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Copyright of Acta Zoologica Lilloana is the property of Fundacion Miguel Lillo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

El anfípodo Hyalella patagonica está muy extendido en aguas interiores andinas de la Patagonia argentina y chilena, esta especie habita en zonas litorales de ríos, arroyos, lagos y lagunas, que según la literatura tienen patrones de distribución espacial principalmente agregados. El objetivo del presente estudio es aplicar diferentes tipos de modelos de agregación para explicar la distribución espacial de H. patagonica colectada en un arroyo del norte de la Patagonia. Se aplicaron diferentes tipos de coeficientes de dispersión para comprender el patrón espacial de H. patagonica. Los resultados revelaron que la población de H. patagonica tiene una distribución agregada, pero no necesariamente una distribución binomial negativa, que es frecuente en el modelo probabilístico asociado a la distribución espacial agregada. Los resultados serían similares a los patrones observados para el género Hyalella en aguas interiores de la Patagonia.

All Pseudocorynosoma species inhabit freshwater environments of the American continent, but little is known about their life cycles. We report Pseudocorynosoma enrietti (Molfi & Freitas Fernandes, 1953) from natural and experimental specimens in Patagonia and identify the intermediate and definitive hosts of its life cycle for the first time in South America. Adult worms were recovered from Anas platyrhynchos (Linnaeus) and from a new definitive host, Coscoroba coscoroba Molina. Naturally infected amphipods, Hyalella patagonica Ortmann, were collected to obtain cystacanths that were fed to Gallus gallus domesticus (Linnaeus) and Anas platyrhynchos. Specimens of P. enrietti are described in detail using light and scanning electron microscopy. A key to species of the genus Pseudocorynosoma is included. Worms are characterized in both sexes by fore-trunk spines, and genital spines in an isolated field. The proboscis has 19–20 hook rows; males have 9–11 (10) hooks per row and females 7–9 (8). Males with four cement glands similar in size. Eggs elongated, with filaments. Experimental male and female worms were recovered from A. platyrhynchos at seven and 14 days, post-infection. [ABSTRACT FROM AUTHOR]

The southern South American inland waters have many endemic species and some of them are considered as endangered for IUCN, that inhabits in unpolluted ecosystems, one of these ecosystems are the sub-Antarctic perennial forests located in the Cape Horn Biosphere Reserve at 54° S. The aim of the present study is to analyze the spatial patterns of Pisidium chilense Ituarte, 1999 (Mollusca Bivalvia) and Hyalella patagonica (Cunningham, 1871) (Crustacea, Amphipoda) in an unpolluted stream. Both species had aggregated spatial distribution, both have a negative binomial distribution pattern, and both are associated. The present results would agree with similar patterns in Patagonian rivers where both species coexist.

The southern South American inland waters have many endemic species and some of them are considered as endangered for IUCN, that inhabits in unpolluted ecosystems, one of these ecosystems are the sub-Antarctic perennial forests located in the Cape Horn Biosphere Reserve at 54° S. The aim of the present study is to analyze the spatial patterns of Pisidium chilense Ituarte, 1999 (Mollusca Bivalvia) and Hyalella patagonica (Cunningham, 1871) (Crustacea, Amphipoda) in an unpolluted stream. Both species had aggregated spatial distribution, both have a negative binomial distribution pattern, and both are associated. The present results would agree with similar patterns in Patagonian rivers where both species coexist. [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]