科研之友
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摘要
Para a an芍lise da ecologia alimentar de Rhinodoras dorbignyi, foram realizadas coletas bimestrais, durante o per赤odo de dezembro de 1999 a janeiro de 2002, em tr那s pontos do rio Ibicu赤, Rio Grande do Sul, Brasil. O espectro alimentar da esp谷cie foi analisado por meio do 赤ndice de importancia alimentar (IAi), avaliado pela combina o dafreq邦那ncia de ocorr那ncia e do volume de cada item alimentar. A an芍lise espacial baseou-se na dieta e na distribui o da esp谷cie nos tr那s pontos de coleta e nos bi車topos de cada um desses locais. Mudan as temporais na alimenta o e na captura de exemplares foramverificadas sazonalmente e quanto ao ritmo circadiano. A intensidade espa o-temporal da tomada de alimento foi verificada por meio do grau de reple o m谷dio; utilizou-se n赤vel de significancia de 0,05. Ninfas de efem谷ridas da fam赤lia Polymitarcyidae constitu赤ram o principal item alimentar de R. dorbignyi (62,48%). A esp谷cie apresentou diferen as significantes no espectro alimentar em rela o aos pontos de coleta, esta es e ambientes. R. dorbignyi exibiu maior abundancia em ambientes l車ticos, na primavera e no ver o e no per赤odo vespertino-noturno. N o foi observada significancia para diferen as espaciais etemporais na captura de alimento. The study of the feeding ecology of Rhinodoras dorbignyi was conducted in three sites of the Ibicu赤 river, Rio Grande do Sul, Brazil, from December 1999 to January, 2003. The specimens were sampled bimonthly. The feeding spectrum was determined combining the frequency of the occurrence with the volume of each alimentary item, in order to obtain the feeding index (IAi). The spatial analysis was based on the diet and distribution of R. dorbignyi in the threesampling points, and also in their different biotopes. Temporal changes on diet and capture of the specimens were evaluated considering the seasons and the daily feeding rhythm. The intensity of spatial-temporal feeding intake was analyzed using the average stomach fullness. Significance level of 0.05 was used in the analyses. Ephemeroptera nymphs belonging to the family Polymitarcyidae represented the main feeding item (62.48%). The feeding spectrum of R. dorbignyi showed significant differences regarding sampling points, seasons, and biotopes. The species showed highest abundance in lotic environments, during the spring and summer and after sunset. No statistically significant results were observed with regard to spatial and temporal differences in feeding intake.
