Temporal effects and changes in the parasitic community of (Valenciennes, 1837) (Characiformes: Prochilodontidae) in a floodplain.

The construction of dams causes several impacts on aquatic environments, altering the flow of rivers, environmental variables, and all biota present, including parasites. Little is known about how the parasitic community can be influenced in the long term by environmental changes. In this study, it was expected that the impacts caused by environmental disturbances will be directly reflected by the composition of the parasite populations. We evaluated the change in the structure of the Prochilodus lineatus endoparasite community between two periods sampled 15 years apart in the upper Paraná River floodplain. There was a significant difference in the weight-length relationship of P. lineatus between these periods and a total of 15 species of parasites were found: 11 species in Period 1 and nine species in Period 2 and five species occurred in both periods. The species richness and diversity were higher in Period 1, and we observed that the correlation of descriptors (richness, diversity and evenness) increased with fish length in this period. In both periods, digeneans numerically dominated the parasitic community, and we verified changes in the composition of parasites between periods. Both the host and the parasites were possibly affected by the environmental impacts resulting from the construction of dams over time, and it is noteworthy that complex life cycle parasites such as Digenea and Acanthocephala require intermediate hosts to complete their life cycle, and the population responds to fluctuations in the face of modified environments.