The relictual population of the purple clam Amiantis Purpurata (l.) in northern Patagonia (Argentina): the history of a warm-temperate-water neogene survivor

The purple clam Amiantis purpurata (Lamarck) is a warm-temperate species inhabiting shallow water along the coast from Espiritu Santo (Brazil) to northern Patagonia. It is one of the few survivors of the middle–late Miocene faunal turnover which was characterized by the appearance of new taxa, most of them living now along the Argentinean coast. In order to study the biogeographic history of A. purpurata, a detailed review of its records was carried out. The oldest record of this species is from late Miocene rocks in Uruguay, and it appears that A. purpurata survived because its wide thermal tolerance range allowed larvae to migrate southwards from Uruguay, settling on the southern coast of Buenos Aires Province and San Matías Gulf. The characteristics of this gulf would have favored the development and settlement of the larvae, thus giving rise to the most abundant southern population during the Pleistocene. At the end of the Pleistocene, A. purpurata also survived the Last Glacial Maximum. During the Holocene, the population of A. purpurata in San Matías Gulf became isolated, but also represented the most abundant southern population of this species. During its brief Neogene history, Amiantis purpurata followed main global, regional and local events; thus it can be considered as an environmental indicator for this period.La almeja púrpura Amiantis purpurata (Lamarck) es una especie de aguas templado-cálidas que habita en aguas poco profundas desde Espíritu Santo (Brasil) hasta el norte de Patagonia. Es uno de los pocos sobrevivientes del intercambio faunístico del Mioceno medio–tardío, que se caracterizó por la aparición de nuevos taxa, la mayoría de ellos vivientes en la actualidad a lo largo de la costa argentina. Con el fin de reconstruir su historia biogeográfica, se llevó a cabo una revisión detallada de los registros. El registro más antiguo de A. purpurata proviene del Mioceno tardío en Uruguay, y sobrevivió debido a su amplia tolerancia térmica lo que habría permitido que las larvas migren desde Uruguay hacia el sur, donde se establecieron en la costa sur de la Provincia de Buenos Aires y en el Golfo San Matías. Además, las características de este golfo han impulsado el desarrollo y asentamiento de las larvas, lo que daría lugar a la población más abundante situada más al sur durante el Pleistoceno. Al final del Pleistoceno, A. purpurata también sobrevivió al Último Máximo Glacial y, una vez en el Holoceno, la población de A. purpurata del Golfo San Matías quedó aislada, lo que representa la población más abundante y austral de esta especie. A lo largo de su breve historia geológica durante el Neógeno, Amiantis purpurata acompañó a los principales acontecimientos ocurridos a escala global, regional y local; por lo tanto, esta especie puede ser considerada como un indicador ambiental para este período.Fil: Bayer, María Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Gordillo, Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones En Ciencias de la Tierra; ArgentinaFil: Morsán, Enrique . Instituto de Biología Marina y Pesquera Almirante Storni; Argentin

Differential Settlement of Associated Species on Ostrea puelchana

Ostrea puelchana d?Orbigny, 1842 is a common species of commercial interest in Patagonia and is distributed from Rio Grande do Sul (Brazil) to San Matías Gulf (SMG, Argentina). In SMG, the species develops natural banks that provide irregular surfaces suitable for colonization of organisms. We studied the composition and frequency of encrusting and associated species on O. puelchana shells as well as the preferential settlement of epibionts on different areas within left and right valves. A total of 55 taxa were identifi ed. The dominant groups were Annelida, Foraminifera, Bryozoa and Mollusca in two different oyster banks. The lifestyle of the oyster favors a preferential settlement of epibionts on different valves and areas within the valves. Substratum heterogeneity, reproductive cues, gregarious behavior, protection against predation and/or brooding care could be responsible for this differential settlement. The left valve was more encrusted than the right one. Spirorbinae, Cirratulidae, Foraminifera, juvenile O. puelchana, Bryozoa and Hydrozoa showed preferential settlement in different areas on the external left valves. On the external right valves, the same taxa except for Hydrozoa showed a nonrandom distribution between areas.Fil: Romero, María Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo; ArgentinaFil: Brezina, Soledad Silvana. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Hernández, D.. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Casadío, S.. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; ArgentinaFil: Bremec, Claudia Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo; Argentin

A 4096-pixel MAPS device with on-chip data sparsification

A prototype of a mixed-mode ASIC composed of a fast readout architecture that interfaces with a matrix of 4096 Monolithic Active Pixel Sensor (MAPS) was fabricated via STM 130 nm CMOS technology. Groups of 4 x 4 pixels form a macro-pixel (MP). The readout architecture is parallel and could overcome the readout speed limit of big matrices. As the output port can only accept one-hit information at a time, an internal queuing system has been provided to face high hit-rate conditions. The ASIC can work in two different manners as it can be connected to an actual full-custom matrix of MAPS or to a digital matrix emulator composed of standard cells, for testing facilities. For both operating modes a slow-control phase is required to load the chip configuration. Previous versions of similar ASICs were designed and tested. The work is aimed at improving the design of MAPS detectors with an on-chip fast sparsification system, for particle tracking, to match the requirements of future high-energy physics experiments. The readout architecture implemented is data driven extending the flexibility of the system to be also used in first level triggers on tracks in vertex detectors. Preliminary simulations and tests indicate that the readout system can cope with an average hit-rate up to 100 MHz/cm(2) if a master clock of 80 MHz is used, while maintaining an overall efficiency over 99%. (c) 2009 Elsevier B.V. All rights reserved