Browsing by Author "Manuel Rios, Juan"

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    EFFECTS OF NUTRITIONAL AND ANTI-NUTRITIONAL PROPERTIES OF SEEDS ON THE FEEDING ECOLOGY OF SEED-EATING BIRDS OF THE MONTE DESERT, ARGENTINA
    (2012) Manuel Rios, Juan; Mangione, Antonio; Marone, Luis
    Food quality and physiological capacities and limitations in recognizing and processing food are among the factors influencing the choices of desert birds in feeding. Seed-eating birds of the central Monte desert generally select grass seeds rather than forb seeds. We studied some of the mechanisms underlying seed-selection patterns in seed-eating birds of the Monte desert, analyzing nutrients and secondary compounds of the 15 most abundant seeds in the soil and their relationship with the diet of six species of seed-eating birds. Grass seeds contained more starch and less total phenols than did forb seeds and were free from alkaloids. The diet of the most graminivorous birds was correlated with seeds' starch concentration, while generalists' diet was correlated with seed abundance. To assess the plausible mechanisms underlying birds' selection of seed, we experimented with three species differing in the breadth of their diet: a generalist, the Rufous-collared Sparrow (Zonotrichia capensis), and two graminivores, the Many-colored Chaco-Finch (Saltatricula multicolor) and Common Diuca-Finch (Diuca diuca). We postulated that the level of starch and the presence of phenolic compounds and alkaloids influence food preference. Results suggest that most graminivorous birds prefer high-starch diets and avoid diets with phenols and alkaloids. In contrast, the generalist foraged regardless of starch content, and its food intake was reduced only by some of the phenols and alkaloids tested. Seed chemistry may explain some important features of seed selection by birds in the Monte desert.
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    Energetic costs and implications of the intake of plant secondary metabolites on digestive and renal morphology in two austral passerines
    (2016) Barcelo, Gonzalo; Manuel Rios, Juan; Maldonado, Karin; Sabat, Pablo
    Seed-eating birds have a diet of high nutritional value; however, they must cope with plant secondary metabolites (PSM). We postulated that the detoxification capacity of birds is associated with a metabolic cost, given that the organs responsible for detoxification significantly contribute to energetic metabolism. We used an experimental approach to assess the effects of phenol-enriched diets on two passerines with different feeding habits: the omnivorous rufous-collared sparrow (Zonotrichia capensis) and the granivorous common diuca-finch (Diuca diuca). The birds were fed with one of three diets: control diet, supplemented with tannic acid, or supplemented with Opuntia ficus-indica phenolic extract (a common food of the sparrow but not the finch). After 5 weeks of exposure to the diets, we measured basal metabolic rates (BMR), energy intake, glucuronic acid output and digestive and kidney structure. In both species, detoxification capacity expressed as glucuronic acid output was higher in individuals consuming phenol-enriched diets compared to the control diet. However, whereas sparrows increase energy intake and intestinal mass when feeding on phenol-enriched diets, finches had lower intestinal mass and energy intake remains stable. Furthermore, sparrows had higher BMR on phenolenriched diets compared to the control group, whereas in the finches BMR remains unchanged. Interspecific differences in response to phenols intake may be determined by the dietary habits of these species. While both species can feed on moderate phenolic diets for 5 weeks, energy costs may differ due to different responses in food intake and organ structure to counteract the effects of PSM intake.
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    Feeding and digestive responses to fatty acid intake in two South American passerines with different food habits
    (2014) Manuel Rios, Juan; Barcelo, Gonzalo F.; Narvaez, Cristobal; Maldonado, Karin; Sabat, Pablo
    Specific fatty acids (FA) such as unsaturated (UFA) and saturated (SFA) fatty acids contained in foods are key factors in the nutritional ecology of birds. By means of a field and experimental approach, we evaluated the effect of diet on the activity of three esterases involved in FA hydrolysis; carboxylesterase (CE: 4-NPA-CE and a-NA-CE) and butyrylcholinesterase, in two South American passerines: the omnivorous rufous-collared sparrow (Zonotrichia capensis) and the granivorous common diuca-finch (Diuca diuca). The activity of the three esterases was measured in the intestines of freshly caught individuals over two distinct seasons and also after a chronic intake of a UFA-rich or SFA-rich diet in the laboratory. In turn, we assessed the feeding responses of the birds choosing amongst diets contrasting in the kind of specific FA (UFA- vs. SFA-treated diets). During summer, field CE activities (4-NPA-CE and a-NA-CE) in the small intestine were higher in the rufous-collared sparrow (25.3 +/- A 3.3 and 81.4 +/- A 10.8 A mu mol min(-1) g tissue(-1), respectively) than in the common diuca-finch (10.0 +/- A 3.0 and 33.9 +/- A 13.1 A mu mol min(-1) g tissue(-1), respectively). Two hour feeding trial test indicated that both species exhibited a clear preference for UFA-treated diets. On average, the rufous-collared sparrow consumed 0.46 g 2 h(-1) of UFA-rich diets and 0.12 g 2 h(-1) of SFA-rich diets. In turn, the consumption pattern of the common diuca-finch averaged 0.73 and 0.16 g 2 h(-1) for UFA-rich and SFA-rich diets, respectively. After a month of dietary acclimation to UFA-rich and SFA-rich diets, both species maintained body mass irrespective of the dietary regime. Additionally, the intestinal 4-NPA-CE activity exhibited by birds fed on a UFA-rich or SFA-rich diet was higher in the rufous-collared sparrow (39.0 +/- A 5.3 and 44.2 +/- A 7.3 A mu mol min(-1) g tissue(-1), respectively) than in the common diuca-finch (13.3 +/- A 1.9 and 11.2 +/- A 1.4 A mu mol min(-1) g tissue(-1), respectively). Finally, the intestinal a-NA-CE activity exhibited by the rufous-collared sparrow was about two times higher when consuming an UFA-rich diet. Our results suggest that the rufus-collared sparrow exhibits a greater capacity for intestinal FA hydrolysis, which would allow it to better deal with fats from different sources.
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    Individual diet specialisation in sparrows is driven by phenotypic plasticity in traits related to trade-offs in animal performance
    (2019) Maldonado, Karin; Newsome, Seth D.; Razeto-Barry, Pablo; Manuel Rios, Juan; Piriz, Gabriela; Sabat, Pablo
    Individual diet specialisation (IS) is frequent in many animal taxa and affects population and community dynamics. The niche variation hypothesis (NVH) predicts that broader population niches should exhibit greater IS than populations with narrower niches, and most studies that examine the ecological factors driving IS focus on intraspecific competition. We show that phenotypic plasticity of traits associated with functional trade-offs is an important, but unrecognised mechanism that promotes and maintains IS. We measured nitrogen isotope (delta N-15) and digestive enzyme plasticity in four populations of sparrows (Zonotrichia capensis) to explore the relationship between IS and digestive plasticity. Our results show that phenotypic plasticity associated with functional trade-offs is related in a nonlinear fashion with the degree of IS and positively with population niche width. These findings are opposite to the NVH and suggest that among individual differences in diet can be maintained via acclimatisation and not necessarily require a genetic component.
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    Subchronic exposure to chlorpyrifos affects energy expenditure and detoxification capacity in juvenile Japanese quails
    (2016) Narvaez, Cristobal; Manuel Rios, Juan; Piriz, Gabriela; Sanchez-Hernandezc, Juan C.; Sabat, Pablo
    Effects of pesticides on non-target organisms have been studied in several taxa at different levels of biological organization, from enzymatic to behavioral responses. Although the physiological responses may be associated with higher energy costs, little is known about metabolic costs of pesticide detoxification in birds. To fill this gap, we exposed orally (diet) 15-d old Coturnix cotumix japonica individuals to sublethal doses of chlorpyrifos (10 and 20 mg active ingredient/kg dry food) for four weeks. Carboxylesterase (CbE), butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) activities were periodically measured in multiple tissues along with measurements of resting (RMR) and maximum metabolic rates (M-sum). Furthermore, glucuronic acid in bird excreta was also assessed at the end of the trial. While CbE and BChE activities were inhibited by chlorpyrifos in all tissues during the third and fourth weeks following pesticide treatment, AChE activity was unaffected. At this sampling times, both M-sum and RMR expansibility decreased. These results suggest that the exposure to chlorpyrifos caused a negative effect on aerobic performance. Additionally, excretion rate of glucuronic acid was up to 2-fold higher in the 20-mg/kg group than in the control and 10-mg/kg chlorpyrifos groups. The inhibition of CbE and BChE activities corroborated that these enzymes are fulfilling their role as bioscavengers for organophosphate pesticides, decreasing its concentration and thus protecting AChE activity against inhibition by chlorpyrifos. (C) 2015 Elsevier Ltd. All rights reserved.
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    Tolerance to Dietary Phenolics and Diet Breadth in Three Seed-eating Birds: Implications for Graminivory
    (2012) Manuel Rios, Juan; Marcelo Mangione, Antonio; Marone, Luis
    The ability to cope with plant secondary compounds (PSCs) has profound implications for an animal's behavior. In the present study, we assessed the tolerance to dietary phenolics in three seed-eating birds: Zonotrichia capensis, Saltatricula multicolor, and Diuca diuca, which differ in their diet breadth. Seeds in their habitat have distinct chemical composition: grass seeds have less PSCs, specifically, less total phenolics than forb seeds. Based on the detoxification limitation hypothesis and using published data of the natural history of these birds in the central Monte desert, we postulate that predominantly and exclusively graminivorous birds such as D. diuca and S. multicolor, respectively, are less tolerant due, in part, to a lower detoxification capacity than those with greater diet breadth, Z. capensis. To achieve this goal, we measured the food intake of diets varying in their concentration of tannic acid (TA). Indicators of tolerance were body mass change, food, TA and water intake, and glucuronic acid output throughout the experiment. Zonotrichia capensis performed better along the tolerance experiment: it maintained body mass from 0 to 4% TA diet, food and TA intake were higher than the other two species at the end of the experiment, and glucuronic acid output by Z. capensis was greater than D. diuca and S. multicolor from 2% TA diet until the end of the experiment. Our results suggest that Z. capensis is the most tolerant species and this physiological trait may explain their greater diet breadth. J. Exp. Zool. 00A:1-9, 2012. (c) 2012 Wiley Periodicals, Inc.