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This study reviews the amphipod species of the genus Hyalella in the inland waters of Patagonia, Tierra del Fuego Island, Cape Horn Biosphere Reserve, and adjacent islands (38-54°S). This southern zone has numerous kinds of continental water bodies such as lakes, wetlands, and streams, and the main species in benthic assemblages are amphipods of the genus Hyalella. The literature mentions the presence of H. costera, H. chiloensis, H. falklaidensis, H. franciscae, H. neonoma, H. patagonica, H. rionegrina, and H. simplex. The distribution of these species agrees with biogeographical studies about the presence of widespread, endemic species in southern Patagonia and the sub-Antarctic zone. In spite of the presence of introduced predatory species, the literature indicates that the amphipods are more abundant due to the presence of particulated organic matter. [ABSTRACT FROM AUTHOR]

Toxicity to the locally dominant amphipod Hyalella curvispina was assessed in a first-order stream running through a cultivated farm. Cypermethrin, chlorpyrifos, endosulfan and glyphosate were sprayed throughout the studied period. Toxicity was assayed under controlled laboratory conditions with runoff and stream water samples taken from the field under steady state and flood conditions. Ephemeral toxicity pulses were observed as a consequence of farm pesticide applications. After pesticide application, runoff water showed 100% mortality to H. curvispina for 1 month, but no mortality thereafter. Toxicity persistence was shortest in stream water, intermediate in stream sediments and longest in soil samples. Runoff had a more important toxicity effect than the exposure to direct aerial fumigation. The regional environmental features determining fast toxicity dissipation are discussed. [Copyright &y& Elsevier]

Soybean production in Argentina comprises 15 million ha. Cypermethrin is the main insecticide applied amounting 150 g of active ingredient per hectare, thus representing roughly 2.3 thousand tons yearly released to the environment. Toxicity pulses have been observed in small streams draining agricultural basins, most of them sustaining macrophyte growth. Cypermethrin concentrations and its toxicity to the amphipod Hyalella curvispina was compared following an addition to laboratory mesocosms with and without a vegetation cover of the floating macrophyte Lemna sp. Both concentrations and toxicity decreased faster in the treatments covered with Lemna. Fast adsorption of the hydrophobic pesticide to the roots and fronds of Lemna was suggested. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the present study was to evaluate alterations in the reproduction induced by acanthellae and cystacanths of the acanthocephalans Acanthocephalus tumescens and Corynosoma sp. in the amphipod Hyalella patagonica from Lake Mascardi. Specimens of H. patagonica were separated in two categories: paired amphipods (joined specimens during precopulatory mate guarding period until fertilization) and unpaired amphipods (alone specimens). Different analyses were performed: first with paired (n =406) and unpaired (n =375) amphipods, and second only with female amphipods (n =1949), that were classified into three categories (without internal oocytes and eggs, only with internal oocytes, and with eggs). Also, carotenoid extraction was performed of amphipods uninfected (n =75) and infected (n =105) by cystacanths of Corynosoma sp. Unpaired amphipods had significantly higher prevalence of cystacanths of both acanthocephalan species than paired ones; but such differences were not found in prevalence of acanthellae. Female amphipods without internal oocytes and eggs showed significantly higher prevalence of cystacanths of both acanthocephalan species than the two other female categories; while females with eggs had significantly higher prevalence of A. tumescens acanthellae. Amphipods infected by Corynosoma sp. showed lower carotenoid concentration than uninfected ones. In Lake Mascardi, there is indirect evidence of both reduced mating success and female fecundity of H. patagonica provoked by both cystacanths species (A. tumescens and Corynosoma sp.). However, infections by acanthellae seem to have no effects. [Copyright &y& Elsevier]

The aim of this work is to evaluate the toxic effect of water and sediment contaminated with Cu2+ on the survival and growth of juveniles of Hyalella pseudoazteca. The LC50 96 h for Cu2+ in moderately hard water was 0.17 mg/L. The concentration of 100 mg Cu2+/kg in sediment was found to have an inhibitory growth effect. This study provides information on the toxic effects of Cu2+ on a native benthic species occurring in the Pampean region, Argentina and contributes to validate, in this region, the interim use of Cu2+ values recommended by the sediment quality guidelines for the Northern hemisphere. [ABSTRACT FROM AUTHOR]