Parasitic Helminths Associated with Two Species of Serrasalmus Lacepède, 1803 in the Neotropical Region

Abstract Objectives This study investigated the helminth fauna of Serrasalmus maculatus and Serrasalmus marginatus in a protected area (Santa Helena Biological Refuge) and in the lower São Francisco Falso River, Brazil. The main objective was to compare the parasitic helminth fauna of these species between the areas of occurrence and to develop an updated list of the recorded parasite species. Methods Fifty individuals of each host species were collected between November 2018 and November 2019 using gillnets. Results Twelve parasitic taxa were identified, two of which were recorded for the first time: Spinoxyuris sp. in S. marginatus and Raphidascaris sp. (larvae) in S. maculatus . The most abundant parasite species in both hosts and sampling areas were Austrodiplostomum compactum metacercariae and Rhinoxenus arietinus . The helminth fauna differed among the hosts, with S. marginatus parasitized with Philometridae gen. et sp., Spinoxyuris sp., Digenea gen. et sp.1 and et sp. 2, while S. maculatus hosted Ichthyouris brasiliensis , Raphidascaris sp., and exclusively Anacanthorus sp., Notothecium sp., and Rhinoxenus euryxenus . Conclusion This study provides a revised list of helminths associated with S. maculatus and S. marginatus , including new records of hosts and geographic regions. Comparative analysis highlights differences in the richness and composition of parasite communities between the two Serrasalmidae species, contributing to the understanding of host-parasite relationships in Neotropical freshwater ecosystems.