increase ventilation volume as a response to the enhanced metabolic demand associated with SDA. The magnitude of SDA as a proportion of gross energy ingested (SDA coefficient) averaged 35 ± 2.2 %. This demonstrates that the absolute energetic cost of SDA in SBT is approximately double that recorded in other teleost species. 3. This study examines the effects of sardines (Sardinops sagax) with high- (12.9%) or low- (1.8-4.0%) lipid level on specific dynamic action (SDA) and swimming velocity of southern bluefin tuna (SBT) (Thunnus maccoyii). Fish swam faster during the SDA period with the increase in velocity being greatest for the fish that ingested the high-lipid sardine. Magnitude of SDA was also greater for fish that ingested the high-lipid sardines. However, the energetic cost of SDA as a proportion of ingested energy was not significantly different between fish that ingested the high- (34.3 ± 2.4%) and low-lipid sardines (31.5 ± 2.9%). These results confirm that the high energetic cost of SDA is ecologically relevant. 4. In this study the metabolic and behavioural responses of both fasted and postprandial southern bluefin tuna (Thunnus maccoyii, SBT) to low dissolved oxygen (DO) was examined. In moderate hypoxia (4.44 and 3.23 mg l⁻¹), swimming velocity (U) and routine metabolic rate (RMR) of fasted fish was mildly enhanced. At 2.49 mg l⁻¹, U increase to over double in the normoxic speed, possibly as an escape response. At 1.57 mg l⁻¹, both U and RMR were suppressed and SBT failed to survive the entire 20 h exposure period. This reveals that SBT are remarkably well adapted to low DO. Feeding did not greatly influence their hypoxia tolerance. In a subsequent experiment there were no significant differences in U, RMR and gastric evacuation rates of postprandial SBT in hypoxia (2.84 mg l⁻¹) compared to those in normoxia (7.55 mg l-¹). 5. In this study, 768 h of simultaneous recordings of metabolic rate (MR, = heat production) and visceral temperature were made in both fasted and postprandial southern bluefin tuna (SBT, Thunnus maccoyii) of two sizes (~10 and 20 kg) and at two water temperatures (~19 and 16°C). Duration and magnitude of specific dynamic action (SDA) were strongly related to duration and magnitude of postprandial visceral warming providing the first empirical evidence of a link between SDA and postprandial visceral warming. Visceral temperature of fasted SBT was also directly related to MR. In this case, source of heat is thought to be metabolic work performed within the red muscles which warmed the viscera through thermal conductance. Visceral excess temperatures were over 1°C warmer in larger than smaller SBT. Better heat retention ability of the larger SBT is likely attributed to improved retia mirabilia development and greater thermal inertia. SBT at 16°C maintained visceral excess temperatures significantly warmer than similarly sized fish at 19°C. This demonstrates some ability of SBT to physiologically regulate visceral warming. 6. In this study, the effect of progressively severe hypoxia levels on the swimming performance and metabolic scope of juvenile mulloway (Argyrosomus japonicus) were investigated. In normoxic conditions (6.85 mg l⁻¹), standard metabolic rate (SMR) and cost of transport were typical for subcarangiform fish species. Mulloway had a moderate scope for aerobic metabolism (5 times the SMR). The critical dissolved oxygen level was 1.80 mg l⁻¹ revealing that mulloway are well adapted to hypoxia. In all levels of hypoxia (5.23, 3.64, and 1.86 mg l⁻¹) the active metabolic rate was reduced however, the critical swimming velocity was reduced only at 3.64, and 1.86 mg l⁻¹. Mulloway metabolic scope was significantly reduced at all hypoxia levels, suggesting that even mild hypoxia may reduce growth productivity. / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2007

Antarctic fish from the Perciform suborder Notothenioidei inhabit arguably the most thermally stable ocean environment on earth. In order to populate the subzero environment Antarctic fish have evolved numerous adaptations. However, specialisation to -1.9°C has incurred a trade off, thermal flexibility is lost likely due to modifications to the cold and as a result Notothenioidei are extremely stenothermic. Climate change mediated warming is predicted to increase the ocean temperature surrounding the Antarctic continent by 2°C within the next century. This increase is projected to affect individuals, populations and the community structures of those inhabiting the area and therefore the physiological study of the acclimation ability and thermal limitations of Antarctic fish is an area scientific interest. The present study is a series of discrete experiments relating to one species, Trematomus bernacchii, a circumpolar benthic Notothenioidei found in nearly all inshore waters surrounding the Antarctic coastline. These studies included investigation of the response of this species to both chronic and acute temperature exposure prior to and following a feeding event, a reduction in environmental oxygen and an exhaustive exercise event, as well as examination of T. bernacchii ability to recovery from these challenges. T. bernacchii demonstrated variable success when acclimated to +3°C. Failure appeared to be determined by the recovery period following capture and aquarium housing, 7 days housing following capture resulted in 100% mortality, conversly 3 months resulted in 100% survival. Following successful acclimation T. bernacchii showed physiological adjustment as acclimated resting metabolic rate mirrored that of T. bernacchii tested at environmental temperature, 20.63 ± 1.3 compared to 22.38 ± 1.02 mg. O₂. kg⁻¹. h⁻¹. The previously undefined specific dynamic action response (SDA), in T. bernacchii was characteristic of polar species. At environmental temperatures SDA scope was small 14.52 ± 3.52 mg O₂. kg⁻¹. h⁻¹, and lengthy ,72 hours; SDA duration was reduced to 9 hours in acclimated fish. Resting metabolic rate was elevated following acute exposure to +3°C, 34.27 ± 2.35 mg O₂. kg⁻¹. h⁻¹, masking the SDA response and associated parameters. T. bernacchii were relatively sensitive to hypoxia, Pcrit over four acute temperature exposures, ranged between 69 and 102mmHg, higher than the average range for teleosts (40 – 60 mmHg). Above -1°C Pcrit increased, rising with acute temperature exposure. Ventilation rate was temperature dependent and completely absent at +4 and +6°C. A bradycardia (beginning at 60 and 70mmHg) was observed at all temperature exposures, this response was consistent as all heart rates reduced by 25%. Recovery from both hypoxia and acute temperature exposure was rapid. Following an exhaustive exercise event aerobic Scope of T. bernacchii was constrained over an acute temperature increase, reducing from 38.58 ± 5.64 to 24.41 ± 4.92 mg.O₂. kg⁻¹.h⁻¹ over a 7°C temperature increase, respiratory scope too was reduced such that at +4 and +6°C scope was absent. Heart rate of T. bernacchii was highly constrained at -1°C, increasing by 2.54 ± 0.9 bpm following exercise. Acute temperature increase resulted in an increase in cardiac scope, maximum 6.29 ± 1.2 bpm at +2°C, due likely to a thermally mediated loss of cholinergic tonus following exhaustive exercise. Recovery of all parameters was temperature dependent and rapid upon return to -1°C. The present study is the first to quantify and assess the effect of acute and chronic temperature exposure on the SDA response of T. bernacchii. Furthermore, it supplements the current literature on acclimation ability, acute temperature exposure, aerobic scope and hypoxia tolerance for this species. This work will be of use in future investigations of the effects of rapid climate change on Antarctic notothenioid fish and the interconnected ecosystem.

Made available in DSpace on 2016-06-02T19:22:58Z (GMT). No. of bitstreams: 1 5274.pdf: 984660 bytes, checksum: be57989a598b10b572f7a8db0e3cfc54 (MD5) Previous issue date: 2013-02-28 / Universidade Federal de Sao Carlos / Despite all the knowledge about the excitation-contraction coupling (E-C) in mammals, there are still large gaps in the knowledge of the cardiac myocytes physiology in other vertebrates. Thus, the study of groups underexplored such as reptiles is very important. Python snakes are of great interest regarding to the studies of the postprandial metabolism because the physiological responses are exacerbated when digesting large preys. Studies with these snakes showed hypertrophy of the cardiac tissue 2 to 3 days after feeding, coinciding with the peak of the specific dynamic action (SDA), but the consequences of this remodeling in myocardial contractility have not been studied, which was the purpose of this work. Specimens of Python molurus of both sexes, provided by the Jacarezário of UNESP / Rio Claro were brought to the Laboratory of Comparative Biochemistry and Zoofisiologia, UFSCar, where they remained for at least 15 days for acclimatization (30 °C). The snakes were divided into two groups: 28 days (sacrificed 28 days after feeding) and 2 days (sacrificed 2 days after feeding, in the peak of the SDA). Each snake (n = 10) was fed (Wistar rats with a 30% weight of the snake) and the sacrifice (decapitation) occurred according to the experimental feeding regime. After sacrifice, the hearts were removed, weighed to calculate the relative ventricular mass (MVR) and ventricular strips were prepared to analyse the following parameters: peak force (Fc), times to peak force (TPT) and to 50% relaxation (THR), the effect of experimental time (40 min), elevation of the stimulation frequency and post-rest tension, being the latter two protocols performed in the presence and absence of ryanodine. Differences were considered significant at p <0.05 (Student's t test). When compared to group 28 days, animals of group 2 days showed a significant increase in MVR. The Fc values in the protocols of effect of time and increasing frequency of electrical stimulation were higher in group 2 days when compared to the group 28 days. The rates of contraction and relaxation were lower in group 2 days, and the derivatives of the maximum contraction and relaxation showed higher values for this group compared to the group 28 days, indicating greater efficiency in the processes of contraction and relaxation during E-C coupling. In the post-rest tension protocol, there was no significant difference in force developed before and after the pause in control preparations, but the ryanodine reduced Fc of the first contraction after the pause in both groups. The increasing frequency of stimulation in the presence of ryanodine abolished the difference between the values of all analyzed parameters presented by the two experimental groups. The increase in the MRV of group 2 days associated with a greater efficiency of Ca2+ transport in cardiac tissue was responsible for the increase in Fc, important for maintaining cardiac output and blood flow at the high metabolism during digestion. The RS appears to contribute significantly to the calcium dynamics during E-C coupling of P. molurus, but further studies are necessary to fully understand this process. / Apesar de todo o conhecimento acerca do acoplamento excitação-contração (E-C) de mamíferos, restam ainda grandes lacunas no conhecimento da fisiologia dos miócitos cardíacos dos demais vertebrados. Desta forma, o estudo da fisiologia de grupos ainda pouco explorados como os répteis, é de fundamental importância. As pítons são serpentes de grande interesse no estudo do metabolismo pós-prandial por apresentar respostas exacerbadas quando da digestão de grandes presas. Estudos com estas serpentes mostraram hipertrofia do tecido cardíaco de 2 a 3 dias após a alimentação, no pico da chamada ação dinâmica específica (SDA), mas as conseqüências desta remodelação na contratilidade miocárdica não foram estudadas, o que se constituiu na meta do presente trabalho. Exemplares de Python molurus de ambos os sexos, cedidas pelo Jacarezário da UNESP/Rio Claro, foram trazidas para o Laboratório de Zoofisiologia e Bioquímica Comparativa da UFSCar, onde permaneceram por pelo menos 15 dias para aclimatação (30 ºC). As serpentes foram dividas em dois grupos: 28 dias (sacrificadas 28 dias após a alimentação) e 2 dias (sacrificadas 2 dias após alimentação, no pico da SDA). Cada serpente (n = 10) foi alimentada (1 rato Wistar com 30% peso da serpente) e o sacrifício (decaptação) ocorreu de acordo com o regime de alimentação do experimental. Após sacrifício, os corações foram retirados, pesados para o cálculo da massa ventricular relativa (MVR) e tiras ventriculares foram preparadas para avaliação dos seguintes parâmetros: pico de força (Fc), tempos para o pico de força (TPT) e para 50% de relaxamento (THR), efeito do tempo experimental (40 min), da elevação da freqüência de estimulação e da tensão pós-pausa, sendo os dois últimos protocolos realizados na presença e ausência de rianodina. Diferenças significativas foram consideradas quando p < 0,05 (teste t de Student). Os animais do grupo 2 dias apresentaram aumento da MVR em relação ao grupo 28 dias. Os valores de Fc, nos protocolos de efeito do tempo e do incremento da frequência de estimulação elétrica, foram maiores no grupo 2 dias quando comparados aos do grupo 28 dias. As taxas de contração e relaxamento foram menores no grupo 2 dias, e as derivadas máximas da contração e relaxamento apresentaram valores maiores para tal grupo comparando-se ao grupo 28 dias, indicando maior eficiência nos processos de contração e relaxamento durante o acoplamento E-C. No protocolo de tensão pós-pausa, não observou-se diferença significativa no desenvolvimento de força antes e após a pausa nas preparações controle, mas a rianodina reduziu a Fc na primeira contração após a pausa em ambos os grupos. O incremento da frequência de estimulação em presença de rianodina aboliu as diferenças entre os valores dos parâmetros estudados nos dois grupos experimentais. O aumento na MRV do grupo 2 dias associado a maior eficiência no transporte de Ca2+ no tecido cardíaco foi responsável pelo aumento da Fc, importante para a manutenção de um débito cardíaco e fluxo sanguíneo para a condição de elevado metabolismo durante a digestão. O RS parece contribuir significativamente na dinâmica de cálcio durante o acoplamento E-C das serpentes, no entanto mais estudos se fazem necessários para compreender plenamente seu papel.

Diving vertebrates are constrained by an aquatic existence because they carry a limited store of oxygen whilst submerged and must return to the surface to breathe. Therefore, oxygen stores must be used efficiently in order to maximise aerobic dive duration. The ability to use additional, non-pulmonary gas exchange to obtain oxygen from the water provides a mechanism to alleviate the use of body oxygen stores and extend dive duration. The partitioning of gas exchange between aerial and aquatic modes is predicted by the theory of optimal breathing. As the cost of obtaining oxygen by one mode increases, the reliance on this mode should decrease whilst the reliance on the alternate mode should increase. A number of environmental, physiological and ecological factors can affect metabolic rate and/or the partitioning of gas exchange between aerial and aquatic modes, with consequences for dive duration. The overall aim of this study was to examine the effects of temperature, specific dynamic action and predation on respiratory partitioning and diving behaviour in the Arafura filesnake, Acrochordus arafurae. Filesnakes provide an excellent model to address the aims of this study because they are fully-aquatic and respire bimodally, utilising both aerial and aquatic (cutaneous) gas exchange. Metabolic rate and diving behaviour are usually thermally dependent in diving ectotherms. Given this knowledge, we tested whether A. arafurae was capable of up-regulating cutaneous oxygen uptake to compensate for the temperature induced increases in metabolic rate. Metabolic rate had a Q10(20-32°C) of 2.33, however cutaneous oxygen uptake was independent of temperature and all elevated metabolic demands were met by increasing aerial oxygen uptake. Consequently, maximum dive duration was reduced by 70%, from 77 min at 20°C to 28 min at 32°C. The temperature independence of cutaneous oxygen uptake suggests that blood PO2 remained stable across temperatures and the increased blood flow expected with an elevated metabolic rate did not enhance the capacity for oxygen uptake (diffusion limited rather than perfusion limited). Although cutaneous oxygen uptake was not regulated, its contribution to extending dive duration was significant. When the ability to respire aquatically was removed (severe hypoxia), dive duration was reduced by up to 30%. Acrochordus arafurae feeds infrequently on large, high-protein meals thus the postprandial metabolic response was significant. Meal size and fast length (13 days or one month) were both positively related to the peak metabolic scope. After fasting for one month, peak rate of oxygen consumption was up to 12-fold standard metabolic rate (SMR) with the largest meal size. By comparison, an animal that was fasted for 13 days and fed an equivalent meal size incurred a six-fold increase in SMR. The energetic costs of digestion (specific dynamic action, SDA) increased with meal size, but fast length had no effect, suggesting the up-regulation of gut function was not a significant cost in the SDA. Pulmonary and cutaneous gas exchange increased with elevated metabolic demands however pulmonary oxygen uptake was the dominant mode. Despite the increase in cutaneous oxygen uptake during digestion, maximum dive duration decreased by between 50% and 90% of fasted values. The significant reductions in dive duration following feeding may have implications for predator vulnerability. Diving animals are most vulnerable to predation at the water’s surface. The theory of optimal diving under predation predicts that animals should make shorter, more frequent surface intervals or longer, less frequent surfacing intervals to minimise exposure to predators. Acrochordus arafurae is prone to aerial (birds of prey) and aquatic (crocodiles, large fish) predation. Simulated avian predation did not change dive or surface duration or proportion of time at the surface or spent active. However, a greater number of longer dives were observed with fewer long surface intervals suggesting an increase in the use of cutaneous oxygen uptake. The nocturnal diving patterns of A. arafurae provide an in-built anti-predator strategy. The threat of aquatic predation by a large fish produced atypical anti-predator responses; A. arafurae became increasingly active, reduced dive duration and increased surface interval which was indicative of a foraging response. The field diving behaviour of adult A. arafurae was determined using acoustic telemetry and interpreted in the context of environmental and ecological conditions. The mean dive duration was 6.6 min, with 85% of dives less than 10 min in duration. The maximum dive duration was 153 min. There was no diel pattern in dive duration. Snakes were located at an mean depth of 0.62 m, however, they occasionally ventured to greater depths (up to 6 m) but very infrequently. Snake body temperature reflected water temperature and fluctuated by approximately 1°C on a daily basis. The short and shallow dives of A. arafurae minimise travel costs associated with surfacing and may be an anti-predator strategy. Metabolic rate and respiratory partitioning is dependent on physiological and ecological factors with consequences for dive duration. Temperature and postprandial induced increases in metabolic demands were met by increasing the reliance on aerial gas exchange given the limitations of cutaneous gas exchange; and dive duration was substantially reduced as a result. Ecological factors, such as predation, can increase the cost of surfacing and promote the use of aquatic gas exchange. However, changes to behaviour, including habitat choice, residence depth and the employment of a diving strategy that does not maximise dive duration may be just as effective at minimising the costs and maximising the gains of a dive.

Mysid shrimps (Mysidacea, Crustacea) are efficient zooplanktivores in both marine and freshwater systems as well as lipid rich prey for many species of fish.  Although some efforts have been made to study the role of mysids in the Baltic Sea, very few studies have been carried out in recent time and there are still knowledge gaps regarding various aspects of mysid ecology. This thesis aims to explore some of these gaps by covering a mixture of topics. Using multifrequency hydroacoustics we explored the possibility to separate mysids from fish echoes and successfully established a promising and effective method for obtaining mysid abundance/biomass estimates (paper I). An investigation of the current mysid community in a coastal area of the northern Baltic proper (paper II) demonstrated that the formerly dominant, pelagic mysid Mysis mixta had decreased substantially (~50%) in favor for phytoplanktivorous, juvenile Neomysis integer and Mysis relicta sp. By examining different aspects of mysid behavior, we studied the vertical size distribution of mysids in the field and found that size increased with depth/declining light, irrespective of temperature; indicating that their vertical size distribution primarily is a response to predation (paper II). In paper III, a combination of ecological and genetic markers was used to investigate intraspecific differences in migratory tendency. Both marker types indicated that some part of the Mysis salemaai population is sedentary on the bottom and that this strategy is a phenotypically plastic but persistent trait, analogous to the partial migrations seen in many birds and fishes. In paper IV a temperature and weight specific respiration model was developed for the littoral Praunus flexuosus. Routine respiration was moreover elevated by post-prandial effects (specific dynamic action) for longer times than previously suggested. Consequently, ignoring such effects could significantly bias respiration measurements. / At the time of doctoral defence the following papers were unpublished and had a status as follows: Paper  2: Accepted; Paper 3: Submitted; Paper  4: Accepted

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Agradecemos a compreensão. on 2017-01-24T13:40:19Z (GMT) / Submitted by Luá Taibo Timpone null (101010913@rc.unesp.br) on 2018-03-02T20:05:16Z No. of bitstreams: 1 Dissertação_VersãoFinal_Completa_Luá.pdf: 1544050 bytes, checksum: 3ff859d190848f5e447a8680e9b509cb (MD5) / Approved for entry into archive by Vivian Rosa Storti null (vstorti@reitoria.unesp.br) on 2018-04-04T12:42:54Z (GMT) No. of bitstreams: 1 timpone_lt_me_rcla.pdf: 1544050 bytes, checksum: 3ff859d190848f5e447a8680e9b509cb (MD5) / Made available in DSpace on 2018-04-04T12:42:54Z (GMT). No. of bitstreams: 1 timpone_lt_me_rcla.pdf: 1544050 bytes, checksum: 3ff859d190848f5e447a8680e9b509cb (MD5) Previous issue date: 2016-10-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O tamanho do alimento e a temperatura corpórea são dois fatores que reconhecidamente influenciam a resposta metabólica pós-prandial dos vertebrados ectotérmicos. Leptodactylus latrans é uma espécie generalista que consome desde invertebrados até pequenos vertebrados, de forma que sua dieta é composta por itens de tamanho variável, os quais sempre são ingeridos inteiros. A temperatura corpórea de L. latrans está sujeita a disponibilidade de nichos térmicos adequados nos ambientes onde ocorre, os quais são possivelmente explorados através da termorregulação comportamental. No presente estudo, nós avaliamos os efeitos do tamanho da presa e da temperatura corpórea sobre a resposta metabólica pós-prandial, em indivíduos adultos da rã-manteiga, Leptodactylus latrans (Anura, Leptodactylidae) através da quantificação das taxas de consumo de oxigênio antes e após a alimentação. A resposta metabólica pós-prandial de L. latrans pode ser caracterizada por um rápido aumento nas taxas de consumo de oxigênio logo após a ingestão do alimento, até atingir valores máximos entre 85,93 ± 9,92 e 224,54 ± 26,08 mLO2.kg-1. h-1, dentro de 1-2 dias. Após este pico, houve um retorno paulatino da taxa metabólica aos níveis de jejum entre 3 a 7 dias após a alimentação. De maneira geral, encontramos que a ingestão de presas maiores causa um maior incremento metabólico e aumenta a duração da digestão. Já o incremento da temperatura é acompanhado pela diminuição da duração da digestão às expensas de taxas metabólicas pós-prandiais mais elevadas. Tanto em um caso como no outro, não encontramos indicações de que fatores cardiorrespiratórios pudessem atuar na limitação do tamanho da presa ou na temperatura na qual a digestão pode ocorrer. No entanto, é plausível que outros fatores de cunho ecológico sejam relevantes na consideração dos efeitos do tamanho do alimento e da temperatura na digestão de L. latrans. Em especial, um maior retorno energético absoluto ao se alimentar de presas maiores e a diminuição do tempo de digestão em temperaturas mais elevadas, ambos aspectos documentados em L. latrans, podem representar benefícios ecológicos importantes. / Meal size and body temperature affect markedly the post-prandial metabolic response of ectothermics vertebrates. Leptodactylus latrans is a generalist anuran species feeding on diverse prey itens, from invertebrates to small vertebrates, with considerable size variation and that are always ingested whole. The body temperature of L. latrans is largely dependent of the availability of thermal niches in the environment, which are possibly explored by means of behavioral thermoregulation. In the present study, we investigated the effects of meal size and body temperature on the post-prandial metabolic response of adults of the Neotropical leptodatylid frog, Leptodactylus latrans (Anura, Leptodactylidae) by quantifying the rates of oxygen consumption before and after meal ingestion. The post-prandial metabolic response of L. latrans can be characterized by the rapid increase in the rates of oxygen consumption shortly after meal ingestion, until reach peak between 85,93 ± 9,92 e 224,54 ± 26,08 mLO2.kg-1. h-1, within 1-2 days post-feeding. Thereafter, metabolism gradually return to the pre-feeding values within 3 to 7 days post-feeding. In general, we found that the ingestion of larger meals were followed by greater metabolic increment and by longer digestion duration. Temperature increment caused digestion duration to decrease at the expenses of greater post-prandial metabolic rates. In both cases, we did not found evidences that cardiorespiratory compromises could limit meal size or the temperature in which meal digestion could occur. On the other hand, some ecological considerations seems to be relevant in considering the effects of meal size and body temperature on the digestion of L. latrans. More specifically, the greater gross energetic gain when feeding on larger prey and the shortening of digestion duration at higher temperatures, both observed in L. latrans, are likely to yield substantial ecological advantages. / Capes Demanda Social

Made available in DSpace on 2016-06-02T19:22:10Z (GMT). No. of bitstreams: 1 5716.pdf: 1902370 bytes, checksum: 9a5b25a55be97bb37553eeb1f8130b09 (MD5) Previous issue date: 2014-01-28 / Financiadora de Estudos e Projetos / Phenomena as feeding and thermoregulation can challenge both the cardiac output and heart rate (fH). Postprandial changes in many physiological patterns are typically recorded for ectotherms, although predominantly studied in snakes. Furthermore, thermoregulation is a critical process to ensure different survival and reproduction strategies from reptiles. Ventricular preparations in vitro were used to investigate the inotropic plasticity at 30 ºC and 25 ºC and during fasting (30 days fasting group) and after feeding (2 days digesting group). No significant differences were verified in the relative ventricular mass (RVM) after feeding. The peak tension (Fc) was significantly higher and rates (dFc/dt) of contraction (TC) and relaxation (TR) were faster at 25° C than at 30° C for both experimental groups. However, feeding caused significant increase in peak tension (PT) at both temperatures (396.7 % at 30 ºC and 416.7 % at 25 ºC). A significant post-rest potentiation was recorded for digesting group at 25 ºC (121.0 ± 6.4 %), which was inhibited by ryanodine (86.0 ± 2.9 %). At 30 ºC, myocytes from fasting group were able to support higher frequencies (up to 1.6 Hz) than at 25 ºC (up to 1.0 Hz), even with the sarcoplasmic reticulum (SR) blocked by 10 &#956;M ryanodine (RYA). Data from digestion group showed greater values of the Fc and reached higher frequencies than fasting group, at both temperatures. However, pre-treatment with RYA decreased PT in frequencies between 1.4 and 1.8 Hz for digesting group at 30 ºC. Sarcolemma mechanisms were more representative in the fasting group at 25 ºC, but the SR must contribute to increased speed of contractility under those conditions. During SDA, the SR seem representative at 25 ºC, however the positive inotropic effect caused by SDA enlarged sarcolemma mechanisms representativeness. The SR significance at 30 °C seems critical during high frequencies. At this temperature, the SDA increases the contractility efficiency, even with the RS blocked, despite the relaxation and Fc development at high frequencies been present impaired. Our results indicate that Caiman latirostris myocytes show large inotropic plasticity at different temperatures, frequencies and metabolic states. / A digestão e a termorregulação são processos que podem desafiar tanto o débito quanto a frequência cardíaca (fH). Alterações pós-prandiais em diferentes padrões fisiológicos são comumente identificadas para ectotérmicos, embora sejam predominantemente estudados em serpentes. Além disso, a termorregulação é um processo crítico para garantir diferentes estratégias de sobrevivência e reprodução nos répteis. Preparações ventriculares in vitro foram utilizadas para investigar a plasticidade inotrópica dos miócitos ventriculares do Caiman latirostris a 25 e 30 °C, durante o período pós- absortivo (30 dias - após a alimentação) e após a alimentação (2 dias - grupo digestão). A massa ventricular relativa (MVR) após 2 dias da alimentação não apresentou diferenças significativas em relação ao grupo pós-absortivo. A força de contração (Fc) foi significativamente maior e as taxas (dFc/dt) de contração (TC) e relaxamento (TR) foram mais rápidas a 25 °C do que a 30 °C, para ambos os grupos experimentais. No entanto, a alimentação causou aumento significativo na força de contração (Fc) em ambas as temperaturas (316.7% a 30 °C e a 296.7% 25 °C). Uma significativa potenciação pós-pausa foi identificada no grupo digestão a 25 °C (121.0 ± 6.4 %), que foi inibida pela rianodina (86.0 ± 2.9 %). No grupo pós-absortivo a 30 °C, os miócitos foram capazes de suportar frequências de estimulação superiores (até 1.6 Hz) às suportadas a 25 °C (até 1.0 Hz), mesmo com a função do retículo sarcoplasmático (RS) bloqueada pela adição de 10 &#956;M de rianodina (RYA). As preparações ventriculares do grupo digestão apresentaram valores maiores de Fc e alcançaram frequências superiores do que o grupo pós-absortivo, em ambas as temperaturas. Contudo, o pré-tratamento com RYA reduziu a Fc em frequências entre 1,4 e 1,8Hz no grupo digestão a 30 °C. Os mecanismos sarcolemais são mais representativos no grupo pós-absortivo a 25 °C, porém o RS pode contribuir com o aumento da velocidade da contratilidade nessas condições. Durante a SDA, o RS parece representativo nessa condição de temperatura, porém a SDA causou efeito inotrópico positivo e ampliou a representatividade dos mecanismos sarcolemais. A importância do RS a 30 °C parece crítica apenas em altas frequências de estimulação. Nessa temperatura, a SDA garante a eficiência da contratilidade mesmo com o RS bloqueado, apesar do prejuízo significativo no desenvolvimento da Fc e do relaxamento em altas frequências. Nossos resultados indicam que os miócitos ventriculares do Caiman latirostris apresentam ampla plasticidade inotrópica, capaz de assegurar o débito cardíaco em diferentes temperaturas, frequências e estados metabólicos.

Using a high throughput closed respirometry method to measure oxygen consumption, I determined metabolic rates in asexual and sexual Schmidtea mediterranea and Girardia dorotocephala, as a function of temperature, taxon, stressors, reproductive mode, age, regeneration, and specific dynamic action. This study has shown that oxygen consumption can reliably be measured in planaria using optode closed respirometry, and also provided a reliable method for measuring wet mass in planaria, which has been a challenge to researchers in the past. This research revealed that oxygen consumption in S. mediterranea is 1.5-2.1X greater in the sexual strain over the asexual strain at 13-18°C. Within the sexual strain, oxygen consumption is 1.5 -2.2X greater in sexually mature adults over the sexually immature groups (hatchlings, juveniles, and regenerating sexuals). Furthermore, I was able to quantify differences in sexual morphology between these groups exhibiting significant differences in oxygen consumption. The results of this research supports a theory of higher metabolic costs with sexual maturity in S. mediterranea. Therefore, this study has established sexual and asexual S. mediterranea as simple, yet attractive models for investigating energetic costs between sexual and asexual phenotypes. This research also provided quantitative values for specific dynamic action in planaria, with a maximum increase in oxygen consumption of 160% induced by feeding, as well as metabolic relationships in planaria involving temperature, age, and regeneration. These values establish planaria as one of the simplest animal models in which common metabolic patterns, such as SDA and poikilothermic temperature sensitivity, have been demonstrated. Therefore, this research has contributed to the overall knowledge of the basic physiology in this animal, providing the framework for future metabolic studies in planaria involving environmental factors, reproduction, regeneration, development, and aging. Information from this study may supplement interpretation and understanding of modern cellular, molecular, and genomic studies in planaria.