The relationship between structure and location in the nest of the Yellow-winged Blackbird ( Agelasticus thilius)

La estructura y la ubicación del nido deben maximizar el beneficio que proporciona a la nidada, tanto en el aislamiento del ambiente como en la protección contra predadores. El Varillero Ala Amarilla (Agelasticus thilius) construye nidos abiertos entrelazados a la vegetación palustre en zonas de bañado. Se estudió la altura a la que estas aves construyen su nido y el espesor de sus paredes laterales y de la base, buscando un patrón que correlacione estas características. Los nidos fueron construidos en la mitad inferior de las varas de totora y se encontró una correlación positiva entre la altura de la totora y la distancia del nido a la punta de la vara. Tanto el espesor de la pared como el de la base aumentaron con la distancia entre el nido y la punta de las varas a las que estaban entrelazados, lo cual podría reforzar su estructura permitiéndole soportar los efectos del viento sin romperse. El espesor de la pared fue mayor en los nidos construidos a menor altura pero no se encontró el mismo patrón en el espesor de la base. Los factores ambientales que ponen a prueba la fortaleza de la estructura del nido podrían tener importancia en la determinación de la estructura y la posición de los nidos, mientras que la influencia del riesgo de predación podría ser menor.Nest structure and location must maximize the benefit provided to chicks through isolation from the environment as well as protection against predators. The Yellow-winged Blackbird (Agelasticus thilius) builds open nests intertwined to trowel vegetation in marshlands. The height to which these birds build the nest and the thickness of their lateral walls and base were studied to look for a pattern that relates these characteristics. Nests were built in the lower half of bulrush canes and a positive correlation between height of canes and the distance between the nest and the cane tip was found. The thickness of both nest wall and base increased with the distance between the nest and the cane tip. This could reinforce nest structure improving its resistance to the effect of the wind without damage. Wall thickness was higher in nests built at a lower height, but base thickness was not correlated with this distance. Environmental factors that test the strength of the nest structure may be important in determining nest structure and location, while the influence of predation risk would be lower.Fil: Montalti, Diego. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Graña Grilli, Maricel. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Variation in diet composition during the breeding cycle of an Antarctic seabird in relation to its breeding chronology and that of its main food resource

This work had two aims related to the diet of brown skuas (Stercorarius antarcticus lonnbergi) breeding at Laurie Island (South Orkney Islands, Antarctic). The first aim was to explore whether there are changes throughout the breeding season. The second aim was to determine whether those changes relate to differences in food resource availability of their main prey, penguins, at different time periods of the penguins’ breeding cycles, or to different moments of the skuas breeding cycle, which may variably restrict the foraging activities of parents. Diet was analyzed from pellet samples grouped in two different ways. They were grouped in three periods defined for the skuas breeding cycle (laying and incubation; early parental care; later parental care), or the pellets were assigned to five periods based on the type of food resources available at the penguin colonies (eggs; eggs and small chicks; small and large chicks; large and fledged chicks; fledged chicks). A temporal variation in diet composition was evident from the analysis of contingency tables for both sample grouping methods. The more represented item in every period for both analyses was adult penguins, which may be related to the proposed cleaning function of the gut of penguin feathers. Both ways of grouping the samples suggest a relationship between the kind of resources available at the penguin colonies and the easiness of delivering them to the skuas chicks, reflected in a successive predominance of use of penguin eggs first and of penguin chicks and other birds later.Fil: Graña Grilli, Maricel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico Zoología Vertebrados; ArgentinaFil: Montalti, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico Zoología Vertebrados; Argentin

Evaluación de la capacidad probiótica de Pseudobutyrivibrio xylanivorans para su posible aplicación como herramienta de manipulación de la fermentación ruminal en cabras Criollas

RESUMEN DE PROYECTO: Recientemente, este equipo de investigación logró el aislamiento de la especie bacteriana ruminal Pseudobutyrivibrio xylanivorans a partir del rumen de cabras Criollas. Los avances de estas investigaciones nos han conducido a destinar esta cepa como futuro agente probiótico. Como parte de la caracterización probiótica de P. xylanivorans, fue necesario profundizar los conocimientos del ambiente microbiano ruminal, donde tendrá lugar la interacción del futuro probiótico con la microbiota habitual del animal hospedador. Con la colaboración del Livestock Research Group de Nueva Zelanda, este equipo formó parte del Censo Global de Rumen, logrando la caracterización de las comunidades microbianas mediante high-throughput sequencing, lo cual resultó en una publicación en una de las revistas científicas más prestigiosas del mundo: Scientific Reports de Nature. Además, en colaboración con la Academia de Ciencias de República Checa, se ha trabajado en el análisis molecular de las comunidades bacterianas ruminales de cabras sometidas a diferentes condiciones de alimentación. Esto generó un convenio de colaboración, reafirmando las intenciones de apoyo científico y tecnológico de los investigadores checos. El abordaje de los objetivos propuestos en el presente proyecto, permitirán continuar con el análisis de las comunidades bacterianas del rumen de cabras en desarrollo y sometidas a diversas condiciones de crianza, mediante la aplicación de novedosas herramientas moleculares (Next Generation Sequencing). Además, como parte de la caracterización probiótica de P. xylanivorans se ejecutarán novedosas técnicas de cultivo de bacterias anaerobias para la realización de xilanogramas y ensayos de producción de ácidos grasos volátiles por parte la futura especie probiótica, en la Academia de Ciencias de República Checa. Finalmente, realizaremos ensayos de adherencia bacteriana, a partir de la utilización de la técnica de Microscopía Electrónica de Transmisión (TEM), a fin de establecer un análisis ultraestructural de los contactos que se generan entre dichas bacterias y el epitelio del rumen

Digestive microbiota associated with colorectal cancer : potential use of P:xylanivorans 2 as a probiotic in the management of this disease

Nuestro equipo de investigación logró aislar y caracterizar una bacteria wild-type de la especie Pseudobutyrivibrio xylanivorans (cepa 2), a partir del contenido ruminal de cabras Criollas. En esta cepa se identificó el gen xynAPx perteneciente a la familia de genes xynA, que codifican para enzimas glicosilhidrolasas, el cual estuvo relacionado con la actividad enzimática de esta cepa. La actividad de las xilanasas secretadas por P. xylanivorans 2 fue superior a la de especies bacterianas ruminales involucradas en la digestión del xilano, el principal componente de la hemicelulosa contenida en la pared celular vegetal. Recientemente, demostramos la capacidad adherente de P. xylanivorans 2 a células del cáncer de colon humano. A partir de estos hallazgos, se propuso el uso de la cepa P. xylanivorans 2 como potencial bacteria probiótica. El cáncer colorrectal (CCR) es uno de los tipos de cáncer más comunes en el mundo y sus tasas de morbilidad y mortalidad están aumentando debido a las alteraciones en el estilo de vida y los hábitos alimenticios humanos. La composición de la comunidad de bacterias intestinales es diferente entre individuos sanos y pacientes con CCR. Pseudobutyrivibrio ruminis fue una de las especies bacterianas que aumentaron en los pacientes humanos sanos en comparación con los pacientes con CCR. Esto podría deberse a que Pseudobutyrivibrio spp. producen butirato, un nutriente importante para las células colónicas normales, que reduce la proliferación e induce la apoptosis de las células del carcinoma de colon humano. El butirato se sintetiza a partir de la fermentación bacteriana de la fibra vegetal no digerible en el colon humano. A pesar de las potenciales propiedades probióticas ya demostradas de P. xylanivorans, hasta el momento no se han encontrado reportes que evalúen la abundancia de esta especie bacteriana en el microbioma digestivo de pacientes sanos o con CCR. Así como tampoco se han demostrado patrones consistentes de poblaciones bacterianas asociadas al CCR. Por lo tanto, pretendemos caracterizar la microbiota digestiva asociada al CCR, para evaluar el potencial uso de P. xylanivorans 2 como probiótico en el manejo de esta enfermedad.Recently, we were able to isolate and characterize a "wild-type" bacterium of the specie Pseudobutyrivibrio xylanivorans (strain 2), from the ruminal content of Creole goats. In this strain, the xynAPx, which code for glycosyl hydrolases enzymes, was identified and related to the enzymatic activity of this strain. From these findings, the use of the P. xylanivorans 2 as a potential probiotic bacterium was proposed. Colorectal cancer (CRC) is one of the most common cancers in the world and its morbidity and mortality rates are increasing due to alterations in lifestyle and human eating habits. The composition of the intestinal bacteria community is different between healthy individuals and patients with CRC. Pseudobutyrivibrio ruminis was one of the bacterial species that increased in healthy human patients compared to patients with CRC. This could be because Pseudobutyrivibrio spp. they produce butyrate, an important nutrient for normal colonic cells, which reduces proliferation and induces apoptosis of human colon carcinoma cells. Butyrate is synthesized from the bacterial fermentation of non-digestible plant fiber in the human colon. Despite the potential proven probiotic properties of P. xylanivorans, there have been no reports so far evaluating the abundance of this bacterial species in the digestive microbiome of healthy patients or with CRC. Moreover, consistent patterns of bacterial populations associated with CRC have not been demonstrated. Therefore, we intend to characterize the digestive microbiota associated with CRC, to evaluate the potential use of P. xylanivorans 2 as a probiotic in the management of this disease

Uniformity of diet composition of Brown Skua chicks at different ages and between siblings

The diet of chicks may change according to their growth and also vary between siblings due to their competitive relationship. Diet composition of 81 Brown Skua (Stercorarius antarcticus lonnbergi) chicks was analysed from regurgitated stomach contents in order to determine changes in diet composition related to chick age and differences between siblings. Fifty-nine of the samples belonged to chicks whose age was estimated by applying culmen measurement to a regression function. The remaining 22 samples belonged to 11 sibling pairs whose stomach contents were simultaneously sampled. The diet was constituted mostly by soft tissues of penguins. Marine resources were a minor part of the diet of chicks, appearing in the third week of their life. The qualitative composition of the stomach content of siblings was similar in most cases, but mass of regurgitates differed between siblings (1.3– 90.0% = 0.5–9 g), which suggests the potential existence of aggressive food monopolization by one sibling, an issue to be elucidated with further research.Facultad de Ciencias Naturales y MuseoConsejo Nacional de Investigaciones Científicas y Técnica

Uniformity of diet composition of Brown Skua chicks at different ages and between siblings

The diet of chicks may change according to their growth and also vary between siblings due to their competitive relationship. Diet composition of 81 Brown Skua (Stercorarius antarcticus lonnbergi) chicks was analysed from regurgitated stomach contents in order to determine changes in diet composition related to chick age and differences between siblings. Fifty-nine of the samples belonged to chicks whose age was estimated by applying culmen measurement to a regression function. The remaining 22 samples belonged to 11 sibling pairs whose stomach contents were simultaneously sampled. The diet was constituted mostly by soft tissues of penguins. Marine resources were a minor part of the diet of chicks, appearing in the third week of their life. The qualitative composition of the stomach content of siblings was similar in most cases, but mass of regurgitates differed between siblings (1.3– 90.0% = 0.5–9 g), which suggests the potential existence of aggressive food monopolization by one sibling, an issue to be elucidated with further research.Facultad de Ciencias Naturales y MuseoConsejo Nacional de Investigaciones Científicas y Técnica

The relationship between structure and location in the nest of the Yellow-winged Blackbird (<i>Agelasticus thilius</i>)

La estructura y la ubicación del nido deben maximizar el beneficio que proporciona a la nidada, tanto en el aislamiento del ambiente como en la protección contra predadores. El Varillero Ala Amarilla (Agelasticus thilius) construye nidos abiertos entrelazados a la vegetación palustre en zonas de bañado. Se estudió la altura a la que estas aves construyen su nido y el espesor de sus paredes laterales y de la base, buscando un patrón que correlacione estas características. Los nidos fueron construidos en la mitad inferior de las varas de totora y se encontró una correlación positiva entre la altura de la totora y la distancia del nido a la punta de la vara. Tanto el espesor de la pared como el de la base aumentaron con la distancia entre el nido y la punta de las varas a las que estaban entrelazados, lo cual podría reforzar su estructura permitiéndole soportar los efectos del viento sin romperse. El espesor de la pared fue mayor en los nidos construidos a menor altura pero no se encontró el mismo patrón en el espesor de la base. Los factores ambientales que ponen a prueba la fortaleza de la estructura del nido podrían tener importancia en la determinación de la estructura y la posición de los nidos, mientras que la influencia del riesgo de predación podría ser menor.Nest structure and location must maximize the benefit provided to chicks through isolation from the environment as well as protection against predators. The Yellow-winged Blackbird (Agelasticus thilius) builds open nests intertwined to trowel vegetation in marshlands. The height to which these birds build the nest and the thickness of their lateral walls and base were studied to look for a pattern that relates these characteristics. Nests were built in the lower half of bulrush canes and a positive correlation between height of canes and the distance between the nest and the cane tip was found. The thickness of both nest wall and base increased with the distance between the nest and the cane tip. This could reinforce nest structure improving its resistance to the effect of the wind without damage. Wall thickness was higher in nests built at a lower height, but base thickness was not correlated with this distance. Environmental factors that test the strength of the nest structure may be important in determining nest structure and location, while the influence of predation risk would be lower.Facultad de Ciencias Naturales y Muse

The relationship between structure and location in the nest of the Yellow-winged Blackbird (<i>Agelasticus thilius</i>)

La estructura y la ubicación del nido deben maximizar el beneficio que proporciona a la nidada, tanto en el aislamiento del ambiente como en la protección contra predadores. El Varillero Ala Amarilla (Agelasticus thilius) construye nidos abiertos entrelazados a la vegetación palustre en zonas de bañado. Se estudió la altura a la que estas aves construyen su nido y el espesor de sus paredes laterales y de la base, buscando un patrón que correlacione estas características. Los nidos fueron construidos en la mitad inferior de las varas de totora y se encontró una correlación positiva entre la altura de la totora y la distancia del nido a la punta de la vara. Tanto el espesor de la pared como el de la base aumentaron con la distancia entre el nido y la punta de las varas a las que estaban entrelazados, lo cual podría reforzar su estructura permitiéndole soportar los efectos del viento sin romperse. El espesor de la pared fue mayor en los nidos construidos a menor altura pero no se encontró el mismo patrón en el espesor de la base. Los factores ambientales que ponen a prueba la fortaleza de la estructura del nido podrían tener importancia en la determinación de la estructura y la posición de los nidos, mientras que la influencia del riesgo de predación podría ser menor.Nest structure and location must maximize the benefit provided to chicks through isolation from the environment as well as protection against predators. The Yellow-winged Blackbird (Agelasticus thilius) builds open nests intertwined to trowel vegetation in marshlands. The height to which these birds build the nest and the thickness of their lateral walls and base were studied to look for a pattern that relates these characteristics. Nests were built in the lower half of bulrush canes and a positive correlation between height of canes and the distance between the nest and the cane tip was found. The thickness of both nest wall and base increased with the distance between the nest and the cane tip. This could reinforce nest structure improving its resistance to the effect of the wind without damage. Wall thickness was higher in nests built at a lower height, but base thickness was not correlated with this distance. Environmental factors that test the strength of the nest structure may be important in determining nest structure and location, while the influence of predation risk would be lower.Facultad de Ciencias Naturales y Muse

Trophic interactions between brown and south polar skuas at Deception Island, Antarctica

It is broadly accepted that the brown skua (Stercorarius antarcticus lonnbergi) competitively excludes the south polar skua (S. maccormicki) from penguin colonies when breeding sympatrically, forcing the latter to feed on marine resources. The purpose of this work was to examine the diets and trophic niche breadths of each species where they co-occur and to determine the degree of overlap. To this end, we analyzed 169 pellets of brown skuas, collected in two different areas (20 individuals), and 152 of south polar skuas, collected in three different areas (18 individuals), on Deception Island, South Shetland Islands, Antarctica, during the austral summer 2000. Pellet analysis often underestimates the amount of easily digestible prey, but allows for comparisons of the relative contributions of different items in the diet. South polar skuas at our study locations consumed seven different food items and had a trophic niche breadth of 0.133 compared to brown skuas that fed on 10 different items and had a trophic niche breadth of 0.078. The niche overlap between the species was 82.1%. Penguins were the principal food source of both species, however, brown skuas fed mostly on chicks, while south polar skuas fed on adults (carcasses). The use of different age classes of penguins as a food source offers an alternative to competitive exclusion, allowing the coexistence of these species on Deception Island.Facultad de Ciencias Naturales y Muse

The reliability of morphometric discriminant functions in determining the sex of Chilean flamingos Phoenicopterus chilensis

Monomorphic birds cannot be sexed visually and discriminant functions on the basis of external morphological variations are frequently used. Our objective was to evaluate the reliability of sex classification functions created from structural measurements of Chilean flamingos Phoenicopterus chilensis museum skins for the gender assignment of live birds. Five meas-urements were used to develop four discriminant functions: culmen, bill height and width, tarsus length and middle toe claw. The functions were tested on a sample of live flamingos from a zoo. The best classification for museum flamingos was given by a function using tarsus length, bill width and middle toe claw (97%). However, this function did not give the best classification for the zoo-based flamingos (81%) which had the best sex assignment by a function including measurements of tarsus, culmen and bill height and width (85%). This shows that a function giving good results in the sample from which it originated may not be as good when applied to another group of animals. Our study emphasizes the need for assessing the accuracy of a function by testing it with other methods to ensure its suitability when being applied.Facultad de Ciencias Naturales y Muse