Parasitism influence on the hepato, splenosomatic and weight/length relation and relative condition factor of Prochilodus lineatus (Valenciennes, 1836) (Prochilodontidae) of the Upper Paraná River floodplain, Brazil.

One hundred and forty-nine specimens of Prochilodus lineatus (Valenciennes, 1836) were collected on the Upper Paraná River floodplain (Brazil) from February 2000 to June 2001. Both parasitized and unparasitized fish showed alometric growth. The parasitized fish presented relative condition factor (Kn) values that were significantly higher than those of the unparasitized fish. In the age classes with unparasitized fish, the mean relative condition factor was always lower. Starting from two years of age, the Kn values were higher in the parasitized hosts. The monogenean Rhinonastes pseudocapsaloideum, the copepod Gamispatulus sp. and the digenean Saccocoelioides magnorchis presented significant positive correlation between their abundance and the relative condition factor of the host. No species presented correlation between abundance and the hepatosomatic relation. The acanthocephalan Neoechinorhynchus curemai presented positive correlation and the metacercariae Tylodelphys sp. presented negative correlation between the splenosomatic relation and abundance of parasitism.