Oxydoras

Abstract: The aim of this study was to investigate the parasitic endohelminth fauna of Metynnis hypsauchen from Jari River basin, in Brazilian Amazon. The 30 examined fish were parasitized by one or more species of endoparasites. A total of 4337 parasites were collected including Dadayus pacuensis, Procamallanus (Spirocamallanus) inopinatus, Spinoxyuris oxydoras, Contracaecum sp. and Acanthocephala gen. sp. However, there was a dominance of D. pacuensis followed by S. oxydoras, and all parasites showed an aggregate dispersion. There was positive correlation between the abundance of P. (S.) inopinatus and the length and abundance of D. pacuensis with the weight of the host. The body condition of the hosts was not affected by parasitism. This first study on parasites of M. hypsauchen showed that this fish is an intermediate or definitive host for some species of these parasites.

Abstract: We examined 44 specimens of Metynnis lippincottianus (Cope, 1870) (Characidae), collected in the Upper Parana 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.

Abstract: The present study provides the first investigation on the ecological aspects of the parasites M. lippincottianus from the Amazonian basin, as well as the parasite-host relationship . 76 out of the examined fish ( 98.7%) were parasitized by at least one species of parasites. A total of 8,774 parasites were collected, being Ichthyophthirius multifiliis , Anacanthorus jegui , Dadayius pacupeva , Digenea gen. sp. (metacercariae), Procamallanus ( Spirocamallanus ) inopinatus , Procamallanus ( Spirocamallanus ) sp., Spinoxyuris oxydoras , Contracaecum sp. larvae, Dolops longicauda and Hirudinea gen. sp. Ichthyophthirius multifiliis was the dominant species, followed by A. jegui . Among the endoparasites, S. oxydoras and D. pacupeva were predominant. The mean diversity of parasites was HB = 0.96 ± 0.32 and there was aggregate distribution pattern. A positive correlation of body weight with the abundance of I. multifiliis and S. Oxydoras was observed, whereas a negative correlation of body weight with abundance of the Contracaecum sp. larvae was found. The relative condition factor (Kn) was not negatively affected by parasites, and a positive correlation between Kn and abundance of I. multifiliis , S. oxydoras and D. pacupeva was found. This study is the first one to record I. multifiliis , D. longicauda and A. jegui parasitizing M. lippincottianus , as well as the first record of D. pacupeva and S. oxydoras in the Amazonas river system.