Search Results

You are looking at 1 - 4 of 4 items for

  • Author: L. Ceschini x
Clear All Modify Search
Open access

T. Ceschini, R. Takemoto, F. Yamada, L. Moreira and G. Pavanelli

Abstract

Paranaella luquei is a monogenean from family Microcotylidae, which was found parasitizing the gills of Steindachnerina brevipinna (Eigenmann & Eigenmann, 1889), collected in two different tributaries of Paranapanema River, Paraná, Brazil. This parasite was the first species of Microcotylidae described parasitizing freshwater fishes (Hypostomus sp., Hypostomus regani (Ihering) and Rhinelepis aspera Spix & Agassiz (Loricariidae) in the country.

Open access

L. Moreira, R. Takemoto, F. Yamada, T. Ceschini and G. Pavanelli

Abstract

We examined 44 specimens of Metynnis lippincottianus (Cope, 1870) (Characidae), collected in the Upper Paraná River floodplain, Brazil, from March 2006 to December 2007. Of the total number of fishes, 32 (72.7 %) were infected by at least one species of helminth (endoparasites). One digenean, Dadayus pacupeva, and four nematode species, Spinoxyuris oxydoras, Contracaecum sp. (larval stage), Procamallanus (Spirocamallanus) inopinatus and Raphidascaris (Sprentascaris) mahnerti were identified. D. pacupeva and S. oxydoras showed the highest values of prevalence, mean intensity and abundance. The typical pattern of overdispersion or aggregation was observed for all endoparasites. Dominance by D. pacupeva and S. oxydoras was observed in the parasite community. Positive association between D. pacupeva and two nematode species (S. oxydoras and P.(S.) inopinatus) was observed, including positive and significant covariation between their abundances. These results suggest that species are coexisting without competition. There was no correlation between parasitism and sex for M. lippincottianus.

Open access

T. Ceschini, R. Takemoto, F. Yamada, L. Moreira and G. Pavanelli

Abstract

In order to examine the ecological relationships of metazoan parasites and their hosts, 63 specimens of Steindachnerina brevipinna have been collected from April to September 2006, in the rivers Guairacá and Corvo, tributaries of the low Paranapanema River. Five different parasite species have been found (Paranaella sp., Sphicterodiplostomum musculosum, Cosmoxynema vianai, Travnema travnema and Spinoxyuris sp.), with parasite richness from 1 to 4. The dominance index (C > 0.25) was calculated for S. musculosum and aggregation of S. musculosum and Paranaella sp. were reported. There were no associations or covariations between the species of parasites. Values did not show interference of parasite abundance at different gonadal maturity stages. The relative condition factor (Kn) did not show significant values regarding quantitative and qualitative data on parasitism. Statistical tests were significant between the prevalence and the abundance of parasites and the standard length of the hosts, as well as for the parasite abundance in different months and tributaries.

Open access

A. Morri, L. Ceschini, M. Pellizzari, C. Menapace, F. Vettore and E. Veneri

Abstract

The effect of austempering parameters on the microstructure and mechanical properties of 27MnCrB5-2 steel has been investigated by means of: dilatometric, microstructural and fractographic analyses; tensile and Charpy V-notch (CVN) impact tests at room temperature and a low temperature.

Microstructural analyses showed that upper bainite developed at a higher austempering temperature, while a mixed bainitic-martensitic microstructure formed at lower temperatures, with a different amount of bainite and martensite and a different size of bainite sheaf depending on the temperature. Tensile tests highlighted superior yield and tensile strengths (≈30%) for the mixed microstructure, with respect to both fully bainitic and Q&T microstructures, with only a low reduction in elongation to failure (≈10%). Impact tests confirmed that mixed microstructures have higher impact properties, at both room temperature and a low temperature.