Descripción: Stenurus globicephalae Baylis et Daubney, 1925 (Nematoda: Pseudaliidae) was found in the cranial air sinuses of a false killer whale, Pseudorca crassidens (Owen), stranded on the coast of Uruguay in 1999. Although this species has been reported once in P. crassidens from the North Atlantic, this is the first record for South America. A total of 920 specimens were obtained, of which 663 were females (body length: 4.34 ± 0.45 cm) and 257 were males (2.99 ± 0.18 cm). Morphometric details are presented for S. globicephalae in this host, which do not show significant differences from those parasitizing Globicephala melas (Traill), but are distinct from those parasitizing Peponocephala electra (Gray), The host's skull revealed loss of osseous mass with the disappearance of the left zygomatic arch, and the left jaw had three osseous fenestrations in the region related to the organ of acoustic reception. These lesions support the hypothesis that this infection, known as stenurosis, was related to the stranding.

Descripción: Three species of Eryngium that constitute new records or problematic taxa for the Floras of Argentina and Uruguay are presented. E. balansae, known from Paraguay and Brazil, is recorded from Argentina for the first time. E. regnellii, originally described from Brazil, is recorded here from Argentina and Uruguay. This species, abundant in highlands of both countries, was in previously confused with E. stenophyllum in floristic and ecological studies. This last name designates an infrequent and poorly known species, and thus it is considered appropriate to here recharacterize it. For each of these three taxa a description, illustrations and a distribution map is provided, as well as a key to the Argentine species of Eryngium sect. Parmiculata ser. Latifolia, the group to which the three entities belong.

Descripción: A hydrodynamic numerical study at the mouths of the Paraná and Uruguay rivers and the upper Río de la Plata is presented in this paper. Water Quality Mapping numerical model was implemented and realistic and very simple boundary conditions were specially developed for this complex estuarial system. A set of numerical experiments were carried out using different constant discharges for the Paraná and Uruguay rivers but unrealistic currents were generated. In order to obtain more realistic results, a set of numerical simulations were carried out imposing water level timeseries at the open boundaries. M2, S2, K1 and O1 harmonic constants were used to generate water levels at Zárate (Paraná river), Nueva Palmira (Uruguay river) and the eastern boundary of the domain (La Plata-Colonia). A mean water level equal to zero was set between La Plata and Colonia. Positive mean water levels (0.3-0.4m) were imposed at Zárate and Nueva Palmira to simulate the hydraulic slope of both rivers and, consequently, to generate realistic and unsteady discharges. These boundary conditions, built by means of the addition of a mean water level and the astronomical tide, significantly improve the simulated currents at the northernmost region of the RDP estuary. © 2011 Elsevier Inc.

Descripción: The present study describes a new species, Ligophorus uruguayense, parasitizing the gills of Mugil platanus Günther, 1880 from the coast of Uruguay. It differs from all other species of the genus mainly in the shape of the ventral bar, the thick process at the distal end of the inner root of ventral anchors, the J-shaped penis accessory piece and the vaginal tube showing transverse annulations at its distal end, the host species, and geographical distribution. This is the first description of a species of Ligophorus from a mullet in the South Atlantic Ocean. © 2009 Versita Warsaw and Springer-Verlag Berlin Heidelberg.

Descripción: A database of daily extreme temperature was created for as many stations as possible for Uruguay, as far back as possible. This is the first attempt to gather all the different data sources together, perform a quality control and homogeneity assessment. We work with seven stations; it should be taken into account that Uruguay is a small country (around 177 000 km2) and this represents most of the available data. There are three old series with starting dates in 1930, and four that start around 1950. From this database, a set of four extreme temperature indices was constructed for the oldest five stations, warm days (TX90), cold days (TX10), warm nights (TN90) and cold nights (TN10). The index TN10 shows the largest significant negative trend for the period 1960-2002, while TN90 shows a positive but not significant trend for this period indicating a strong warming of nighttime temperature. A spectral analysis was performed using the multi taper methods (MTM) to the de-trended annual, summer Dec-Feb (DJF) and winter Jun-Aug (JJA) indices time-series. This analysis shows that on inter-annual timescales, the most significant range of frequencies is from 2 to 2.5 years and from 3 to 6 years. Low frequencies of variability were detected when the MTM was applied to de-trended smoothed annual time-series, around the range of frequencies of 15-25 years for almost all the indices analysed. Links with global sea surface temperature (SST) were studied for two stations (Paysandu and Rocha), and it was found that the indices showed largest correlations with SST anomalies in the Pacific Ocean. We detected changes in the response of the TN10 index for Rocha station when the series was split up into two different periods (1942-1976 and 1977-2005). Copyright © 2007 Royal Meteorological Society.

Descripción: The Marsh Seedeater Sporophila palustris is one of the most endangered and least known of the capuchino seedeaters. Breeding populations are patchy, occurring in north-east Argentina, southern Brazil, and Uruguay. We present data on the breeding biology of the species, and describe nests and eggs, behaviour (including courtship, nesting, incubation and parental care), breeding sites and food items. Marsh Seedeaters breed in well-preserved grasslands with wet soils and tall vegetation. In general, these habitats are used for extensive livestock ranching. Main threats are overgrazing, widespread use of fire, conversion of grasslands to pastures of exotic grasses and rice fields, afforestation, and illegal trapping. Most breeding sites are located in Important Bird Areas, but only one in Brazil and one in Argentina are protected. We propose a series of actions to promote the conservation of Marsh Seedeaters and other endangered birds that coexist in grassland habitats. Copyright © BirdLife International 2013 Â.

Descripción: The continental deposits found in southern and western Uruguay show important climatic changes along the Cenozoic. The sequence begins with Paleocene palustrine carbonates known as the Queguay Formation, associated with calcretes of phreatic origin which developed mainly on fluvial sediments of Mercedes Formation (Late Cretaceous), and indicates a semiarid climate, seasonally contrasted. The Asencio Formation (Early Eocene) is separated from Mercedes Formation by the Yapeyu paleosurface, limiting two sedimentary cycles. Fluvial deposits lies above this surface, on which Ultisols developed under a warm and humid climate; periods of intense dryness would provoked their induration and formation of ferricretes, which under subsequent increased precipitation were dismantled. Above, Fray Bentos Formation (Oligocene-Early Miocene) lies unconformably. It is composed by loessic sediments deposited in a semiarid climate, paleosols and diverse pedogenic calcretes developed on these sediments, among which a new type named tubular calcrete, are here described; in the latter the tubular units are related to a coarse prismatic structure derived from shrink-swell processes and the surface morphology of this calcrete refers to a gilgai microrelief, typical for Vertisols. The pedogenic calcretes point to a seasonal semiarid climate. The Raigón Formation (Late Pliocene- Middle Pleistocene) of fluvial origin was formed in a humid period, and shows a paleosol at the top developed in a seasonally contrasted climate. Lying unconformably, the Libertad Formation (Early to Middle Pleistocene) is composed by loesses deposited during glacial periods that were subsequently modified by pedogenesis during interglacial periods.

Descripción: Daily station precipitation totals are used to develop a gridded dataset for the region (14°-40°S, 45°-70°W) on a 0.5° × 0.5° latitude/longitude grid, primarily for comparison with regional climate model (RCM) simulations. The gridded dataset covers the period 1961-2000. Much of the paper discusses the quality control of the basic station precipitation series. Although the primary aim of the development has been RCM validation, we have assessed trends in seasonal precipitation totals as well as trends in two measures of precipitation extremes (R95p, the daily precipitation amount exceeded only 5% of the time and Rx5day, the maximum 5-d precipitation total during each season). Relatively few regions across the large domain have statistically significant trends, but those that do tend to be located in the eastern two thirds of the grid, particularly over southeastern Brazil and Uruguay. Significant trends are also more evident in the DJF and MAM seasons. There is good spatial agreement between the trends in seasonal totals and trends in the extreme indices. © 2012 Royal Meteorological Society.

Descripción: A palaeomagnetic study was performed on three Neoproterozoic sedimentary successions exposed in central and eastern Uruguay in order to better constrain the palaeogeographic evolution of the Río de la Plata craton by the latest Proterozoic. These units comprise the latest Ediacaran to Early Cambrian calcareous Cerro Victoria Fm., exposed in the central Nico Pérez terrane, the late Ediacaran clastic Yerbal Fm. and the calcareous Polanco Fm., exposed in the Dom Feliciano belt, and the Ediacaran clastic Rocha Fm. exposed in the easternmost Punta del Este suspect terrane. The study showed that none of the units carry the original remanence and that they were affected by remagnetizations. The most widespread remagnetization is shown by the Cerro Victoria, Yerbal and Rocha Formations. A dual-polarity post-folding remanence, carried by hematite, was isolated in all these units. Mean directions from them are CV (Cerro Victoria): Dec: 179.1°, Inc: 59.0°, α95: 2.9°, n = 79 samples; Y (Yerbal): Dec: 182.4°, Inc: 61.9°, α 95: 4.5°, n = 38 samples; R (Rocha): Dec: 4.2°, Inc: -64.9°, α 95: 2.7°, n = 42 samples. Their corresponding pole positions are virtually identical (CV: 82.6°S, 309.3°E, A95: 3.9° Y: 77.0°S, 298.4°E, A95: 5.9° R: 76.6°S, 291.0°E, A95: 4.2°) suggesting the same magnetization age and process. Comparison with the South American path suggests the Late Permian-Early Triassic or the latest Cretaceous-Palaeogene as the most likely times for its acquisition. These poles are also identical to the pole of the Late Proterozoic La Tinta Fm., which is interpreted as affected by the same remagnetization, and therefore, invalid for palaeogeographic reconstructions. A different magnetic component, also dual polarity and post-folding, was defined at two sites of the Cerro Victoria Fm. and other two of the Polanco Fm., possibly carried by magnetite. The mean geomagnetic poles from both units (CVc: 4.2°N, 343.2°E, A95: 13.8° and P: 3.2°N, 325.8°E, A95: 15.2°) fall on the Middle Cambrian to Early Ordovician segment of the Gondwana APWP, suggesting that age for the remagnetization. This permits to establish the age of the tectonic event affecting the Neoproterozoic units of the Río de la Plata craton as Early Cambrian (ca. 525 Ma.). The available palaeomagnetic poles for this craton permit to constrain its palaeogeographic evolution only since approximately 600 Ma. © 2008 The Authors Journal compilation © 2008 RAS.

Descripción: A regression approach was used to quantitatively estimate the attribution of the notable growth in the river flows of the Plata Basin during 1960-1999. The study was conducted in seven large basins that account for most of the Plata River discharge. Annual rainfall integrated over each basin and annual river flows at their closing points were used for the analysis. The contribution of rainfall changes during each of the three phases of El Niño-Southern Oscillation to total rainfall change in these basins was also calculated. The two main drivers for the generalized growth of the river flows were the increased precipitation and the decreased evaporation attributable to land use change, including deforestation of natural forest and crop switch from sugarcane and coffee trees to soybean. Other evaporation changes played a minor role. There was a north-south gradient in the respective importance of each driver, with land use change having greater weight in the northern basins and the precipitation increase in the southern ones. Thus, in the northern part of the Upper Paraná Basdespite the negative trend in precipitation there was a strong augment of the river flow caused by land use change. The contribution to the positive trend of the stream flows in the middle of the Plata Basin came from both land use change and increased precipitation. Finally, in the south, the Uruguay River flow change was basically due to the precipitation trend that was not only observed during the El Niño phase, but also during the Neutral phase. Only in the Middle Paraguay Basin was the shift to more frequent and intense El Niño events that took place in the 1970s an important factor in the contribution of precipitation to streamflow trends. © 2010 Royal Meteorological Society.

Descripción: Guido bonarelli is an important figure in the field of geology in Argentina and he constituted one of the most relevant geologists in the oil exploration in our country. of Italian origin, he was born in Ancona on July 25, 1871 and he died in montereano, January 11, 1951. He excelled in stratigraphy, geological survey, historical geology and paleontology, becoming a specialist in the taxonomy of Jurassic ammonites and the stratigraphy of the Central Apennines. His professional work began in Italy and continued in southeast Asia, south America, bolivia, Chile, Argentina and uruguay. During 1911-1918, he worked in the Dirección General de minas, Geología e Hidrografía of Argentina. He defined the sub-Andean ranges as an orographic complex and he pointed out the locations of oil and natural gas reservoirs. He developed his researches in several Argentinean provinces and in the pacific Chilean coast. During his second period of research in Argentina (1923 -1927), Guido bonarelli organized the Geological Division of YpF, and he intensified the oil exploration in the northwestern of Argentina, as well as in the provinces of mendoza, neuquén and the Comodoro rivadavia region. He developed a professional and academic team that dealt with the geology and the hydrocarbon exploration in the country. bonarelli discovered in 1891 a sedimentary horizon that has great importance and it serves as a baseline to characterize the global anoxic event known to the Cenomanian-turonian transition. this world-famous skyline has been named Livello Bonarelli as a posthumous tribute to his discoverer.

Descripción: Trivalents resulting from polymorphic Robertsonian rearrangements must have a regular orientation in metaphase I if the polymorphisms are to be maintained. It has been argued that redistribution of proximal and interstitial chiasmata to more distal positions is necessary for a convergent orientation, the only one that produces viable gametes. Cornops aquaticumis a South-American grasshopper that lives and feeds on water-hyacinths, and has three polymorphic Robertsonian rearrangements in its southernmost distribution area in Central Argentina and Uruguay. The orientation of trivalents in metaphase I, the formation of abnormal spermatids and the frequency and position of chiasmata in the trivalents, was analysed in a polymorphic population of C. aquaticus. In this study we observed a correlation between the number of trivalents with the frequency of abnormal spermatids; additionally, the number of chiasmata, especially proximal and interstitial ones, was strongly correlated with the frequency of the linear orientation. Therefore we confirmed our previous assumption, based on other evidence, that the chiasmata redistribution in fusion carriers is essential to the maintenance of the polymorphisms. Copyright © 2009, Sociedade Brasileira de Genética.

Descripción: During the austral autumn of 1997, a sequence of record low ozone events with anomalous behavior occurred at subtropical latitudes to midlatitudes over southern South America, also known as the South Cone (Chile, Argentina, Uruguay, and Southern Brazil). The extreme low ozone events took place in May and early June 1997, i.e., at a time of the year when according to the climatological studies for Northern Hemisphere ozone miniholes, the most significant events would not be expected (if such studies could be simply extrapolated to the Southern Hemisphere). The first and most prominent ozone minihole, with a quasi-stationary evolution, reached values near 200 DU, i.e., a negative anomaly near 90 DU, close to 40°S. Simultaneously, extreme weather conditions were observed over the South Cone: three significant blocking events took place separated by short intervals. Both the behavior of the ozone layer over the region and the evolution of the blocking events were analyzed. As expected, the evolution of the total ozone column is shown to be linked to these perturbed weather conditions. Despite the apparently similar nature of the blocking events and of the ozone decrease during each of these events, the present study shows that the response of the UT/LS region is different in each case. The respective roles of the vertical displacement of the tropopause and the horizontal advection/divergence of ozone is discussed for the two most important events, showing how these two mechanisms combine in different ways to yield very low total ozone values. The vertical displacement of the tropopause, coupled to the size of the tropopause pressure gradient, appears to be the most efficient mechanism to modify the total ozone column amounts. Copyright 2002 by the American Geophysical Union.