Desarrollo larvario de Pilumnoides hassleri (Decapoda: Brachyura: Pilumnoididae) cultivado en laboratorio, con una revisión de la sistematica de Pilumnoididae utilizando caracteres larvarios

The genus Pilumnoides is an interesting taxon because its systematic position, based on adult characters, remains unclear. These xanthoid crabs have been related to the Carpiliidae, Goneplacidae and Eriphioidea. P. hassleri A. Milne Edwards, 1880 lives in Brazilian, Uruguayan and Argentinian coasts as far south as the Magellan Strait (southwestern Atlantic). Larvae of P. hassleri from females collected in the harbour of Mar del Plata were reared in the laboratory from zoea I to megalopa and the first larval stage, and described. The species passed through 5 zoeal stages and a megalopa. Larval characters were compared with the previous description of larvae from the southeastern Pacific species P. perlatus and with species of Carpilius, Goneplax and Eriphia in order to review the relationships between these taxa.El género Pilumnoides es un taxón interesante dado que su posición sistemática, basada en caracteres adultos, permanece poco clara. Estos cangrejos xantoideos han sido relacionados con las familias Carpiliidae, Goneplacidae y Eriphioidea. P. hassleri A. Milne Edwards, 1880 vive en las costas de Brasil, Uruguay y Argentina hasta el Estrecho de Magallanes (Atlántico Sudoccidental). Se cultivaron larvas de P. hassleri, provenientes de hembras colectadas en el puerto de Mar del Plata, desde la zoea Ihasta la megalopa y el primer estadio de cangrejo, y posteriormente se describieron. La especie pasa por 5 estadios de zoea y una megalopa. Las características larvarias se compararon con descripciones previas de larvas de P. perlatus del Pacífico Suroriental, y con especies de Carpilius, Goneplax y Eriphia con el objetivo de rever las relaciones entre estos taxa

Prey preference of the stone crab Platyxanthus crenulatus (Decapoda: Platyxanthidae) in laboratory conditions

The preference for a particular type of prey implies an active behavioral choice of the predator. The present work deals with the prey preference of the large stone crab Platyxanthus crenulatus among similar sized gastropods and bivalves of different substrates using a recent proposed methodology based on a two-stage approach. In laboratory, crabs received different mollusk species separately to determine the consumption in number of each species when choice was not possible. Further, crabs were offered the same mollusc species but together to record differences of specific consumption when choice was possible. Results were then compared to assess prey preferences. Platyxanthus crenulatus is able to effectively attack and consume the majority of the sympatric mollusk species, although preferred the dominant species Brachidontes rodriguezii over the others. Such preference seems to be driven by shell shape and thickness which may be a common pattern in prey preference among large stone crab species

Prey preference of the stone crab Platyxanthus crenulatus (Decapoda: Platyxanthidae) in laboratory conditions

The preference for a particular type of prey implies an active behavioral choice of the predator. The present work deals with the prey preference of the large stone crab Platyxanthus crenulatus among similar sized gastropods and bivalves of different substrates using a recent proposed methodology based on a two-stage approach. In laboratory, crabs received different mollusk species separately to determine the consumption in number of each species when choice was not possible. Further, crabs were offered the same mollusc species but together to record differences of specific consumption when choice was possible. Results were then compared to assess prey preferences. Platyxanthus crenulatus is able to effectively attack and consume the majority of the sympatric mollusk species, although preferred the dominant species Brachidontes rodriguezii over the others. Such preference seems to be driven by shell shape and thickness which may be a common pattern in prey preference among large stone crab species

Mitochondrial genetic structure of two populations of Uca urugayensis fails to reveal an impact of the Rio de la Plata on gene flow

The Rio de la Plata. located between Uruguay and Argentina, generates a tremendous freshwater influx from the estuary into the coastal sea. It is thus suggested to constitute a biogeographic barrier for many taxa exhibiting a marine planktonic larval dispersal. However, evidence for corresponding intraspecific dispersal constraint has yet to be provided. We compared mitochondrial haplotypes of ten individuals for each of two populations of Uca (Leptuca) uruguayensis north and south of the estuary to examine the potential effect of the Rio de la Plata on the species' distribution. The populations are separated by nearly 2,000 km and were collected in São Paulo State (Brazil) and Mar Chiquita (Argentina). We found no significant indication for restricted gene flow between them, based on 823 basepairs of the mitochondrial cytochrome c oxidase subunit I gene. The structure of the corresponding haplotype network and the estimated nucleotide diversities, however, suggest that the Argentinean population is genetically more diverse than the one from Brazil. In order to establish possible significant differences in haplotype distribution, further research including more populations and larger sample sizes will be necessary

State-dependent motional squeezing of a trapped ion: Proposed method and applications

We show that the motion of a cold trapped ion can be squeezed by modulating the intensity of a phase-stable optical lattice placed inside the trap. The method we propose is reversible (unitary) and state selective: it effectively implements a controlled-squeeze gate. This resource could be useful for quantum information processing with continuous variables. We show that the controlled-squeeze gate can prepare coherent superpositions of states which are squeezed along complementary quadratures. Furthermore, we show that these states, which we denote "X states," exhibit a high sensitivity to small displacements along two complementary quadratures, which makes them useful for quantum metrology.Fil: Drechsler, Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Farías, M. Belén. University Of Luxembourg; LuxemburgoFil: Freitas, Nahuel. University Of Luxembourg; LuxemburgoFil: Schmiegelow, Christian Tomás. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Paz, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin

Fish farming water quality and environmental concerns in Argentina: a Regional approach

In spite of the steady increase in fish farming in Argentina, studies on water quality are scarce. Eight fish farms from two different regions in the northeast and east of Argentina were studied to explore source and effluent water quality. Ammonium (NH4), nitrate (NO3-), and nitrite (NO2-) levels were measured. High nitrate concentrations in water source were observed in the eastern region farms. An increase in NH4-, NO3-, and NO2- in effluent water was determined in most of the sampled farms. Heavy metals (i.e.,cadmium, chromium, copper, iron, manganese, nickel, and zinc) and arsenic concentrations were analyzed. Heavy metal concentrations were below the detection limit in the northern region. However, As was detected in the water source of five farms and was over the recommended limit (100 lgl-1) for aquaculture in one. An increase in Mn and Zn concentrations in effluent water was observed in two farms. The lack of treatment of the effluent water in these farms leads to an increase of nutrients and heavy metal concentrations in the surrounding areas. Environmental effects of fish-farming practices in Argentina are discussedFil: Schenone, Nahuel Francisco. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Vackova, Lenka. Institute Of Chemical Technology Prague; República ChecaFil: Fernandez Cirelli, Alicia. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentin