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Cortelezzi A.,National University of Central Buenos Aires | Cortelezzi A.,CONICET | Sierra M.V.,Institute Limnologia Dr Raul A Ringuelet Ilpla | Sierra M.V.,CONICET | And 5 more authors.
Environmental Monitoring and Assessment | Year: 2013

Our objective was to assess the effect of the physical habitat degradation in three lowland streams of Argentina that are subject to different land uses. To address this matter, we looked into some physical habitat alterations, mainly the water quality and channel changes, the impact on macrophytes' community, and the structural and functional descriptors of the epipelic biofilm and invertebrate assemblages. As a consequence of physical and chemical perturbations, we differentiated sampling sites with different degradation levels. The low degraded sites were affected mainly for the suburban land use, the moderately degraded sites for the rural land use, and the highly degraded sites for the urban land use. The data shows that the biotic descriptors that best reflected the environmental degradation were vegetation cover and macrophytes richness, the dominance of tolerant species (epipelic biofilm and invertebrates), algal biomass, O2 consumption by the epipelic biofilm, and invertebrates' richness and diversity. Furthermore, the results obtained highlight the importance of the macrophytes in the lowland streams, where there is a poor diversification of abiotic substrates and where the macrophytes not only provide shelter but also a food source for invertebrates and other trophic levels such as fish. We also noted that both in benthic communities, invertebrates and epipelic biofilm supplied different information: the habitat's physical structure provided by the macrophytes influenced mainly the invertebrate descriptors; meanwhile, the water quality mainly influenced most of the epipelic biofilm descriptors. © 2012 Springer Science+Business Media Dordrecht.

Miquelarena A.M.,Institute Limnologia Dr Raul A Ringuelet Ilpla | Lopez H.L.,Institute Limnologia Dr Raul A Ringuelet Ilpla
Neotropical Ichthyology | Year: 2010

Hyphessobrycon nicolasi is described from the Uruguay River basin in the Mesopotamian Region, Entre Rios, Argentina. The new species can be distinguished from all congeners by the presence of a well-defined oblique and marginal black stripe on each lobe of the caudal fin. Other characters defining H. nicolasi are the possession of 1-3 teeth with 3-10 cusps on maxilla; outer premaxillary row with 2-3 small teeth, with 5 or 7 cusps; iv-vi, 27-36 anal-fin rays; 33-36 scales on the longitudinal series; two vertical dark spots on the humeral region; dorsal and anal fins dappled in black and base of caudal fin bearing conspicuous black spot; and the presence of bony hooks on the rays of dorsal, anal and caudal fins of the mature males. © 2010 Sociedade Brasileira de Ictiologia.

Donato M.,Laboratory Of Sistematica Y Biologia Evolutiva Lasbe | Siri A.,Institute Limnologia Dr Raul A Ringuelet Ilpla
Neotropical Entomology | Year: 2010

The male and female of the new species Metriocnemus puna sp. n from the Argentinean Puna are described and illustrated. A parsimony analysis including 24 well-described species of the genus plus the new species based on the adult male was conducted in order to access the phylogenetic position of the new species and to provide the first phylogenetic hypothesis for the genus.

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