Changes in the diet and body size of a small herbivorous mammal (hispid cotton rat, \u3ci\u3eSigmodon hispidus\u3c/i\u3e) following the late Pleistocene megafauna extinction

The catastrophic loss of large-bodied mammals during the terminal Pleistocene likely led to cascading effects within communities. While the extinction of the top consumers probably expanded the resources available to survivors of all body sizes, little work has focused on the responses of the smallest mammals. Here, we use a detailed fossil record from the southwestern United States to examine the response of the hispid cotton rat Sigmodon hispidus to biodiversity loss and climatic change over the late Quaternary. In particular, we focus on changes in diet and body size. We characterize diet through carbon (δ13C) and nitrogen (δ15N) isotope analysis of bone collagen in fossil jaws and body size through measurement of fossil teeth; the abundance of material allows us to examine population level responses at millennial scale for the past 16 ka. Sigmodon was not present at the cave during the full glacial, first appearing at ~16 ka after ice sheets were in retreat. It remained relatively rare until ~12 ka when warming tempera­tures allowed it to expand its species range northward. We find variation in both diet and body size of Sigmodon hispidus over time: the average body size of the population varied by ~20% (90–110 g) and mean δ13C and δ15N values ranged between −13.5 to −16.5‰ and 5.5 to 7.4‰ respectively. A state–space model suggested changes in mass were influenced by diet, maximum temperature and community structure, while the modest changes in diet were most influenced by community structure. Sigmodon maintained a fairly similar dietary niche over time despite contemporaneous changes in climate and herbivore community composition that followed the megafauna extinc­tion. Broadly, our results suggest that small mammals may be as sensitive to shifts in local biotic interactions within their ecosystem as they are to changes in climate and large-scale biodiversity loss

The accelerating influence of humans on mammalian macroecological patterns over the late Quaternary

The transition of hominins to a largely meat-based diet ~1.8 million years ago led to the exploitation of other mammals for food and resources. As hominins, particularly archaic and modern humans, became increasingly abundant and dispersed across the globe, a temporally and spatially transgressive extinction of large-bodied mammals followed; the degree of selectivity was unprecedented in the Cenozoic fossil record. Today, most remaining large-bodied mammal species are confined to Africa, where they coevolved with hominins. Here, using a comprehensive global dataset of mammal distribution, life history and ecology, we examine the consequences of “body size downgrading” of mammals over the late Quaternary on fundamental macroecological patterns. Specifically, we examine changes in species diversity, global and continental body size distributions, allometric scaling of geographic range size with body mass, and the scaling of maximum body size with area. Moreover, we project these patterns toward a potential future scenario in which all mammals currently listed as vulnerable on the IUCN\u27s Red List are extirpated. Our analysis demonstrates that anthropogenic impact on earth systems predates the terminal Pleistocene and has grown as populations increased and humans have become more widespread. Moreover, owing to the disproportionate influence on ecosystem structure and function of megafauna, past and present body size downgrading has reshaped Earth\u27s biosphere. Thus, macroecological studies based only on modern species yield distorted results, which are not representative of the patterns present for most of mammal evolution. Our review supports the concept of benchmarking the “Anthropocene” with the earliest activities of Homo sapiens

Dissolution of lead- and lead-arsenic-jarosites at pH 2 and 8 and 20 C: Insights from batch experiments

Lead- and Pb-As-jarosites are minerals common to acidic, sulphate-rich environments, including weathering zones of sulphide ore deposits and acid rock or acid mine drainage (ARD/AMD) sites, and often form on or near galena. The structures of these jarosites are based on linear tetrahedral-octahedral-tetrahedral (T-O-T) sheets, comprised of slightly distorted FeO6 octahedra and SO4 2- (-AsO4 3- in Pb-As-jarosites) tetrahedra. To better understand the dissolution mechanisms and products of the break down of Pb- and Pb-As-jarosite, preliminary batch dissolution experiments were conducted on synthetic Pb- and Pb-As-jarosite at pH 2 and 20 C, to mimic environments affected by ARD/AMD, and at pH 8 and 20 C, to simulate ARD/AMD environments recently remediated with slaked lime (Ca(OH)2). All four dissolutions are incongruent. Dissolution of Pb-jarosite at pH 2 yields aqueous Pb, Fe and SO4 2-. The pH 8 Pb-jarosite dissolution yields aqueous Pb, SO4 2- and poorly crystalline Fe(OH)3, which does not appear to resorb Pb or SO4 2-, possibly due to the low solution pH (3.44-3.54) at the end of the experiment. The pH 2 and 8 dissolutions of Pb-As-jarosite result in the formation of secondary compounds (poorly crystalline PbSO4 for pH 2 dissolution; poorly crystalline PbSO4 and Fe(OH)3 for pH 8 dissolution), which may act as dissolution inhibitors after 250 to 300 h of dissolution. In the pH 2 dissolution, aqueous Fe, SO4 2- and AsO4 3- also form, and in the pH 8 dissolution, Fe(OH)3 precipitates then subsequently resorbs aqueous AsO4 3-. The dissolutions probably proceed by preferred dissolution of the A- and T-sites, which contain Pb, and SO4 2-and AsO4 3-, respectively, rather than Fe, which is sterically remote, within the T-O-T Pb- and Pb-As-jarosite structures.These data provide the foundation necessary for further, more detailed investigations into the dissolution of Pb- and Pb-As-jarosites

Body size downgrading of mammals over the late Quaternary

Since the late Pleistocene, large-bodied mammals have been extirpated from much of Earth. Although all habitable continents once harbored giant mammals, the few remaining species are largely confined to Africa. This decline is coincident with the global expansion of hominins over the late Quaternary. Here, we quantify mammalian extinction selectivity, continental body size distributions, and taxonomic diversity over five time periods spanning the past 125,000 years and stretching approximately 200 years into the future. We demonstrate that size-selective extinction was already under way in the oldest interval and occurred on all continents, within all trophic modes, and across all time intervals. Moreover, the degree of selectivity was unprecedented in 65 million years of mammalian evolution. The distinctive selectivity signature implicates hominin activity as a primary driver of taxonomic losses and ecosystem homogenization. Because megafauna have a disproportionate influence on ecosystem structure and function, past and present body size downgrading is reshaping Earth’s biosphere. Includes Supplementary materials

Changes in the diet and body size of a small herbivorous mammal (hispid cotton rat, \u3ci\u3eSigmodon hispidus\u3c/i\u3e) following the late Pleistocene megafauna extinction

The catastrophic loss of large-bodied mammals during the terminal Pleistocene likely led to cascading effects within communities. While the extinction of the top consumers probably expanded the resources available to survivors of all body sizes, little work has focused on the responses of the smallest mammals. Here, we use a detailed fossil record from the southwestern United States to examine the response of the hispid cotton rat Sigmodon hispidus to biodiversity loss and climatic change over the late Quaternary. In particular, we focus on changes in diet and body size. We characterize diet through carbon (δ13C) and nitrogen (δ15N) isotope analysis of bone collagen in fossil jaws and body size through measurement of fossil teeth; the abundance of material allows us to examine population level responses at millennial scale for the past 16 ka. Sigmodon was not present at the cave during the full glacial, first appearing at ~16 ka after ice sheets were in retreat. It remained relatively rare until ~12 ka when warming tempera­tures allowed it to expand its species range northward. We find variation in both diet and body size of Sigmodon hispidus over time: the average body size of the population varied by ~20% (90–110 g) and mean δ13C and δ15N values ranged between −13.5 to −16.5‰ and 5.5 to 7.4‰ respectively. A state–space model suggested changes in mass were influenced by diet, maximum temperature and community structure, while the modest changes in diet were most influenced by community structure. Sigmodon maintained a fairly similar dietary niche over time despite contemporaneous changes in climate and herbivore community composition that followed the megafauna extinc­tion. Broadly, our results suggest that small mammals may be as sensitive to shifts in local biotic interactions within their ecosystem as they are to changes in climate and large-scale biodiversity loss

La influencia de UBER como modelo de servicio en la preferencia de los usuarios del segmento B entre los 20-25 años de Ate Vitarte en el año 2018.

Al buscar en las tiendas de App que nos ofrecen los teléfonos móviles, el nombre de “UBER” en este navegador nos devuelve una gran cantidad de buenos comentarios. Frente a este buen número de comentarios, también aparece un notorio número de App’s, donde distinguimos la aparición de los sectores de Taxi. Como si se tratara de la venta de camisetas en los estadios, antes y después del evento deportivo, mucha variedad para elegir. Pero siempre al encontrar una buena opción dejas de lado otra, como en este caso sería la preferencia de App’s sobre el uso de taxis informales, casi habitual entre un fenómeno reciente de nuestra economía y un sector con muchos años a su espalda. Modernidad y tradición se enfrentan de nuevo, cuál enfrentamiento de animales hambrientos, algo que analizaremos en este documento, no es ningún fruto de casualidad

Gastric Tube Placement in Children 1-215 Months Old

poster abstractFeeding by a nasogastric/orogastric (NG/OG) tube is preferred when the gastrointestinal system is functional and the need for assisted feeding is expected to be short-term. Preliminary studies in children show that between 21% and 44% of these tubes are placed incorrectly. When tubes are out of place, children can be seriously harmed, causing increased morbidity and occasionally death. The aims of this study were to determine the best method to predict the insertion distance for placing NG/OG tubes and to determine the best clinical methods of testing the location of NG/OG tubes once they were inserted. A randomized clinical trial was conducted. The three insertion-distance prediction methods tested were nose-ear-xiphoid (NEX); nose-ear-mid-umbilicus (NEMU); and age-related, height-based (ARHB). An abdominal radiograph was obtained immediately following tube insertion to determine the internal location of the tube tip and orifice(s). Based on data from 95 children age 1-220 months (M = 51.8, SD = 54.9, median = 33.4), both the ARHB and NEMU methods were superior to NEX in placing the tube in the stomach (p = .0064). ARHB and NEMU were not significantly different from each other. NEX was frequently too short (41.93% of tube insertions) leaving the tube tip and/or orifices in the esophagus. The three clinical methods of testing tube location were CO2 monitoring and measuring pH and bilirubin in tube aspirate. Measuring pH of tube aspirate was the superior clinical method of determining tube location. Aspirate was available for testing in 84 children (88.42%). Based on a pH cutoff of 5 (recommended by Metheny in fasting adults), the sensitivity was 26.67 (low), specificity was 80.60 (high), positive predictive value was 23.53 (low), and negative predictive value was 83.08 (high). Measuring the NEX distance is the method most commonly used by nurses in practice; therefore, based on the results of this study and studies of other researchers, a practice change to either ARHB or NEMU should improve the safety of enteral feeding in children. Because of the low sensitivity in predicting misplaced tubes using pH, the superior clinical method, obtaining an abdominal x-ray to ensure placement in the stomach at the time of tube insertion is recommended

Late Pleistocene megafauna extinction leads to missing pieces of ecological space in a North American mammal community

The conservation status of large-bodied mammals is dire. Their decline has serious consequences because they have unique ecological roles not replicated by smaller-bodied animals. Here, we use the fossil record of the megafauna extinction at the terminal Pleistocene to explore the consequences of past biodiversity loss. We characterize the isotopic and body-size niche of a mammal community in Texas before and after the event to assess the influence on the ecology and ecological interactions of surviving species (\u3e1 kg). Preextinction, a variety of C4 grazers, C3 browsers, and mixed feeders existed, similar to modern African savannas, with likely specialization among the two sabertooth species for juvenile grazers. Postextinction, body size and isotopic niche space were lost, and the δ13C and δ15N values of some survivors shifted. We see mesocarnivore release within the Felidae: the jaguar, now an apex carnivore, moved into the specialized isotopic niche previously occupied by extinct cats. Puma, previously absent, became common and lynx shifted toward consuming more C4-based resources. Lagomorphs were the only herbivores to shift toward C4 resources. Body size changes from the Pleistocene to Holocene were species-specific, with some animals (deer, hare) becoming significantly larger and others smaller (bison, rabbits) or exhibiting no change to climate shifts or biodiversity loss. Overall, the Holocene body-size-isotopic niche was drastically reduced and considerable ecological complexity lost. We conclude biodiversity loss led to reorganization of survivors and many “missing pieces” within our community; without intervention, the loss of Earth’s remaining ecosystems that support megafauna will likely suffer the same fate