Los peces eléctricos: extraños poseedores de "baterías orgánicas"

Las relaciones entre los peces y el medio se establecen a través de los sentidos (vista, olfato, gusto, oído, tacto), de un sistema particular, que es el de la línea lateral (línea de poros en los flancos del pez), equipado con mecanorreceptores y electrorreceptores. Además, adquiere relevancia la comunicación mediante impulsos eléctricos. Los peces constituyen el único grupo, dentro del reino animal, equipado con órganos especialmente adaptados para producir descargas eléctricas que les sirven para defenderse de enemigos, atraer presas o para formar un campo eléctrico con ondas electromagnéticas cuya perturbación es registrada por órganos sensoriales especiales, que forman parte del sistema de la línea lateral. Por ejemplo, si otro pez entra en un campo eléctrico produce un cambio de potencial que es captado por el pez que lo produce. Esta capacidad se ha desarrollado independientemente en siete familias de peces que incluyen especies de rayas, torpedos, bagres, peces hocico de elefante, anguilas y frailes.Fundación Museo La Plat

Los peces eléctricos: extraños poseedores de "baterías orgánicas"

Las relaciones entre los peces y el medio se establecen a través de los sentidos (vista, olfato, gusto, oído, tacto), de un sistema particular, que es el de la línea lateral (línea de poros en los flancos del pez), equipado con mecanorreceptores y electrorreceptores. Además, adquiere relevancia la comunicación mediante impulsos eléctricos. Los peces constituyen el único grupo, dentro del reino animal, equipado con órganos especialmente adaptados para producir descargas eléctricas que les sirven para defenderse de enemigos, atraer presas o para formar un campo eléctrico con ondas electromagnéticas cuya perturbación es registrada por órganos sensoriales especiales, que forman parte del sistema de la línea lateral. Por ejemplo, si otro pez entra en un campo eléctrico produce un cambio de potencial que es captado por el pez que lo produce. Esta capacidad se ha desarrollado independientemente en siete familias de peces que incluyen especies de rayas, torpedos, bagres, peces hocico de elefante, anguilas y frailes.Fundación Museo La Plat

Occurrence of Centroscyllium-Fabricii (Reinhardt, 1825) (Elasmobranchii, Squalidae) in the Beagle Channel, Southern South-America

Fil: Menni, Roberto Carlos. División Zoología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Burgess, GH. Fil: García, Mirta Lidia. División Zoología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin

Pisces, Atheriniformes, Atherinopsidae, Odontesthes perugiae Evermann and Kendall, 1906: Distribution extension, new records and geographic distribution map for the species

In this work, we report the presence of Odontesthes perugiae from the Camba Cué lagoon, in the Apipé Island, upper Paraná River. This distribution is the northernmost one for the species.Facultad de Ciencias Naturales y Muse

Desde el agua dulce hasta el talud: ecología de comunidades de peces en el Río de la Plata y el mar adyacente

The spatial pattern of fish assemblages and its relationship with factors along an environment gradient, from fresh to marine water environment along the Río de la Plata estuary (36°S, 56°W) the shelf and part of the slope, was examined using data from 22 sampling stations. Fish were sampled from all station with an Engel type trawl (200 mm stretched mesh in the wings, 120 mm stretched mesh in the cod ends, 4 m vertical opening and 15 m horizontal aperture) towed at 4 knots for 20 to 30 min per set. Cluster analysis and ordination analysis MDS were used to define spatial distribution of fish assemblages based on fish composition (abundance and biomass). BIO-ENV process was used to estimate assemblage association with depth, temperature and salinity of surface and bottom waters. The results of these analyses showed that the fish community along the riverine-marine gradient was structured in four assemblages: riverine, estuarine, shelf and slope. These assemblages were found to differ significantly in their species composition. Each assemblage was characterized by several common and discriminator species and characterized by differing environmental conditions. Bottom salinity and bottom temperature were the environmental variables most strongly associated with differences in assemblage structure across the various areas. The changes in assemblage structure between areas were gradual, with no sharp boundaries.Facultad de Ciencias Naturales y Muse

Desde el agua dulce hasta el talud: ecología de comunidades de peces en el Río de la Plata y el mar adyacente

The spatial pattern of fish assemblages and its relationship with factors along an environment gradient, from fresh to marine water environment along the Río de la Plata estuary (36°S, 56°W) the shelf and part of the slope, was examined using data from 22 sampling stations. Fish were sampled from all station with an Engel type trawl (200 mm stretched mesh in the wings, 120 mm stretched mesh in the cod ends, 4 m vertical opening and 15 m horizontal aperture) towed at 4 knots for 20 to 30 min per set. Cluster analysis and ordination analysis MDS were used to define spatial distribution of fish assemblages based on fish composition (abundance and biomass). BIO-ENV process was used to estimate assemblage association with depth, temperature and salinity of surface and bottom waters. The results of these analyses showed that the fish community along the riverine-marine gradient was structured in four assemblages: riverine, estuarine, shelf and slope. These assemblages were found to differ significantly in their species composition. Each assemblage was characterized by several common and discriminator species and characterized by differing environmental conditions. Bottom salinity and bottom temperature were the environmental variables most strongly associated with differences in assemblage structure across the various areas. The changes in assemblage structure between areas were gradual, with no sharp boundaries.Facultad de Ciencias Naturales y Muse

Ictiofauna de las Islas Malvinas y Tierra del Fuego

Fil: García, Mirta Lidia. División Zoología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: López, Hugo Luis. División Zoología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin

Lista comentada de la ictiofauna del Canal Beagle.

Inventario de la ictiofauna de la región, evaluación de aspectos de distribución y biología de las especies presentes. Además se incluyó la información completa de todas las entidades tratadas. Como resultado de este análisis se obtuvo un panorama actualizado del estado del conocimiento de los peces presentes en este sector. (PDF tiene 85 paginas.

Diving behaviour of the critically endangered tope shark Galeorhinus galeus in the Natural Reserve of Bahia San Blas, northern Patagonia

Background: Tope sharks (Galeorhinus galeus) aggregate in large numbers during spring and summer in closed gulfs and bays in northern Patagonia; these locations are considered the main nursery areas for the species. However, little is known about the spatial ecology or diel behaviour of this critically endangered species. The aim was to evaluate the short-term diving behaviour and habitat preferences of tope sharks using electronic tagging. Findings: Five female tope sharks, four adult and one sub-adult, were tagged with pop-up satellite archival tags in the Natural Reserve of Bahía San Blas, northern Patagonia, during spring 2011 and 2012. High-resolution archived data were collected for 40 days, including 29 days for two recovered tags. Sharks travelled up to 51.2km after release. Archived data indicated that female tope sharks preferred to remain within 24.5m of the surface and that there were no diel changes in preference. Individuals spent most of the time within 10m of the surface during the day (80%) and at night (83%), and were primarily in water between 17°C and 19°C (day, 75%; night, 70%). Moreover, tope sharks exhibited vertical oscillatory movement ('yo-yo diving'). Maximum vertical speeds and dive depths were recorded at night. Ascents from depth had a greater speed than descents, overall. Conclusions: Female tope sharks were found in shallow coastal areas during November at Bahía San Blas, near the surface at relatively restricted depths and temperatures. Longer tracking periods will be important for describing the species' migratory movements across the south-west Atlantic.Facultad de Ciencias Naturales y Muse

Fish assemblages in a small temperate estuary on the argentinian coast: spatial variation, environmental influence and relevance as nursery area

The effects of different environmental variables on the fish community structure were evaluated in a small temperate estuary. The biological and environmental data were collected bimonthly between 2007 and 2009 along the main estuarine axis. Multivariate analyses were applied (CLUSTER, SIMPER, CCA) to determine the spatial structure of fish community and to estimate the environmental influence on it. A total of 48 species of “teleost” fishes were observed, with the families Characidae and Sciaenidae presenting the largest number of species, 90% of the catches being juveniles. The fish community was overwhelmingly dominated by one species (Micropogonias furnieri, 88.9%), and only four species contributed more than 1% of total catch (Odontesthes argentinensis 5.4%, Brevoortia aurea 1.1%, Paralonchurus brasiliensis 1.1%, and Mugil platanus 1.0%). Estuarine and freshwater stragglers dominated in number of species, followed by freshwater migrants and marine migrants. Three areas with different fish assemblages, with distinctive species and functional guilds, were defined along the main axis. The occurrence and spatial spread of these areas were linked to spatial variation in salinity, which was consistently influenced by discharge from the Río de la Plata and local precipitation. The results highlight the importance of shallow environments as nursery areas and permit emphasis on their susceptibility to environmental changes.Foram avaliados os efeitos das diferentes variáveis ambientais na estrutura da comunidade de peixes em um pequeno estuário temperado. Dados biológicos e ambientais foram obtidos bimestralmente entre 2007 e 2009, ao longo do eixo principal do estuário. Análises multivariadas foram aplicadas (CLUSTER, SIMPER, CCA) para determinar a estrutura espacial da comunidade de peixes e para estimar a influência ambiental sobre ela. Um total de 48 espécies de "teleósteos" foi observado, com as famílias Characidae e Sciaenidae apresentando o maior número de espécies e sendo 90% das capturas formada por juvenis. A comunidade de peixes foi altamente dominada por uma só espécie (Micropogonias furnieri, 88,9%) e quatro espécies contribuiram com pouco mais de 1% cada para o total das capturas (Odontesthes argentinensis 5,4%, Brevoortia aurea 1,1%, Paralonchurus brasiliensis 1,1% e Mugil platanus 1,0%). Retardatários estuarinos e de água doce dominaram em número de espécies, seguidos por migrantes de água doce e marinhos. Ao longo do eixo principal foram definidas três áreas distintas, cada uma apresentando assembleias de peixes com espécies e guildas funcionais distintas. A ocorrência e abrangência espacial dessas áreas estiveram ligadas à variação espacial na salinidade, que consistentemente foi influenciada pela descarga do Rio da Prata e pela precipitação local. Os resultados destacam a importância dos ambientes rasos como áreas de berçário e permitem enfatizar sua susceptibilidade às mudanças ambientais.Facultad de Ciencias Naturales y Muse