The influence of parasitism on the relative condition factor (Kn) of Metynnis lippincottianus (Characidae) from two aquatic environments: the upper Parana river floodplain and Corvo and Guairac芍 rivers, Brazil = Influ那ncia do parasitismo sobre o fator de condi o relativo (Kn) de Metynnis lippincottianus em dois ecossistemas aqu芍ticos: plan赤cie de inunda o do alto rio Paran芍 e rios Corvo e Guairac芍, Brasil

作者：Luis Henrique de Aquino Moreira; Fabio Hideki Yamada; Tiago Lopes Ceschini; Ricardo Massato Takemoto

来源：Acta Scientiarum - Biological Sciences, 2010.

• ecology
• parasites
• nematode
• digenetic
• hydroelectric plants
• ecologia
• parasitas
• nematoides
• digeneticos
• hidreletricas

The study analyzed 84 specimens of Metynnis lippincottianus (Cope, 1870) (Characidae) from two environments with different degrees of impact due to a hydroeletric plant; 44 hosts from the upper Parana river floodplain (low degree of impact) and 40 from Paranapanema tributaries (Corvo and Guairac芍 rivers, high degree of impact). The prevalence found, among the total collected fishes, was 77.4%. One digenetic species, Dadayus pacupeva, and four nematodes, Spinoxyuris oxydoras, Contracaecum sp. (larval stage), Procamallanus (Spirocamallanus) inopinatus and Raphidascaris (Sprentascaris) mahnerti were identified. In the floodplain, the fishes parasitized by D. pacupeva and S. oxydoras presented better relative condition factor (Kn) than non-parasitized species. Positive correlation between Kn and abundance of these parasites was found in the same area. In the tributaries, the Kn did not differ significantly between parasitized an non-parasitized fishes, not even correlation with abundance of any parasite found. Foram coletados 84 esp谷cimes de Metynnis lippincottianus, peixe carac赤deo, em dois ecossistemas com diferentes n赤veis de impacto, resultante da constru o de usinas hidroel谷tricas; 44 hospedeiros na plan赤cie de inunda o do alto rio Paran芍 (baixo impacto) e 40 nos tribut芍rios do rio Paranapanema (rios Corvo e Guairac芍) com alto impacto. Foi encontrada preval那ncia parasit芍ria de 77,4% no total de peixes coletados. Uma esp谷cie de digen谷tico: Dadayus pacupeva e quatro de nematoides: Spinoxyuris oxydoras, Contracaecum sp. (est芍gio larval), Procamallanus (Spirocamallanus) inopinatus e Raphidascaris (Sprentascaris) mahnerti foram identificadas. Na regi o da plan赤cie, os peixes parasitados por D. pacupeva e S. oxydoras apresentaram melhor fator de condi o relativo (Kn) quando comparado aos n o-parasitados. Verificou-se correla o positiva entre o Kn e a abundancia dos parasitos citados anteriormente na mesma regi o. Nos tribut芍rios, n o houve diferen a estatisticamente significativa entre o Kn dos peixes parasitados e n o-parasitados, nem correla o do mesmo com a abundancia de nenhum parasito encontrado.