This study provides an updated list of parasite species and their respective hosts in the upper Paraná River floodplain. The list of parasites is structured by phylum, class, order and family, followed by a record of each host species. A total of 315 taxa of parasites were reported, of which 201 were identified at the species level. These 201 species comprise 3 Flagellata, 3 Myxozoa, 50 Monogenea, 43 Digenea, 40 Cestoda, 41 Nematoda, 8 Acanthocephala, 6 Copepoda, 5 Branchiura and 2 Pentastomida, arranged in 84 host fish species. This work carried out in the floodplain of the upper Paraná River contributes to the listing of parasite species and host interactions of the local ichthyofauna. Little is known about these communities and its riches are underestimated due to the high density of fish found in this region, highlighting the importance of conducting studies on the local fauna.
Endoparasites that are trophically transmitted are closely intertwined and constrained by the structure of the food chain. Each fish species can be used as an intermediate or definitive host; thus, the position it occupies in the food web and the body size can be determining factors for the presence of parasites and their transmission. Considering that fish can be parasitized by larval and adult stage endoparasites and that they are exposed to a wide variety of parasite species, we used a helminth dataset from 70 fish species and tested whether the total parasite richness, larval and adult, of fish from the upper Paraná River floodplain can be explained by body size and trophic level. For the trophic level, we observed an increasing trend in the richness of larval parasites. Regarding the richness of adult parasites and the total richness, we observed an increase as a function of the body size of the host. The tropic position and body size of the fish were good predictors, indicating that the position of the host in the trophic chain can influence and determine its life cycle.
Considering the lack of studies on freshwater fishes of the genus Colomesus, we conducted a survey the parasite fauna of Colomesus tocantinensis collected from the Tocantins River, Brazil. We first recorded the presence of the ectoparasites Ergasilus colomesus and Lernaea sp. where 96.77% of the fish were parasitized.
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