1,721,201 research outputs found

    La medusa Craspedacusta sowerbii Lankester, 1880: nuova osservazione nei laghi trentini e distribuzione in Italia

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    Nell’agosto del 2015 sono stati osservati esemplari della medusa Craspedacusta sowerbii Lankester nel Lago di Levico (Trentino). La specie era già stata trovata in altri laghi della provincia a partire dagli anni ’90 (Lago Santo di Cembra, Lago di Lavarone, Lago dei Poiani, Lago di Garda). Allo stato attuale questa medusa risulta segnalata in 40 ambienti di acque ferme e correnti in Italia. Le segnalazioni, basate sulla osservazione dello stadio pelagico (medusa) e non sulla ricerca dello stadio bentonico (polipo), probabilmente sottostimano la distribuzione della specie in Italia.The first documented sighting of the jellyfi sh Craspedacusta sowerbii Lankester from Lake Levico (Trentino, Northern Italy) was in August 2015, but records of this species in other lakes of the province (Lago Santo di Cembra, Lago di Lavarone, Lago dei Poiani, Lago di Garda) go back to the early 1990s. C. sowerbii has a relatively wide distribution in Italy, with records from 40 freshwater ecosystems. These sightings, based on the observation of the pelagic stage (medusa) and not on the benthic stage (polyp), probably underestimates the real distribution in Ital

    First record of Corbicula fluminalis (Müller, 1774) in Lake Garda (Italy), living in sympatry with Corbicula fluminea (Müller, 1774)

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    The first record of Corbicula fluminalis (Müller, 1774) (Mollusca: Bivalvia: Veneroidea: Corbiculidae) in Lake Garda (Italy) is presented. This clam was observed in July 2008 along the lake shore, with a high number of shells; sampling of lake sediment revealed the presence of live specimens. C. fluminea (Müller, 1774) has already been recorded in Lake Garda since 2002. The need for further studies on the presence and the spread of the two clams and the biodiversity of the invertebrate community of the lake is underlined, in relation to recent records of other invasive species, such as Dikerogammarus villosus (Sowinsky, 1894)

    Going Beyond Counting First Authors in Author Co-citation Analysis

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    The present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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