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Barboza, P. S., Bennett, A., Lignot, J. H., Mackie, R. I., McWhorter, T. J., Secor, S. M., et al. (2010). Digestive Challenges for Vertebrate Animals: Microbial Diversity, Cardiorespiratory Coupling, and Dietary Specialization. Physiol. Biochem. Zool., 83(5), 764–774.
Résumé: The digestive system is the interface between the supply of food for an animal and the demand for energy and nutrients to maintain the body, to grow, and to reproduce. Digestive systems are not morphologically static but rather dynamically respond to changes in the physical and chemical characteristics of the diet and the level of food intake. In this article, we discuss three themes that affect the ability of an animal to alter digestive function in relation to novel substrates and changing food supply: (1) the fermentative digestion in herbivores, (2) the integration of cardiopulmonary and digestive functions, and (3) the evolution of dietary specialization. Herbivores consume, digest, and detoxify complex diets by using a wide variety of enzymes expressed by bacteria, predominantly in the phyla Firmicutes and Bacteroidetes. Carnivores, such as snakes that feed intermittently, sometimes process very large meals that require compensatory adjustments in blood flow, acid secretion, and regulation of acid-base homeostasis. Snakes and birds that specialize in simple diets of prey or nectar retain their ability to digest a wider selection of prey. The digestive system continues to be of interest to comparative physiologists because of its plasticity, both phenotypic and evolutionary, and because of its widespread integration with other physiological systems, including thermoregulation, circulation, ventilation, homeostasis, immunity, and reproduction.
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Rogers, N. J., UrbinaLt, M. A., Reardon, E. E., McKenzie, D. J., & Wilsonl, R. W. (2016). A new analysis of hypoxia tolerance in fishes using a database of critical oxygen level (P-crit). Conserv. Physiol., 4, cow012.
Résumé: Hypoxia is a common occurrence in aquatic habitats, and it is becoming an increasingly frequent and widespread environmental perturbation, primarily as the result of anthropogenic nutrient enrichment and climate change. An in-depth understanding of the hypoxia tolerance of fishes, and how this varies among individuals and species, is required to make accurate predictions of future ecological impacts and to provide better information for conservation and fisheries management. The critical oxygen level (P-crit)m has been widely used as a quantifiable trait of hypoxia tolerance. It is defined as the oxygen level below which the animal can no longer maintain a stable rate of oxygen uptake (oxyregulate) and uptake becomes dependent on ambient oxygen availability (the animal transitions to oxyconforming). A comprehensive database of P-crit values, comprising 331 measurements from 96 published studies, covering 151 fish species from 58 families, provides the most extensive and up-to-date analysis of hypoxia tolerance in teleosts. Methodologies for determining Pcrit are critically examined to evaluate its usefulness as an indicator of hypoxia tolerance in fishes. Various abiotic and biotic factors that interact with hypoxia are analysed for their effect on P, including temperature, CO,, acidification, toxic metals and feeding. Salinity, temperature, body mass and routine metabolic rate were strongly correlated with P-crit; 20% of variation in the P-crit, data set was explained by these four variables. An important methodological issue not previously considered is the inconsistent increase in partial pressure of CO, within a closed respirometer during the measurement of P-crit. Modelling suggests that the final partial pressure of CO, reached can vary from 650 to 3500 mu atm depending on the ambient pH and salinity, with potentially major effects on blood acid-base balance and P it itself. This database will form part of a widely accessible repository of physiological trait data that will serve as a resource to facilitate future studies of fish ecology, conservation and management.
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