RESUMO
The growth of personality research has led to the integration of consistent variation of individual behaviour in multidimensional approaches including physiological variables, which are required to continue building a more comprehensive theory about coping strategies. In this study, we used wild-caught males of Ctenomys talarum (tuco-tucos), a solitary subterranean rodent, to assess the relationships among personality traits and several physiological variables, namely stress response, testosterone, immunity, and energy metabolism. Subjects (n = 21) were used in experimental tests assessing behaviour, energy metabolism, testosterone levels, inflammatory cell-mediated and humoral immunity, and stress response to a simulated predator attack. The structural equation model explained a moderate portion of the variance of personality behaviours related to activity (52%), boldness (35%), and socioaversion (30%). More active and bold individuals showed higher oxygen consumption. While those subjects had lower baseline cortisol levels, there was no relationship between cortisol levels of the stress-induced response. Cell-mediated immune response was related to activity levels. Finally, testosterone only affected boldness. Despite some of these relationships diverge in direction to predicted ones, overall they support the existence of coping styles in male C. talarum; and are discussed in the light of current hypotheses and particular behavioural and ecological traits of tuco-tucos.
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Grapevine is a widely grown fruit crop that is seriously affected by different viruses, reducing grape yield and quality, as well as threatening profitability. Vineyard disease management requires accurate identification of viral infections. This study aimed to survey the presence of ten grapevine viruses in four geographic sites in the Mendoza province of Argentina. Two hundred twenty-three composite cane samples from 1060 plants of six cultivars were collected from 26 blocks distributed across 11 vineyards. The cane samples were screened by RT-PCR for the following viruses: grapevine leafroll-associated viruses 1-4 (GLRaV 1, 2, 3, and 4), grapevine fanleaf virus (GFLV), grapevine fleck virus (GFkV), grapevine virus A (GVA) and B (GVB), grapevine rupestris stem pitting associated virus (GRSPaV), and arabis mosaic virus (ArMV). The results showed an uneven occurrence of viruses through the sampled regions, with GRSPaV being prevalent (71.1%), followed by GFLV (28.9%), GFkV (20.6%), and GLRaV-2 (14.7%). GVB was not detected. This study revealed a moderate prevalence of viruses associated with economically impactful diseases in the vineyards surveyed.
Assuntos
Flexiviridae , Doenças das Plantas , Fazendas , Argentina , Flexiviridae/genéticaRESUMO
The acute phase response (APR), coordinated by a complex network of components of the immune and neuroendocrine systems, plays a key role in early immune defense. This response can be elicited by a wide variety of pathogens at different intensities (frequencies and doses), hence experimental immune challenges with antigen gradients makes it possible to evaluate sickness progression with a better representation of what occurs in natural systems. However, how infection intensity could shape the APR magnitude in wild species is still poorly understood. Here, the immune response was activated in the subterranean rodent Ctenomys talarum with a gradient of lipopolysaccharide (LPS) doses (0.5, 1, 1.5, and 2 mg/kg of body mass). Changes in body temperature, body mass, and energetic costs were evaluated over time. We also assessed cortisol levels, white blood cells counts and neutrophil: lymphocyte ratios, before and after injection. Results indicated that during the APR, C. talarum shows a hyperthermic response, which is maintained for 6 h, with slight differences among antigen doses in the pattern of thermal response and body mass change. A maximum increase in body temperature of 0.83°C to 1.63°C was observed during the first hour, associated with a metabolic cost that ranged from 1.25 to 1.41 ml O2 /gh. Although no clear effects of treatment were detected on leukocyte abundance, we found increments in neutrophil: lymphocyte ratios and gradual increases in cortisol levels corresponding to the intensity of simulated infection, which may indicate redistribution of immune cells and enhancement of immune function. An evident sickness syndrome was observed even at the lowest LPS dose that was characterized by an increase in body temperature, energy expenditure, and N: L ratio, as well as a dose-dependent increase in cortisol levels. Although in nature, other constraints and challenges could affect the magnitude and costs of immune responses, C. talarum mounts an effective APR with a low increase in their daily energy expenditure, regardless of LPS dose.
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Reação de Fase Aguda , Doenças dos Roedores , Animais , Hidrocortisona , Roedores/metabolismo , Lipopolissacarídeos/toxicidade , ImunidadeRESUMO
Understanding how evolutionary variation in energetic metabolism arises is central to several theories in animal biology. Basal metabolic rate (BMR) -i.e., the minimum rate of energy necessary to maintain thermal homeostasis in endotherms- is a highly informative measure to increase our understanding, because it is determined under highly standardized conditions. In this study we evaluate the relationship between taxa- and mass-independent (residual) BMR and ten environmental factors for 34 subterranean rodent species. Both conventional and phylogenetically informed analyses indicate that ambient temperature is the major determinant of residual BMR, with both variables inversely correlated. By contrast, other environmental factors that have been shown to affect residual BMR in endotherms, such as habitat productivity and rainfall, were not significant predictors of residual BMR in this group of species. Then, the results for subterranean rodents appear to support a central prediction of the obligatory heat model (OHM), which is a mechanistic model aimed to explain the evolution of residual BMR. Specifically, OHM proposes that during the colonization of colder environments, individuals with greater masses of metabolically expensive tissues (and thus with greater BMR) are favored by natural selection due to the link between greater masses of metabolically expensive tissues and physiological capacities. This way, natural selection should establishes a negative correlation between ambient temperature and both internal organ size and residual BMR.
Assuntos
Evolução Biológica , Metabolismo Energético , Modelos Biológicos , Roedores/fisiologia , Aclimatação , Altitude , Distribuição Animal , Animais , Metabolismo Basal , Comportamento Animal , Regulação da Temperatura Corporal , Peso Corporal , Clima , Feminino , Masculino , Tamanho do Órgão , Filogenia , Roedores/crescimento & desenvolvimento , Estações do Ano , Especificidade da Espécie , Vísceras/crescimento & desenvolvimentoRESUMO
A traditional approach used to assess whether immune defense is costly is to explore the existence of trade-offs between immunity and other functions; however, quantitative studies of the energetic costs associated with the activation of the immune system are scarce. We assessed the magnitude of a PHA-triggered immune response and the associated energetic costs in 60-day old Ctenomys talarum. We expected that the magnitude of the macroscopic inflammatory response to PHA is lower in young tuco-tucos compared with that of adults, given the allocation of substantial energy to growth, and that the magnitude of the inflammation is lower in male pups compared to females, due to the higher investment in growth of the larger sex. Concomitantly, we expected that the pups challenged with PHA show an increase in oxygen consumption compared to control animals and that a positive association exists between magnitude of the PHA-induced inflammation and oxygen consumption. Contrary to what was expected, young tuco-tucos mounted a higher inflammatory response compared with adults and there were no differences in the magnitude of this response between sexes. The inflammatory response induced by a PHA injection did not represent a significant energetic cost for young tuco-tucos. There were no differences in oxygen consumption between PHA-injected and control animals, and tuco-tucos that mounted a higher inflammatory response to PHA did not show higher oxygen consumption. Energy expenditure, however, is not the only physiological cost involved in trade-offs between immune response and various functions of the organism, and other currencies are discussed.
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Envelhecimento , Animais Selvagens/fisiologia , Metabolismo Energético , Imunidade Inata , Infecções/veterinária , Modelos Biológicos , Roedores/fisiologia , Animais , Argentina , Feminino , Pé , Fatores Imunológicos/toxicidade , Infecções/imunologia , Infecções/metabolismo , Inflamação/induzido quimicamente , Inflamação/imunologia , Inflamação/metabolismo , Inflamação/veterinária , Masculino , Consumo de Oxigênio , Fito-Hemaglutininas/toxicidade , Reprodutibilidade dos Testes , Caracteres SexuaisRESUMO
Subterranean rodents inhabit closed tunnel systems that are hypoxic and hypercapnic and buffer aboveground ambient temperature. In contrast to other strictly subterranean rodents, Ctenomys talarum exhibits activity on the surface during foraging and dispersion and hence, is exposed also to the aboveground environment. In this context, this species is a valuable model to explore how the interplay between underground and aboveground use affects the relationship among basal metabolic rate (BMR), cold-induced maximum metabolic rate (MMR), shivering (ST), and non-shivering thermogenesis (NST). In this work, we provide the first evidence of the presence of NST, including the expression of uncoupling proteins in brown adipose tissue (BAT), and shivering thermogenesis in Ctenomys talarum, a species belonging to the most numerous subterranean genus, endemic to South America. Our results show no differences in BMR, cold-induced MMR, and NST between cold- (15 °C) and warm- (25 °C) acclimated individuals. Furthermore, thermal acclimation had no effect on the expression of mitochondrial uncoupling protein 1 (UCP1) in BAT. Only cytochrome c oxidase (COX) content and activity increased during cold acclimation. When interscapular BAT was removed, NST decreased more than 30%, whereas cold-induced MMR remained unchanged. All together, these data suggest that cold-induced MMR reaches a maximum in warm-acclimated individuals and so a probable ceiling in NST and UCP1 expression in BAT. Possible thermogenic mechanisms explaining the increase in the oxidative capacity, mediated by COX in BAT of cold-acclimated individuals and the role of ST in subterranean life habits are proposed.
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Aclimatação/fisiologia , Ecossistema , Metabolismo Energético/fisiologia , Roedores/fisiologia , Termogênese/fisiologia , Tecido Adiposo Marrom/metabolismo , Análise de Variância , Animais , Argentina , Metabolismo Basal , Western Blotting , Canais Iônicos/metabolismo , Proteínas Mitocondriais/metabolismo , Espectrofotometria , Temperatura , Proteína Desacopladora 1RESUMO
Liolaemini lizards occur in southern South America in a variety of dietary habits across a broad latitudinal and altitudinal distribution. We studied standard metabolic rates of 19 Liolaemini species and analyzed these data using both conventional and phylogenetically informed statistics. Oxygen consumption showed a significant and positive relationship with body mass (SMR = 0.109 × body mass(0.876±0.023)), with a higher slope than that expected on the basis of the three-quarter power law model. After phylogenetically informed and conventional analyses, no significant differences in metabolic rates were found to be related to diet or elevation. We hypothesize that small body size, ecological conservatism and physiological compensation may explain the lack of differences in metabolic rates observed among these lizards.
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Ecologia , Metabolismo Energético/fisiologia , Lagartos/metabolismo , Altitude , Animais , Metabolismo Basal , Tamanho Corporal , Peso Corporal/fisiologia , Dieta , Feminino , Masculino , Consumo de Oxigênio/fisiologia , América do SulRESUMO
The present work is aimed to establish, in Ctenomys talarum, the physiological and behavioral adjustments undergone by individuals when they are allowed to dig burrows in soils with different hardness and fed with diets of different quality. For each soil-diet combination, we estimated: resting metabolic rate (RMR), body temperature (T(b)), body mass, digestibility, food consumption rate, transit time, reingestion rate, feces production and time devoted to feeding, resting, locomotor activity and coprophagy. Soil type and diet quality affected RMR, but response to soil hardness was verified later. Animals fed with high quality (HQ) diet showed similar body temperature irrespective of soil condition, while animals fed with low quality (LQ) diet showed lower T(b) under soft soil (SS). Individuals fed with LQ diet showed lower RMR and both, lower digestibility and high transit time of food than those fed with HQ diet. Moreover, increments in feeding and defecation rates were observed in the former group. Number of reingested feces did not differ between animals fed with diets of different quality. However, when incidence of reingestion was considered, animals fed with HQ diet showed higher values of feces ingestion. Either feeding, resting and activity patterns were arrhythmic. However, for animals fed with LQ diet a tendency to rhythmic coprophagy was observed and it could be considered as a way to optimize feeding. This study shows that RMR is limited by digestive efficiency which is influenced by diet quality, but also thermal stress may limit the conversion of assimilated energy into work and heat.
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Dieta , Meio Ambiente , Roedores/metabolismo , Solo , Animais , Metabolismo Basal , Comportamento Animal , Temperatura Corporal , Coprofagia , Digestão , Ingestão de Alimentos , Metabolismo Energético , Feminino , MasculinoRESUMO
Subterranean mammals show lower mass-independent basal metabolic rates (BMRs). Several competing hypotheses were suggested to explain how microenvironmental conditions and underground life affect subterranean mammalian energetics. Two of these are the thermal stress and the cost-of-burrowing hypotheses. The thermal stress hypothesis posits that a lower mass-independent BMR reduces overheating in burrows where convective and evaporative heat loss is low, whereas the cost-of-burrowing hypothesis states that a lower mass-independent BMR may compensate for the high energy expenditure of digging. In this article, we assessed the relationship between BMR of Ctenomys and environmental variables through conventional statistics as well as independent contrasts. Moreover, we tested both the thermal stress and the cost-of-burrowing hypotheses at an interspecific level in a very homogeneous genus of subterranean rodents, the South American genus Ctenomys. We compared species from different geographic localities that have contrasting habitat conditions. We measured BMR through open-flow respirometry. After conventional as well as independent contrast analyses, our results support neither the thermal stress nor the cost-of-burrowing hypotheses. We observed that only body mass affects the variability in BMR. Contrasting climatic and soil conditions, habitat productivity, and net primary productivity were not correlated with BMR variability. We suggested that, because BMR and maximum metabolic rates (MMRs) are correlated, low BMRs among Ctenomys species could also be determined by factors that affect MMR rather than BMR.
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Comportamento Animal/fisiologia , Metabolismo Energético/fisiologia , Roedores/fisiologia , Animais , Peso Corporal , Ecossistema , Proteínas de Membrana , Proteínas de Saccharomyces cerevisiaeRESUMO
The low basal metabolic rate (BMR) observed in subterranean rodents, compared to that of surface-dwelling species of comparable size, has been proposed to be an adaptation to underground life. Two main hypotheses have been proposed to explain this finding, the cost of burrowing and the thermal stress. The former states that the low BMR is due to the high cost of extending the tunnel system whereas the other relates it to the possibility of overheating in burrows where evaporative and convective heat exchange are restricted. Additionally, both hypotheses related the energetics of subterranean rodent with spatial distribution. The genus Ctenomys is an excellent model to evaluate the cost of burrowing or thermal stress, since they are widely distributed, with members differing markedly in body mass. The aim of this study was to assess digging and basal energetics in two Ctenomys species that live in sympatry in a coastal grassland, but differ in their microspatial distribution by soil preference. We used the obtained energetic data to test both energy-distribution hypotheses. We measured BMR and digging metabolic rate (DMR) through open flow respirometry in two species exposed to soft and hard soils. In brief, DMR in Ctenomys talarum (100-170 g), as in Ctenomys australis (250-600 g), was unaffected by soil hardness. Within thermoneutral zone of each species, DMR/RMR quotient was lower in the smaller species. Our data did not support the thermal stress hypothesis, but the cost of burrowing hypothesis was not rejected. Other alternative hypotheses are proposed to explain the distribution of C. talarum and C. australis.