Browsing by Author "Ramirez-Otarola, Natalia"

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    Are levels of digestive enzyme activity related to the natural diet in passerine birds?
    (2011) Ramirez-Otarola, Natalia; Sabat, Pablo
    Digestive capabilities, such as the rates nutrient hydrolysis and absorption, may affect energy intake and ultimately feeding behavior. In birds, a high diversity in gut biochemical capabilities seems to support the existence of a correlation between the morphology and physiology of the intestinal tract and chemical features of the natural diet. However, studies correlating the activity of digestive enzymes and the feeding habits at an evolutionary scale are scarce. We investigated the effect of dietary habits on the digestive physiological characteristics of eight species of passerine birds from Central Chile. The Order Passeriformes is a speciose group with a broad dietary spectrum that includes omnivorous, granivorous and insectivorous species. We measured the activity of three enzymes: maltase, sucrase and arninopeptidase-N. Using an autocorrelation analysis to remove the phylogenetic effect, we found that dietary habits had no effect on enzymatic activity. However, we found that granivorous and omnivorous species had higher levels of disaccharidase activities and insectivores had the lowest. The major difference in enzymatic activity found at the inter-specific level, compared to the reported lower magnitude of enzyme modulation owing to dietary acclimation, suggests that these differences to some extent have a genetic basis. However, the lack of a clear association between diet categories and gut physiology suggested us that dietary categorizations do not always reflect the chemical composition of the ingested food.
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    Early fitness consequences and hormonal correlates of parental behaviour in the social rodent, Octodon degus
    (2010) Ebensperger, Luis A.; Ramirez-Otarola, Natalia; Leon, Cecilia; Ortiz, Maria E.; Croxatto, Horacio B.
    Males are expected to assist their mates whenever this behaviour raises survival of offspring with little expense in terms of mating opportunities At a more proximate level cortisol and testosterone hormones seem involved in the expression of parental care in mammals We examined the consequences to postnatal offspring development and survival of the males presence in the social rodent Octodon degus Offspring quality and quantity and maternal condition of females were contrasted among females rearing their litters in the presence of the sire females breeding in the presence of a non-breeding female and females breeding solitarily We related these differences to variation in parental behaviour and plasma levels of testosterone and cortisol Twenty two females and their litters were studied under constant conditions of adult density nest availability food availability and breeding experience Males huddled over and groomed offspring However neither the number nor the mass of pups from dams that nested with the sire differed from those recorded to breeding females that nested with a non-breeding female and females that nested solitarily Body weight loss and associated levels of plasma cortisol in dams nesting with the sire were similar to those of solitary females but higher than mothers nesting with a non-breeding female Thus male care had no consequences to offspring and seemed detrimental to breeding females Circulating levels of cortisol and total testosterone were either poor (mothers) or no (fathers non-breeding females) predictors of parental care (C) 2010 Elsevier Inc All rights reserved
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    Membrane-bound intestinal enzymes of passerine birds: dietary and phylogenetic correlates
    (2011) Ramirez-Otarola, Natalia; Narvaez, Cristobal; Sabat, Pablo
    Bird species exhibit great diversity in digestive tract morphology and enzymatic activity that is partly correlated with the chemical composition of their natural diets. However, no studies have assessed whether the activities of digestive enzymes of the enterocytes correlate with dietary chemical composition data analyzed as a continuous variable at an evolutionary scale. We used a phylogenetically explicit approach to examine the effect of diet on the hydrolytic activity of three digestive enzymes (maltase, sucrase, and aminopeptidase-N) in 16 species of songbirds (Order Passeriformes) from Central Chile. The total activities (mu mol/min) of these enzymes were positively associated with body mass using both conventional least squares regressions and phylogenetically independent contrasts. After removing mass effects, we found a significant negative correlation between the ratio of aminopeptidase-N and maltase to the proportion of seeds found in the gizzard, but this relationship was no longer significant after controlling for phylogeny. When we analyzed the specific nutritional content of the diet, we found that the percentage of nitrogen in diet was negatively correlated with residual maltase activity and positively correlated with the ratio aminopeptidase-N/maltase. Given the large interspecific differences in biochemical capacity, we conclude that these differences reflect genetically determined evolutionary changes associated with the nutrient contents of each species' natural diet.